长期施肥对玉米生育期土壤微生物量碳氮及酶活性的影响

以小麦-玉米轮作长期肥料定位试验为平台,探讨不同养分管理对玉米生育期塿土微生物量碳、氮和酶活性动态变化的影响。试验包括6个处理,分别为不施肥(CK)、单施氮肥(N)、氮磷配合(NP)、氮磷钾配合(NPK)、NPK+秸秆(SNPK)以及有机肥+NPK(MNPK)。结果表明玉米生育期土壤微生物量碳、氮变化显著。不同施肥管理下土壤微生物量碳、氮的高低显著性分别为MNPK>SNPK、NP、NPK>N、CK。玉米生育期内土壤酶活性也变化显著,蔗糖酶、脲酶和纤维素酶在玉米抽雄期达到活性高峰,而磷酸酶在玉米拔节期出现活性高峰。不同施肥管理对土壤酶活性的影响总体表现为MNPK处理最高,其次为SNPK处理,再次为NPK和NP处理,N和CK处理最低。不同施肥处理间土壤微生物量碳、氮以及酶活性与土壤有机碳、全氮、速效磷水平密切相关。塿土长期施用氮磷或氮磷钾化肥可以提高土壤微生物量碳、氮以及酶活性。一季作物秸秆还田配合氮磷钾化肥与氮磷钾相比有提高土壤微生物量碳、氮以及酶活性的趋势。在等氮量下,有机肥配合化肥与其他施肥模式相比,均显著提升土壤化学肥力因素、微生物量碳氮和酶活性。因此,塿土上建议进行有机无机肥配合以提高土壤肥力,保持土壤生物健康。

Effects of long-term fertilization on soil microbial biomass carbon and nitrogen and enzyme activities during maize growing season

This study was designed to examine the effects of continuous fertilization, straw incorporation, and manuring on the soil microbial biomass and activities of enzymes by a long-term fertilizer field trial with winter wheat and summer maize rotation system under temperate conditions in a loess soil in Shaanxi of China. Treatments at the site included application of recommended doses of nitrogen (N), nitrogen and phosphorus (NP), nitrogen, phosphorus and potassium (NPK), wheat/maize straw (S) with NPK (SNPK), dairy manure (M) with NPK (MNPK) and un-amended control (CK), totally six treatments. The results showed that soil microbial biomass carbon and nitrogen changed significantly during maize growing season. The effects of fertilization regimes on soil microbial biomass carbon and nitrogen can be arranged (based on statistical significance) in the following orders: MNPK > SNPK, NP, NPK > N, CK. Soil enzyme activities also significantly changed with maize development stage. Invertse, urease and cellulase activities reached the peak at the silk stage, but alkaline phosphatase activities was the highest at the jonting stage. The effects of fertilization regimes on soil enzyme activity generally followed the order: MNPK > SNPK > NPK, NP > N, CK. The difference in soil microbial biomass carbon, nitrogen and enzyme activity was related to the levels of organic carbon, total nitrogen and Olsen P in soils. Overall, long-term application of NP or NPK could significantly increase soil microbial biomass carbon, nitrogen and enzyme activity relative to CK. Compared with NPK, SNPK treated soil had a tendency to increase microbial biomass and enzyme activity. At the same N application rate, manure combined with chemical fertilizer significantly enhanced soil chemical and biochemical fertility compared with the other fertilization regimes. It is, therefore, recommended that NP application combined with crop straw could be a suitable way in the loess soil in order to improve soil fertility and maintain land productivity if organic manure were not applicable.