Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. aa Te aS : “Py UNITED STATES DEPARTMENT OF AGRICULTURE %; BULLETIN No. 881 ¥# Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief Washington, D. C. vV August 10, 1920 EFFECT OF ALFALFA ON THE SUBSEQUENT YIELDS OF IRRIGATED FIELD CROPS. By C. 8S. Scorrep, Agriculturist in Charge, Office of Western Irrigation Agriculture. CONTENTS. 7 Page. Page Aim OL (he-experiments.=-.2.-5:--cces~eeecns 1 | Results of the experiments—Continued. Description of the experiments.............- 2 Oats sateceetece cae entne nee cee eee 7 Results of the experiments...........-------- 3 Supar beetst as. susseccccwes oes) citesas 9 MTISHeNOcAbOCS se esme nase cose eee sees SWE SUMIM AR Yewasccemieniac suc cece cet somoee 12 AIM OF THE EXPERIMENTS. It has long been recognized that the growing of alfalfa has a beneficial effect upon the producing capacity of irrigated lands; in other words, crops grown on land following alfalfa give larger yields than those following nonleguminous crops. In the series of experi- ments here reported it is aimed to show the extent of this beneficial effect as observed with three common field crops in several different rotations at three different locations in the northern Great Plains. These experiments were conducted by the Bureau of Plant Industry at the following places: (1) The Scottsbluff Field Station,’ located on the North Platte Reclamation Project, near Mitchell, Nebr.; (2) the Belle Fourche Field Station, located on the Belle Fourche Reclamation Project, near Newell, S. Dak.; and (8) the Huntley Field Station,? located on the Huntley Reclamation Project, near Huntley, Mont. These stations are so situated as to be representa- tive of conditions on much of the irrigated land in the northern Great Plains, and it is believed that the results secured are generally applicable to that region.® | 1 The work of this field station is conducted and supported cooperatively by the United States Depart- ment of Agriculture and the Nebraska Agricultural Experiment Station. 2 The work of this field station is conducted and supported cooperatively by the United States Depart- ment of Agriculture and the Montana Agricultural Experiment Station. 8 For a brief description of the agricultural and soil conditions of this region, see Scofield, C. S., Effect of farm manure in stimulating the yields of irrigated field crops. In Jour. Agr. Research, v. 15, No. 9, pp. 493-503. 1918. 185530°—20— Bull. 881 2 BULLETIN 881, U. S. DEPARTMENT OF AGRICULTURE. DESCRIPTION OF THE EXPERIMENTS. These experiments are a part of an extensive series of rotations conducted under irrigation at the three statious specified. The experiments were started with the crop season of 1912 and have been continued without modification. The field plats, which include one- fourth of an acre each, are laid out in series. The series are separated by 40-foot roads, and the plats in the series are separated by 5-foot alleys. The plats at Scottsbluff are 132 feet long by 82.5 feet wide; those at Belle Fourche are 264 feet long by 41.25 feet wide, and those at Huntley are 227 feet long by 48 feet wide. The present bulletin deals with the effect produced by growing alfalfa for one, two, or three years on plats which are later used for two or three years for other crops and then are reseeded to alfalfa. The alfalfa crops are cut for hay, and at the end of the alfalfa period the land is plowed soon after the last cutting, so that only the stubble is plowed under. The results are based on seven pairs of rotations, the two members of each pair differing from each other only in that one member includes either two years or three years of alfalfa, while the other does not. Each rotation occupies as many plats as there are years in the cycle, so that each crop is represented each year. The crops and sequences involved in the 14 rotations are as follows: Rotation 20: Rotation 40: Rotation 22: Rotation 42: Rotation 24: Rotation 44: Rotation 28: Rotation 48: Rotation 30: Rotation 60: Rotation 31: Rotation 61: Rotation 32: Rotation 62: Potatoes, sugar beets. Alfalfa, alfalfa, potatoes, auger beets. Oats, sugar beets. Alialia, alfalia, oats, sugar beets. Potatoes, oats. Alfalfa, alfalfa, potatoes, oats. Wheat, oats. Alfalfa, alfalfa, wheat, oats. Potatoes, oats, sugar