水稻的氮素营养問題——Ⅰ.土壤氮素供应强度及其持續时間对水稻器官协調生长的影响

The present paper deals with the influence of the intensity and its persistence of nitrogen supply to the formation and development of the organs of rice plant and also with the resulting physiological feature of these influences. Pot culture experiments with paddy soils were conducted in open field. Organic manure and ammonium sulphate were applied at different stages of growth, i.e. tillering, internode elongating and panicle differentiating stage. The results are summarized as follows:1. Experiments revealed that various organs of rice plant gave different responses to the status of nitrogen supply, and to the same organs, their responses of nitrogen varies at different stages of growth. At the tillering stage, a strongly intensified and less persistent supply of nitrogen, as in the case of ammonium sulphate, promoted the assimilation of dry matter in leaf blade, and consequently enlarged the leaf areas. Such an effect on the leaf blade, however, terminated after the internode elongating stage, and more accumulation of dry matter was found in the stems. Top dressing of manures, pertinently after the internode elongating stage, gave a moderate but persistent supply of nitrogen at that time and resulted the formation of large and healthy ears. Under theexperimental condition, such treatments have been proved favourable to the growth and yield of rice.2. The influence on the growth of the organs, as resulted by changing the status of nitrogen supply, is mainly induced by the rate of accumulation and translocation of nitrogen in plant. A strongly intensified, but less persistent, nitrogen supply accelerates the rate of translocation of nitrogenous materials, while a less intensified but rather persistent supply of nitrogen retains more nitrogenous materials in leaf blade.3. It is evidently that the demand of nitrogen supplying status of rice plant differs at different growing stages. Under the experimental condition, high yields of rice crops were attained by a slower but persistent rate of nitrogen suppy in the tillering stage; a faster but less persistent rate in the internode elongating stage and also a moderate but persistent rate in the penicle differentiating stage. Since property of soil nitrogen varies in different soil type, the regulation of nitrogen supplying status by fertilization should be different in cach cases.