Although there has been a significant amount of work done on the availability of legume-nitrogen for corn following alfalfa, several questions have arisen as to the sufficiency and availability of the legume N to wheat as a following crop. This is especially true if the wheat is planted soon after the alfalfa is killed. The synchrony of nitrogen released from legumes with crop demand for N has been a concern even with crops such as corn where N uptake can occur throughout the summer (Stute and Posner, 1995). Using mesh bags, these researchers found that 50% of the clover or vetch residue was not yet released by 1 June after spring burial. Since uptake of N by wheat may precede this time period, the residue decomposition and crop N need may be out of synchrony. Some previous work has shown that wheat following forage legumes used as green manure results in increases in grain yield and quality (Badaruddin and Meyer, 1990), but little work has been done following legume forage crops. For corn, it has been shown that once killed, forage legume stands release mineralized N sufficiently rapidly that few N responses are seen for corn following alfalfa (Kelling et al., 1992; Morris et al., 1994; Bundy and Andraski, 1994) and few differences have also been observed between fall or spring tillage on the availability of legume N (Harris and Hesterman, 1987; Kelling et al., 1992). Some experiments have also been done on the influence of tillage systems on N availability to corn following alfalfa. These results have indicated no significant difference in crop performance when comparing no-till with conventional till (Triplett et al., 1979; Levin et al., 1987), although some cases showed that conventional tillage increased the total available N somewhat more rapidly than no-till (Dow et al., 1994). This may be particularly important where wheat is the following crop.This article was posted in Uncategorized.
Soil Science Extension
University of Wisconsin Madison