INTERCROPPING CORN AND SOYBEAN FOR SILAGE IN A COOL-TEMPERATE REGION - YIELD, PROTEIN AND ECONOMIC-EFFECTS

Corn (Zea mays L.) and soybean (Glycine max[L.] Merr.) were intercropped for silage in 1985 and 1986 at the Central Experimental Farm, Ottawa, Canada to evaluate silage yield, protein and economic effects. In both years, a complete 2 × 2 ×3 factorial was analysed for two corn hybrids (dwarf and tall), two corn cropping systems (monocropped and intercropped), and three N fertilizer levels (0, 60 and 120 kg N ha-1). In addition to the complete factorial treatments, monocropped soybeans with 0 kg N ha-1 and an intercrop treatment of dwarf and tall corn at 120 kg N ha-1 were grown. In 1986, four population-density levels of the intercropped tall corn and soybean, at 60 kg N ha-1, were also compared. Total yields averaged over corn hybrids and cropping systems had a quadratic response, increasing from 0 to 60 kg N ha-1 and then decreasing slightly between 60 and 120 kg N ha-1, in both years. Monocrops of corn yielded significantly more in both years than intercrops, except tall-corn intercrops in 1986 grown at monocropped-corn population densities. Both corn and soybean of the dwarf-corn intercrops in the dry year of 1985 had a consistent trend of lower dry-matter and protein yields than in tall-corn intercrops at the same levels of N. These differences did not consistently favour either corn hybrid in 1986. The concentration of crude protein was significantly higher in intercropped than monocropped silage in both years. In 1986, this was also true for the protein yield ha-1. Increasing N application resulted in higher total silage protein concentrations in both years. The total silage protein concentration was, on average, 1.53 and 2.15 percentage points higher in intercrops than in the corresponding monocropped corn hybrid at the same level of N in 1985 and 1986, respectively. The total silage protein concentrations in both years and the protein yield in 1986 were greater for tall corn than for dwarf corn. All treatments at 0 kg N ha-1, the dwarf-corn intercrops in 1985 and monocropped dwarf corn at 120 kg N ha-1 in both years, were less cost-effective than the standard, monocropped tall corn at 120 kg N ha-1. In 1985, the tall corn intercrop at 60 kg N ha-1 had a $135 ha-1 cost-effective advantage over the standard treatment. In 1986, this intercrop had a $132 ha-1 advantage, which was improved to $261 ha-1 when the corn population was maintained at monocrop levels and the population of soybeans was reduced by 50%. Land equivalent ratios (lers) based on dry-matter weights ranged from 0.97 to 1.11 in dwarf-corn intercrops and from 1.16 to 1.23 in tall-corn intercrops in 1985. The ler range in 1986 was from 1.11 to 1.12 in dwarf-corn intercrops, and from 1.04 to 1.23 in tall-corn intercrops. © 1990.