beets. Alfalfa, alfalia, alfalfa, potatoes, oats, sugar beets. Potatoes, oats, sugar beets (manured). Alfalfa, alfalfa, alfalfa, potatoes, oats, sugar beets (manured). Corn, oats, sugar beets. Alfalfa, alfalfa, alfalfa, corn, oats, sugar beets. It will be noted from the list of rotations that the comparisons to determine the effect of the alfalfa are made between 2-year and 4-year rotations and between 3-year and 6-year rotations. In the first set of comparisons a 2-year period of alfalfa is used and in the second set a 3-year period. As these rotation experiments were started in 1912, in each case on land that had not previously grown alfalfa, there was no effect to be observed until 1913, and the crops grown that year following alfalfa were from plats that had been in alfalfa only one season. The first full effect of the alfalfa in the rotation was obtained in the 4-year rotations in 1914 and in the 6-year rotations in 1915, and then only in the case of crops which immediately succeed alfalfa in the rotation. EFFECT OF ALFALFA ON YIELDS OF FIELD CROPS. 5) In the above list of the seven rotations which include alfalfa, that crop was followed by potatoes in four cases and by oats, wheat, and corn in the other three. The second-year effect of alfalfa is shown in two cases on sugar beets and in five cases on oats. In the three 6-year rotations, sugar beets are grown the third year fol- lowing the alfalfa and presumably, therefore, derive the least benefit from that crop. The cultural operations used with these rotations have been only those demanded by good farming. With respect to any one crop, the same variety has been used in all rotations at each station each year. Thesame varieties have not been used at the different stations, nor has the same variety been used for all years at the same station. It has been the aim to use one of the best of the locally adapted varieties in each case. In the rotations where alfalfa follows sugar beets, the alfalfa has been seeded in the spring following the beet crop, and consequently it has done little more than get well established the first year. Where the alfalfa follows oats it has been customary to seed it in the fall in the oat stubble, and in general this has resulted in a good stand and nearly a full crop the following season. At the close of the alfalfa period in these rotations the alfalfa sod has been plowed immediately after the last cutting. This first plowing or ‘‘crowning,” as it is called, is done only 3 or 4 inches deep, in order to cut the roots close to the surface and kill the plants. After the inverted sod has dried out well it is disked, and the land is then plowed to a depth of 8 or 9 inches. The field work of these rotation experiments has been under the direction of the farm superintendent at each station and under the immediate supervision of a scientific assistant, who is charged with performing or directing the cultural operations, the irrigation, and _the harvesting, and with taking the field notes and reporting the results each year.' RESULTS OF THE EXPERIMENTS. IRISH POTATOES. There are four pairs of rotations at each station in which the mem- bers of the pairs differ from each other only in that one includes a period of alfalfa and the other does not. In two of these cases, 1 The following is the personnel concerned with the field work of these rotation experiments: At Scotts- bluff, Mr. Fritz Knorr was superintendent from 1910 to theend of 1916. Mr. James A. Holden wasin charge of the irrigated rotations from the spring of 1912 until the end of 1916, when he succeeded Mr. Knorr as farm superintendent. Mr. David W. Jones supervised the irrigated rotation work during 1917 and the early part of 1918, when he entered the military service; during the remainder of the season Mr. Holden directed the work. At Belle Fourche, Mr. Beyer Aune has been superintendent since 1909. He has kept ~ in close touch with the irrigated rotation work, being assisted at different times by Mr. John B. Wentz, Mr. N. L. Mattice, Mr. George T. Ratliffe, and Mr. Oscar R. Mathews. At Huntley Mr. Dan Hansen has been superintendent since 1910. The irrigated rotations were under the supervision of Mr. John M. Spain during 1912, Mr. John W. Knorr during 1914,and Mr. Edward G. Noble from 1915 untilthe summer of 1918, when Mr. Noble entered the military service. Mr. Hansen directed the work in 1913 and during the latter part of 1918. 