Relay-intercropped soybean in different water regimes, planting patterns, and winter wheat cultivars.

摘要

Relay-intercropping soyabeans into winter wheat at the boot stage may be a profitable production alternative in environments where double-cropped soyabean production after wheat harvest is unreliable. The influences of water regimes, sowing patterns, and wheat cultivars on soyabean growth and yield were compared in field trials in 1988 and 1989 near Manhattan and Rossville, Kansas. Five wheat cultivars were sown in solid and skip-row patterns and soyabeans cv. Resnik were intercropped in wheat at the late boot stage. All plots received equal irrigation prior to wheat harvest and different amounts (limited vs. full) during the remaining growing season. Soyabean yields at Rossville were not affected by irrigation regime, but at Manhattan, fully irrigated soyabean yields were 27% greater than soyabeans under limited irrigation. The intercrop competition period averaged 16 days longer in 1989 than in 1990. Wheat was sown in 8-inch rows in a solid and one-out-of-three skip-row pattern. Soyabeans in all sowing patterns were in 24-inch rows between the 8-inch wheat rows, in the middle of the 16-inch skip, or in a conventionally tilled, sole cropped (SC) system. When intercropped in solid wheat stands (SI), soyabeans yielded 52 and 37% of soyabeans in skip-row intercropped (SRI) and SC patterns, respectively, in 1989, and 80 and 64% of SRI and SC yields, respectively, in 1990. Solid intercropped soyabeans received 36 and 64% of the total measured photosynthetically active radiation that reached SC andSRI soyabean canopies, respectively. Seventy-six percent of unharvested soyabean plots (reduced or eliminated populations) were SI. Soyabeans intercropped into short wheat cultivars had higher (14 to 20%) yields than soyabeans in taller wheat cultivars.Wheat cultivar maturity had no consistent effect on intercropped soyabean yield. Of the soyabean plots abandoned because of reduced populations, 76% were intercropped into tall or medium-late maturing wheat cultivars. If relay intercropping soyabeans into winter wheat is to be implemented on soils that are droughty or have low moisture-holding capacity, supplemental irrigation must be available. Using an SRI sowing pattern with wheat cultivars of shorter stature will increase chances for soyabean survival and profitable yields.