September 1920.
Botanical Series
Vol XI, No >.
memoirs or tDe
Of Hdrlculture
In maia
SOME ASPECTS OF THE INDIGO
INDUSTRY IN BIHAR
PART I
THE WILT DISEASE OP INDIGO IN BIHAR
PART II
THE FACTORS UNDERLYING THE SEED
PRODUCTION AND GROWTH OF
JAVA INDIGO
BY
ALBERT HOWARD, CLE., M.A
Imperial Economic Botanist
AND
GABRIELLE L. C. HOWARD, M.A
Second Imperial Economic Botanist
{With the assistance oj Ohowdhary Ram Dhan Singh and Maulvt Abdur
Rahman Khan, Assistants to the Imperial Economic Botanist.)
AGRICULTURAL RESEARCH INSTITUTE, PUSA
PKIMKD AND PCBLISHED FOE
THE IMPERIAL DEPARTMENT OF AGRICULTURE IN INDIA
THACKEE, SPINK & CO., CALCUTTA
W. THACKER & CO., 2, Cbeed axz, LONDON
PrKM, R. 1-2 or 2*
Cr^f
Edited bt
The Council of the Pusa Agricultural Research Institute
which is not, as a body, responsible for the opinions
expressed in the Memoir.
^UE RGYAL CANADIAN INSTiTUTL
/ 6" // ^^
MEMOIRS OF THE
DEPARTMENT OF AGRICULTDHE
IN INDIA
BOTANICAL SERIES
Volume XI
AGRICULTURAL RESEARCH INSTITUTE, PUSA
PETOTBD AND PTJBUSHED FOE
THE IMPERIAL DEPARTMENT OF AGRICULTURE IN INDIA
THAOKER, SPINK & CO., CALCUTTA
W, THAOKER & CO.. 2, Ceebd Lake. LONDON
Edited by
The Council of the Pusa Agricultural Research Institute,
which is not, as a body, responsible for the opinions
expressed in these Memoirs.
CONTENTS
Volume XI
Page
No 1. Howard, Albert; and Howard, Gabrielle L. C. (with the
assistance of Cliowdliary Ram Dhan Singh and Maulvi Abdur
Rahman Khan). Some Aspects of the Indigo Industry in
Bihar. Part I— The Wilt Disease of Indigo in Bihar.
Part 11^ — The Factors underlying the Seed Production and
Growi:h of Java Indigo (with seven text-figures and five
plates) . . . . . . . . . . 1
No. 2. Shaw, F. J. F. Studies in Diseases of the Jute Plant. (1)
Diplodia CorcJiori Syd. (with eleven plates, of which one
coloured) . . . . . . . . . . 37
No. .3. MiTRA, Manoranjan. Morphology and Parasitism of Acrothe-
cium Penniseii n. sp. (A new Disease of Pennisetum
typhoidewm) (with one text-figure and four plates, of which
one colom'ed) . . . . . . . . 57
No. 4. Patel, Maganlal L. Studies in Gujarat Cottons, Part I (with
seven text-figures and eight plates) . . . . . . 75
No. 5. Dastur, Jehangir Fardunji. Die-back of ChiUies {Cajm-
cum spp.) in Bihar (with two plates) . . . . . . 129
No. 6. Youngman, W. The Influence of Atmosj^heric conditions
upon the Germination of Indian Barley (with two plates) . . 145
No. 7. Hector, G. P. Correlation of Coloiu' Characters in Rice
(with a double coloured plate) . . . . . . 153
No. 8. Parnell, F. R. (with the assistance of G. N. Rangaswami
Ayyangar, K. Ramiah and C. R. Srinivasa A}yai;gar).
The Inheritance of Characters in Rice, II (with five plates,
of which three coloured) . . . . . . 185
No. 9. SuNDARARA>UN, S. A new Ginger Disease in Godavari
District (with fom' plates, of which two colom'ed) , . . 209
No. 10. MiTRA, M. HelmintJiosporium spp. on Cereals and Sugarcane
in Lidia, Part I (Diseases of Zea Mays and Sorghum
vulga/re caused by species of HelmintJiosporium (with thiee
plates) ... .. .. .. .. 219
w^
September 1930, Botanical Series. Vol. XI, No 1
MEMOIRS OF THE
DEPARTMENT OF AGRICULTURE
IN INDIA
SOME ASPECTS OF THE INDIGO
INDUSTRY IN BIHAR
PART I
THE WILT DISEASE OF INDIGO IN BIHAR
PART II
THE FACTORS UNDERLYING THE SEED PRODUCTION
AND GROWTH OF JAVA INDIGO
BY
ALBERT HOWARD, CLE., M.A
Imperial Economic Botanist
AND
GABRIELLE L. C. HOWARD, M.A
Second Imperial Economic Botanist
(With the assistance oj Chowdhary Ram Dhan Singh and Maiilvi Abdur
Rahman Khan, Assistants to the Imperial Economic Botanist )
AGRICULTURAL RESEARCH INSTITUTE, PUSA
PRINTED AND PDBLI8HED FOK
THE IMPERIAL DEPARTMENT OF AGRICULTURE IN INDIA
BY
THACKER, SPINK & CO, CALCUTTA
W. THACKER & CO., 2, Crekd Lane, LONDON
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CONTENTS.
PART I. The wilt disease of indigo in Bihar.
I. The Factors
Soil
Rainfall
Temperature
Soil aeration
II. The cause of wilt
Root development in Java indigo . .
Observations and experiments on the cause of wilt
The root system of wilted and healthy plants
The occurrence of wUt under monsoon conditions
The artificial production of wilt
Recovery from wilt
Conclusions
Confirmatory evidence
III. The DEGENER.'iTION OF JaVA INDIGO IN BiHAR
Pollination and fertilization
Natal indigo
The kinds of indigo now grown in Java
The composition of the Java crop in Bihar
IV. The REMEDIES against wilt
Selection . .
Improved drainage
Appendix. (By Jatindra Nath Mukheijee.)
Variation of carbon dioxide in the soil gas in the different
plots in the Botanical Area, Pusa, during the period
January to November 1919
Page
2
2
3
5
ib.
6
7
9
ib.
12
14
16
17
ib.
20
ib.
ib.
21
ib.
23
ib.
24
ib.
CONTENTS
PART II. The factors underlying the seed production and
GROWTH OF Java indigo in Bihar.
I. Seed production . . . . . . . . 27
The factors underlying seed production . . . . 28
Fertilization . . . . . . . . ib.
Rapid growth . . . . . . . • ib.
An improved method of seed growing . . . . 31
IT. The growth of Java indigo . . . . . . 32
Soil aeration . . . . • • • • 33
Manuiing . . . . • • • • 36
SOME ASPECTS OF THE INDIGO INDUSTRY
IN BIHAK.
PART I.
THE ^YILT DISEASE OF INDIGO IN BIHAR.
BY
ALBERT HOWARD, CLE., M.A.,
Imperial Economic Botanist ;
AND
GABRIELLE L. C. HOWARD, M.A.,
Second Imperial Economic Botanist.
{With the assistance of Chou'dhary Ham Dhan Singh and Maulvi Abdur Rahman
Khan, Assistants to the Imperial Economic Botanist.)
[Received for publication on 23rd November, 1919.]
When the Indigo Research Station at Sirsiah was closed on March 31st,
1913, investigations on the agricultural and botanical aspects of this industry
were transferred to the Botanical Section of the Agricultural Research Institute
at Pusa. About this time, the cultivation of Java indigo in Bihar had
reached its lowest point, having fallen from 70,000 to about 15,000 bighas
between 1910 and 1914, largely on account of the wilt disease and the difficulty
of obtaining seed. These and other aspects of the industry have been under
investigation during the last six years. An account of the earlier results
appeared in Bulletins 51, 54 and 67 of the Agricultural Research Institute,
Pusa. The present paper deals with the causes of indigo wilt and with its
prevention.
Java indigo {Indigojera arrecta Hochst.) is a perennial tropical crop which
was first introduced into Bihar from Java in 1898. The climate of Bihar is
X
2 SOME ASPECTS OF THE IXDIUO INDUSTRY IN BIHAR
tropical, as far as temperature is concerned, from March to November, but
December, January, and February are too cold for the growth of this crop.
When first introduced, Java indigo did exceedingly well, yielding heavy crops
of leaf, rich in indican, as well as abundant seed. After some years, however,
the plant began to show increasing signs of want of vigour and finally began
to die of wilt during the second half of the rainy season. At the same time,
the yield of seed diminished. The degeneration was progressive and by 1913,
when we took uj) thi.i investigation, many planters had already abandoned
the cultivation while others had considerably restricted the area under this
species.
Wilt usually makes its appearance after the first cut durmg July and
August, the s-everity of the attack depending on the season. Affected plants
stand out clearly from normally grown individuals and are easily recognized
in the field. At first, there is a slowing down of growth while the foliage
alters in appearance, the leaves become folded longitudinally and assume
a yellowish-green, slaty colour. Leaf-fall is then rapid until only a tuft
of stunted foliage is left at the tips of the branches. Afterwards, the
plants die off in stages, the process taking place slowly, a branch at a
time.
