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Agronomic Feasibility of a Continuous Double Crop of Winter Wheat and Soybean Forage in the Southern Great Plains
Author(s) -
MacKown Charles T.,
Heitholt James J.,
Rao Srinivas C.
Publication year - 2007
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2006.10.0683
Subject(s) - agronomy , sowing , forage , biology , fertilizer , hay , crop , cropping system
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.