Corn-Soybean Cropping Sequences in the Kansas River Valley

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Corn-Soybean
Much of the corn in the Kansas River valley is continuous corn. Research in other areas has shown that corn following a previous soybean crop yields more than corn following corn. It is likely that at least some of this yield increase is attributable to nitrogen fixed by the previous soybean crop when N is insufficient on corn following corn. Research has also shown that soybeans grown in a cropping sequence with corn or grain sorghum yield more than continuous soybeans.

Procedure
A study conducted at the Kansas River Valley Experiment Field from 1979 through 1987 was designed to evaluate various corn-soybean cropping sequences and nitrogen rates. The cropping sequences included continuous corn and soybeans, first and second year corn following soybeans, soybeans following 1 year of corn, and soybeans following 2 years of corn. The continuous soybeans and each corn crop received annual applications of nitrogen at 0, 75, 150, and 225 pounds per acre. The soybeans in the cropping sequence received no nitrogen, but were evaluated for their response to possible residual N from the treatments applied to the previous corn crop(s).
The plots were initiated in 1978, so the 1979 data did not include the 3-year cropping sequences. The plots were disked and chiseled in the fall when weather con-This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu. -1983-1984and Sherman-1987. The nitrogen fertilizer treatments were applied in early April as anhydrous ammonia. Corn was planted in mid-April and soybeans in early May. Fertilizer (130 lbs 8-32-16/ a) was banded at planting on all corn and soybean plots. Herbicides were applied preplant, incorporated, and a corn rootworm insecticide was applied in the furrow at planting. Both crops were cultivated and furrowed for ditions permitted and were disked in the spring when a preplant, incorporated herbicide was applied. Corn was planted at 26,200 seeds per acre in 30-inch rows and soybeans were planted at 10 seeds per foot of 30-inch row. Corn hybrids planted were: Bo-Jac 56-1979-1982Bo-Jac 601-1983;andPioneer Brand 3377-1983-1987. Soybean varieties planted were: Union-1979Union- -1981Douglas-1982Douglas- , 1985Douglas- , 1986  This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.

Desoto
irrigation and irrigated as needed. Crops were harvested with a combine adapted for plot harvesting.
In 1979, 1981, and 1982, total dry matter and N content at physiological maturity were measured on the 0 N plots of the corn following soybeans and continuous corn plots in an effort to evaluate the amount of N contributed by the previous soybean crop.

Results
Corn Yields. Yields were depressed by hot weather in 1980 and by hail in 1981, but were good in 1979 and from 1982-87 (Table 1). Because of the poor yields in 1980 and 1981, these years were not included in the average. Corn following soybeans with no applied ni-  1979 1980 1982 1983 1984 1985 1986 1987   trogen yielded from 30 to 82 bushels per acre more than continuous corn (51 bu/a avg.). The addition of 75 pounds N per acre decreased this average yield differential to 20 bushels per acre. There was still a slight trend of increased yield for corn following soybeans at the 150 pounds N per acre rate. However, these yield advantages disappeared in second year corn after soybeans. Nitrogen fertilization up to 150 pounds N per acre increased yields in all years, with no significant increase in yield occurring with the next 75 pound N per acre increment (225 lb N/a). Soybean Yields. Yields were good except in 1981 when hail occurred (Table 2). Soybean yields were not affected by the hot weather in 1980, as corn yields were. Soybeans following corn have yielded more than continuous soybeans by an average of 4.0 bushels per acre (ranging from -3.7 to 17.2 bushels per acre). The yield advantage for soybeans following corn in 1982 and 1984 was attributed partly to a high infestation of eastern black nightshade in the continuous soybeans. This emphasizes the advantage of using a cropping sequence to help control weeds that could become problems in a monoculture system. Granular Lasso was applied over the row from 1983 to 1987 in an effort to control the black nightshade. Good control was obtained in 1983 and 1985 to 1987, but control was poor in 1984. Application of 225 pounds N per acre significantly decreased yields of continuous soybeans in 1984 (caused mainly by more black nightshade), but the same trend was evident in other years.
Nitrogen Uptake. The data collected in 1979The data collected in , 1981The data collected in , and 1982 indicate that corn following soybeans with no applied N had more total dry matter and more N uptake than continuous corn. Corn following soybeans ranged from 28.9 pounds more total N uptake than continuous corn per acre in 1982 to 57.1 lb/a in 1979, with 1981 being intermediate. However, the 1981 data were collected from corn that received significant hail damage, and the 1982 data were collected from corn following soybeans, which yielded well but had been heavily defoliated by hail in 1981. If the N uptake figures for these two years are discounted, and the value obtained in 1979 is compared to the 1978 soybean yield, the result is approximately 1 pound of N produced per bushel of previous soybean crop. This agrees closely with values previously reported in the literature.

Summary
Yields of corn following a previous soybean crop averaged 51 bushels per acre higher than yields of continuous corn when no N was applied. This yield advantage decreased as N fertilization rate increased to 150 pounds N per acre. Soybeans following corn yielded an average of 4 bushels per acre higher than continuous soybeans. Nitrogen uptake data suggest that 1 pound of N per bushel of soybeans can be supplied to a subsequent corn crop, when no N fertilizer is applied.

4-88-3M
This publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information is available from http://www.ksre.ksu.edu.