'LI B RAR.Y OF THL UNIVERSITY OF ILLINOIS Ufcb no AGRICULTURE CIRCULATING CHECK FOR UNBOUND CIRCULATING COPY EXPERIMENTAL OF LADING CLOVER-GRASS PASTURE at the Dixon Springs Experiment Station Bulletin 640 University of Illinois Agricultural Experiment Station CONTENTS Experimental Fields 4 Management 4 Forage Sampling 6 Water Supply and Irrigation Equipment 7 Soil-Moisture Measurements 8 Rainfall 8 Soil Moisture, Frequency, and Amount of Irrigation 9 Experimental Results 12 Summary 26 Appendix A 28 Appendix B 30 AUTHORS G. E. McKIBBEN, Associate Professor of Agricultural Re- search and Extension, Dixon Springs Experiment Station; L. E. CARD, Assistant Professor of Agricultural Research, Dixon Springs; R. J. WEBB, Professor of Agricultural Re- search and Extension and Superintendent of Dixon Springs Experiment Station; H. A. GATE, Assistant Professor of Agricultural Extension, Dixon Springs; B. A. JONES, JR., Associate Professor of Agricultural Engineering, Agricul- tural Experiment Station at Urbana. Urbana, Illinois March, 1959 Publications in the Bulletin series report the results of investigations made or sponsored by the Experiment Station EXPERIMENTAL IRRIGATION OF LADINO CLOVER-GRASS PASTURE PASTURE IS AN IMPORTANT CROP IN SOUTHERN ILLINOIS, but tion is often limited by lack of moisture. Even in years that are not considered drouth years, available moisture is low in July and August; as a result, animal carrying capacity is an uncertain factor in this area. An irrigation project was undertaken at the Dixon Springs Experi- ment Station in southern Illinois to study the effect of supplemental irrigation of Ladino clover pasture on plant growth, animal carrying capacity and animal gain. The objectives of this project were (1) to determine the most effective amount of irrigation water and the fre- quency with which it should be applied; (2) to find the fertilizer treat- ment with irrigation that produces the largest yield per dollar invested; and (3) to study the effect of irrigation on available soil moisture, plant growth and animal gains, and species of pasture plants. Moisture studies were conducted from 1942 to 1945 on nonirrigated pastures at the Dixon Springs Experiment Station. 6 * These studies showed that for periods of between 20 and 80 days from June through August the moisture, as measured by Bouyoucos blocks, was deficient for optimum growth or at a critical level for plant survival, with only about 20 percent of available moisture remaining in the soil. Pasture production was retarded during these periods. Moisture was at a critical level in 1944; as a result, many pasture plants died and the weed population was high the following year. These preliminary studies (1942-1945) showed that under southern Illinois weather conditions a minimum of 2 inches of water is required every two weeks from the middle of June to the middle of September for the soils to maintain satisfactory production of shallow-rooted crops such as Ladino clover. Weather records were surveyed from April through September for the years 1938 to 1948. This survey showed that there were 30 periods in which less than 2 inches of rain fell during the preceding 14 days. The intervals between these 14-day periods varied in length from 5 to 158 days; and since many of these intervals occurred in June or July, pasture production was retarded early in the season and re- mained low for the entire season. This bulletin reports the results of 7 years of research (1948-1954) on irrigation of Ladino clover-grass pasture in southern Illinois. * This number and similar numbers refer to "References" listed on page 27. 4 BULLETIN NO. 640 [March, EXPERIMENTAL FIELDS The field layout for the project is shown in Fig. 1. The soil types are Grantsburg silt loam, Robbs silt loam, and Henry silt loam. These soils have brown to dark grayish-brown surface horizons, yellowish-brown to gray subsurface horizons, and mottled yellowish- brown to light brownish-gray subsoils. Grantsburg has a siltpan in the lower subsoil, and Henry has a claypan subsoil; Robbs is intermediate in properties. The silty clay loam subsoils are compacted and very slowly permeable. The tight subsoil strata occur at a depth of 18 to 36 inches and limit percolation to less than i/ inch per hour. This layer also limits root penetration. The natural drainage of Grantsburg silt loam is moderately good; of Robbs silt loam, somewhat poor; and of Henry silt loam, poor. However, the surface drainage was adequate. These soils are naturally low in fertility and organic matter, and are similar in soil-treatment history. The two fields were plowed in the fall of 1947 and given equal applications of 3 tons of limestone and 1,000 pounds of 32-percent rock phosphate. Soil tests showed that an adequate amount of potassium was available on both fields. A grass mixture consisting of 3 pounds of orchard grass, 3 pounds of alta fescue, 2 pounds of Kentucky blue- grass, 2 pounds of redtop, and 2 pounds of timothy per acre was seeded in the fall. In the spring of 1948, 2 pounds of Ladino clover were broadcast over the fields, and satisfactory stands were obtained. MANAGEMENT The fields were grazed by sheep in 1948, by sheep and beef cattle in 1949, and by beef cattle in 1950, 1951, 1952, 1953, and 1954. Each 5-acre field was pastured as a single unit from 1948 through 1952. During the 1953 and 1954 seasons, each field was divided into 7 graz- ing strips to improve pasture management by allowing a longer time for crop growth between irrigation and pasturing. The establishment of these grazing strips resulted in greater uniformity of grazing, less trampling, and more complete utilization of a more mature forage. Livestock were weighed onto the pastures at the beginning of the season, at 3- or 4-week intervals during the season, and when they were removed at the end of the season. J959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 301 C2 SOIL MAP OF EXPERIMENTAL FIELDS (Fig. 1) EXPLANATION OF SYMBOLS 5- ACRE NONIRRIGATED FIELD The first number indicates the soil type: 301 Grantsburg silt loam 335 Robbs silt loam 336 Henry silt loam The letter indicates the dominant slope of the area: A to 1.5 percent slope B 1.5 to 4 percent slope C 4 to 7 percent slope D 7 to 1 2 percent slope Tha last number indicates depth to subsoil or degree of erosion: Depth to subsoil More than 14 inches. No apparent erosion or recent deposition. 1 Usually between 7 and 14 inches. Slight erosion. 2 Usually between 3 and 7 inches. Plow layer is a mixture of surface and subsoil. Moderate erosion. 