A good deal of attention has been devoted by previous investigators to
the cause of indigo wilt. Neither insects, fungi nor bacteria have been shown
to be responsible for the trouble. Our investigations indicate that wilt
results from the destruction of the fine roots and nodules under circimistances
when regeneration is diflicult or impossible. In the following pages, the
evidence is recorded on which this conclusion is based. Before dealing with
the actual observations and experiments, a brief reference to the chief factors
underh'ing the cultivation of Java indigo in Bihar is necessary to brmg out
the significance of much of the following.
I. The Factors.
Soil. The soil of the Bihar indigo districts is a silt (often containing large
quantities of finely divided calcium carbonate) belonging to the older allu-
vium of the Gangetic plain. Its main characteristics, from the point of view
of the indigo plant, are its depth, the uniformity of its fine particles, its water
holding capacity during the hot months of April, May. and June, the com-
parative nearness to the surface of the sub-.soil water and the low content of
oxygen in the deeper layers, as shown by the analyses of well-waters. The
sub-soils often show rust coloured markings associated with green and blue
HOWARD AND HOWARD 6
tints which, according to Hilgaid,' indicate a lack of aeration in consequence
of imperfect drainage. Tlie indigo soils easily run together on the surface
after moderate rain forming a well-defined crust, known to the cultivator as
the fapri. After long continued heavy rain, this crust may become several
inches thick, the porosity of which is not recovered until the land dries and
is cultivated. Aii excessive rainfall besides jjroducing these impermeable
crusts, also leads to the waterlogging of the pore spaces of the upper soil
(probably due to deflocculation of the clay particles) for comparatively long
periods. 2
RainJnU. The average annual rainfall is in the neighbourhood of 50
inches, most of which falls during the period May to September (Table 1).
iHilgard, "Soils," 1906, p. 45.
"^ Agr. Jonr. oj India, Special Indian Science Congress Number, 1919, p. 381.
SOME ASPECTS OF THE INTOfJO INDUSTRY IN BIHAR
03
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HOWARD AND HOWARD 5
July ami August are the wettest months. From November to Apiil very
little rain is received. Tlie jumiidity is generally high and is lowest in March
and April when it falls to about 60.
Temperature. There is a well-marked cold season, December to Feb-
ruary, when the minimum temperature remains in the neighbourhood of 50^F.
In the hot weather months, March, April and May, the dry west winds are
important agents in improving the aeration of the soil. The monsoon period
June to September is hot and damp. After the middle of October, the tem-
perature gradually falls till cold weather conditions set in at the end of
November.
Soil aeration. Periodical determinations of the amount of carbon dioxide
in the soil atmosphere have been carried out in the Botanical area at Pusa by
Mr. Jatindra Nath Mukherjee under the direction of Dr. Harrison, Imperial
Agricultural Chemist, on cultivated and grass land for a period of eleven
months. The results are given in Table II and in Plate I. A note by Mr.
Mukherjee on the methods adopted is appended to this joaper.
Table II.
Percentage of CO-2 in the soil gas Jroin three different jjlots in the Botanical Area,
Pusa, in 1919.
Date and month when the
soil gas was aspirated
and analysed
^Plot No. 1
Grassed down
Plot No. 2
Grassed down
;_but partially
aerated by
trenches
Plot No. 3
Surface
cultivated
Rainfall in
inches since
1st January,
1919
13th, 14th and 17th Janu-
ary
0-444
0-312
0-269
Nil.
20th and 21st li'ebruary
0-472
0-320
0-253
1 -30"
21st and 22nd March
0-427
0-223
0-197
1 -33"
23rd and 24th April
0-454
0-262
0-203
2-69'
loth and 17th May.
0-271
0-257
0-133
3-26"
17th and 18th June
0-341
0-274
0-249
4-53"
17th and ISth July
1-540
1-090
0-304
14-61"
25th and 2«th August
1-590
0-830
0-401
23-29"
19th and 20th September ..
1-908
0-931
0-450
30-67"
21st and 22nd October
1-297
0-602
0-365
32-90"
14th and 15th November . .
0-853
0-456
0-261
32-90'
These figures and the curves (Plate I), give a general idea of the soil
aliiiosphere as regards ventilation in a vear exceedingly favourable to the
indigo crop. Aeration is at its best duiing tlie perii.d of the west winds —
March to May. After the monsoon has set in, the proportion of carbon dioxide
6 SOME ASPECTS OP THE INDIGO INDUSTRY IN BIHAR
rises and remains at a fairly liigli level till October when it ra])idly falls.'
Of ]RMliaiJS greater significance in this respect are the movements of the
ground water. In the indigo areas of Bihar, the flow of the rivers is often
checked during the monsoon by the rise of the level of the Ganges. As a
result, the rivers overflow and the lowlying areas go under water. The rise
in the level of the rivers is followed by a rise in the water-level of the wells.
These movements of the river level and of the general ground water are illus-
trated in the curves opposite (Plate II) which represent the state of affairs
of the river at Pusa and of one of the wells (about a quarter of a mile distant
from the river bank) for the years, 1910, 1912, 1913 and 1914. This upward
movement of the gromid water, which must push in front of it the soil air
from the deeper layers, occurs at a period when the general drainage of the
comitry is checked and when the permeability of the surface soil is p)oor due
to consolidation by heavy rain. We should expect, therefore, that the aeration
of the soil will be at its lowest point during the second half of the rainy
season.
Briefly stated these are the conditions under which a tropical leguminous
plant has to grow in Bihar. The range is wide. The crop is sown at the end
of the rains in late September or early October, when the surface soil is suffi-
ciently warm and moist for rapid germination. By the beginning of the cold
weather in December, the plant is three or four inches high. Growth then
ceases till March. After the rains set in towards the end of May or early in
Jmie, growth is exceedingly lapid and the first cut is taken at the end of June
or early in July. The stumps shoot again and the second crop is harvested
in late July or early August, followed, in good years, either by a final cut ia
September or by a crop of seed during the cold weather. After this, the
stumps are dug out and the land is prepared for other crops. The original
practice in Bihar was to raise the seed after at least two crops of leaf and at a
period in the life-history of the plant when its vigour was at its lowest point.
II. The Cause of Wilt.
The earlier results relating to the cause of wilt of Java indigo were published
in 1916, in Pusa Bulletin 67. Since that time, the subject has been investi-
gated afresli but in much greater detail with the consequence that our former
conclusions have been confirmed in all respects. Briefly stated, we have
foimd that when the roots and nodules of an indigo plant have suffered exten-
sive damage, wilt invariably results from any cause which interferes with
' It is possible tliivt ulher deleterious substances beside cnrbon dioxide are produced in
IJihar subsoils during tho rainy season. The subject needs further investijjatiun.
PLATE II.
ic
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Jtt FIE mZ. Act. M«y Ju« July Aug. Sepl 0«. Nov Dec. Jan. FA Mat. Apr, M»y June July Aug Sept Oct No*. Dec
CHANGES IN THE RIVER AND WELL LEVELS AT PIJSA.
The well levels shown by dotted lines. The
observations are expressed in (eet above
mean sea level.
fiOWARD AND HOWARt) 7
normal root regeneration. Several factors have been discovered wliicli prevent
the repair of the root system. In indigo cultivation, the chief source of
damage to the active roots and nodules arises from the complete cutting back
of the plant.' This results in the destruction of practically all the fine roots
and nodules and root regeneration is necessary before new growth can take
place. If the absorbing root system is destroyed when the soil aeration is
poor, when the amount of reserve material in the tap root is insufficient for
new roots to be formed, or when the soil temperature is too low for growth,
root regeneration becomes exceedingly difficult and wilt follows. Thus although
the cause of wilt is the same in all cases, the agents which produce it may be
different. In considering the incidence of wilt in Bihar, it is necessary, there-
fore, to understand fully in every case the factors which are concerned in root
regeneration. If this is done, all the known ca.ses of wilt fall together and
are capable of a simple explanation.
As the nodules and active root system apjoeared to be of particular impor-
tance in this question, a great deal of attention has been paid thereto. The
condition of the roots and nodules, however, cannot be determined with pre-
cision by observation of the above ground portion of the crop. It was neces-
sary to find some easy method of rapidly exposing without damage the com-
plete root system including the finer branches and the nodules. This was
accomplished by the use of an ordinary knapsack sprayer. The results
obtained by following the root development throughout the year have proved
of the very greatest value in the elucidation of this interesting problem.
Root development in Java indigo.
The development of the root system of the ordinary indigo crop, sown in
late September or early October, has been examined for several seasons by
means of periodical root washings. At first, the tajo root extends rajjidly
in length and by the beginning of the cold weather practically no large laterals
are developed. The root system at this stage consists of a long taj) root with
comparatively fine laterals and a certain amount of nodular develo25ment.
