【摘要】 <正> 由于土壤供氮、水稻需氮、施肥补氮三者之间的平衡协调关系,对水稻的良好生育及高产稳产有重要影响,为此研究三者相互关系的演变规律,可为制订“因土施肥”最佳方案提供重要的基础资料。考虑到浙江省代表性的耕作制度系以双季稻为主的复种形式,更多还原

【Abstract】 Field trials and micro-plot experiments using ¹⁵N-labelled ammounium sulfate were conducted on a silty clay paddy soil developed on alluvial deposits of the Hangzhou Bay. The experiments with same design for the early rice and late rice were laid out separately in the same field for comparative investigation. The results obtained are summarized as follows: （1）. The A-value of the soil and the amount of soil N assimilated by the late rice were considerably higher than that of the early rice, which may mainly be due to the difference in temperature regime between the two growing seasons. The amount of N taken up by the late rice was 3.66—4.18% of the total N content in the plowed layer, and was only 2.69—3.21% for the early rice. Correspondingly, the grain yield of the late rice in the control plot was much higher than that of the early rice. （2）. Soil N was the predominant source of the total N accumulated in either early rice or late rice. In the treatments of organic manure and chemical fertilzer, the percentage of soil-derived N in the total assimilated N of the double-cropping rice ranged from 48.6—81.4%, while the fertilizer-N and manure-N were 14.3—40.3% and 11.1—19.6% respectively. （3）. The percentage of soil-derived N in the total N accumulation in different organs tended to decrease in the order of roots, shoots and panicles, and the reverse was true for the fertilizer-N. （4）. Under the same method of application of nitrogen fertilizer, there was no significant difference in N recovery from ¹⁵N-labelled ammounium. sulfate by early rice or late rice, their recovery percentages were 28.8—35.3% and 28.3—31.2% respectively. However, the efficiency of the fertilizer on increasing the grain yield of early rice was much lower than that of late rice, this may be due to the different soil N supplying capacity in different growing seasons. Around 65% of the assimilated fertilizer-N was distributed in panicles which might be related to the higher efficiency of nitrogen fertilizer applied at th anicle formation stage. （5）. Under the same method and rate of application of pig manure, the N recovery by late rice was higher than that by early rice. And the highest grain yield of early rice and late rice was obtained in the treatment of the application of pig manure in combination with ammounium sulfate, which may imply the consistency of nitrogen supplying status in the soil of this treatment with the demand of the rice.更多还原