4 BULLETIN 881, U. S. DEPARTMENT OF AGRICULTURE. rotations 40 and 44, the alfalfa period covers two years and in rota- tions 60 and 61 it covers three years. In the above-enumerated rotations the 1913 potato crops followed only one year of alfalfa. In 1914 they followed two years of alfalfa, which is the normal course for the first two rotations, 40 and 44, while for rotations 60 and 61. the normal course of three years of alfalfa was first reached for the . crop of 1915. Table I shows the yields of potatoes for the four pairs of rotations at each of the three stations. These yields, given in bushels per_acre, are for the total crop, including small and diseased potatoes. The annual difference in yield between the crops following alfalfa and the check plats are also shown in the table, together with the mean annual yield of the crop for each rotation and the mean of the annual duerentes in yield. With each of the means the probable error is given. The results given in Table I shew that in nine cases out of twelve the mean of the annual differences in yield was in favor of the crops following alfalfa. But in only six of the nine cases is this mean difference significant; that 1s, more than three times the probable error. In the other six cases the mean is less than three times thé probable error and is not regarded as significant. It has been customary in connection with these experiments to sort the potatoes in the field at the time of digging. This sorting has been done by means of a wire screen with 2-inch meshes. The smaller potatoes that pass through this screen are classed as un- marketable, while those passing over the screen are marketable. It has been observed that at Scottsbluff the percentage of marketable potatoes has been significantly larger from the plats following alfalfa than from the check plats. This has not been true, however, at Belle Fourche or at Huntley. It is clear from the facts set forth in Table I that. the beneficial - effect of alfalfa on subsequent yields of potatoes has been much more marked and consistent at Scottsbluff than at the other two stations. This may be due to the fact that the soil at Scottsbluff is a light sandy loam, while at both the other stations the soil is a heavy clay loam. The essential facts concerning these yields for each of the three sta- tions are summarized in the following paragraphs. At Scottsbluff the yield of potatoes, large and small, for the 48 plat years has averaged 236 bushels per acre, with a mean annual difference resulting from alfalfa of 100+7. The yield of marketable 1 The probable error of the mean as used in these tables is obtained by Merriman’s formula 36, whichis stated as follows: r 0 p= = In other words, the probable error of the mean is obtained by multiply- ing the sum of the departure from the mean by the quotient of n+/n—1 into 0.4853, where n equals the number of yields involved. (Merriman, Mansfield. Method of Least Squares, ed. 8, p. 228. New York, London, 1913.) BR EFFECT OF ALFALFA ON YIELDS OF FIELD CROPS. 5 potatoes from the same plats excepting 1918, when this classification was not made, has averaged 192 bushels per acre, with a mean annual difference in favor of those following alfalfa of 101+7. Again omitting the crop of 1918, the percentage of the total yield classed as marketable is 76, while the mean annual difference in percentage marketable in favor of those following alfalfa is 12+1.3. TaBLEe I.—E fect of alfalfa on the yields of Irish potatoes at the Scottsbluff, Belle Fourche, and Huntley Field Stations, for the 6-year period from 1913 to 1918, inclusive. Station and rotation No. Scottsbluff: 20 (no alfalfa) 40 (following alfalfa) Difference 24 (no alfalfa) 44 (following alfalfa) DIE REM COM sates eee SOX Gra oyallifallifay seen cere ee 60 (following alfalfa) Difference Se Olallifallfay) eer eats foley ators 61 (following alfalfa) Difference Belle Fourche: ZU (nolaltalia) a yasstee eee eee 40 (following alfalfa) Difference 7241 (GOK) GHEE IE cos me pam ei eee ee 44 (following alfalfa) Difference SOLO alias) Sees ee oe ete 60 (following alfalfa) ah Difference Sle(ovalitaliayseness 2 eS a 61 (following alfalfa) Wifterences. | see Se ee Huntley: ZOHO Ia; a eget oa se ee 40 (following alfalfa) Difference ZAG Oa Alig, eae = eee 44 (following alfalfa) Difference SOlGorabtalitay wae oe hp ete 60 (following alfalfa) Difference Suk (ra Oral fall ia) a5 49-59 yee rele sas Pane 61 (following alfalfa) Difference Yield of potatoes per acre (bushels). 