Forages: Yield and quality of forage soybean

Tall forage soybean [Glycine max (L.) Merr.] cultivars in maturity groups V, VI, and VII have been developed to supply forage. Our objective was to determine the effect of harvest date and row spacing on the forage yield and quality of these new soybean cultivars. We grew forage and standard grain soybean in Minnesota with harvests in early and late September. Average maturity of tall forage soybean was R3 (early harvest) to R4 or R5 (late harvest) and average maturity of grain soybean was R6 (early harvest) to R7 (late harvest). Herbage of forage soybean was mostly leaves and stems at both harvests, whereas herbage of grain soybean contained an average of 400 and 595 g kg^-1 pods at the early and late harvests, respectively. There was no harvest date x soybean entry interaction for forage yield or forage quality. Forage and grain soybean had similar forage yields (∼8.8 Mg ha^-1). Because adapted grain soybean was more mature and had a greater pod proportion than forage soybean, grain soybean had greater crude protein (CP) and lower fiber concentration than forage soybean. Average forage CP for forage and grain types was 146 and 218 g kg^-1, respectively, while neutral-detergent fiber (NDF) concentration was 523 and 400 g kg^-1, respectively. Decreasing row width from 76 to 25 cm increased forage yield 0.8 Mg ha^-1 but had no effect on total herbage quality.