Intercropping Irrigated Corn With Two Soybean Maturity Groups At Different Planting Rates For Forage

Increasing silage production and quality is paramount for dairy and beef feedlot production. We aimed to (a) increase dry matter, protein production, and profit per acre of corn (Zea mays L.) by intercropping it with soybean [Glycine max (L.) Merr.]; (b) compare soybean maturity groups (MGs) intercropped or grown as the sole crop; and (c) quantify the soybean planting rate's influence on land equivalent ratios (LER), total dry matter yield, nutrient concentration and economic return per acre in corn-soybean intercropping systems. A 2-yr field study was conducted with two soybean MGs (MG1 and MG7) and four soybean planting rates: 0 (control), 38,000 (1x), 76,000 (2x), and 152,000 (4x) seeds acre(-1). Intercropping with MG7 increased soybean dry weight by 33% compared with MG1. The MG7 4x rate in 2012 and the 1x and 2x rates in 2013 maximized yield and LER when forage contained 7 to 10% soybean. Averaged over years, the MG7 soybean planting rate had a significant quadratic influence on nutrient value, peaking at the 2x rate at $23 ton(-1) more than monoculture corn. Intercropping with the 2x MG7 soybean increased the net economic return per acre on a nutrient value basis by $238 acre(-1). The soybean concentration in the mix that produced the highest total dry matter yield 5 and 7% and 7 and 10% for gross economic return per acre in 2012 and 2013, respectively. On a tonnage only basis, intercropping 2x MG7 soybean increased yield and produced $26 acre(-1) more profit than monoculture corn.