3 Usually between and 3 inches, with the plow layer composed pri- marily of subsoil. Severe erosion. 6 BULLETIN NO. 640 [March, FORAGE SAMPLING Each field was divided into 7 plots to study various fertilizer treat- ments. These plots were sampled for forage yields, forage consump- tion, and forage species. Forage yields and consumption are reported on an oven-dry basis. Forage species are reported as percentages on both a green and dry basis. Stand counts were also obtained for all treatments. The two systems of grazing employed, continuous and rotation, re- quired somewhat different methods for sampling forage. Under continuous grazing (1948 to 1952), forage was sampled as follows: 1. Measurements of dry-matter production and consumption were obtained by a B-C cage system. Three cages were used for each fertility plot. A 4-foot square sample was cut when the animals were put on the pasture, and a protecting cage was placed over this area. This sample was called a "B sample." At the end of 28 days, or at the animal-weigh period, the new growth under the cage was cut and added to the B sample to obtain both yield and forage available for consumption for the period. At the same time that the sample was cut under the cage, a 4- foot square area was cut outside the cage - a "C sample." The C sample was a measure of the forage that remained following grazing, and was subtracted from the forage available for consumption to give a value of forage consumed for the period. A cage was immediately placed over the C-sample area to protect it from grazing so that new growth was a measure of forage production for the next grazing period. The first C sample, plus the growth under the second cage, gave the amount of forage available for the second grazing period. Samples were taken at random, oven-dried, and converted into pounds of dry matter per acre. 2. Forage species were estimated as a percentage of each sample. All C samples were hand-separated by species. 3. Each fall, stand counts were obtained by point quadrat. Under rotation grazing in 1953 and 1954, the system of forage sampling was as follows: 1. Forage yields were obtained by random sampling of a 4- foot- square area on each of the 7 fertility plots just prior to turning the cattle onto each grazing strip. This sample was called a "B sample." Protective cages were not used. Following the grazing of each strip, 7959J IRRIGATION OF LADING CLOVER-GRASS PASTURE a 4- foot-square sample was cut at random on each fertility plot to measure the remaining forage. This was called a "C sample." The difference between yield, sample B, and forage remaining, sample C, gave consumption. This system of sampling did not show forage growth during the very short time the animals were grazing a strip, but little growth occurred during this 3- to 4-day period, and it was difficult to get a second measurable growth sample. 2. Visual estimates of species as a percentage of the whole were taken with each sampling. All B samples were hand-separated. 3. Stand counts were obtained each fall by point quadrat. WATER SUPPLY AND IRRIGATION EQUIPMENT Irrigation water was pumped from a 1^-acre pond with a capacity of approximately 9 acre-feet when filled to spillway level. This capac- ity was sufficient for six 2-inch applications to the 5-acre irrigated field. The entire water supply was used during the 1953 season, and pond capacity was increased approximately one-third before the 1954 season. The water was applied by a sprinkler system designed for a square 5-acre field. Two sets of equipment were used during the experiment. The equipment consisted of portable aluminum quick-coupling pipe, a gasoline engine-centrifugal pump unit, and rotating sprinklers. The first system, used for 3 years, had a capacity of 60 g.p.m. at 40 p.s.i. pressure. This system had a 3-inch main line extending through the middle of the field and a 2-inch lateral extending across one-half of the field. The lateral had 6 rotating sprinklers. Each sprinkler had 3/16- by 3/32-inch nozzles and was rated at 8.1 g.p.m. at 40 p.s.i. pressure. The sprinklers were spaced at 40-foot intervals on the lateral, and the lateral was moved 60 feet along the main line. Six hours were required per setting to apply 2 inches of water. Therefore, 16 moves and a total of 96 hours were required to cover the 5-acre field. The second system, used for 4 years (1951-1954), had a capacity of 120 g.p.m. The pipe in the lateral line was changed from 2-inch to 3-inch diameter, and additional pipe was purchased so that the lateral extended across the entire field. Twelve sprinklers were used with this lateral, making it possible to apply 2 inches of water to the entire field in 48 hours with 8 moves of the lateral line. 8 BULLETIN NO. 640 [March, SOIL-MOISTURE MEASUREMENTS Soil moisture was measured to determine the effect of irrigation in maintaining usable soil moisture and as an indication of when irriga- tion was needed. The plaster of paris moisture-block electrical- resistance method developed by Bouyoucos w>as used to measure the percent of usable soil moisture. In 1948, 189 Bouyoucos blocks were calibrated and installed at 20 locations on the irrigated field and at 7 locations on the nonirrigated field at H/2-, 41/2-, 7i/ 2 -, 10i/ 2 -, 15-, 21-, and 36-inch depths. Analysis of measurements made during 1948 and 1949 indicated that fewer block locations and depths would give equally accurate indications of soil moisture on the irrigated field. Therefore, before the 1950 season, new blocks were calibrated and installed at 1 1 locations on the irrigated field at depths of 4, 8, and 12 inches. (These blocks were also replaced before the 1953 season.) These locations and depths were used for the remainder of the project. On the nonirrigated field, the original blocks were replaced in 1950 and 1953 in the original locations, but the depths were changed to 4, 8, 12, 18, 24, and 36 inches. The blocks were located at greater depths on the nonirrigated field because the available soil moisture was depleted to a lower level in this profile. The 1942-1945 studies showed that irrigation should begin before the usable soil moisture is 65-percent exhausted. 