Strip intercropping and nitrogen effects on seed, oil, and protein yields of canola and soybean

Increased world demand for high-quality edible oil requires agronomic practices that increase oilseed yields with minimal environmental impact. We hypothesized that strip intercrops of canola (Brassica napus L.) and soybean [Glycine max (L.) Merr.] would increase seed, oil, and protein yields compared with sole crops. Canola (cv. Global) was grown in 4.5-m wide strips adjacent to 4.5-m strips of later-planted soybean (cv. Chippewa) at Rosemount, MN, in 1991 and 1992, and at St Paul, MN, in 1992. Zero or 134 kg N ha(-1) was applied at planting in the Rosemount studies, and 134 kg N ha(-1) was applied at St. Paul. Seed yield, oil, and crude protein (CP) concentrations were determined for individual rows. Land equivalent ratios (LER) were calculated, using inner rows of the strip to represent sole crop yields. Canola border row yields were 225 to 590% of those of sole crop rows. Without N fertilization, soybean border row yields were similar to sole crop rows, but with added N fertilizer were only 50 to 65% of the sole crop yields. Projected LERs (range: 1.02 to 1.65) were significantly greater than 1.0 for strip widths of 1 to 4 m without N, and 1 to 6 m with fertilizer N. Strip intercrops produced edible oil and CP yields up to 170% of the mean of the two sole crops. Intercropping canola and soybean in strips has the potential to reduce fertilizer applications and enhance oil and protein yields compared with sole crops.