麦秸和氮肥对大豆结瘤固氮和植株氮形态的影响

利用高C/N比麦秸的“氮因子效应”,探讨麦秸和氮肥配合施用,以达到调节土壤氮素转化形态和大豆对土壤(肥料)氮源和根瘤氮源同化的协调。设计了施麦秸和无麦秸均配以等量氮的两级试验,于各生育期中测定大豆结瘤量和固氮酶活性,同时进行植株水溶质中氮形态(硝态、酰胺和酰脲态)的分析和土壤速效态氮的测定。结果表明,由于麦秸在旺盛腐解的过程中固定了土壤中的有效态氮,从而缓解了播种时施入尿素氮对大豆结瘤和固氮的抑制,并在结荚期又重新释放所固定的氮供籽实发育所需,从而使大豆生育期中对两种氮源同化得以协调,故获得麦秸+氮(10毫克/100克干土)比单施麦秸处理增产大豆11.0％,比单施等量氮增产43.8％的显著效果。

THE EFFECTS OF WHEAT STRAW AND FERTILIZER-N ON NODULATION,N 2-FIXATION AND SOLUBLE NITROGEN FORMS OF SOYBEAN PLANTS

An over-application of fertilizer-N on soybean will inhibit its nodulation and N2-fixation and then result in a decrease of output. Theexperiment on sandy loam told that the amount of Urea-N of above5 mg on every 100g of soil of dry weight would obviously inhibitsoybean's nodulation and N2-fixation at its early staged.when a wheat straw of higher C/N was applied based on the "N-fact or effects" to control the N-forms during manure-transforsmation in soil,it was proved that there was not evident inhibition on nodulation or N2 fixation unless the amount of Urea-N used was higher that 10mg on every 100g of soil of dry weight,and at the same time it was foundthat in soybean plant the amourt of nitrate nitrogen decreased and that of vreides nitrogen increased which made the inhibition of excessive inorganic nitrogen by over application of urea in early and middle stages on nodulation and N2-fixation relaxed. The nitrogen fixed by a wheat straw could be used in the period of formation and development of grains in-which soil nitrogen was inadequated, because this section of nitrogen released before this period.It was also proved that the treatment of a wheat straw added with urea-N of 10mg of 100g of soil of dry weight resulted in a increase of grain output by 11% campared with ck that was only treated with a wheat straw, and by 43.8% compared with the situation without any treatment.