6 If irrigation is started at this moisture level, the entire field can be irrigated before any part of it reaches the critical 80-percent exhausted level the level at which temporary wilting, particularly of the clovers, occurs. RAINFALL Analyses were made of the rainfall data taken at Dixon Springs and at 5 weather bureau stations within 35 miles of the experiment station. The 55-year average (1900-1954) at the 5 stations for May through October was 21.26 inches, and for the 7 years covered by the experiment, 21.25 inches. At the Dixon Springs Station, the 7-year average for this 6-month period was 20.54 inches. The averages by years were as follows: 1948, 21.16 inches; 1949, 25.32 inches; 1950, 27.28 inches; 1951, 26.39 inches; 1952, 13.75 inches; 1953, 12.13 inches; and 1954, 17.72 inches. Thus, in the 7-year experimental period, the rainfall for May through October was typical for the area, and covered a wide range J959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 9 from 6.02 inches above to 9.13 inches below the 55-year average at the 5 weather stations. An analysis was made to determine the number of years that irrigation would have been required to provide moisture equal to the average rainfall plus irrigation and maintain crop growth at the same level as that on the irrigated field. The 7-year average rainfall was 20.54 inches, and the average water application was 13.71 inches a total of 34.25 inches of water per season. The average amount of water for each 2-week period was 2.63 inches (0.63 inch greater than the 2-inch minimum suggested by the 1942-1945 studies), or 5.71 inches per month for the six months' season. The total rainfall plus irrigation for June, July, and August averaged 3.23 inches for a 2-week period or 7.08 inches per month. In order to supply this amount of water in any year from 1900 to 1947, the following amounts of irriga- tion w 7 ould have been required: Irrigation required Years Percent of years 22 inches 2 4.2 20 inches 3 6.2 18 inches 6 12.5 16 inches 6 12.5 14 inches 9 18.8 12 inches 6 12.5 10 inches 7 14.6 8 inches 3 6.2 6 inches 3 6.2 4 inches 2 4.2 2 inches 1 2.1 Twelve inches or more of irrigation would have been required for 32 of the years (two-thirds of the total number of years) to maintain the level of production achieved during the experiment. SOIL MOISTURE, FREQUENCY, AND AMOUNT OF IRRIGATION To determine the effectiveness of different amounts of irrigation, the irrigated field was divided for the 1948 season. One-half of the field received 1-inch applications of water, and the other half received 2-inch applications. The soil moisture curves for 1948 (Fig. 2) show the effect of irrigation on available soil moisture at the average of l l /2~, 41/2-, 71/2-, and 10i/2-inch depths for each of the applications. The 2-inch applications not only increased the available moisture supply more effectively, particularly at the lower depths, but also cost less per 10 BULLETIN NO. 640 8*0 -r IRRIGATION 1" IRRIGATION _ MONIRRIGATED Note: Perwnt utobie moisture a overage of readings at four soil depth! 1 V, 4V, 7V and 10V. \ INCHES OF WATER _ 10 01 * PI 300 o o o | NATURAL RAINFALL \ IRRIGATION 1 1 . I ill I 1 I.I. u 1 1 I I 1. MAY-R36'' JUNE-2.88' ' JULY-3.73' AUGUST-1.52' SEPTEMBER-450' OCTOBER-aiS' NOVEMBER-aOe" MONTHLY RAINFALL- 1948 GRAZING SEASON Effects of rainfall and irrigation on the usable soil moisture during the 1948 grazing season. (Fig- 2) acre-inch of water applied. For these reasons, only 2-inch applications were used after the 1948 season. The available moisture on the irrigated field was also compared with that on the nonirrigated field (Fig. 2). The chart at the bottom of Fig. 2 shows the rainfall and irrigation schedule during the 1948 grazing season. The soil-moisture curves, Figs. 3 and 4, show the need for and the effects of irrigation in maintaining soil moisture in years of above- and below-average rainfall (1950 and 1952 grazing seasons, respectively). (For soil moisture curves of the 1949, 1951, 1953, and 1954 grazing season, see Appendix A.) The curves are the average of readings at 4-, 8-, and 12-inch depths. The highest rainfall over the 7-year period occurred in 1950. But even though the rainfall during the growing season was high, the rain- fall for June and July was less than the 3.23 inches per 14 days re- quired for abundant forage production, and the soil moisture fell below the 35-percent usable level on the irrigated field (see Fig. 3). On the PERCENT OF USABLE MOISTURE REMAINING IN S( ivjoi-frcnai^jcoc oooooooooc f IRRIGATION NON IRRIGATED Note Percent usable moisture is average of readings at three soil depths 4" 8" and 12* /^ / "X / "\ L , - . ^ A A // .: --X -* ^ ^> / 7 \/ / 1 / *"""\ 7 5O | NATURAL RAINFALL I IRRIGATION s 3.0 B M i 1 1 o . 1 ll t , i li ;., .I J Ik | , MAY-519" JUNE-3.17" JULY- 376 AUGUST-897" SEPTEMBER -3 69" OCTOBER-2 50" NOVEMBER MONTHLY RAINFALL -I95O GRAZING SEASON Effects of rainfall and irrigation on the usable soil moisture during the 1950 grazing season. (Fig. 3) Effects of rainfall and irrigation on the usable soil moisture during the 1952 grazing season. (Fig. 4) 990 2" IRRIGATON NONIRRK5ATED I 70 |H [N Note: Percent usable moisture is overage of readings at three soi depths 4; 8" and 2" A ^ A r J_ \ /^ i / \ _ ^ X, ^ \ / t J V ^ '"'- -.... s T~ f --.,._ / *^ -' | NATURAL RAINFALL IRRIGATION i J j ,| , 1 i j ,, ,1 J | i 1 JULY- 160" AUGUST-106" SEPTEMBER-247" OCTOBER -106" MONTHLY RAINFALL- 1952 GRAZING SEASON 12 BULLETIN NO. 640 [March, nonirrigated field, soil moisture did not go above the 35-percent usable level until the third week of July, and forage production was low dur- ing this period. The initial sudden drop in available soil moisture on the irrigated field is attributed to the water demand of the heavier stand of forage. The least rainfall of the years in which usable moisture was meas- ured on both fields occurred during the 1952 season (Fig. 4). (Meas- urements were not made on the nonirrigated field during 1953.) During the 1952 season, 21 inches of irrigation water the entire available supply was applied; 14 inches of this amount was applied in June, July, and August. The usable moisture on the nonirrigated field was below 10 percent most of the season. Forage production was low, and many plants died. EXPERIMENTAL RESULTS Fertilizer Treatment and Forage Produced Each of the 5-acre fields was divided into 7 plots for fertilizer- treatment studies. The average and total amounts of each fertilizer applied to the plots during the 7 years are shown in Table 1. The 7-year average yield of dry matter in pounds per acre from the soil-treatment plots and the increase from irrigation are shown in Fig. 5. (Yields from individual plots by years are shown in Ap- pendix B.) The results indicate the following: the limestone, rock and superphosphate, potash, and