Intercropping corn and soybean for high-protein silage in a cool temperate region

摘要

The overall hypothesis of this research was that silage biomass and protein yields would be higher in corn-soybean intercrops than in monocrops on the same land area. Yields, European corn borer infestation and N transfer were tested over tall and dwarf corn hybrids, nodulating and nonnodulating soybean genotypes and at 0, 60 and 120 kg N ha$sp{-1}$. Land Equivalent Ratios ranged from 0.97 to 1.23, but most were higher than 1.10. Protein concentrations of corn-soybean silage, up to 10.76%, were on average 9.24% vs. 7.41% in corn silage. A general trend of higher protein yield ha$sp{-1}$ in intercrops compared to corn monocrops was significant in 1986. Corn-soybean intercrops at 60 kg N ha$sp{-1}$ and three population densities were $132 to $261 ha$sp{-1}$ more cost effective than monocropped tall corn at 120 kg N ha$sp{-1}$. European corn borer infestation was reduced by intercropping and was higher at 120 kg N ha$sp{-1}$ than at 60 or 0 kg N ha$sp{-1}$. Under normal rainfall, dwarf corn had higher protein and yield levels when intercropped with nodulating rather than nonnodulating soybean. On N-depleted soil, N transfer was detected from nodulating soybean to nonnodulating soybean and to corn by the $sp{15}$N dilution method, and to corn by direct $sp{15}$N labelling of nodulating soybean.