During the cold weather, the extent of the active absorbing system is small
and little or no growth of roots takes place. With the renewal of activity at
the beginning of the hot weather in March, new absorbing roots are copiously
developed and the laterals increase in thickness. Nodulaj- development begins
1 A large numbei- of root washings havo been made, at all stages of growth, after indigo
plants have been cut back to varyins e.xtents. Complete cutting back always kills the fine
roots and mos< of the ncdulcs. Heavy pruning results in extensive root and nodularj_,
destruction but not to the same extent as when the plants are completely cut back.
^
SOME ASPECTS OK THE lXJ)U:o INDUSTRY IN lilllAK
ill April, but does not become intense till the soil is cooled and moistened by
the early monsoon rains in May wlien the numbers formed are very large.
As would be expected, these bodies are much more abmidant in the first four
inches of soil than in the deeper layers. No further changes occur till the
first cut is taken. Cutting back is followed by the destruction of practically
all the fine roots and of most of the nodules. Before new growth can take
place, root regeneration is necessary. The extent and speed of this regener-
ation is found to depend on the aeration of the soil. If the rainfall is low and
if the levels of the rivers and wells do not rise to any great extent, as in 1919,
the fine roots and nodules are rapidly renewed. Thus in the case of the root
systems of three plants exposed on Jmie 14th, 1919, 194 nodules were found
on the upper laterals. These were removed and the .soil quickly replaced.
A month later, the roots of these plants were again exposed and numerous
new fine roots and no less than 942 fresh nodules were found. The reaction
of the roots to alterations in the soil atmosphere during the rains is very
striking. After the middle of July and at the beginning of September of the
present year, 1919, when heavy rains, combined with the ri.^e of the ground
water, adversely affected the aeration of the soil, an immediate root response
to the changed soil conditions took place. The fine roots in the deeper layers
of soil were quickly killed, new roots were only formed near the surface of the
ground while the finer branches of the upper laterals were found to exhibit
marked aerotropism and to bend upwards towards the air. This continued
on both occasions till a break in the rains and a fall of the ground water restored
soil aeration when normal root development again ensued. During the late
rains, the formation of fine roots and nodules is almost always restricted to
the u})per four inches of soil. At this time, the lower regions of the tap-root
and the lower laterals are practically devoifl of nodules and small roots and
the current of crude sap i.s maintained entirely by the fine roots near the surface
of the ground. This is efl'ective while monsoon conditions prevail but when
the rains cease and the upper layers of the soil dry, the plants either become
wilted or else shed theii- leaves and pass into a resting condition during the
cold weather.' l^)ot and shoot growth are resumed when the soil tempera-
ture ri.ses in .March.
in the case of .Java indigo sown for seed in August, the feature of the
root sy.stem is the development of abundant nodules on tlie ujjjier roots dui'ing
late September and October. These, however, become ab.sorbed during
' •Mulching the suil to iiroveiit the loss of moisture acts as a preventative of will during
Octiober, November and December.
HOWARD AND HOWARD »
November and December after flowering sets in. Dm-ing the cold weather, the
roots of seed plants show few active rootlets and extensive regeneration does
not take place till the temperature of the soil rises in March.
In both the ordinary and the seed crop, therefore, the features of the root
system may be summed up as follows : —
(1) The periods of intense nodular development are at the break of and
during the early rains and, in the case of the seed crop, in September and
October.
(2) Temperature, soil aeration and moisture are the chief factors in the
formation of absorbing roots and nodules.
(3) Although the nodules and fine roots are easily destroyed, the main
tap-root and the larger laterals possess remarkable vitality and are capable
of remaining dormant in the soil without damage from December to March,
after which they often produce a new set of absorbing roots and nodules.
Observations and experiments on the cause of wilt.
The evidence on which we have based our conclusions as to the cause of
wilt has been obtained by several methods. The root systems of numerous
healthy and wilted plants have been compared in detail, the occurrence of
wilt in Bihar has been studied under various conditions extending over many
years, actual cases of wilt have been produced artificially in no less than five
difierent ways while many examples of recovery have been closely examined.
The conclusions arrived at, as a result of these experiments and observations,
have been confirmed by a study of the behaviour of other crops during the
rains at Pusa and also by the growth of indigo, on soils difl'ering widely as
regards aeration, in other parts of India.
The root siistems of wilted and hcaltJii/ jilaufs. The roots of a very
large number of wilted plants have been exposed by the spraying machine
and compared with those of healthy plants. The results have always been the
same. Where the wilted condition is well marked, healthy nodules are never
found while the number of active roots is exceedingly small. Dead and dis-
coloured fine roots and nodules are, however, abundant. In the case of the
roots of healthy plants examined at the same time for comparison, there have
always been abundant fine roots and root nodules in an actively growing
condition. Indigo wilt is, therefore, associated with the recent destruction of
the absorbing root system.
In the rains, wilt occurs on deep-rooting types to a much greater
extent than on those with a shallow root system. Java indigo, as grown
in Bihar, is an exceedingly mixed crop and consists of a large number of
10 SOME ASPECTS OV THE INDtGO INDUSTRY IX BIHAR
types whicli, however, fall iuto two main classes as regards brancliing and root
development : —
( 1 ) Bushy types which branch to very varying degrees from the base, the
branches coming off nearly at right angles to the main axis. There is a
general correspondence between the method of branching of the stem and
of the root. The root system is the mirror image of the shoot. In those
bush types which branch at right angles to the axis, the lateral roots are
also given off at right angles to the main tap-root.
(2) Tall vertical types whose branches arise at an acute angle from the
stem. In the vertical types, the lateral roots arise at an angle very similar
to that in the case of the branches.
These general differences are shown in Figs. 1 and 2 and in Plate III.
Running through both these classes of branching are great divergencies in the
time of flowering and in the rate of growth. Some are early, others are ex-
ceedingly late. Some grow slowly, others much more rapidly. All gi'ades of
intermediates naturally occur. Five main types of root-development have
up to the" present been found : —
(a) Early bu.sh types in which nearly all the laterals arise at right angles
and are concentrated near the surface. Our selected indigo, known as Type
15, belongs to this group. The root system is shown in Fig. 1.
Fia. 1. The root- ran/re of an early
bush type of Java indigo.
PLATE III.
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HOWARD AND HOWARD
11
(b) Early types with a vertical lialiit in which nearly all the laterals are
concentrated near the surface but all jmint dowiiwanls. The selection known
as Type 1 1 , the I'oots of which are shown in Fig. 2, belongs to this type.
Fig. 2. The root-range of a plant of Java indigo
of vertical habit.
(c) Late bushy forms in which there is a development of lateral roots
from the surface to a great distance down the main root.
(d) Late types of vertical habit with lateral roots pomting downwards
arising at regular intervals down the long main root.
• (r) Types with hardly any side branches but a deep tap-root. These types
scarcely branch at all either above or below ground.
12 SOME ASPECTS OF TUE IXDKIO INDUSTRY IN BIHAU
It will be obvious tliat if poor soil aeration is a factor of importance in the
j>roiliictiiin of wilt, the types which will be affected most are deep-rooting types
like (b), (c), (d) and (e) while («) will be least affected, la 1917, a comparison
was made between the groW'th and wilt resistance of Type 11, an early type
with a vertical habit whose laterals point downwards (Fig. 2) and Tvpe 15, an
early bush tyjte with laterals near the surface (Fig. 1). The former proved
to be much more wilt liable than the latter. In 1918, this point received
further confirmation. It was found that after the first cut, all the plants
which did not shoot and which were attacked by wilt could not be uprooted
by hand as the laterals ran deep into the soil. On the other hand, the plants
which formed healtliv new growth could be pulled up with comparative ease
as the laterals were much nearer the surface. In 1919, every case of wilt
examined in detail during the monsoon was found to be associated with deep-
rooting while the h(>althy plants examined for comparison were all found to be
surface -rooted.
Th'j occurrence of wilt under monsoon conditions. The amount of wilt
during the rainy season and the general vigour of the indigo crop under
estate conditions, have been found to depend on two factors — the rainfall
and the rise of the ground water. If the rainfall is heavy, particularly
during July and August, and if the ground water rises rapidly and remains
at a high level during this period, the second crop is a failure and wilt
is widespread. Although unfavourable years are common, they are not
universal. In 1919. the monsoon rainfall was about 12 inches below the
average, there were no Hoods and the rise of the ground water was not con
siderable. The details relating to the rainfall and to the movements of the river
and well levels at Pusa, in 1919, are given in Plate l\ . Wilt was negli-
gible and only made its appearance on two occasions — between July 23rd
and August 7th — and again during the first three weeks of September. Both
these attacks were associated with an increased rainfall and a rise in the well
levels. Thev were, liowever. not severe and had little influence on the yield.
Tliree good cuts of indigo were obtained at Pusa and for many years tlic
indigo croj) has never been so healthy after the rahis.
Although wilt is often tmiversal during the late rains, it is not uncommon
in Pihar to find young self-sown indigo jilants in September and October,
growing vig(n'ously in fields piactically destroyed by disease. In 1912, at
Pusa, this occurre<l on the large .scale in a wilted field in which the blank sjiaces
in the lines had been filled by re.sowing dining the first week in .\ugust. The
late sown |)lants without exception were lujl alfected hy wilt but grew
well and gave heavy croj)s of well-ripened Veed. Here, healthy and wilted
PLATE IV.