nitrogen treatment was the most produc- tive, superphosphate increased production when added to rock phos- phate, and nitrogen had little effect on the yield from the irrigated area. In 1953 and 1954, 10-10-10 fertilizer was added to check strips on all treatment plots. The check strips on the irrigated field showed enough increases in production to justify the use of additional ferti- lizer. The 10-10-10 fertilizer did not give profitable increases on the nonirrigated field. The dry matter produced from the two 5-acre fields for the 7-year period averaged 2,495 pounds per acre per year more on the irrigated field than on the nonirrigated field. The highest average production on both fields was on plot 2. Although this plot had a complete ferti- lizer treatment, production was increased only 21 percent the lowest average annual increase for irrigation. The largest 7-year average increase for irrigation was from plot 6. This plot was treated with lime, rock phosphate, and potash. Plots 5 and 7 showed similar increases for irrigation. A comparison of nonirrigated plot 2 with irrigated plots 4, 5, 6, and 7 points up the 1959] IRRIGATION OF LADINO CLOVER-GRASS PASTURE 13 10,000 - 8.00O - 6,000 - o 4,OOO - 2,000 PLOT I L-rP-sP-K PLOT Z L-rP-sP-K-W Seven-year average yield of dry matter and increase for irrigation. (Fig. 5) importance of an adequate fertility program. The average production from plot 2 was greater than that from the irrigated plots. The most complete fertilizer treatment, plot 2 of the nonirrigated field, produced 75 percent more dry matter than plots 4, 5, 6, or 7 in the same field. A comparison of the same group of plots in the irrigated field showed only a 28-percent increase in dry matter. To determine the best fertility practices under irrigation, it is necessary to compare the cost of the various fertility elements and water applications with the return in forage. If the average yields (1948-1954) for the soil treatments on the irrigated and nonirrigated fields are considered replications, there is no significant difference (P less than 0.05) between treatments 1, 2, and 3, or between treatments 4, 5, 6, and 7. However, the difference between these two groups of treatments on the same field is highly significant (P less than 0.01). Fertilizer Costs for Forage Produced The most satisfactory fertilizer treatment, economically speaking, is the one that produces the largest yield per dollar invested. The costs of the combined fertilizers used on the irrigated and nonirrigated fields, including and excluding the cost of the limestone and rock- phosphate applied to all fields, are shown in Table 2. 14 BULLETIN NO. 640 [March, Table 1. Average and Total Amounts of Fertilizer Applied to Irrigated and Nonirrigated Fields, 1948-1954 (In 1947 each plot received a basic treatment of 1,000 pounds of 32-percent rock phosphate and 3 tons of lime per acre) 1954 or K 10-10-10 Total Average 1948- 1948- 10-10-10 1954 1954 (pounds per acre) Fertilizer applied Plot 1 N (33%). sP (20%) K (60%) . Plot 2 N (33%). sP (20%) K (60%). PlotS N (33%). sP (20%) K (60%) . Plot 4 N (33%). sP (20%) K (60%) . Plots N (33%). sP (20%) K (60%) . Plot 6 N (33%). sP (20%) K (60%) . Plot 7 N (33%). sP (20%) K(60%). Plot 1 N.. . 500 ... . 417 . . 364 . . . . 500 .... 417 . . 364 .... 417 . . . . . . . . 224 224 (") 417 417 74 74 320 250 320 250 600 426 374 600 426 374 426 120 256 123 120 256 123 256 97 684 192 283 160 103 53 269 303 212 97 684 192 283 160 103 53 269 303 212 97 160 103 53 000 97 160 356 178 53 000 97 160 53 000 97 160 356 178 53 000 97 160 53 Actual fertilizer units 32 137 38 57 32 62 32 89 100 70 32 137 38 57 32 62 32 89 100 70 32 000 32 62 32 000 32 000 32 214 107 32 000 32 000 32 32 000 32 32 214 107 32 32 32 32 391 411 216 391 411 216 411 411 411 78 246 71 78 246 71 246 246 246 84 138 46 84 138 46 84 138 46 84 138 46 84 138 46 84 138 46 84 138 46 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 28 181 2,948 1,456 2,143 2,948 1,456 2,143 298 1,456 181 298 1,461 181 298 99 181 298 1,461 181 298 99 60 590 874 707 590 874 707 60 874 60 380 877 60 380 60 60 60 877 60 60 60 26 421 208 306 421 208 306 43 208 26 43 209 26 43 14 26 43 209 26 43 14 8.6 84 125 101 84 125 101 8.6 125 8.6 54 125 8.6 54 8.6 8.6 8.6 125 8.6 8.6 8.6 PlzOo... 100 KzO . . . . 250 Plot 2 N 120 PjOo .. 100 K 2 O . . . . 250 Plot 3 N. 120 PzOo... . . . . K 2 O 250 Plot 4 N . . . PzOs KzO Plots N PlOo... KzO . . . . Plot 6 N. PjOo... . . . . K2O Plot 7 N.. . . . . . P2O 5 ... K2O m Additional 1,000 pounds of 32-percent rock phosphate applied. 7959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 15 The basic treatment of limestone and rock phosphate gave the lowest fertilizer cost per ton of forage produced. However, the addi- tion of superphosphate and potash to the basic treatment gave the most economical increase on both the irrigated and nonirrigated fields. Considering the increased yield and quality of forage obtained, the limestone, rock and superphosphate, potash, and nitrogen treatment gave an economical production increase (8,013 pounds of dry matter per acre as compared with 6,899 pounds) on the nonirrigated field. Plots 5, 6, and 7 (Table 2) show the necessity of adequate fertility regardless of whether water is applied. Plot 3 of the irrigated field shows the low response to commercial nitrogen with legumes in the field. Effect of Soil Treatment on Soil Reactions Samples were taken at intervals to study the effect of the soil treatments on soil reaction as shown by pH, the available phosphate content, and the exchangeable potash in the soil. Although similar amounts of lime were applied to both the irrigated and the nonirrigated fields, pH levels were lower on the nonirrigated field throughout the experiment (Table 3). However, it is improbable that the low pH level was a limiting factor in the production of Ladino Table 2. Average Fertilizer Costs for the Irrigated and Nonirrigated Fields, 1948-1954 (Fertilizer costs only; fixed costs not included) Plot 1 Plot 2 Plot 3 Plot 4 Plot 5 Plot 6 Plot 7 Soil treatment* L-rP- L-rP-sP- L-rP- L-rP- L-rP-(rP) L-rP-K L-rP sP-K K-N K-N (rP)-K Fertilizer cost per acre b Including L-rP pretreatment J19.ll 332.98 325.40 312.99 37.64 311.56 36.21 Excluding L-rP pretreatment 315.97 329 . 