秸秆全量还田对稻田土壤溶解有机碳含量和水稻产量的影响

以南粳44为供试材料，在粘土和砂土土壤中，设置麦秸秆不还田和全量还田(6000 kg·hm^-2)及3种施氮量(0、225、300 kg·hm^-2)试验，研究了麦秸秆全量还田的腐解率和有机碳释放量动态变化，及其对稻田0～45 cm土壤溶解有机碳(DOC)含量和水稻产量的影响.结果表明： 麦秸秆还田的前期(0～30 d)其腐解率和有机碳释放量最高，腐解率为35.0%(粘土)和31.7%(砂土)，有机碳释放率为34.1%(粘土)和33.1%(砂土)；30 d后两者均减小.施用氮肥可显著促进秸秆腐解和有机碳释放量，粘土中麦秸秆腐解率和有机碳释放量明显大于砂土.麦秸秆还田后土壤DOC含量逐渐增加，至25 d达最大值，粘土和砂土分别为60.18和56.62 mg·L^-1，此后逐渐减小并趋于稳定.麦秸秆还田处理15 cm处土壤DOC含量显著高于未还田处理，但两者在30和45 cm处土壤DOC含量差异不显著，说明秸秆还田主要增加了稻田0～15 cm土层DOC含量.与不施氮处理相比，施氮处理土壤DOC含量降低，2种施氮处理间差异不显著.秸秆还田减少了水稻前期分蘖发生量，显著降低了有效穗数，增加了穗粒数、结实率和千粒重，显著提高了水稻产量.

Effects of wheat-straw returning into paddy soil on dissolved organic carbon contents and rice grain yield.

A tank experiment using conventional rice cultivar Nanjing 44 as experimental material was conducted at the Experimental Farm of Yangzhou University to investigate the dynamics of wheat straw decomposition rate and the amount of carbon release in clay and sandy soils, as well as its effects on the content of dissolved organic carbon (DOC) and rice yield. The two rates of wheat straw returning were 0 and 6000 kg·hm^-2, and three N application levels were 0, 225, 300 kg·hm^-2. The results showed that, the rate of wheat straw decomposition and the amount of carbon release in clay and sandy soils were highest during the initial 30 days after wheat straw returning, and then slowed down after, which could be promoted by a higher level of nitrogen application. The rate of wheat straw decomposition and the amount of carbon release in clay soil were higher than that in sandy soil. The DOC content in soil increased gradually with wheat straw returning into paddy soil and at the twenty fifth day, and then decreased gradually to a stable value. The DOC content at the soil depth of 15 cm was significantly increased by wheat straw returning, but not at the soil depth of 30 cm and 45 cm. It was concluded that wheat straw returning increased the DOC content in the soil depth of 0-15 cm mainly. N application decreased the DOC content and there was no difference between the two N application levels. Straw returning decreased the number of tillers in the early growth period, resulted in significantly reduced panicles per unit area, but increased spikelets per panicle, filled-grain percentages, 1000-grain mass, and then enhanced grain yield.