Iff "•"■• ^■tt^'.n
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u^mJo jjvf puv 3<ri^
,..Jf*f •
HOWARD AND HOWARD 13
plants grew next to next witli interlocking root systems and in no single
instance did wilt spread to the late sown plants. Since 1912, many similar
examples have been noted wliirh prove conclusively that wilt is neither a
disease in the ordinary sense, nor is it caused by any deficiency in the soil
Solution.
Not only may wilted and healthy plants exist side by side, but it is easy to
produce a wilted branch as well as vigorous growth on the same plant at the
same time. This phenomenon occurs if a branch is left at the first cut in June
to maintain the transpiration current. The result of this is that the damage
to the fine roots and nodules (as shown by root washings) is less than if the
plant is completely cut back while the new shoots are formed much mors
quicklv. It often happens in such cases that after the new growth is well
established near the ground, the old branch left begins to show signs of wilt
which, however, does not spread to the new shoots. This is probably due
to the utilization of the crude sap by the new growth near the ground level
and the consequent slow starvation of the upper branch.
Both during the early and the late rains, deep cultivation has the effect of
producing wilt. Two well-marked cases of this have occurred at Pusa recently.
In 1918, Java indigo, sown in double lines to admit of intercidture during
the monsoon, steadily lost in vigour compared with the broadcast crop side
by side and also developed more wilt. In the present season, 1919, the experi-
ment was repeated with four types of indigo and on dift'erent classes of land.
In most cases, the indigo grown in double lines with interculture yielded less
green plant and also developed more wilt than the neighbouring broadcast
plots. The effect of the cultivation was found to destroy the lateral roots near
the surface and to stimulate root formation in the deeper soil layers. The
lower roots were destroyed by poor soil aeration and the plants therefore
developed wilt.
Wilt is easily produced after the rains during October and November
by the cultivation of old indigo which has hitherto managed to survive at
this period, the only active roots are close to the surface and the indigo plants
are dependent on the.se. Cultivation or the natural drying of the .surface
soil destroys the surface roots and wilt occurs. It can be jirevented by
mulching such plants with .straw or dried grass after the sowing rains in
October. The mulch preserves the moisture and so assists the surface roots
to maintain the indigo till growth ceases during the cold whether.
In 1919, a comparison was made between mulched and non-mulched
plants. The former held their leaves and resisted wilt while the latter were
afEected by the trouble.
14 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR
The artificial prnduction of wilt. Wilt can be artificialh- produced in the
following ways : —
{a) By mutilation of the root system.
{h) By cutting back young rapidly growing August sown plants in
October, when the reserve materials in the tap-root are insufficient for root
regeneration.
(c) By October and November cultivation of old indigo dependent for
its crude sap on superficial roots.
((/) By complete cutting back in the cold weather, when the root rege-
neration of surface-rooted types is difficult on account of the low soil tempe-
rature.
(e) By waterlogging slowly from below during the rains by closing the
drainage openings of lysimeters.
Undoubted wilt has been produced by root mutilation in two cases. The
first occurred in a plant which was pruned on June 21st, 1919. The roots
were exposed on July 15th, and foimd healthy in all respects. Before
replacing the soil, the tap-root was severed at a depth of one foot
below the surface and most of the fine roots were destroyed. Wilt
developed. The second example occurred in the case of a plant which was
pruned on June 21st. 1919. The roots were exposed on August 5th and
were found to be normal. Before replacing the soil, all the fine roots
and nodules on the laterals were removed to a depth of one foot but
the tap-root was left intact. Wilt rapidly developed and when the root
system was again exposed on August 29th, very few active roots were
found.
The complete cutting back, about mid October, of young actively growing
August sown indigo is certain to result in numerous cases of wilt. In 1914,
three plots of August sown indigo, each a quarter of an acre in area, were cut
back about the middle of October. Most of the plants died but a certain
number produced weak wilted shoots. Root regeneration was found to be
practically impossible due to the lack of reserve materials in the yoimg roots.
In another plot, plants with larger roots, when cut back at a later period, shot
normally. These experiments have been repeated several times since with
similar results.
Another method of producing wilt is to cut back tall August sown plants
during the cold season, when the temperature of the soil is too low for root
regeneration to take place easily. In December 1918, a number of lines of
very healthy well-developed August sown plants were cut back when over
five feet high. It was found the following February that the new growth
HOWARD AND HOWARD
15
exhibited all stages from healthy to wilted foliage. Counts were luaile on
February 17th, 1919, with the following results (Table III).
Table III.
Effect of cutting back indif/o in the cold weather.
No. of row
No. of plants
cut back
Badly wilted
Partly wilted
Normal
1
2
3
4
205
176
136
124
31
50
46
35
72
47
36
30
102
79
54
59
Total
641
162
185
294
Thus more than half the plants cut back developed wilt.i A number of
root washings were made and in all ca.ses wilt was found to be associated with
the practical absence of root regeneration. These plants were kept under
observation till April, by which time a remarkable change had taken place. The
rise in the soil temperature in March and the imjjrovement in the aeration of
the soil caused the wilted plants to recover : root regeneration took place and
the growth became normal.
Perhaps the most interesting case of the artificial jjroduction of wilt took
place during the rains of last year. At the beginning of the monsoon of 1918,
Java indigo was grown in two sets of lysimeters. These were air-tight cemented
tanks 1/1000 of an acre in area, four feet high, built about the ground level
and provided with drainage openings which could be closed at will. In
one set, alluvial soil obtained from the Kalianpur farm near Cawnpore
was used, in the other set, light Pusa soil was employed. Kalianpur soil
is exceedingly rich in available phosphate (0-318 per cent) while Pusa
soil, when analysed by Dyer's method, gives very low figures for available
' The plants which developed wilt were those which had their laterals near the surface,
the deeper-rooted plants produced normal growth. Thus the monsoon results are reversed
during the cold weather. The explanation is simple. In the cold weather, the factor which
checks root regeneration is low soil temiierature, This affects surface-rooted plants much more
tJi^O deep-rooted types.
IG SOME ASPECTS OF THE IXDinO INDUSTRY IN BIHAR
pliospliate (O'UUl per cent). The results obtained may be sununecl up as
follows : —
{</) In liotii Pusa and Kalianpur soil, the indigo in the lysinieters with
Iree drainage eseaped wilt.
(/)J When the drainage ojx'niTigs were elosed and waterlogging from
below took place, all the plants were wilted in both Kalianpur
and in I'usa soil,
(f) The wilt in Ivalianpur .soil (rich in available phosphate) was
much worse than in Pusa soil (said to be low in available
pho.sphate).
((/) The growth in Kalianpur soil was nuicli slower than in Pusa
soil.
Recureri/ from trtll. Cases of complete recovery from wilt occur fre-
quently. Good examples occurred during the rains of f919. As previously
mentioned, wilt first made its appearance this year between July 23rd and
August 7th, and again during the fir.st three weeks of September. After the
first attack, which was slight, it was observed that plants freqnently recovered
and after showing wilted foliage produced normal shoots. The roots of two
plants which recovered from wilt were e,xposed on August 21st, and were
found to have produced numerous new healthy roots. This regeneration was
evidently due to improved soil conditions. In one of the two cases examined,
a branch, which showed wilted foliage, continued to grow in length and to
form healthy leaves. This does not often occur in cases of recovery. As a
rule, the wilted branches die and new healthy shoots are jiroduced.
A second interesting case of recovery from wilt on the large scale occurred
in March, 1919, in the case of two plots, which were badly affected at the end
of the previous monsoon. Both plots, however, .showed a remarkable recovery
in March and April 1919, The diseased plants conunenced to grow and the
shoots and roots formed were perfectly healthy. Similar results were obtained
in a plot of Type 15, which had yielded two heavy crops of leaf during
1918. Many of the j>lants were attacked by wilt during the cold wcaUier
of 1918-19, but there was a remarkable recovery in March and April
of 1919. The new growth was abundant and healthy and so vigorous
were some of the individuals that they survived the monsoon of 1919,
and at the present time, Oetobei' I'.tPt. jiromise to give a .second seed
crop.
The most striking cases of reco\er)- from severe attacks of wilt occurred
in the lysimeter experiments of 1918. In two cases, in lysinieters which had
been waterlogged from below during the rains and in which all the plants were
HOWARD AND HOWARD 17
exceedingly badlv wilted, complete recovery took place in March 1919, when
the stunted diseased individuals which had been looked upon as dead, threw
out vigorous healthy shoots.
Conclusions.