84 322.26 3 9.85 34.50 3 8.42 33.07 Increase over Plot 1 312.90 326.77 319.19 3 6.78 31.43 3 5.35 30.00 Pounds of dry matter per acre Actual yield Irrigated field 9,704 9,707 8,546 7,037 7,442 7,917 7,946 Nonirrigated field 6,899 8,013 6,866 4,654 4,412 4,609 4,638 Increase over Plot 7 Irrigated field 1,758 1,761 600 -909 -504 -29 Nonirrigated field 2,261 3,375 2,228 16 -226 -29 Cost of fertilizer per ton of dry matter Irrigated field 3 3.94 3 6.80 3 5.94 3 3.69 32.05 3 2.92 31.56 Nonirrigated field 3 5.54 3 8.23 3 7.40 3 5.58 33.46 3 5.02 32.68 Fertilizer cost per ton of increase in dry matter over Plot 7 Irrigated field 214.68 330.39 363.97 (') (') ( c ) Nonirrigated field ?11.42 315.88 317.23 3847.50 ( c ) (') See Table 1 for amounts applied. All plots received 10-10-10 fertilizer in 1953 and 1954. b The following costs were used in these computations: limestone, 34 per ton; rock phosphate, 320 per ton; superphosphate, 3/10 per ton; potash (60%), 355 per ton; nitrogen, 15^ per pound of nitrogen applied; 10-10-10 fertilizer, 372 per ton. The cost of dry matter is assumed to be 320 per ton. c Since yields on these plots were less than those on Plot 7, fertilizer costs were not recovered. 16 BULLETIN NO. 640 [March, Table 3. Laboratory Tests of Effect of Lime on pH of the Irrigated and Nonirrigated Fields 1949 1950 1952 1954 Differences between 1949 and 1954 Irr. Xonirr. Irr. Xonirr. Irr. Xonirr. Irr. X T onirr. Irr. Xonirr. 1 2 3 4 5 6 7 Average 6.1 6.5 6.3 6.2 5.9 6.0 7.0 5 5 4 4 5 5 5 .7 .3 .8 .9 .2 .1 .7 6.9 6.3 5.8 6.7 6.6 6.2 6.4 5.9 5.2 4.8 5.1 5.3 5.5 5.9 6.5 6.5 6.1 6.3 5.7 5.9 5.7 5.9 5.1 5.2 5.3 5.9 6.0 5.8 6.8 6.5 6.0 6.2 6.2 6.4 6.0 6.1 5.2 4.9 5.3 5.6 5.5 5.7 + .7 - .3 + .3 + .4 -1.0 + .014 + .4 -.1 + .1 + .4 + .4 + .4 + .229 clover. Equal stands and yields have been obtained from other experi- ments at the Station where pH levels were 5.34, where fertility tests showed available P 2 O 5 to be slight to medium, and where the addition of lime to rock phosphate and superphosphate gave no increase in yield over rock phosphate or superphosphate alone. 5 Effect of phosphate. By 1952, sufficient quantities of phos- phorus (Table 4) were available to maintain high yields on plots 1, 2, 4, and 5, where additional phosphate had been top-dressed. From 1948 through 1954, plots 1 and 2 received 590 pounds of P 2 O 5 as 20- percent superphosphate, and plots 4 and 5 received 380 pounds of P 2 O 5 as 32-percent rock phosphate (Table 1). These quantities were in addi- tion to the original 320 pounds of P 2 O 3 applied as 32-percent rock phosphate. Effect of potash. Potash added to lime and rock phosphate did not give an increased yield in dry matter either with or without irriga- tion (plots 6 and 7, Appendix B). An average annual application of 208 pounds of 60-percent potash did not quite maintain available potas- sium on plots 1 and 2 of the irrigated field (Table 5). Annual produc- tion on these plots averaged 9,700 pounds of dry matter per acre per year. The annual application of 208 pounds of potash was more than Table 4. Laboratory Tests of Available Phosphorus (Ps) on the Irrigated and Nonirrigated Fields Differences between Plot 1949 1950 1952 1954 1949 and 1954 Irr. Xonirr. Irr. Xonirr. Irr. Xonirr. Irr. Xonirr. Irr. Xonirr. (pounds per acre) 1 27.6 46.0 125.2 32.0 97.8 74.5 57.5 122.3 + 29 .9 + 76.3 2 55.1 52.0 111 .5 35.9 119.0 122.5 60.8 104.0 + 5 .7 + 52.0 3 34.0 14.0 42.0 25.0 56.0 28.5 63.0 47.0 +29 .0 +33.0 4 44.0 38.0 146.6 23.2 62.0 95.5 120.0 122.5 + 76 .0 + 84.5 5 25.0 32.0 143.6 35.6 89.0 107.0 137.0 147.0 + 112 + 115.0 6 16.0 17.0 97.6 21.4 53.0 48.0 40.5 30.0 + 24 .5 + 13.0 7 20.0 39.0 65.2 42.8 36.5 43.0 42.5 143.0 + 22 5 + 104.0 7959J IRRIGATION OF LADING CLOVER-GRASS PASTURE ^7 Table 5. Laboratory Tests of Available Potassium on the Irrigated and Nonirrigated Fields Differences between Plot 1949 1950 1952 1954 1949 and 1954 Irr. Nonirr. Irr. Nonirr. Irr. Nonirr. Irr. Nonirr. Irr. Nonirr. (pounds per acre) 1 198 145 252.0 266.2 187.3 237 145.5 256.8 -52 .5 + 111.8 2 156 171 297.6 239.2 191.0 269 163.0 275.8 + 7 ,0 + 104.8 3 211 205 307.0 265.8 269.5 240 254.0 281.5 +43 ,0 + 76.5 4 197 242 273.2 222.4 307.0 253 287.5 230.5 + 90 .5 -11.5 5 103 88 111.4 135.0 147.5 169 125.0 136.0 + 22 .0 + 48.0 6 233 239 274.0 222.8 238.0 305 258.5 287.5 + 25 .5 + 48.5 7 127 104 219.2 174.0 246.0 157 287.5 221.5 + 160 .5 + 117.5 adequate on all other plots, both irrigated and nonirrigated, to maintain available potash at high levels. The percentage of Ladino clover re- mained high on plots 4, 5, 6, and 7 of the irrigated field (Table 6). This fact seems to indicate that potash and rock phosphate had an important influence on the maintenance of Ladino in the stands on the irrigated field. The importance of additional fertilizer over a basic treatment to keep yields high is shown in Table 7. Lime, rock phosphate and super- phosphate, and potash helped maintain high yields on the irrigated field. Supplemental nitrogen was an important addition on the non- irrigated field because of the absence of legumes in the stand. How- ever, the increased yields resulting from commercial nitrogen are not always as well distributed throughout the growing season as the yields resulting from nitrogen converted by legumes. The effects of irrigation and the various soil treatments on yields are also shown in Table 7. Although irrigation with the basic treatment results in much higher percentage increases, total yields are much lower than in those cases where the treatment is complete. The yields from irrigated plots 1 and 5 and nonirrigated plot 5 are compared in Fig. 6. In addition to the basic fertilizer treatment, plot 5 received only one application of rock phosphate in 1949. This fertility level with irrigation gave a 7-year average annual increase in dry matter of 3,030 pounds over the same treatment without irriga- tion. The benefit of fertility is shown by comparing irrigated plots 1 and 5. Plot 1 received 20-percent superphosphate (421 pounds an- nually) and 60-percent potash (208 pounds annually) in addition to the basic fertilizer treatment. As a result, the annual dry matter per acre from plot 1 averaged 2,262 pounds more than that from irrigated plot 5. Although the response for water is good with low fertility, both high fertility and adequate water are necessary to produce the highest yields. 18 BULLETIN NO. 640 [March, 12,000 10,000 8,000 6,000 4,000 2,000 PLOT I -IRRIGATED FIELD PLOT 5-IRRIGATED FIELD PLOT 5-NONIRRIGATED FIELD 1950 1951 1953 1954 Effects of higher fertility and irrigation on yield irrigated plots and nonirrigated plot 5. AVER. 1 and 5 (Fig. 6) 420 360 ESSSSI IRRIGATED V/SSA NONIRRIGATED I INCREASE FOR IRRIGATION 1948 1949 1950 1951 1952 1953 1954 Increase in animal-unit days per acre as a result of irrigation. (Fig. 7) J959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 19 Table 6. Percentage of Ladino Clover on the Irrigated Field as Determined by Point Quadrat Plot Soil treatment 11 1948 1949 1950 1951 1952 1953 1954 1 L-rP-sP-K 46.0 32, 28. 