1913 | 1914 | 1915 | 1916 | 1917 | 1918 398 146 88 142 131 87 403 280 206 285 273 179 ae ee Pao est Sele n4Se | eT 4 aul A igo 235 146 109 217 134 150 402 319 228 308 290 227 IGT (Geel7s | eetOul tengde |. eet 56n ln eta 77 329 216 146 226 167 | 79 322| 272 231 319 281 238 SEE ibe Wee Sonia OS one etd: ace 1 50 353 243 175 ”4| 211 81 380 299 220 306 346 249 + 27) 56 | 45 | 62 | 94135 |" +168 128 86 102 157 133 167 8S 96 94 129| 124 203 READE Pe OR re Sol 28h le oe Oe ee 6 109 112 111 151 120/191 177 127 144 149 170 153 pease +68] +15] +33| — 2| + 50] — 38 74 68 59 166 139 168 97 105 105 119 108 170 42 OE) toeey |) | ee | en ee 90 140 137 188 205 231 139 112 115 124 130 165 + 49] — 28| —22| —64| — 75). — 66 200 179 350 228 241 390 250 156 350 247 224 445 ual) 2 28 Oil: Hee Top les Seances 316 171 273 236 | 229 315 113 195 190 166 182 373 Sr O03 tee 24s |e. Se e358 | B70) | ee rele ee 8 188 156 | _228 224 175 286 285 293 397 292 238 345 HE .97 | -137. fet 169) |e tetas 59 160 140 273 212 91 324 277 184 420 402 297 474 eit ial 2 44a) cela ee TOON e206 1150 Mean. 165+ 29 271+ 20 +106+14 165415 296418 +131+13 194+ 24 277+11 + 83+15 218+ 23 300417 ; + 82417 1294 9 122+11 7Ti 7 132+ 10 1538+ 5 SES ALE bt 112417 1I7+ 7 + d5+11 165+ 16 131+ 5 — 34413 265+ 20 279430 9) + 14410 257 +17 203+ 21 — 54425 209+ 14 308+ 16 + 99414 200+ 26 6 BULLETIN 881, U. S. DEPARTMENT OF AGRICULTURE. At Belle Fourche the yield of potatoes, large and small, for the 48 plat years has averaged 135 bushels per acre, while the mean annual difference resulting from the growing of alfalfa has been a decrease of 4+6. The yield of marketable potatoes from the same plats has averaged 107 bushels per acre, with a mean annual decrease for the plats following alfalfa of 4+5.6. The percentage of the total yield lassed as marketable for the 48 plats is 81, with a mean annual difference in favor of the plats following alfalfa of 0.542.2. These results indicate that at Belle Fourche there has not been, so far, any beneficial effect from alfalfa on subsequent yields of potatoes. At Huntley the total yield of potatoes for the 48 plat years has averaged 258 bushels per acre, while the mean annual difference in favor of the plats following alfalfa is 50+12.6. The yield of market- able potatoes from the same plats has averaged 241 bushels per acre, with a mean annual difference in favor of the plats following alfalfa of 55+11.4. The percentage of the total crop classed as marketable is 93, with the difference in favor of the plats following alfalfa of 1+0.55. Thus, the results from the Huntley station indicate that the beneficial effect of alfalfa on subsequent potato crops, though fairly large, is, when judged by the size of the probable error, barely significant. In an earlier paper, the effects of farm manure on the crop yields in certain of these irrigated rotations was reported,' and it seems proper to present here a comparison between the effects of periodical applications of farm manure and the use of alfalfa in the rotation. Such a comparison of results appears to be justified, because the two tests were made in the same fields and the same set of plats were used as checks in both cases. The experiments reported for the test of farm manure covered the 6-year period from 1912 to 1917, while those of alfalf-. covered the 6-year period from 1913 to 1918. There were, however, only three rotation pairs for the potato ex- periments with manure, while there were four pairs with alfalfa. Also, in the manure experiments the manure was applied immedi- ately preceding the potato crop in two of the three cases and to the sugar-beet crop, which preceded the potatoes, in the third case. In the alfalfa experiments the potato crop followed the alfalfa in all four cases. : The comparative features of the two experiments are summarized in Table II. The results brought together in Table IT show clearly that on the lighter soil of the Scottsbluff station both manure and alfalfa have a beneficial effect on the yield of potatoes. 