These are the facts relating to the occurrence and production of wilt so
far as they have been ascertained under Bihar conditions. The conclusion
is irresistible that the trouble results from the destruction of the roots and
nodules under circumstances when regeneration is impossible. Undei' estate
conditions, the indigo crop, with very rare exceptions, does well till the first
cut. This operation, however, destroys the fine roots and nodules, and before
new growth can take place root regeneration is necessary. If the soil aeration
is sufficient at this period, the plant shoots well and, provided these conditions
continue, as m 1919, an excellent second crop follows. If, however, at the time
of the first cut. floods cause the ground water to rise and if heavy rain water-
logs the surface soil for long periods, root regeneration is verv difficult and
the result is wilt and a poor second cut. The wilt which often attacks old
indigo in November and December is due to the fact that this plant has been
forced to develop surface roots in the late rains. These suffer from want of
water as the ground dries after the monsoon and the advent of the cold
weather prevents the formation of more roots.
Confirmatory evidence.
If our view of the cause of wilt is correct and if the aeration of the soil is
really defective in Bihar during the second half of the rainy season, several
consequences naturally follow. Firstly, wilt should not be confined to Java
indigo, but should affect other deep-rooted plants while surface-rooted species,
on the other hand, should escajae. In the second place, as two rainy seasons
in India are never the same and long breaks occur, soil aeration in Bihar in
August and September should occasionally improve and lead to the recovery of
wilted plants and to greatly increased crops of indigo. In the third place,
indigo wilt should not occur in other locnlilies provided the soil ventilation is
efficient diuing the whole of the monsoon phase. Confirmatory evidence has
been obtained in all these directions.
Wilt in Bihar during the monsoon is by no means confined to Java indigo.
It is common on many deep-rooted varieties of jiatwa {Hibiscus cannabinus L.)
and sann (Crotalaria juncen L.) while shallow rooted types of these two species
are little affected. Further, surface-rooted species like Eoselle (Hibiscus
Sabdariffa L.) thrive no matter how wet the monsoon mav be. The difier-
'4
18
SOME ASPECTS OF THE IXDIGO INDUSTRY IN BIHAR
ences between the distribution of tlie roots of Roselle and of deep-rooted types
of jnUwa are shown iji Fig. 3, while in Fig. 4 the roots of an early and late type
Fig. 3. The root .'jstem of Bibheus Sabdariffa Qeft) and S. cannabinus {right).
FlO. 4. Early (left) ard late (right) types of root-systems in H. cannabinus.
of patmi are illustrated. The surface-rooted Roselle crop and the early tvj)es
of ])(itira do well at Pusa even when the soil is waterlogged. The deep-rooted
types of 2i(i(u'a in such seasons, on the other hand, suffer severely from wilt.
Similar results are obtained in the case of sarin varieties. The local Bihar
variety with surface roots sets seed but the deep-rooted tall variety fioni the
PLATE V.
F,u. 1. INDIGO ON BHATA.
^10^^
^m-
'#r
.if^
F,«. 2 INDIGO ON BLACK SOIL.
HOWARD AND HOWARD 19
black sfiils of the Central Provinces sufiers from wilt and hardly yields any
seed. Thus the deep-rooted varieties of patwa and sann behave exactly like
the deep-rooted varieties of Java indigo and are severely attacked by wilt in
the late rains. Roselle and the shallow rooted types of paiuxi and sunn on the
other hand escape wilt.
The general experience of 1919 affords considerable support to our views
on the cause of wilt in indigo. For several years past, the rainfall has been
heavy and floods have been the rule. Indigo has not done well and wilt has
been common. The year 1919, however, was a year of short rainfall combined
with the absence of floods. In consequence, the rise of the subsoil water was
not considerable. The soil aeration was, therefore, above the average. Slight
wilt occurred on two occasions only but the plant rapidly recovered. Three
cuts of indigo were obtained at Pusa and the old plant is now exceedingly
healthy after the rains. Many of the Bihar estates, particularly those which are
most liable to waterlogging, did remarkably well in 1919, and for the first time
for many years have reaped an excellent second cut. Although the area imder
indigo in Bihar in 1919 was 14 jjer cent less than in 1918, the outturn is expected
to be greater than in 1918. Such a result would not be possible if the Bihar
soils are suffering from depletion of one of the essential constituents of the soil
solution.
Indigo wilt is not met with during the rains in India on porous soils where
the aeration is efficient. This interesting fact has been studied in two cases —
at Dehra Dun in the submontane zone and at Chandkhuri in the Chattisgarh
Division of the Central Provinces. At Dehra Dun, the monsoon rainfall is very
high, often more than 100 inches. At the Harbanswala Tea Estate, where Java
indigo was grown for some years, there is excellent surface drainage and the soil'
is remarkably porous, so permeable in fact that it is possible to walk over the
fields a few hours after five inches of rain have been received. Here Java
indigo grows with great rapidity, the plants are at least ten feet high and
no signs of wilt can be detected. At Chandkhuri near Raipur in the Central
Provinces, the results were similar. Grown on the porous laterite soils (hhalu)
under a maximum rainfall of over 60 inches, Java indigo thrives remarkably
and no trace of wilt is to be seen'. Good crops of seed are produced although
the soil is particularly poor in total and available phosphoric acid. When
grown on the stiff and poorly aerated but richer black .soils under similar rain-
fall and similar climatic conditions, Java indigo develo])s much more slowly,
(Plate V).
' Ciouston, D. and radnianallia Aiyar, A.l?., Ayr. Jour, vj India, Siiecial Indian frcicnce
tougress Number, 1918, p. 89.
20 SOME ASPECTS OF TTIE IXDICO INDUSTRY IN BIHAR
Til. The degeneration of Java indhio in Bihar.
It lias been sliown above that wilt during the monsoon phase in Bihai
is due to the destruction of the fine roots and nodules at a time when regeneration
is difficult on account of poor soil aeration. This, however, does not explain
why the crop gradually became susceptible to wilt and why the soil aeration
factor should destroy the crop in say 1911. and should have had little or no
effect twelve years earlier. As is well known, the earlier consignments of
selected seed obtained from the estates of the Dutch ])lanters in Java gave
excellent results. The plants grew well and gave at least three cuts of leaf,
followed by high yields of .seed. On several estates, the crop behaved as a
true perennial and gave cuts of leaf during the second monsoon. Slowly the
size, vigour and seed producing power of the crop fell off and wilt made its
appearance in the late rains in increasing amounts. By 1914, the area had
decreased to 1.5,000 highas. The progressive degeneration of the indigo crop
has been found to be due to a gradual change in the gametic constitution of
the crop which has been in progress since Java indigo was first introduced
into Bihar. The evidence on which this conclusion is based has been arrived
at from an investigation of the methods of pollination and fertilization of the
indigo plant, a botanical examination of Natal indigo from which the Java
plant was originally developed, a detailed stiudy of the various indigos now
grown in Java and of the constitution of the croj) as cultivated in Bihar.
Pollination and fertilization.
All the species of indigo we have examined at Pusa, including Natal
indigo and the various kinds now growing in Java, rarely set seed under net.
The floral mechanism is of the ordinary explosive type designed to ensure
crossing. Fertilization in Bihar is almost entirely brought about by insect
visitors, the chief agents being two common Indian bees {Afis florea and
Halictus gutturosus). Even in a single generation from self-fertilized seed
there is a marked falling off in the size and vigour of the offs])ring so that both
self-sterility and natural cross-fertilization have to be considered in any
iiiipi-ovenient by selection.
Natal indigo.
Java indigo was originally iiitroducrd into .lava from Natal, where it was
found growing in tlic wild state. Java indigo, as grown by the Dutch ])lanters,
is, however, quite a different plant from the wild indigo of Natal, and is said
to have aiLsen by crossing between Natal indigo and one of the .species formerly
cultivated in Java. In 1913, through the good offices of the Hon'ble Mr. F. B,
•HOWARD AND HOWARD 21
Smith, Secretary for Agriculture to the Government of the Transvaal, the
seeds of single plants of the wild indigo of Natal were separately collected in
that country for growth at Pusa. The samples were sown separately in lines
next to next and the progeny was examined. The rows were remarkably
uniform in themselves and there were no great differences to be observed
between the various lines. Natal indigo proved to be erect in habit with little
branched, green stems and a deep root system. The foliage was somew'hat
sparse. The reddi.sh stems and leaves and the much branched habit of many
of the types found in Java indigo were entirely absent. As regards su.scep-
tibility to Psylla and wilt, the Natal plant show^ed far less resistance than the
Java cultures growing side by side.
The kinds of indigo now grown in Java.
In 1916, a collection of the various kinds of indigo now growing in Java
was obtained through the kind assistance of Dr. Koch of the Buitenzorg Bota-
nical Gardens. These consisted of the following samples — Java-Natal indigo
from the Koeto Sani Estate, Java indigo from Soerabaya, Natal indigo from
Soerabaya, Bengal indigo, wild indigo, Presi indigo, Sumatrana indigo and
Indigofem suffrutkosa. These were grown at Pusa in plots side by side and
their behaviour under Bihar conditions, and after cutting back, was carefully
studied. In most cases, the root system was also examined. The range in
general habit, in the size of plant, in root development, in the proportion of
leaf to stem, in vegetative vigour, in the power of repair after cutting back
was very great. Some were perennials and others proved to be annuals. Wild
indigo and Presi indigo showed low vegetative vigour and little power of
repair after cutting back, behaving very much like Sumatrana indigo. Natal
indigo grew like the species obtained from Natal and showed itself to be a
deep-rooting perennial, unsuited, however, on account of its deep root develop-
ment, to Bihar conditions. The sample which most nearly resembled the old
Java plant which did so well in Bihar, was the Java-Natal from the Koeto Sani
Estate. The examination of the ]jlants raised from these samples showed
that there are many types of indigo now growing in Java only one of which
was in the least suited to Bihar conditions.