22.5 18.5 12 5 17.0 2 L-rP-sP-K-N 17.0 13 5 16 23.5 23.0 19 9.0 3 L-rP-K-N 11.0 10 4 14.0 19.0 16 19.0 4 5 6 L-rP-(rP)-K L-rP-(rP) L-rP-K b b b 27 22 12 23 43 25 29.0 28.0 16.0 18.0 24.0 27.0 20 29 18 25.0 31.0 26.0 7 L-rP 38.0 17 26 26.0 29.0 9 .0 30.6 See Table 1 for amounts applied. All plots received 10-10-10 fertilizer in 1953 and 1954. b Part of plot 7 in 1948. Table 7. Increase in Yields of Dry Matter for Irrigation and Increase for Soil Treatments With and Without Irrigation, Average 1948-1954 Plot Increase in dry matter for irrigation (percent) Soil treatment 11 Increase in dry matter for each treatment compared with Plot 7 (percent) Irr. Nonirr. 1 40.7 L-rP-sP-K 22.1 48.7 2 21.1 L-rP-sP-K-N 22.2 72.7 3 24.5 L-rP-K-N 7.6 48.0 4 5 6 51.2 68.7 71.8 L-rP-(rP)-K L-rP-(rP) L-rP-K -11.4 -6.3 -.4 3.4 -48.7 -.6 7 71.3 L-rP 11 See Table 1 for amounts applied. All plots received 10-10-10 fertilizer in 1953 and 1954. Table 8. Yields of Dry Matter on the Irrigated and Nonirrigated Fields With and Without 10-10-10 Fertilizer, 1953 Irrigated field Nonirrigated field Plot Soil treatment 8 With 10-10-10 Without 10-10-10 Increase for 10-10-10 With 10-10-10 Without 10-10-10 Increase for 10-10-10 (pounds per acre) 1 L-rP-sP-K 7,337 5,462 1,875 1,582 1,042 540 2 L-rP-sP-K-N 7,600 6,100 1,500 5,554 5,454 100 3 L-rP-K-N 7,397 5,732 1,665 2,606 2,210 396 4 L-rP-(rP)-K 4,952 3,842 1,110 2,858 2,130 728 5 L-rP-(rP) 6,366 5,236 1,130 3,363 3,114 249 6 L-rP-K 6,058 4,567 1,491 4,481 3,805 676 7 L-rP 6,882 4,907 1,975 2,756 2,106 650 a See Table 1 for amounts applied. All plots received 10-10-10 fertilizer in 1953 and 1954. 20 BULLETIN NO. 640 [March, In July, 1953, 10-10-10 fertilizer was top-dressed on all plots on the irrigated and nonirrigated fields at the rate of 320 pounds per acre (Table 8). This treatment resulted in increases on the irrigated field of 1,110 to 1,975 pounds of dry matter per acre. The increases were much smaller on the nonirrigated field, ranging from 100 pounds to 728 pounds of dry matter per acre. The average increase of dry matter was 1,581 pounds per acre for the irrigated field and 429 pounds per acre for the nonirrigated field. Animal Carrying Capacity The annual pasture days (animal-unit days per acre) and the in- crease as a result of irrigation are shown in Fig. 7. Irrigation gave greater carrying capacity and a longer grazing season. Animal units per acre on the nonirrigated field ranged from 0.36 to 1.40, with a 7-year average of 1.02. Animal units per acre on the irrigated field ranged from 0.82 to 2.14, with a 7-year average of 1.48 an average increase due to irrigation of 0.46 animal unit or 45 percent. From 1948 to 1951, the fields were pastured for the same number of days. From 1952 to 1954, the nonirrigated field was pastured for 107, 155, and 166 days, and the irrigated field was pastured for 203, 195, and 221 days an increase due to irrigation of 96 days or 90 percent in 1952; 40 days or 26 percent in 1953; and 55 days or 33 per- cent in 1954. Over the 7-year period, the irrigated field was pastured 27 more days annually than the nonirrigated field, an increase of 17.5 percent. As a result, the total carrying capacity was increased 71 per- cent or 111 animal-unit days per acre. Examples of the increased carrying capacity of the irrigated over the nonirrigated field in a wet and dry year are shown in Figs. 8 and 9. In 1950, the wet year, the carrying capacity of the nonirrigated field dropped to about 1/2 animal-unit per acre from July 17 to August 21. The carrying capacity on the irrigated field was 1.7 animal units per acre, and it remained at this high level until September 18. In 1954, the dry year, the carrying capacity of the nonirrigated field was zero from July 30 until October 21. During this same period, the carrying capacity of the irrigated field was 1.25 animal units from July 30 to September 9, and 1.67 animal units from September 9 to October 21. The carrying capacity of the nonirrigated field during 1954 was very low because numerous plants, especially Ladino clover, had died during the two previous seasons. Both of these seasons were dry. J959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 21 APRIL MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. 1950 Carrying capacity of the two fields during a wet year. (Fig. 8) Carrying capacity of the two fields during a dry year. (Fig. 9) E3 NONIRRIGATED PASTURE CD INCREASE FOR IRRIGATION \ IRRIGATED PASTURE NONIRRIGATED PASTURE APRIL MAY JUNE JULY AUG. SEPT OCT. NOV DEC 22 BULLETIN NO. 640 [March, Animal Gain and Dry-Matter Consumption Animal gains on both fields, and the increase due to irrigation are shown by years in Fig. 10. The 7-year average animal gain was 248 pounds per acre on the nonirrigated check field and 363 pounds per acre on the irrigated field an increase of 115 pounds per acre or 46 percent due to irrigation. The dry matter consumed per acre and the pounds of dry matter consumed per pound of animal gain are shown in Table 9. The average consumption per acre for the 7-year period was 7,951 pounds or 91 percent of production on the irrigated field, and 5,551 pounds or 98 percent on the nonirrigated field. Therefore, the percentage of consumption was practically the same for the 7-year period. The highest consumption on the irrigated field was 10,739 pounds per acre in 1950, and the lowest was 4,573 pounds in 1948, the first year of establishing the pasture. On the nonirrigated field, the highest consumption also occurred in 1950 --8,560 pounds per acre. The lowest consumption was 2,871 pounds per acre in 1948. The average number of pounds of dry matter consumed per pound of animal gain varied widely during the 7 years. In 1951, 34.10 pounds of dry matter were consumed on the irrigated field per pound of animal gain, and in 1953, 13.41 pounds. The average annual consump- tion per pound of animal gain on the irrigated field was 21.89 pounds. 