Agronomic feasibility of a continuous double crop of winter wheat and soybean forage in the southern Great Plains

In the southern Great Plains, dryland double-cropping soybean [Glycine max (L.) Merr] after winter wheat (Triticum aestivum L.) could provide quality summer forage, partially offset mineral fertilizer N applied to winter wheat, and lessen soil erosion. Waiting for wheat grain to mature, however, delays soybean planting and subjects growth to dry and hot conditions. Planting soybean after a hay crop of wheat investigated to determine the feasibility of the system as a source of livestock feeds and N uptake by both crops. Twelve treatment com-112 kg N ha(-1)) and six summer management treatments (fallow: conventional and no-till; soybean: grazed, cut for hay, green manure, and mulch) were arranged in strips across four replications. Soybean biomass ranged from 1.35 to from 129 to 220 g kg(-1) resulting in a 3-yr average uptake of 44 kg ha(-1). Within each N fertilizer level, average wheat forage yields were not different, but yield increased 29% with N fertilizer and crude protein was inversely related to yield.,Double-cropped soybean failed to offer any yield-enhancing N benefit to wheat or enhance soil N and C content after 3 yr, even when used. as a green manure. Unless a producer is willing to accept the low productivity of soybean as a double crop with wheat, the feasibility of this dryland double-crop forage system is limited.