The composition of the Java crop in Bihar.
In 1910, the botanical composition of the Java crop, as gro\vn in Bihar, was
examined in detail and compared with Java indigo as it existed in 1905 eleven
years earlier. By a fortunate circumstance, we grew several plots of Java
indigo at Pusa, in 1905 and 1906, and thus became familiar with the plant which
I
22 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR
at first did SO well in Bihar. To enable the changes in botanical composition
which liave taken phxce in recent years, to be understood, some reference to
the methods of seed su])])ly in Bihar is necessary. Up to ver}^ recent years,
the method of raising seed in vogue was to aliow the best of the fields to flower
after the second cut of leaf was taken in August. This involved the production
of seed from plant greatly diminished in vigour, both by the growth of two
cuts of leaf and hv the unfavouralile soil conditions set up by the monsoon.
The result was insufficient seed and moreover the wrong type of seed. This
arose from two causes. In the first place, the early, rapidly growing types in
tlie mixture flowered in September and early October, when the air was too
(lamp for fertilization to take place. These naturally became suppressed.
Consequently, the bulk of seed was obtained from the later deep-rooting types.
The method of seed growing, therefore, rapidly altered the botanical compo-
sition of the crop and favoured deep-rooting unthrifty types. A shortage of
.seed resulted which necessitated a considerable amount of importation. At
first, this was obtained from Java, not however, from the Dutch planters,
who had by this time practically given up indigo, but from the natives who
naturally jiaid no attention either to the tyjie or to selection. It was no
surprise, therefore, to find in 191 G, that the Java crop in Bihar contained such an
extraordinary range of types. It consisted of every gradation between
rapidlv-growing surface-rooted annuals and slow-growing dee^j-rooted peren-
nials. The range in the type of foliage and in the proportion of leaf to stem
was considerable. Weak, procumbent types like the wild indigo of Java,
were met with as well as forms resembling Presi indigo. Besides, a host of
intermediates occurred which, when sown separately, 3'ielded a wide range of
types. Examination of the plants rai.sed from a sample of seed from Java,
imported by one of the planters in 1916, showed that the admixture of forms
was even greater than that met with in the ordinary Bihar crop. The onlv
conclusion that could be arrived at was that the natives of Java, who for manv
years had been supplying the Bihar planters with their indigo seed, had been
in the habit of growing together all kinds of indigo found in Java and that a
great deal of natural crossing had taken place in consequence. In the process,
the original tyi)e grown by the Dutch planters had become altered almost
beyond recognition. The methods of seed growing in Bihar and the entire
absence of selection did nothing to improve matters.
These facts and observations fully exj)lain the degeneration which has
taken jjlace in Java indigo. "While contimious selection was practised by the
Dutch planters a type of plant suitable for growth in heavy rice soils was
maintained and this seed naturally did well under Bihar conditions and was
HOWARD AND HOWARD 23
able to survive the rainy season. The stoppage of selection, the mixing of
kinds which is such a characteristic of native agriculture and the resulting
crossing with types which do not suit Bihar soon completely altered the bota-
nical composition of the crop and rendered it unsuitable for growth under
monsoon conditions. Indigo wilt is, therefore, another example of degeneration
through vicinism.
IV. The REMEDIES AGAINST WILT.
Now that the nature and cause of wilt have been discovered, the question
of remedies can be considered. Wilt has arisen from mirestricted natural
cross-fertilization which, in the course of time, has completely altered the
original type wliich did so well in Bihar. This crossing with annuals
combined with the complete cessation of selection has lowered the general
vigour of the crop, has rendered it much more suscejjtible to waterlogged
conditions and has altered the type of root-system. The problem is now to
recover by selection the original type which suited Bihar conditions and to
maintain it by continuous selection. The maintenance of the type will pro-
bably prove to be the most difficult portion of the work.
Java indigo only sets seed if visited by bees and the crop is a mass of freely
crossing heterozygotes. If grown from self-fertilized seed, there is a rapid
loss of vigour through self-sterility. The ordinary methods of selection,
therefore, do not apply. Crossing can only be controlled, it cannot be 2>re-
vented. To maintain the type required, constant selection will be essential
and the greatest attention will have to be paid to seed growing. The present
practice of importing into Bihar any kind of seed which happens to be offered
for sale, will have to be given up and arrangements wOl have to be made to
grow all the seed required locally and to carry out the necessary selection on
the estates themselves.
Selection.
A considerable amount of selection work has been done on the ordinary
indigo crop and on the samples obtained from Java. Several of these selection's
have already been tested on an estate scale. Three types have survived the
early trials and have been retained for further work. These are as follows : —
Type 10. A mixture of quick growing early maturing forms selected
from the seed imported from Java in 1916. The selection work in progress
on this type proiaises to isolate a type of Java indigo which might replace
Sumatrana. Sufficient seed has already been obtained for trials on an estate
scale which have been arranged for.
Type 15. This is a somewhat bushy indigo with surface roots which
shoots well after the first cut and which seeds well in Bihar. It is now being
24 SOME ASPECTS OF THE [NOIGO INDUSTRY IN BIHAR
grown succesKfully on several estates and is being further improved by selection
at Pusa.
Tjipe 20. This has been selected from the Java-Natal indigo obtained
from the Koeto Sani Estate in Java. It is a tall rapidly growing pereimial
indigo which resembles the original Java-Natal first introduced into Bihar.
A number of plants of the oiiginal sample have given two crops of seed and have
survived the intervening monsoon. Selection is in jirogress on this type by
which the vigour is being increased and by which the power of repair after
cutting back is being improved.
As the soil conditions of the various indigo estates in Bihar vary con-
siderably, it is quite possible that one type of ])Iant will not prove to be the
most efficient in all cases. The soils of most of the estates in the northern
portion of the indigo tract are heavier and moister than those of the south.
Different types may, therefore, be required for the various tracts. Should this
be found to be the case, it will add considerably to the labour of selection.
Improved drainage.
As poor soil aeration has been found to be an important factor in the well-
being of the indigo crop, it follows that any improvement in the general or
local drainage of Bihar during the i-ains would tend to reduce wilt. Regarded
in its widest asjject this is a large subject as the efficiency of the local rivers,
on which the monsoon drainage is based, depends on the rise and fall of the
Ganges, on the area under inundation in Bengal and on tlie obstructions (in the
shape of embankments) to surface drainage in Bihar. The wider aspects of the
subject, however, demand attention as there can be no question that the flood
level in Bihar is rising and that the damage done to the monsoon crops is
increasing. Improvements in local drainage are in many cases possible by
the adoption of the Pusa system, a method which has been taken u]5 already
on a number of estates.^
Al'PENDIX.
Vnnation. nj (_'0.> in the soil f/as Jttim flic different jAols in the Botanical Area,
Pusa, durituj the period JaniKirf/ to Noceniher 1919.
Apparatus and methods employed.
A hole was first made in tlie i)lot by means of a half-inch auger. A brass
tube (2 feet .'5 inches in length, inner diameter 0-()") sharpened at one end with
'^ Bulletin 53, Agr. Mcs. Insl., Pusa, 1915.
HOWARD AND HOWARD
^5
holes y in diameter on its side every half-inch apart up to a length of G" from
the sharpened end, was driven firmly into the soil at an angle of about 30°,
so that the end of the tube penetrated to a depth of about 12" from the surface.
Three inches of the tube remained outside the soil. The open end of the
tube T outside the soil was connected by means of a rubber .stopper R and a tap
Fid. 5.— Apparatus used in determiniiiK the amount of carbon dioxide in the soil
atmonphere.
U to a capillary tube V to a Reiset's apparatus A, containing a measured volume
of baryta water of known strength. The Reiset's apparatus was connected to a
15 litre aspirator bottle B filled with water. The aspirator bottle was grad-
uated by means of a paper scale to \ litres. Soil gas was aspirated through the
apparatus by allowing the water to flow by means of the exit tube C attached
26 SOMK ASPECTS OF THE INDIOO INDUSTRY IN BIIIAR
to the aspirator. Tlie flow of tlie gas was regulated by means of the screw
clip D and was kept at about 3 litres per hour. Before opening the tap T
all the connections were tested for leakage. On opening the tap T, soil gas
passes through the baryta solution which absorbs the COo, forming barium
carbonate. The three perforated silver cones, a, b and c in the tower of the
Reiset's apparatus allow complete absorption of the CO2 by the baryta solu-
tion. About 10 litres of soil gas were aspirated in each case. At the end of
each e.Kperiment, the volume of gas and the temperature (indicated in the
thermometer in the neck of the aspirator bottle) were noted, the tap T was
closed, and the apparatus disconnected and brought to the laboratory. The
baryta water from the Reiset's ajjparatus was filtered quickly, filled into a
burette, a measured portion run out and titrated against standard acid. The
strength of the baryta water used was determined once previous to the aspi-
ration of soil gas and the difference in strength after aspiration gave the
measure for calculating the amount of CO.. contained in the soil gas. By this
method, the amounts of CO2 in the soil gas from (1) grassed down, (2) gra,ssed
down but partially aerated by trenches and {?>) cultivated plots, were deter-
mined once every month and the results obtained are given in Table II and
Plate I.
