■^

GIFT OF

Digitized by tine Internet Arciiive

in 2007 witii funding from

IVIicrosoft Corporation

littp://www.arcliive.org/details/citystreetsweepiOOskinricli

JUL o?™!*"
GIFT

Issued June 14, 1912.

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF SOILS— CIRCULAR No. 66.
MILTON WHITNEY, Chief of Bureau.

CITY STREET SWEEPINGS
AS A FERTILIZER.

BY

J. J. SKINNER AND J. H. BEATTTE,

Scientists in Soil Fertility Investigations.

WASHINGTON:

ttOVERNMENT PRINTING OFFICE.

1912.

BUREAU OF SOILS.

Milton Whitney, Chief of Bureau.
Albert G. Rice, Chief Chrk.

SCIENTIFIC STAFF.

Frank K. Cameron, in charge of Physical and Chemical Investigations.

C. F. Marbut, in charge of Soil Survey.

Oswald Schreiner, in charge of Fertility Investigations.

SCIENTISTS IN FERTILITY INVESTIGATIONS.

Edmund C. Shorey.
M. X. Sullivan.
B. E. Brown.
J. J. Skinner.
F. R. Reid.
2

D, J. McAdam.

E. C. Lathrop.
J. H. Beattie.
A. M. Jackson.
H. Winckelmann.

ADDITIONAL COPIES of this publication
-ii- may be procured from the Superintend-
ent OF Documents, Government I'rinting
OfiQce, Washington, D. C, at 5 cents per copy.

CITY STREET SWEEPINGS AS A FERTILIZER.

This bureau has many requests for information in regard to the
value of street dust and street sweepings as fertihzing material,
both from truckers and gardeners and from officials of large cities
interested in the best means of disposing of city waste.

The debris which is collected from the streets of cities is com-
monly used as fertihzing material, being sold to near-by gardeners,
truckers, and farmers, its rather low cost making it particularly
attractive. The main object of the city official is to dispose of the
material, and in some cases it is burned and in others it is hauled
to a dumping ground and used as filling material.

There is some variation in the character of the material collected
from the streets of different cities, depending on the nature of the
industries, the kind of paving material used, and the character of
traffic on their streets, yet on the whole the collections from sweep-
ings are very similar and consist chiefly of animal manure, leaves,
dirt, and trash, such as paper, fruit skins, particles of coal, etc.
The sweepings may contain also finer particles of the paving sub-
stance and some oily material dropped from vehicles. This is espe-
cially true at the present time, when the use of power vehicles for
pleasure and business is so ex!tensive. The effect of the sweepings
on crops, especially when used continually year after year on the
same field, is a subject of much interest and has caused considerable
speculation.

This article deals with an investigation of the street sweepings
of one of the larger cities. The material was studied from the
point of view of its organic and inorganic constitutents, and through
cultural tests, by means of wliich its effect on plant growth was
observed.

CHEMICAL EXAMINATION FOR MINERAL SALTS.

Three samples of the sweepings were examined. Sample No. 1
consisted of the debris secured by hand sweeping with a brush,
sample No. 2 was that secured by sweeping with a machine, and
sample No. 3 was the decomposed debris from a dump pile which
had been accumulating for some length of time. There was no
apparent physical difference between sample No. 1 and sample No.
2, both being composed mostly of the raw horse manure. Sample
No, 3 consisted principally of well-decomposed horse manure.

38772°— 12 3

4 CITY STREET SWEEPINGS AS A FERTILIZEE.

The chemical analysis of the three samples is given in Table I, the
results being stated in percentage of dry material. The analyses were
made by Mr. J. G. Smith, of the Laboratory of Physical and Chemical

Investigations,

Table I. — Analyses of street sweepings}

Sample
No.

Description.

Hand sweepings

Machine sweepings. . . .
Decomposed sweepings.

Nitrogen Potash
(N). (K2O).

Per cent.
1.34

Per cent.

0.71

.55

.56

Phos-
phate
(P2O,).

Per cent.
1.03
.55
.60

1 A more e.xtended table of the analyses of such street sweepings made in 1898 is found in Bulletin 55, Divi-
sion of Chemistry, U. S. Department of Agriculture. The results, stated in percentages of the original moist
material, varied in the different samples from 0.17 to 1.18 for N, 0.01 to 0.16 for PjOs, 0.08 to 0.50 for KjO and
6.2 to 52.3 for moisture.

This table shows each of the samples to contain appreciable amounts
of nitrogen, potash, and phosphate, sample No. 1 being somewhat
higher in each of these fertilizing constituents. Stable manure, as
determined from an average of a large number of samples, contains
about 1.6 per cent of nitrogen, 1.5 per cent of potash, and about 1
per cent of phosphoric acid, the figures being based on dry material.
Comparing these amounts with those contained in ordinary horse
manure,* it will be seen that the content of nitrogen, potash, and
phosphate is higher in the latter. The lower result might be ex-
pected, as the sweepings are not all horse manure, but contain con-
siderable foreign material, aside from the fact that they are frequently
subjected to leaching by rain.