'The manure has resulted in an increased total yield of the treated plats over that of the check 1$cofield, C.S. Loc. cit. EFFECT OF ALFALFA ON YIELDS OF FIELD CROPS. ti plats of 40 bushels per acre, while the alfalfa has increased the yield by 100 bushels per acre over that of the check plats. At Belle Fourche and at Huntley the beneficial effects of manure have been at least significant. The alfalfa has not produced increased yields at Belle Fourche, though it has done so at Huntley. Taste II.—Comparison of the effect of farm manure and of alfalfa on subsequent yields of Irish potatoes in crop rotations under irrigation at the Scottsbluff, Belle Hounds and Huntley Field Stations. Yield of potatoes per acre. Factors compared. Scottsbluff. Belle Fourche. Huntley. Manure.| Alfalfa. | Manure.| Alfalfa. | Manure.| Alfalfa. Total cro Yield “ mean of check and treated DIAS) odonodeccoeescessousoc UNINAK = 208 236 131 135 239 258 Mean annual difference........- Conte 4047 100+7| 3446.4 —446|] 2648.3] 501412.6 Marketable potatoes: WGC Se BA Ree eee cee ere do. 150 192 105 107 221 241 Mean annual difference in yield. do.. 4647 10147 | 3646.3 | —445.6] 2448.5 | 55411.4 Ren Genta ge Cametacpre cera etre es Serie ee vers 0 92 93 Mean annual difference in percentage..-| 841.5] 1241.3 Tete OE CD 2 OM rete are 14.55 OATS. The effect of alfalfa on the subsequent yield of oats is shown in Table III for six pairs of rotations at Scottsbluff and Belle Fourche and for four pairs at Huntley. The oats crop follows directly after alfalfa in only one rotation (No. 42) at each station. In all the other rotations the oats occur as the second crop after alfalfa, being preced- ed by potatoes in three cases (Nos. 44, 60, and 61), by wheat in one case (No. 48), and by corn in one (No. 62). Because of this position in the rotation the oats did not come on plats that had been in alfalfa until 1914 except in the case of rotation No. 42. Thus, 16 compari- sons are made in Table III, of which 12 show increases in the mean yield of the crops following alfalfa and 4 show decreases. But if we accept as a test of significance of the mean that it shall be at least three times as large as its probable error, then only 5 of the 16 comparisons show definite benefits from the alfalfa, and in one case, (rotation No. 42, at Belle Fourche) there is a consistent reduction in yield following alfalfa. While these results do not show a strikingly beneficial effect from the use of alfalfa in the rotation, it is to be observed that these oat crops have been grown on soil that was virgin at the beginning of the experiment and of relatively high productivity, as shown by the mean yields of all the plats included in the experiment. It has been noted also in connection with these experiments that the plant growth has been more vigorous on the plats of oats following alfalfa, as is shown in the yields of straw. These notes, together with the facts concerning the grain yields for each of the three stations, are summarized below. BULLETIN 881, U. S. DEPARTMENT OF AGRICULTURE. TasBiLe III.—Z fect of alfalfa on the yields of oats at the Scottsbluff, Belle Fourche, and Huntley Field Stations during the 6-year period from 1913 to 1918, inclusive. Station and rotation No. Scottsbluff: 2216nOailtalia) sees cee tere eee eee 42 (following alfalfa) 1 year........... Difference see. sae ae ee 24. (ni oraltalia, ego ese Peer 44 (following alfalfa) 2 years.........- IDIDIKIRAONCOS sass sosecooesseosaoe 28) (mojaltalia) ees eee eases 48 (following alfalfa) 2 years.......... DUTCTEN COs see ocean eee SOMG Oya tallitay) ery eee ee eee 60 (following alfalfa) 2 years.......... ID TiTeEKeN COs sie ee eee eee Sie (MMoaalbtalia) Reese eee eee 61 (following alfalfa) 2 years.......... WTCTENCE eee ee Sew ee S7aMmoralialia) tere pease s seen See 62 (following alfalfa) 2 years.......... AD TMETEM COSene ce eee Aided Belle Fourche: DRG Hehe Paes. os Rees ae Seen se 42 (following alfalfa) 1 year........... ID IMLETEN CO ata ete heey ene PY GIO GLATE Seo obse ees Ses aaoeaosses 44 (following alfalfa) 2 years.......... IDPMeETEM Cesc ee ree ete 2S romiialia) pee ee ce eee wee 48 (following alfalfa) 2 years......_... IDIOMA INCAS See aS e ae ee SO; Gn oralialifa een ewe ene es 60 (following alfalfa) 2 years.......... Ditierence