THE EFFECT OF SOYBEAN VARIETY ON CORN-SOYBEAN INTERCROP BIOMASS AND PROTEIN YIELDS

Soybean intercropped with corn can produce a high-quality silage, but pods of early maturing soybean varieties usually shatter when harveste d, thus reducing the silage protein potential. In 1991 and 1992, an ex periment was conducted in Truro, Nova Scotia, and Sussex, New Brunswic k, to determine whether later soybean varieties can provide sufficient biomass and protein in intercrops and escape pod losses at harvest. E arly, early high protein, medium, late and very late maturing varietie s of soybean were grown as monocrops and intercrops with corn. Eight r esponse variables were measured: soybean shoot biomass yield, intercro p shoot biomass yield, soybean shoot protein concentration, intercrop shoot protein concentration, soybean shoot protein yield, intercrop sh oot protein yield, soybean seed biomass yield and soybean seed protein concentration. The two later soybean varieties had higher yields than the two early varieties, contributing to higher protein yields in the later varieties than in the early varieties, under both monocropping and intercropping. In contrast to the corn monocrop, intercrops with a ll soybean varieties produced higher protein concentrations. Under int ercropping, only the late variety produced significantly higher protei n yields than the corn monocrop; however, none of the varieties result ed in significantly lower biomass yields than the corn monocrop. With the late soybean variety, land equivalent ratios of the intercrop shoo t biomass yield and the intercrop shoot protein yield revealed yield a dvantages of intercrops over monocrops of 21% and 10%, respectively. T he late variety resulted in an increased intercrop shoot protein conce ntration without reducing the intercrop shoot biomass yield, because i t was still green enough to be harvested with minimal pod shattering.