EFFECT ON GROWTH.

The efficiency of street sweepings and other manures of this nature
as fertilizing material should not be judged merely by the percentage
of mineral salts which they contain. The organic material itself has
an important bearing on the question, as it may be of such a nature
or contain such constituents as to cause it to have either a beneficial
or a harmful effect on soils.

Experiments were undertaken to test the effect of sweepings on crops,
by growing plants in soil to which the sweepings had been added.
In these experiments a specially constructed paraffine wire pot,^
possessing certain advantages over the ordinary clay pot, was used.

To test the effect of sweepings on soU, wheat was grown in the
paraffine wire pots for one month. The soU used in the test was a
clay loam. The soil was divided into four portions. To three of
these was added a sample of one of the three types of sweepings, while
to the fourth good stable manure was added, in order that a compari-
son might be made. These cultures were checked against the growth

1 Storer, F. H., Agriculture in Some of Its Relations with Chemistry.
* For description of method see Circular No. 18, Bureau of Soils.

CITY STREET SWEEPINGS AS A FERTILIZER.

in untreated soil. The sweepings and manure were used at the rate
of 5 tons per acre. The tests were conducted in a greenhouse, where
the conditions of temperature and moisture could be controlled.
When the plants had grown for 30 days they were cut and the green
weight recorded. Three pots were used for each treatment, six
plants in each pot.

Table II. — Growth of ivheat in soil treated with street sweepings and stable manure.

Treatment.

Inrrease.

Soil untreated

Soil+hand .sweepings (sample No. 1) '

Soil+ machine sweepings (sample No. 2)

Soil+derom posed sweepings (sample No. 3) '^

Soil+stable manure , .'

Per cent.

The figures in this table show the sweepings to be beneficial, espe-
cially sample N0..I. In this case the growth was improved 31 per
ceiit. In sample No. 2 there was a gain of 10 per cent, and in sample
No. 3 a gain of 5 per cent in growth. The beneficial effect of stable
manure was, however, much greater than that of any of the three
sweepings ; the growth in this case was increased 46 per cent, which
seems to indicate that while the sweepings are beneficial they are
not as efficient as good stable manure.

Another test was made in which corn was grown in the soil treated
with street sweepings and stable manure, the manurial treatments
and general methods being the same as in the first experiment.
Results wliich substantiate those obtained in the latter were secured.
The green weight is given in the table below.

Table III. — Growth of corn in soil treated with street sweepings and stable manure,.

' ^ ^^ '

Treatment.

Increase.

Soil untreated

Soil+hand sweepings (sample No. 1)

Soil+machine sweepings (sample No. 2)

■ Soil+decomposed sweepings (sample No. 3)1
Soil+stable manure

There was an increased growth with samples No. 1 and No. 2, but
a decrease where sample No. 3 was used. Again the stable manure
had a more beneficial effect than the best of the sweepings. The
growth is shown in the cut in figure 1.

Another culture test was made, using a vegetable (radish) as the
plant on which to test the effect of the street d6bris. The growth of
plants in tliis experiment is shown in the cut in figure 2. Pot 1
is the untreated soil, pot 2 is treated with the macliine sweepings
(sample No. 2), pot 3 is treated with the hand sweepings (sample No.
1), pot 4 is treated with the decomposed sweepings (sample No. 3),

6

CITY STREET SWEEPINGS AS A FERTILIZER.

and pot 5 with stable manure. The illustration shows again that the
sweepings are beneficial, the plants in pots 2, 3, and 4 being larger
than in the untreated pot 1. Pot 4, which contains the soil treated
with decomposed sweepings, has smaller plants than any other except
the check. It will be recalled that this treatment showed the least
effect also in the case of wheat and corn. Pot 5, which is treated with
stable manure, has produced the largest growth, which again shows
that the sweepings are not as helpful as good stable manure.

EXAMINATION FOR MINERAL OIL,

The sweepings, as was pointed out, are apt to contain lubricating
oils and fine particles from the decay of the paving materials, which
may be a factor in determining their usefulness as a fertilizer material.
In order to study this point the three samples were repeatedly

Fig. 1.— Effect of street sweepings and stable manure on corn. (1) Soil untreated; (2) soil + stable ma-
nure; (3) soil + sweepings No. 1; (4) soil + sweepings No. 3-. (5) soil + sweepings No. 2.

extracted in an extraction apparatus with petroleum ether until the
solvent was no longer colored. The fatty material was saponified with
alcoholic potash and the amount of mineral oil extracted by petro-
leum ether determined. Sample No. 1 contained 1.7 per cent,
sample No. 2 contained 2 per cent, and sample No. 3 contained 2 per
cent of the crude mineral oil. This high content of mineral oil sug-
gests the possibility of the recovery of low-grade lubricating oil from
city street sweepings, especially in those cities which have consider-
able automobile traffic.

EFFECT OF TH?! OIL ON GROWTH.