Results.
The results at once show that the CO2 has been consistently high in the
gras.sed plot and low in the surface cultivated plot ; the trenched plot being
intermediate between the two as regards COo content. Diu'ing the first three
months, .January to March, whereas the grassed plot had shown practically no
improvement, the other two showed a marked falling off m the COo present
with the lowering of the water-level. During May and June, when the weather
was hottest and when the water-level was its lowest, the CO2 content in all
the three plots was also lowest. With the advent of the monsoon and a fair
amount of rainfall, all the plots showed a considerable rise in the amount of
CO2 present in the soil gas — the increase being about four times as much in
grassed and trenched plots, and one and a half times as much in the cultivated
plot. From July to September, coincident with the increase in rainfall and
the consequent rise of the water-level, there has been a regular rise in the
amount of CO2 in the soil gas from all three plots. The October and Nov-
ember figures show a marked fall in the amount of COo in all three plots.
Nooember \lth, 1919. Jatindka Xath Mukherjee,
First Assistant to the Imperial
Agricultural Chemist, Pusa.
PART II.
THE FACTORS UNDERLYING THE SEED PRODUCTION AND
GROWTH OF JAVA INDIGO IN BIHAR.
I. Seed production.
In 191.3, when we took up the investigation of Java indigo in Bihar, the
seed firoblem was acute and the industry was in danger of e.xtinction from
this cause alone. The supjilies had fallen so low that thej- were insufficient
for sowing while the price had reached a point which seriously reduced the
margin of profit.
The method of raising indigo seed in vogue in 1913, was to allow the best
of the fields to -flower after the second cut of leaf was taken in August. This
involved the production of seed from plant greatly diminished in vigour both
by the growth of two cuts of leaf and by the unfavourable soil conditions set
up by the monsoon. The result was insufficient seed and moreover the wrong
type of seed. This arose from two causes. The early, rapidly growing types
in the mixture flowered in September and early October, when the air was too
damp for fertilization to take j^lace. The bulk of the seed was obtained from
the later deejj-rooting types. This method of seed growing, therefore, adversely
altered the botanical composition of the crop. The shortage of seed which
resulted necessitated a considerable amount of importation. At first, this
was obtained from Java, where the supply for Bihar was grown by the natives,
who naturally paid no attention either to the type or to methods of selection.
In recent j^ears, supjjlies have been purchased from Assam and the United
Provinces, and indeed from any locality in India which happened to have indigo
seed for sale. The feature of these external seed supplies was the entire
absence of selection of forms suitable for Bihar conditions.
The results of our investigation on wilt show that the type of indigo
required in Bihar is a surface-rooting, rapidly growing plant which is also
resistant to waterlogging. As Java indigo is a mass of heterozygotes and as
the range of possible forms is very great, it follows that it is not sufficient
merely to isolate a suitable type by selection. The type must be maintained
28 SOME ASPECTS OK THE IXDIGO INDUSTRY IX BIUAK
by coiitmuous selection or a repetition of the wilt jiroblem is inevitable. To
achieve this object, the seed must be grown in Bihar and the anmial selection
necessary must be carried out locally. Thus the raising of seed is a matter
of the very greatest importance to the future of the indigo industry.
The factors underlying seed production.
The solution of the problem of seed production was found to lie in the
growing of a sjiecial seed crop and in obtaining the seed from the most vigorous
plants. This was accomplished by so^\iug the seed croj) in early August
by which time the rains were half over. Provided high lyiiig land iu good
condition with excellent surface drainage is selected and attention is given to
surface cultivation, the seed crop can be established even in the wettest years.
At first, growth is slow and root-development is largely confined to the upper
layers of soil. As the level of the ground water falls, the soil aeration improves
and the roots invade the deeper layers. By October the crop is established
and growth then becomes rapid. The yield of seed has been found to depend
on two factors — fertilization and the rapid growth of the j^laut.
FetlilizaiioH. The conditions necessary for fertilization were found
to be temperatiu'e and humidity. In Bihar, indigo can be made to flower
at almost any period of the year but it only sets seed if the temjjerature
and humidity are both lavomable. In September and early October, the air
is too damp for setting to take place and although flowers and pods form,
practically no seed is obtained, m December, it is too cold for tertiLization.
The best period m the year is the six weeks between October 15th and
November 30th, when the weather is warm and dry. At this time, fogs
and rain are practically imknown. Bees are very active during this period
when, other things bemg favourable, practically every indigo flower is
visited and yields good seed. For all the tlov ers to be worked over, the
plants must be jJi'opeiiy spaced and allowed to branch freely. Anything iu
the nature of overcrowding pre\euts proper branching and also keeps the air
round the plants too damp. It is best, therefore, to grow the crop in lines,
about three feet apart, and to attend to spacing in the rows from the very
beginning. The plants should be well forward by the middle of October, so
that flowering begins about this time. Any great delay means a reduced
yield of seed.
Rapid (jrowlh. it is obvious that the production of a heavy crop oi
seed necessitates a large and vigorous plant. This is only possible if the soil
conditions are maintained at the optimum. The helds selected must be high
lying, above the flood level and the surface drainage must be good. The
HOWARD AND HOWARD 20
soil must be rich in organic matter to provide the nitrogen needed for rapid
growth and also to preserve the soil texture during the late rains of August and
September. After the last showers at the beginning of October, the soil between
the rows must be deeply cultivated to supply the roots and nodules with abun-
dant air. Thus organic matter, surface drainage and aeration are the chief
soil factors which require attention. The importance of surface drainage
needs no proof — in its absence in a wet season there is no crop.
In the investigation of the effect of aeration and organic matter on seed
production, a modified method of pot culture' was adopted. The pots
consisted of pits, 3 feet square and 18 inches deep, filled with soil diluted with
various aerating materials or mi.xed with various manures. The jjits thus
act as culture pots. If prepared before the rains, the soil settles down and
by August are ready for sowing with indigo. In this way, many difficulties
are avoided such as the water-supply and the effect of temperature. Period-
ical measurements of the height are made, determinations of the soil moisture
and available nitrogen are carried out and after the seed is harvested, the
weight of dry stem, less the leaves, is recorded. The results are set o'lt in
Table I.
' Agr. Jimr. of India. Special Indian Science Congress Xnniber, 1018, ]>. 36,
30
SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR
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HOWARD AND HOWARD 31
An examination of the table discloses several interesting facts. As
regards growth and seed formation, improved aeration by itself has had a
marked effect. Seed production was increased nearly three times and growth
was almost doubled by the substitution of ten per cent of the volume of .soil
by potsherds. The replacement of half the soil by sand led to a similar re!5ult.
The greatest effects, however, were produced by leaf-mould with or without
potsherds. The replacement of forty per cent of the volume of the soil by
leaf-mould (30 per cen) and potsherds (10 per cent) increased seed production
twenty-one times and growth more than tenfold. These results have been fre-
quently confirmed both in the field and in other series of pot cultures. The effect
of temperature is shown by the falling off in the rate of growth which took place
in all the pots after the end of November, no matter what the treatment. This
always happens in the case of Java indigo at this time. After the end of
November, no matter what the size of the plant may be there is practically no
growth and no setting takes place during the cold months of December,
January and February unless the temperature is much above the normal.
An improved method of seed growing.
The discovery of the factors underlying seed production enabled us to
devise an improved method of growing indigo seed in Bihar. Instead of
raising seed after leaf from a partially exhausted plant, it was found better to
reverse the process and to raise a special seed crop which afterwards could be
kept for leaf. For this purpose, the seed is sown early in August on specially
selected high lying fields, known as dee fields. These fields must be above the
flood level and they must have excellent surface drainage. They should lie, if
possible, near the banks of rivers so that the aeration of the soil is improved as
quickly as possible when the water-level falls in September and October. To
enable rapid growth to take place and to preserve the soil texture during the
rains of August and September, the land must be well manured the previous
May or June, with decayed organic matter and afterwards worked as a clean
fallow. The crop should be sown in lines about three feet apart and particular
care must be taken during the rains to break the surface crusts formed by rain
as often as possible. This frequent harrowing is essential as the seedlings of
Java indigo are very susceptible to poor soil aeration and are easily killed by
surface crusts. After the last rains at the beginning of October, a final har-
rowing is necessary, followed by deep cultivation between the lines to provide
copious aeration for the intense nodular development then in progress.
