麦秸与氮肥配施对水稻根际区土壤微生物量碳氮的影响

Effects of wheat straw and nitrogen fertilizer application on the soil microbial biomass carbon and nitrogen in the rhizosphere of rice

土壤微生物生物量碳氮(SMBC、SMBN)是表征土壤肥力高低及变化的关键因子。水稻根际是水稻-土壤-微生物相互作用的场所,根际微生物作为根际生态的重要组成部分,是土壤有机质和养分转化的动力。本试验针对长江中下游典型水稻-小麦轮作区水稻非根际和根际区土壤SMBC和SMBN对麦秸还田与氮肥配施的响应规律开展研究。基于盆栽模拟试验,采用根际袋法研究了不施加秸秆+不施加氮肥(CK)、麦秸直接还田(SN0)、麦秸与低量氮肥配施(SN1)、麦秸与高量氮肥配施(SN2)4种模式下,两种类型土壤(高砂土和黄泥土)水稻成熟期非根际和根际区SMBC和SMBN含量的变化。结果表明:与CK相比,SN0处理下高砂土根际和非根际SMBC含量分别显著提高40.3%和48.1%,而黄泥土根际和非根际区SMBC分别显著提高95.7%和75.4%。与SMBC不同,与CK相比,SN0处理下高砂土根际SMBN含量变化不显著,非根际显著降低19.9%;而黄泥土根际和非根际土SMBN含量分别显著降低19.5%和49.0%。与SN0相比,低量氮肥施用(SN1)显著提高了高砂土根际区和黄泥土非根际区SMBC含量,提高比例约5.1%和11.1%,同时SN1处理也显著提高了两种类型土壤根际和非根际SMBN含量,其中高砂土提高17.3%和9.8%,黄泥土提高36.1%和68.9%;随着施氮量增加,与SN0相比,高量氮肥施用(SN2)显著提高两种类型土壤根际和非根际区SMBC和SMBN含量,其中高砂土提高8.58%和13.5%,黄泥土提高25.6%和232.9%。综合分析认为,无论氮肥施用量高低,秸秆还田配施氮肥都可以有效提高非根际和根际区SMBC和SMBN含量,从而提升土壤养分有效性。因此,秸秆还田配施氮肥对于提高长江中下游稻麦轮作区土壤肥力和促进作物生长具有重要意义。

Soil microbial biomass carbon and nitrogen(SMBC and SMBN,respectively)are key factors that characterize soil fertility and its’change.The rhizosphere is a hotspot of microbial interactions in rice fields.Rhizosphere microbiota are important for rhizosphere ecology and are the impetus of soil organic matter and nutrient transformation.This study investigated bulk and rhizosphere SMBC and SMBN in paddy soils in response to wheat straw addition and different amounts of nitrogen fertilizer application in the typical rice and wheat rotation areas of the middle and lower reaches of the Yangtze River.There were four treatments(in triplicate):no straw or nitrogen fertilizer(CK),straw addition(SN0),straw and low nitrogen fertilizer addition(SN1),and straw and high nitrogen fertilizer addition(SN2).The results showed that,compared to CK,the SMBC contents in the SN0 rhizosphere and bulk of high sandy soil increased by 40.3%and 48.1%,respectively,while those in yellow mud soil increased by 95.7%and 75.4%,respectively.The SMBN contents in the rhizosphere of high sandy soil did not change significantly,but decreased by 19.9%in bulk soil.The SMBN contents in the rhizosphere and bulk of SN0-treated yellow mud soil decreased by 19.5%and 49.0%,respectively.Low nitrogen fertilizer application significantly increased the SMBC content in the rhizosphere of sandy soil and the bulk of yellow mud soil and increased the SMBN content in the rhizosphere and bulk of both soils.With increased nitrogen fertilizer application,SMBC and SMBN contents in the rhizosphere and bulk of both soils significantly increased.Compared with SN0,the SMBC content in the rhizosphere of SN1 in sandy soil increased by 5.1%,that in bulk decreased by 12.9%,and that in the bulk of yellow mud soil increased by 11.1%.There was no significant change in SMBC content in the rhizosphere of yellow mud soil.SN1 treatment led to an increase in the SMBN contents of the rhizosphere and bulk of sandy soil by 17.3%and 9.8%,respectively,and an increase in the SMBN contents of the rhizosphere and bulk of yellow mud by 36.1%and 68.9%,respectively.SN2 treatment led to an increase in the SMBC content in the sandy soil rhizosphere and bulk by 8.6%and 39.3%,respectively,and by 34.58%and 3.05%in yellow mud,respectively,over those of SN0.For the SN2 treatment,sandy soil rhizosphere and bulk SMBN increased by 27.0%and 13.5%,respectively,and they increased by 25.6%and 232.9%,respectively,in yellow mud soil,compared with SN0.These comprehensive analyses show that nitrogen fertilizer addition can increase the SMBC and SMBN contents in bulk and rhizosphere soils,thereby improving soil nutrient availability.Straw returning with nitrogen fertilizer greatly improves soil fertility and promotes crop growth in the rice-wheat rotation areas of the middle and lower reaches of the Yangtze River.