The effect of the oil extracted from the sweepings on growth was
tested with wheat plants. The young wheat seedlings were grown in
distfiled water and nutrient solution cultures. Fifty milligrams of oil
from each sample was put in the culture bottles containing 250 c. c. of
solution. The oils from all of the samples were harmful to growth.

CITY STREET SWEEPINGS AS A FERTILIZER.

the roots as well as the tops being affected. Oils from samples No. 1
and No. 2 reduced the growth of wheat 10 per cent in the case of the
distilled water cultures, and the oil from sample No. 3 reduced the
growth 20 per cent. In a solution containing the nutrient salts the
oils used in the same amount from sample No. 1 reduced growth 6
per cent; from sample No. 2, 7 per cent; and from sample No. 3, 11
per cent.

TEST OF SWEEPINGS AFTER OIL WAS EXTRACTED.

The sweepings from which the oil had been extracted were next
tested as to their effect on growth. The petroleum ether was evap-
orated completely from the manure by allowing it to stand in the
open for a week or more. The same kind of soil was used as in the

Fig. 2.— EflFect of street sweepings and stable manureon radishes. (1) Soil untreated; (2) soil + sweep-
ings No. 1; (3) soil + sweepings No. 2; (4) soil + sweepings No. 3; (5) soil + stable manure.

previous experiments and the extracted sweepings were added to
portions of the soil at the rate of 5 tons per acre. Treatments with
stable manure, extracted with petroleum ether and also in its natural
condition, were included in the test as a means of comparison with
the samples of sweepings. The plants were grown in the paraffin
pots for 30 days, then the green weights were taken. Three pots were
used for each treatment. The growth is given in Table TV.

Table IV. — Effect of street sweepings after being extracted with petroleum ether.

Treatment.

Green weight of—

Wheat. Radish.

Soil untreated

Soil -t- hand sweepings, extracted (sample No. 1)

Soil+ma?hine sweepings, extracted (sample No. 2)

Soil + decomposed sweepings, extracted (sample No. 3)

Soil+stable manure, extracted

Soil-t- stable manure, natural

Orams.
1.910
2.270
2.270
2.190
2.260
2.270

Chrams.
3.700
5.400
5.700
5.200
5.800
5.700

8 CITY STREET SWEEPINGS AS A FERTILIZEE.

An examination of the figures in the table shows that the sweepings
and stable manure had about the same efficiency in causing increased
growth. This is true with both the grain and the vegetable crop.

The oil was also extracted, from the sweepings by using ether as the
solvent, and the swee])ings afterwards tested in soils. Tliis test also
showed that the sweepings were practically as good as the stable
manure.

It will be recalled that the effect of the unextracted sweepings was
not nearly so good as the effect produced by the stable manure. In
other words, after the oil was removed from the street sweepings their
action was practically the same as that of the stable manure. That
the oil is the deleterious constituent of the sweepings is also borne out
by the fact that the oil itself when added to culture solutions in which
plants were growing markedly reduced their growth.

The application of street sweepings to soils will undoubtedly have
a beneficial effect and be a factor in building up the land. The pos-
sible danger of a harmful effect from the oily substance which it
contains must, however, be considered. If the oil could be econom-
ically extracted this danger would be averted. The oil in the debris
for the first year or two may not have any effect, but a continuous
application to a field year after year may eventually impair its pro-
ductiveness, unless through drainage or other natural agencies the
oily material is drained off or changed. In some localities this is
probably the case, as the use of such material is still said to be
effective, although it has been applied for a number of years. No
very definite field information on this point is, however, at hand. In
this connection attention must be called to the fact that the pres-
ence of an unusual amount of oil in such street sweepings has been
the result of automobile traffic, and hence appears only in recent
years as an appreciable factor in the use of street sweepings as fer-
tilizer, and it is not improbable that tjie amount of oil will even
further increase in the next few years.

Aside from the physiological action of the oily material here men-
tioned, there are probably other more strictly physical effects, due to
the coating of soil particles and consequent interference with normal
moisture movement and solubility of the mineral soil constituents.

Vegetable or animal oils undergo changes in soils under the influence
of soil organisms, but so little is known concerning the action of
organisms on the strictly hydrocarbon oils that no statement con-
cerning the possible disappearance or change of tliis oil in street
sweepings can be made.

Approved :

James Wilson,

Secretanj of Agriculture.
Washington, D. C, March 2^,1912.

O

" TBRARY

RETURN TO the circulation desk of any

University of California Library

or to the

NORTHERN REGIONAL LIBRARY FACILITY
Bldg. 400, Richmond Field Station
University of California
Richmond, CA 94804-4698

ALL BOOKS MAY BE RECALLED AFTER 7 DAYS
2-month loans may be renewed by calling

(510)642-6753
1-year loans may be recharged by bringing books

to NRLF
Renewals and recharges may be made 4 days

prior to due date

DUE AS STAMPED BELOW

^I^Rp^l

i99S-

20,000 (4/94)

YC f>789

'*'-' ♦»t;>_j

f