Crop sequence and in-season nitrogen (N) application effects on organic winter wheat (Triticum aestivum L.) yield and quality

摘要

The objective of this study was to determine an optimum combination of N inputs for dryland organic winter wheat (Triticum aestivum L.) (WW). Trials were conducted on separate fields near Concord, Nebraska in 2008-2009 and 2010-2011. WW followed previous crops of alfalfa (Medicago sativa L.)/corn (Zea mays L.) and alfalfa/alfalfa. Cattle manure was applied at three rates (providing approximately 0, 58, and 112 kg ha(-1) predicted plant available N [0, base, and double rates]), in either fall (autumn) or spring. An organicapproved foliar N was applied at three rates (0, 11, and 22 kg ha(-1) N) in late spring (flag leaf stage). In Trial I, yield and N uptake were greater for fall (autumn) manure (4.0 Mg ha(-1) and 82.9 kg N ha-1) than for spring manure (3.5 Mg ha(-1) and 76 kg N ha(-1)). In Trial I, grain protein concentration was slightly improved (similar to 2%) by both rates of foliar N and the double rate of spring manure, and slightly decreased (similar to 2%) by both rates of fall manure. In Trial II no treatment had a clear effect on WW yield, grain protein concentration, or N uptake. In both trials the mean grain yield was 3.7 Mg ha(-1) and protein concentration was above 130 g kg-1, which exceeded the requirement for bread flour. It was concluded that N was not limiting in this system; the alfalfa provided sufficient fertility for WW in both the alfalfa/corn/WW and alfalfa/alfalfa/WW crop sequences. The results indicated that livestock manure may be more effectively used for other phases of the rotation than for WW.