不同耕作措施对黄土高原区域大豆根际土壤微生物量、酶活性和养分的影响

选择免耕(NT)、秸秆覆盖(SM)、地膜覆盖(PM)和起垄覆膜(RPM)4种保护性耕作措施为研究对象,以传统耕作(CT)为对照,通过测定根际土与非根际土的微生物量、酶活性及养分质量分数,研究不同耕作措施对不同微域土壤碳氮质量分数及微生物特征的影响。结果表明:(1)土壤微生物量和酶活性均呈现根际非根际的规律,且与对照相比,各保护性耕作处理均有提高。RPM和SM处理的根际土壤微生物碳质量分数分别提高51.78%和24.62%,微生物量氮的富集率则分别达到48.13%、46.04%;NT、SM、RPM处理的蔗糖酶活性较CT处理分别提高了113.35%、113.10%、74.75%(P0.05);(2)4种不同保护性耕作措施的土壤养分质量分数均有提高,其中RPM和SM与CT相比差异显著,效果更加明显,并且有效降低了土壤pH。根际土壤的全氮、铵态氮、硝态氮和有机碳质量分数均高于非根际土壤,各处理均表现出一定程度的富集,其中全氮和硝态氮的富集率以RPM处理最高,分别为16.9%和45.06%。(3)根际土壤的养分质量分数、酶活性以及微生物生物量之间的相关性程度高于非根际土壤,根际土壤中微生物量与酶活性之间存在着显著的正相关性,过氧化氢酶和蔗糖酶这2种酶均与养分间显著相关,而脲酶则无显著相关。综上,在黄土高原区域内,秸秆还田和起垄覆膜更有利于改良土壤理化性状和提高土壤生物学特性。

Effects of Different Tillage Measures on Soil Microbial Biomass,Enzyme Activities and Nutrients in Rhizosphere Soil of the Loess Plateau

To explore the effect of tillage measures on carbon and nitrogen content, and microbial characteristics in rhizosphere soil, four conservation tillage measures, including no-tillage (NT), straw mulching (SM), plastic mulching (PM), and ridging and plastic mulching (RPM), were selected as subjects in this study, while conventional tillage (CT) was used as a control. We determined the microbial biomass, enzyme activity and nutrient content in rhizosphere and non-rhizosphere soil. The results showed: (1) The rhizosphere soil had higher microbial biomass and soil enzyme activity than non-rhizosphere soil, and conservation tillage treatments had the same tendency compared with the control. In rhizosphere soil, the mass fraction of microbial biomass organic carbon increased by 51.78% in RPM and 24.62% in SM, and the enrichment rate of microbial biomass nitrogen reached 48.13% in RPM and 46.04% in SM; The enzyme activity of rhizosphere soil in NT, SM, RPM increased by 113.35%, 113.10%, and 74.75%, respectively(P<0.05). (2) The soil nutrient mass fraction increased in four conservation tillage managements. Especially, RPM and SM had significantly higher nutrient mass fraction than the control CT, and the soil pH was effectively reduced. The total nitrogen, ammonium nitrogen, nitrate nitrogen and organic carbon in the rhizosphere soil were higher than those in the non-rhizosphere soil, and each treatment showed enrichment to a certain extent. The RPM had the highest enrichment rate, 16.9% for total nitrogen and 45.06% for nitrate nitrogen mass fraction, respectively. (3) The correlation between the indexes of rhizosphere soil was higher than that of non-rhizosphere soil. There was a significant positive correlation between microbial biomass and enzyme activity in rhizosphere soil. Both catalase and sucrase were correlated with soil nutrients. with the exception of urease. In summary, in the Loess Plateau region, ridging and plastic mulching is conducive to improving soil physical and chemical properties and improving soil biological characteristics.