Doublecropping Soybean after Canola and Wheat

Abstract

Canola (Brassica napus L.) can be planted as a winter crop and doublecropped with soybean [Glycine max (L.) Men.] in the southeastern Coastal Plain of the USA, but little information is available about canola's effect on subsequent crops in the rotation. A 2-yr study was conducted to determine the effect of deep tillage on both canola and wheat (Triticum aestivum L.), the subsequent response of doublecropped soybean, and response of wheat grown following the soybean crop when controlled traffic and minimum tillage practices were used. The study was initiated in autumn of 1990 and repeated in 1991 on an Orangeburg loamy sand (fine-loamy, siliceous, thermic Typic Paleudults) near Blackville, SC. Canola yields averaged 37.8 bu/acre in 1991 and 43.2 bu/acre in 1992, whereas wheat yields were 58.0 and 72.5 bu/acre, respectively. In both years, deep tillage (chiseling to 11 in.) had no effect on wheat yields when compared with disking. Deep tillage increased canola yields by 12.5 % in the drier of the two growing seasons. Soybean yields were not significantly affected by the tillage used for the previous crops. Subsoiled soybean yielded 33.7 vs. 31.9 bu/acre for no-till soybean in 1991, and 22.6 vs. 19.4 bu/acre in 1992. The difference was significant (P = 0.05) in 1992, and that year soybean tillage following wheat did not affect soybean yield but following canola, in-row subsoiling resulted in greater soybean yields than no-till. Wheat following soybean was not affected by the tillage practice used for the previous winter crops, and the 1992 wheat yields were unaffected by previous winter crop or soybean tillage. In 1993, soybean tillage did not affect subsequent wheat yield but following canola, in-row subsoiling resulted in greater wheat yields than no-till. These results suggest canola has no adverse effect on either soybean or wheat when grown in sequence on a Coastal Plain soil