连年翻压紫云英对稻田土壤养分和微生物学特性的影响

Effect of turning over Chinese milk vetch( Astragalus sinicus L. )on soil nutrients and microbial properties in paddy fields

【目的】紫云英(Astragalus sinicus L.)是南方稻区主要的冬种绿肥作物。本研究通过紫云英-化肥配施比例不同对水稻产量、土壤养分和微生物学特性的影响探讨化肥的合理施用量,以期最大限度地减少化肥投入。【方法】紫云英—水稻长期轮作定位试验始于2009年,试验设5个处理,对照(不施紫云英和化肥,CK),全量化肥(100%F),紫云英18000 kg/hm2+全量化肥(MV+100%F),紫云英18000 kg/hm2+60%化肥(MV+60%F),单施紫云英18000 kg/hm2(MV)。每个处理3次重复,小区面积15 m2。2012年10月份于水稻收获后采集土壤样品,测定水稻产量、土壤养分、微生物量碳氮、可培养微生物数量和土壤酶活性。【结果】1)与单施化肥相比,在翻压紫云英的条件下,化肥减量40%,对水稻产量没有影响,紫云英可替代部分化肥,达到减少化肥用量,保持产量的目的。2)不同施肥制度对土壤养分含量有一定的影响。与100%F处理相比,化肥结合翻压紫云英和单施紫云英处理能够提高土壤有机质和全氮含量;施肥模式对土壤全磷和全钾含量无显著影响。与100%F处理相比,MV+100%F处理土壤的有效氮含量显著提高;与100%F处理相比,MV和MV+60%F处理的速效磷含量显著减少;100%F处理的土壤速效钾含量最高。不同施肥模式对土壤pH无显著影响。3)100%F、MV+100%F处理的细菌数量较CK分别增加了102.3%、138.8%,而MV+60%F和MV处理与CK无显著差异,说明细菌对土壤养分有很强的依赖性。单施化肥或单施紫云英都不利于真菌和放线菌的生长,而化肥与翻压紫云英配合能显著提高其数量。4)相关性分析可以看出,细菌数量与土壤有效氮、速效钾、速效磷含量呈显著或极显著正相关;真菌和放线菌的数量与铵态氮含量呈显著或极显著正相关,说明氮、磷、钾养分对土壤细菌数量的影响较大,而真菌和放线菌的数量主要受NH+4-N的影响。5)与100%F处理相比,化肥配施紫云英可以显著提高微生物生物碳量(SMBC)和微生物生物氮量(SMBN)的含量。6)除了过氧化氢酶,转化酶、脲酶和酸性磷酸酶总体表现为紫云英与化肥混施大于单施化肥或紫云英。7)土壤酶活性、微生物生物量与土壤氮素的相关性最强。土壤转化酶、脲酶和酸性磷酸酶与水稻产量呈显著或极显著正相关,说明转化酶、脲酶和酸性磷酸酶活性的大小可作为衡量水稻产量多少的依据之一。【结论】MV+60%F处理在保证水稻产量的同时能够减少40%的化肥用量,是一种高效节能的培肥模式。单施化肥不利于土壤有机质、全氮和有效氮的积累,同时不利于微生物的生长和酶活的提高。MV+60%F培肥模式有利于改良土壤的生物学性状,值得推广并有待今后进一步观察验证。

Objectives] Chinese milk vetch ( Astragalus sinicus L.) is a major green manure planting in southern paddy fields .In this study , the effects of turning over Chinese milk vetch on crop yield , soil nutrients and microbial properties were investigated to determine the appropriate application rates of chemical fertilizers.[Methods]Rice-Chinese milk vetch ( MV) rotation Experiment Station was established in 2009.Five fertilization treatments with three replicates ( each replicate plot was 15 m2 ) were designed as control ( CK) , 100%chemical fertilizer (100%F) , 18000 kg/ha milk vetch +100% chemical fertilizer ( MV+100% F) , 18000 kg/ha milk vetch +60% chemical fertilizer ( MV +60% F ) , 18000 kg/ha milk vetch alone ( MV ) .Soil samples were collected after rice harvest in October, 2012, and crop yield, soil nutrients, soil microbial biomass carbon ( SMBC) and soil microbial biomass nitrogen ( SMBN ) , number of culturable microorganisms and soil enzyme activities were determined.[Results]1) There was no significant difference in the crop yields between the 100%F and MV+60%F treatments which demonstrated MV could substitute 40%of chemical fertilizer.2 ) Compared to the 100%F treatment, the MV+F treatments could increase the contents of soil organic matter and total nitrogen, but not those of total phosphorus and total potassium; the MV+100% F treatment could increase the content of available nitrogen;MV and MV+60%F treatments could decrease the content of available phosphorus.The 100%F treatment had the highest content of available potassium.There were no significant differences in pH values from all treatments.3) The number of bacteria in the 100% F and MV+100% F treatments were significantly higher than that in the CK treatment, but there were no significant differences between the MV+60% F, MV and CK treatments.These results imply that bacteria were obviously dependent on the soil nutrients.Chemical fertilizer with MV could increase the number of fungi and actinomyces.4 ) Correlation analysis showed that the contents of available nitrogen, available phosphorus and available potassium in soils were significantly correlated with the number of bacteria, and NH+-N content was significantly correlated with the number of fungi and actinomyces.5) In comparison with 100% F treatment, chemical fertilizer with MV treatments could increase the contents of soil microbial biomass carbon and nitrogen.6 ) Soil enzyme activities in chemical fertilizer with MV treatments were significantly higher than those in the 100% F or MV treatments.7 ) Soil enzyme activities and microbial biomass were significantly correlated with the soil nitrogen content.Invertase, urease and acidic phosphatase activities were significantly correlated with the rice yield.[Conclusions]Compared to the 100% F, the MV+60%F treatment could achieve equivalent rice yield, indicating that application of 60% fertilizer could be considered as the best fertilization model in our study.Contents of soil organic matter, total nitrogen, available nitrogen, microbial properties and enzyme activities in 100% F treatment were lower than those in chemical fertilizer with MV treatmetns.