Effect of Sunn Hemp and Peanut Incorporated as Green Manures on Growth and Nitrogen Uptake of the Succeeding Wheat.

Abstract

Effect of summer legumes incorporated as green manures, sunn hemp (cv. Kobutoriso) and peanut (cv. Chiba-handachi), was examined for nitrogen contribution to the succeeding wheat (cv. Norin 61). The dry weight of sunn hemp, of which the stem occupies the largest proportion, was higher than that of peanut at time of incorporation. Total nitrogen content was higher in peanut compared with sunn hemp. The amount of nitrogen fixed by each legume was estimated by the 'difference method' with non-nodulating peanut (cv. Tarapoto) as a reference crop. In peanut, 18 g N per m2 was calculated as the amount of nitrogen fixed at the late maturity stage. The percentage of nitrogen fixed to the total nitrogen was 60-70% in both legumes. On the yield and nitrogen uptake of the succeeding wheat, the peanut plot was superior to the sunn hemp plot. The percentage contribution of nitrogen accumulated by each legume to total nitrogen of the succeding wheat was 11.2% on the peanut plot and 9.4% on the sunn hemp plot. In peanut, the C-N ratio was approximately 20 at time of incorporation. In sunn hemp, it was 40, and the decomposition rate was found to be slower than that of peanut by a modified method using glass fiber filter papers. The results indicated that peanut crop contributed more nitrogen to the succeeding wheat compared with sunn hemp.