500 - 1948 1949 1950 1951 1952 1953 1954 Animal gains on the two fields and increase for irrigation. (Fig. 10) J959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 23 Table 9. Forage Consumption and Consumption per Pound of Animal Gain, Average of all Plots, 1948-1954 Consumption (pounds per acre) Pounds of dry matter consumed per pound of animal gain Irr. Nonirr. Irr. Nonirr. Continuous grazing 1948 ... , 4,573 a 2,871 32 66 53 17 1949 9,661 7,008 18.13 17 92 1950 10,739 8,560 26 98 24 32 1951 8,798 7,479 34 10 49 20 1952 8,839 4,690 30 91 28 95 Rotational grazing 1953 6,278 3,037 13.41 9 99 1954 6,771 5,212 14 72 16 09 Total 55,659 38,857 21 89 b 22 34 b 7-year average . . . .. . 7,951 5,551 24 42 28 52 a Average of 1-inch and 2-inch irrigation halves. b Weighted average. Table 10. Seven-Unit Rotational Grazing Cycle for the Irrigated and Nonirrigated Fields, 1954 Cycle Animal units per acre Irr. Nonirr. Rotation cycle (days) Irr. Nonirr. Regrowth period (days) Irr. Nonirr. Grazing period (days) Irr. Nonirr. 1 1.93 1.85 21 21 18 18 3 3 2 2.00 1.88 28 28 24 24 4 4 3 2.00 1.88 36 36 30|K 30 6 / 7 5K 5/7 4 1.25 .63 45 7 38 4 / 7 6 6% 1 5 1.38 ( a ) 50 (*) 42?/7 (a) 7/7 (a) 6 1.67 (a) 35 ( a ) 30 ( a ) 5 (") 7 1.67 1.18 7 43 6 36/ 7 1 6/7 No cattle grazed. Table 11. Continuous and Rotational Grazing on the Irrigated and Nonirrigated Fields Average of years Yield of dry matter i (pounds per acre) Pounds of dry natter consumed per pound of animal gain Continuous grazing Irrigated field 1951-1952 9,707 32 42 a Nonirrigated field ... . 1951-1952 6,799 38 75" Rotational grazing Irrigated field 1953-1954 7,325 14.06 Nonirrigated field 1953-1954 5,022 13.14 s a Weighted average. 24 BULLETIN NO. 640 [March, In 1948, 53.17 pounds of dry matter were consumed on the nonirrigated field to produce a pound of animal gain, and 9.99 pounds were required in 1953. The average annual consumption per pound of animal gain for the 7 years was 22.34 pounds. Grazing Management The pastures were grazed as single units from 1948 through 1952. In 1953 and 1954, grazing strips were established in an attempt to achieve more even and uniform grazing, and to reduce trampling. A 7-unit rotation grazing system was used. This system allowed 3 to 7 days for consumption of the forage on each strip, leaving 21 to 49 days for regrowth of the forage. With adequate fertility and mois- ture, regrowth ordinarily occurs within a period of 21 to 28 days. The growth rate of pasture plants may be used as a guide in deter- mining the number of days in the grazing cycle. An example of a 7-unit cycle is shown in Table 10. Except for the first grazing cycle in the spring, grazing may be planned to harvest the forage at a desir- able stage of growth. During the spring, when growth is rapid and the forage may not be consumed, the vegetation from one or two grazing strips may be made into grass silage or hay. As shown in Table 11, the yields of dry matter were lower under the 7-unit grazing system; but the efficiency of management, as meas- ured by the number of pounds of dry matter required to produce a pound of animal gain, was higher. In this experiment, rotational grazing was 131 percent more efficient than continuous grazing in the irrigated field and 195 percent more efficient in the nonirrigated field. Since only one type of grazing system was used in any particular year, the rainfall and environmental conditions cannot be separated from the management factor. For a comparison of the efficiency of rotational and continuous grazing for all 7 years of the project, see Table 9. Species in Forage Desirable species of plants such as Ladino clover can be maintained longer in irrigated than in nonirrigated pastures (Fig. 11). At the end of the 7-year period, Ladino clover accounted for 23 percent of the ground cover on the irrigated field. The drouth in 1952 killed all of the Ladino on the nonirrigated field. A study by months of the amount of forage on the irrigated field indicates that the legume makes an important contribution to total forage production during July and August (Fig. 12). The percentage 7959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 25 25 20 5 15 10 Ladino IRRIGATED NONIRRIGATED 1948 1949 1950 1951 1952 clover as a percent of ground cover on the two fields. (Fig. 11) Percent of total forage sample comprised by legumes and grasses. (Fig. 12) PERCENT 100 90 80 70 60 50 40 30 20 10 PERCENT OF LEGUMES AND GRASSES IN FORAGE (DRY- MATTER BASIS) LEGUMES APR. 8 MAY 6 JUNE 10 JULY 10 AUG. 28 SEPT. 21 OCT. 2 26 BULLETIN NO. 640 [March, of the total dry matter comprised by grasses begins to drop in early June and is less than 35 percent of the forage until cool weather begins late in September. The production pattern of the legumes is reversed, with the legume producing more than 50 percent of the forage during the hot summer months. SUMMARY A study of pasture irrigation was conducted in southern Illinois from 1948 to 1954. Its objectives were (1) to determine the most effective amount of water and the frequency of application; (2) to find the best fertilizer treatment with irrigation from an economical point of view; (3) to study the effect of irrigation on available soil moisture, plant growth and animal gains, and species of pasture plants. The rainfall from May through October during the 7-year experi- mental period was typical for the area. The rainfall was above normal for 3 years, normal for 1 year, and below normal for 3 years. The variations ranged from 6.02 inches above to 9.13 inches below the 55- year average rainfall for the area. Two 5-acre fields were studied one field was irrigated, and the other was a check field. To determine the effectiveness of different amounts of irrigation, the irrigated field was divided for the 1948 season. One-half of the field received 1-inch applications of water, and the other half received 2-inch applications. Soil-moisture measure- ments showed that the 2-inch application was more effective in chang- ing soil moisture, particularly at the lower depths. The cost was also less per acre-inch of water applied. For these reasons, only 2-inch applications were used after the 1948 season. Since grass-legume pasture mixtures have a long growing season, they require large quantities of water. During the 7 years of this experiment, the fields received an average of 34.25 inches of water each year (20.54 inches of rainfall and 13.71 inches of irrigation water). The total rainfall plus irrigation for June, July, and August averaged 3.23 inches for a 2-week period or 7.08 inches per month. The fields were divided into 7 plots to study the effects of various combinations of fertilizers. Rock phosphate, superphosphate, potash, and nitrogen were added in various combinations to a basic treatment of limestone and rock phosphate. Limestone, rock phosphate and super- phosphate, and