In addition to correct soil managenit'iit. the object of which is to rai.-^e a
large strongly growing plant by flowering tinie in mid October, particular
32 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR
attention must be paid to thinning and selection. A good deal of natural
selection takes place by the extinction, through poor soil aeration, ol many of
the deep-rooted constituents which naturally result from the gametic con-
stitution of the crop. It is always found that many of the deep-rooted un-
thrifty plants either die out altogether or lag behind the surface-rooted types.
All small weak plants which survive should be destroyed from time to time,
and the crop at flowering time should consist only of the type required. The
best plants are those which branch copiously and which also flower earlv.
After flowering has set in, a final thinning is required to eliminate those indi-
viduals which, although of suitable habit, show a tendency to flower too
late.
The result is a magnificent crop of seed which in good year.s weighs out
well over half a ton to the acre. Even in the worst years at Pusa, the yield
has not fallen below a quarter of a ton to the acre. The seed produced is
heavv and well matured and far supe7ior to anything produced elsewhere.
It germinates strongly and evenly and tlie resulting crops do well. As the yield
of seed varies considerably with tlie sea.son. estates should hold about half
their annual seed requirements in reserve so as to make up for any deficit
in a year of late floods. Indigo seed retains its germinating power for
several vears if thoroughly dried befor:" .storage in the air-tight seed bins
devised bv the Botanical Section at Pusa which are now on the market in
India.
This improved method of seed growing has been successfully' adopted on
several of the indigo estates in Bihar and during the present year 1919. ex-
cellent crops are to be seen. August sowing in Bihar will by itself improve
the type of indigo as it helps to eliminate the deep-rooting unthrifty types sus-
ceptible to wilt and favours the shallow rooted quick growing wilt lesistant
forms. Hence the importance of producing all the indigo seed required in
Bihar itself and the discontinuance of the practice of importation from outside
sources where natural selection does not operate to anything like the same
extent.
II. Till-: (MuiwTii or Java indigo.
While the investigation of the wilt disease and of the factors underlying
seed luoduction were in juogress, attention has been devoted to the conditions
nece.ssarv for the growth of the ordinary indigo crop. A large amount of
work has been done on this side ot the (jiicstioii and several ini])rovements in
cultivation have resulted. The growth of the indigo crop, other things being
equal, has been found lo di pend mainly on two factors— .soil aeration and
organic matter.
HOWARD AND HOWARD
33
Soil aeration.
From the time the ordinary crop is sown in September or early October
to the following May, iiuligo shows a remarkable response to soil aeration.
After germination and while the seedlings are small, anything in the nature
of a surface crust is fatal and constant harrowing is essential. During the
cold weather and the hot months of March, Ajiril and May, indigo shows a
remarkable response to repeated harrowings with the lever harrow. These
implements were originally introduced into India by the Botanical Section
of the Pusa Institute and are now widely used on the indigo estates. They
enable the surface soil to be broken up to a depth of nearly two inches and the
mulch produced preserves the soil moisture during the hot weather. In
addition, aeration is improved and the large supply of air needed by the intense
nodular development which takes place at the break of the rains, is provided
for. During the early monsoon, soil aeration is maintained by the rain-
fall which is a saturated solution of oxygen and experiments show that culti-
vation at this period is imuecessary and does more harm than good. In the
later rains, the marked aerotropism of the roots (caused b}' the rise of the gases
of the deep soil layers which follows the upward movement of the groimd
water) combined with the destruction of the absorbing root system of the
subsoil, places cultivation out of the question. This should, therefore, stop at
the break of the rains in May.
In addition to improved aeration by means of surface cultivation, the
indigo plant shows a marked response to a more open soil texture and also to
the aeration of the subsoil. As an example of the eii'ect of altered soil lextur^-
the results obtained on growth by the addition of sand or potsherds to the soil
are of interest. (Table II.)
Table II.
TJw effect oj improved soil aeration on the yrowth of indigo.
Kind of soil
Soil only
50% Boil 50% sand
90% soil 10% potsherds
70% soil 30% potsherds
Average length
in cm.
30-7
51-0
48-3
50-9
Percentage
increase
40
31
38
The substitution of only ten per cent of the volume of soil by inert potsherds
suiSced to increase growth by over 30 per cent.
Equally striking are the results obtained by waterlogging the subsoil
before the indigo crop is sown. The efiect of waterlogging the heavier soils
at Pusa durijig September, has been found to result in extensive losses of
o
34
SOME ASPECTS OF TttE INDIGO INDUSTRY IN BIHAR
nitrogen tlirough denitrification. In September 1917, a somewhat stiff piece
of land was waterlogged for a month and sown with Java indigo the following
October. The effect of the waterlogging on this leguminous plant was very
marked. Five months after sowing, equal areas on the waterlogged and
control plots were taken and the heights of the plants were measured. On the
waterlogged plot, the average height of 200 plants was 10-5 cm. ; on the con-
trol, the average height of an equal number of plants was 28'0 cm. When the
root system of the plants on these plots was examined, it was found that the
first effect of waterlogging was to restrict the roots to the upper layers during
the first few months of growth and to change the general character of the root
system. The results are shown in Fig. 1. On the left is represented tlie root
I'IG. 1 The root system of Java indigo showing the effect of waterlogging before sowing
(left) compared with the control (right).
system of a plant from the ])Iot waterlogged a month before sowing, on the
right a specimen of the roots from the control plot is to be seen. In the water-
logged plot, the development of the taj)-root is arrested and one of the laterals
after bending takes its place. In the case illustrated, the acting tap-root was
followed to .some distance and was found to give off verv few branches.
HOWARD AND HOWARD
35
AVheii the subsoil is gradually waterlogged from below after the seed is
sown, still greater changes in the root system are obtained. Gradual water-
logging from below after sowing is obtained by growing the crop in lysimeters,
the drainage openings of which can be closed at will. In 1918, a series of such
experiments was carried out and at the end the growth and root-development
obtained under drained and waterlogged conditions was comjjared. The
results are shown in Fig. 2.
Fig. 2. The effect of waterlogging after sowing on the root-
development of Java indigo.
36 SOME ASPECTS OF TUE INDIGO INDUSTRY IN BIHAR
Manuring.
Although indigo is a leguininous plant there is a coi)ious dcvelopinent of
nodules only after the early rains, so that it responds markedly to nitrogen
applied in the form of organic matter such as leaf-mould, farmyard manure
or oilcake. That nitrogen is required by the young crop is suggested by the
waterlogging exjjeriment carried out in September 1917, which is described
above. This indication has been confirmed by the results of numerous field
experiments and of several series of pot cultures. The chief effect of the orga-
nic matter is to stimulate the seedlings and to help the crop to establish itself.
If the soil is too poor at sowing time, numerous bare patches in the field
develop and the crop looks thin and starved. Organic matter, on the other
hand, leads to dark foliage and to strong growth. The efiects persist till the
break of the rains when they pass off due, in all probability, to the result of
the intense nodular development which is such a feature of the crop at this
period. Even during the rains, the indigo crop appears to make use of com-
bined nitrogen as the cereal crops like wheat and oats wliicli follow indigo
compared with those on fallow land never show any great vegetative vigour
and exhibit all the signs of a reduced supply of available nitrogen.
The effect of available phosphate on growth has been investigated by
growing indigo in two sets of lysimeters — one filled with alluvial soil from
Kalianpur and the other with Pusa soil. Kalianpur soil is exceedingly rich
in available phosphate (0"318 per cent) while Pusa soil, when analysed by
Dyer's method, gives very low figures (O'OOl per cent) for available phosjjhate.
In spite of this the growth has always been greater in Pusa soil than in Kalian-
pur soil as the following measurements taken on September 11th, 1918,
show : —
Average height of i)lants in inches.
Pusa soil . . . . . . . . 10"7
Kalianpur .soil . . . . . . 50
A second similar set of measurements were made on September 15th,
1919, with the following results : —
Average height of plants in inches.
Pusa soil . . . . . . . . 3G'l
Kalianpur soil . . . . . . ■20"1
These figures afl'ord no support to the view that manuring with super-
phosphate will increase the growth of Java indigo.
Pusa :
2Qlh November, 1919.
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AGRICULTURE OF INDIA
TO BE HAD FROU
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Scientific Reports of the Agricultural Research Institute and College, Pusa (including the
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Proceedings of the Board of Agriculture in India, held at Pusa on the 1st December, 1919, and
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Proceedings of the Second Meeting of Mycological Workers in India, held at Pusa on the
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Proceedings of the Third Entomological Meeting, held at Puaa in February 1919. (In the
MEMOIRS OF THE DEPARTMENT OF AGRICULTURE IN INDIA
BOTANICAL SERieS
Vol. IX, No. IV. Studies in Indian Sugarcanes, No. ii. The Classification of Indian Canes
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No. 94. A Preliminary Note on the Behaviour in North India of the first batch of Sugarcane
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INDIQO PUBLICATIONS
So. 1. A Study of the Indigo Soils of Bihar, The Urgent Necessity for Immediate Phos-
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