Agronomic Feasibility of a Continuous Double Crop of Winter Wheat and Soybean Forage in the Southern Great Plains

• Published in: Crop science Vol. 47; no. 4; pp. 1652 - 1660
• Main Authors: MacKown, C.T, Heitholt, J.J, Rao, S.C
• Format: Journal Article
• Language: English
• Published: Madison, WI Crop Science Society of America 01.07.2007; American Society of Agronomy
• Subjects: Agronomy. Soil science and plant productions; Arid zones; Biological and medical sciences; Cereal crops; conventional tillage; crop rotation; crop yield; cropping systems; crude protein; double cropping; dryland farming; Environmental conditions; fallow; fertilizer rates; field crops; Forage; forage crops; forage legumes; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Glycine max; grain crops; grazing; Harvest; Hay; Livestock; Livestock feeds; Loam soils; Mineral fertilizers; nitrogen fertilizers; nitrogen fixation; no-tillage; Oklahoma; planting date; Soil erosion; Soybeans; Summer; Triticum aestivum; Winter; Winter wheat; Oklahoma; Great Plains of America; North America; Southern Great Plains; America; Monocotyledones; Cropping system; Double cropping; Glycine max; Cereal crop; Grain legume; Leguminosae; Gramineae; Dicotyledones; Angiospermae; Spermatophyta; Feasibility; Fodder crop; Triticum aestivum
• ISSN: 0011-183X; 1435-0653
• DOI: 10.2135/cropsci2006.10.0683

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 was investigated to determine the feasibility of the system as a source of livestock feeds and N uptake by both crops. Twelve treatment combinations of two wheat fertilizer N levels (0 and 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 1.90 Mg ha-1 when soybean grazing and harvest occurred at seed fill, and crude protein ranged from 129 to 220 g kg-1 resulting in a 3-yr average N 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.