potash proved to be the most economical soil treatment per ton of dry matter produced on the irrigated field. Commercial nitrogen had little effect on the yield from the irrigated plots. Super- 7959J IRRIGATION OF LADINO CLOVER-GRASS PASTURE 27 phosphate was effective when added to rock phosphate on the irrigated plots. A comparison of irrigated and nonirrigated plots with various combinations of fertilizers points up the importance of an adequate fertility program. The dry matter produced on the irrigated field averaged 1}4 tons per acre per year more than that produced on the nonirrigated field. A comparison of the yields from the most responsive fertilizer-treatment plots shows an average annual increase in dry matter produced for irrigation of approximately 0.85 ton per acre. The animal carrying capacity was 71 percent higher on the irrigated field than on the non- irrigated field an average increase of 111 animal-unit days per acre. The 7-unit rotation grazing system was more efficient in producing animal gain than the continuous grazing system. When cattle were changed from a continuous to a rotational grazing system, the dry matter consumed to produce a pound of animal gain dropped from 32.42 to 14.06 on the irrigated field, and from 38.75 to 13.14 on the nonirrigated field. The legumes in a legume-grass pasture produce more than 50 percent of the forage during the summer. Irrigation was effective in maintaining legumes as 23 percent of the ground cover during the last year of the project. All of the legumes died on the nonirrigated field. References 1. BOUYOUCOS, G. J., and MICK, A. H. An electrical resistance method for the continuous measurement of soil moisture under field condi- tions. Mich. Agr. Exp. Sta. Tech. Bui. 172, 38p. 1940. 2. BOUYOUCOS, G. J., and MICK, A. H. Improvements in the plaster of paris absorption block electrical resistance method for measuring soil moisture under field conditions. Soil Sci. 63, 455-465. 1947. 3. HAMILTON, J. G., BROWN, G. F., TOWER, H. E., and COLLINS, WILKIE, JR. Irrigated pastures for forage production and soil conservation. U. S. Dept. Agr. Farmers' Bui. 1973, 30p. 1945. 4. JONES, B. A., JR., and WAKELAND, H. L. Supplemental irrigation of pastures. Agr. Engin. 36, 181-184. 1955. *5. McKiBBEN, G. E., and GATE, H. A. Soil treatment for pasture grasses and legumes (Experiment 3), 1944-1950. Dixon Springs Experiment Station mimeo DS43, 9p. 1952. *6. McKiBBEN, G. E., CARD, L. E., VAN DOREN, C. A., and FUELLEMAN, R. F. Soil moisture availability in irrigated and nonirrigated pas- tures. Agron. Jour. 42, 565-570. 1950. 7. WHITAKER, R. W., and LYTLE, W. F. Supplemental irrigation of pas- ture. Agr. Engin. 32, 163-165. 1951. * References cited. 28 5 90 Z 00 BULLETIN NO. 640 [March APPENDIX A 2" IRRIGATION NONIRRIGATED TURE REMAINING 5 C Note IWctnt uMblt moisture it overoge of readings at four toll depths li", 4^' 7V and 101k* / // r\ "x ^ / i v / \ r N , '-'/ i 5 30 \ O . / /- *^ / \ "x' '/ fe \ V *, -/' y ^ / ,_.- .---' X / PER CEN D O ! \ J | NATURAL RAINFALL | IRRIGATION 1 I I 1 uJ i LL J III -U IJ J J 1 ' APRIL - I'es*' MAY -2.79" JUNE- 5.30" MONTHLY JULY - 3.38 ' Al. RAINFALL- 1949 GRAZ ^ cusT-5.42 1 'SEPTEMBER -25 G SEASON 1 Ocf6B*--5.f8- 1 ' Effects of rainfall and irrigation on the usable soil moisture during the 1949 grazing season. (Fig. 13) Effects of rainfall and irrigation on the usable soil moisture during the 1951 grazing season. (Fig. 14) MOISTURE REMAINING IN SOIL j 8 00 2" IRRIGAT ON NONIRRIGATED Not*. Percent uso readings at three depths 4" 8" >le ge of soil 2" i ^ \/ \ / ^ -\ ^ PERCENT OF USABLE o 6 o o < V. ^ V / ^ \ s\ \ / V / y N \ / " I NATURAL RAINFALL | IRRIGATION 1 f\ | J ,1 , . 1 1 1 1 'APRIL "-3 70" MAY - 1 85" JUNE - 10 Or JU LY - 3 29" 1 A'UGUST'- 4 30" 'sEPTE'MBER'-Yba^ OCTOBER -"l. 86" ' MONTHLY RAINFALL- 1951 GRAZING SEASON J959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 29 *' 5 c ss d i z A/I Note Percent usable moisture is average of reading at three soil depths-4",8",and 12" tty '1 2$ ^ ^-- ^-" ^-^* ~ ~. -. ~~- o 20 UJUI SS 1 -. I INCHES OF WATER o b b c NA1 'URAL RAIN !LL_ -. IRRIGATION mm 1 _|L ,ll 1 1 1 1 t 1 MAY - 2 66' JUNE - 2.98' MO S JULY-2.24 - AUGUST 24* ' SEPTEMBER-1.19' ' OCTOKR.9Z' NTHLY RAINFALL- 1953 GRAZING SEASON Effects of rainfall and irrigation on the usable soil moisture during the 1953 grazing season. (Fig. 15) Effects of rainfall and irrigation on the usable soil moisture during the 1954 grazing season. (Fig- 16) so 6 .. 2" IRRIGATION NONIRRIGATED Note! Percent usable moisture is average of readings at three soil depths 4"8f, and 12". RE REMAINING IN S S S 2 * / V p^-^ x x^ ^s ^ \ / / PERCENT OF US* \ \ 7 V / \ J " < *^. ^^__ | NATURAL RAINFALL IRRIGATION 1, | ll J 1 I 1 _J 1 1 r L ll 5 MAY -4.62^ JUNE- 2.42" JULY-2.32" AUGUST-294" SEPTEMBER-3Jar OCTOBER^2.24" MONTHLY RAINFALL- 1954 GRAZING SEASON 30 BULLETIN NO. 640 [March, APPENDIX B Yield of Dry Matter in Pounds per Acre Plot treatment 1948 1949 195 1951 1952 1953 1954 Avera g e " Irrigated field 1 L-rP-sP-K 7,334 11,696 13,023 10,754 10,330 7,092 7,700 9,704 2 L-rP-sP-K-N 7,639 11,992 11,721 10,599 9,702 8,031 8,263 9,707 3 L-rP-K-N 6,359 10,612 8,737 10,069 9,968 8,232 5,848 8,546 4 L-rP-(rP)-K b 7,499 9,649 8,094 8,478 5,178 6,177 7,037 5 L-rP-(rP) b 7,974 10,588 8,446 7,288 6,099 7,512 7,442 6 L-rP-K b 8,066 10,008 9,76110,048 6,637 6,711 7,917 7 L-rP 4,187 7,161 9,378 9,783 8,730 7,658 8,722 7,946 Nonirrigated field 1 2 3 4 L-rP-sP-K L-rP-sP-K-!s L-rP-K-N L-rP-(rP)-K 3,668 7 r 4,846 10 4,039 8 . . . b 5 ,643 ,553 ,548 ,062 11,999 11,094 9,219 6,380 9 9 8 6 ,864 ,703 ,140 ,699 5,877 7,501 5,890 3,603 3,142 5,435 4,735 3 435 6 6 7 4 ,098 ,956 ,489 781 6,899 8,013 6,866 4 654 S L-rP-(rP) b 5 ,238 6,081 6 821 2 733 3 291 4 104 4 412 6 L-rP-K b 4 025 5 663 7 291 3 737 3 453 s 477 4 609 7 L-rP 2,618 4 ,908 6,671 6 ,466 2,217 3,811 5 ,777 4,638 "LSD .05 = 1,213 pounds; .01 = 1,842 pounds. b Part of plot 7 in 1948. 7959J IRRIGATION OF LADING CLOVER-GRASS PASTURE 31 ACKNOWLEDGMENTS This project was initiated by the Illinois Agricul- tural Experiment Station in cooperation with the Research Division of the Soil Conservation Service, U. S. Department of Agriculture. The John Effa Supply Company, West Chicago, and the Aluminum Com- pany of America provided irrigation equipment and grant funds. The authors also gratefully acknowledge the assistance of G. F. Cmarik, W. F. Lytle, H. L. Wake- land, and R. W. Whitaker in various phases of the project. SM 3-59 67331 UNIVERSITY OF ILLINOIS-URBANA