Effect of different rates of nitrogenous fertilizers and granulometric ckomposition of soil on symbiosis activity and plant productivity of alfalfa and red clover

摘要

The starting rate of nitrogen (15N) did not effect plant productivity, high rate (100N) suppressed formation of nodules before the beginning of alfalfa flowering. III the experiment with red clover suppression of symbiosis was the stronger, the heavier was soil texture; the weight of nodules on sandy loam soil was 5 times lower than that in control, on medium-textured loam - 7 times lower, on heavy loam-- 10 times lower, and on clay soil- 12 times lower; nitrogenase activity on sandy loam soil and on medium-textured loam is 5--7 times lower, and on clay soil -- 12.5 times lower. The highest dry weight of clover was on medium-textured loam in variant with 15N, the lowest one -- on heavy clay soils.