氮磷添加对燕麦与箭筈豌豆不同种植方式草地土壤微生物-胞外酶化学计量特征的影响

土壤中氮、磷养分是饲草产量与品质提高的重要基础。氮磷添加改变了土壤养分条件并引起微生物生物量及酶活性发生变化。为探究燕麦和箭筈豌豆单播、混播草地土壤微生物特性对不同氮磷处理的响应，本试验以高寒区燕麦单播草地、箭筈豌豆单播草地及燕麦/箭筈豌豆1︰1混播草地为研究对象，设置4种不同氮磷添加处理，包括单施氮肥、单施磷肥、氮磷肥配施和不施肥，研究各处理土壤微生物生物量碳氮磷和土壤胞外酶活性及其化学计量比的变化特征。结果表明：1）单施氮、磷肥均对燕麦单播草地土壤微生物生物量产生负效应；单施磷肥和氮磷配施对箭筈豌豆单播草地土壤微生物生物量产生促进作用；单施氮肥使混播草地微生物生物量碳（SMBC）增加，而氮磷配施使其微生物生物量碳氮（SMBN）降低。2）单施氮肥增加3种草地土壤β-1,4-葡萄糖苷酶（BG）活性，单施磷肥增加3种草地土壤碱性磷酸酶（AP）活性，氮磷配施增加燕麦草地土壤N-乙酰-β-D-氨基葡萄糖苷酶（NAG）、AP酶活性，表明土壤微生物通过增加C、N、P获取酶活性以增加对短缺养分的获取。3）试验3种草地土壤SMBC︰SMBN低于全国平均值，SMBN︰SMBP高于全国平均值，且土壤N︰...

Soil nutrient and microbial activity responses to nitrogen and phosphorus addition in oats and arrowhead peas in monocrop and mixed sowings

Nitrogen and phosphorus are key nutrients for improving forage yield and quality. Nitrogen and phosphorus additions will change soil nutrient conditions and cause changes in microbial biomass and enzyme activities. This study investigated the response of soil microbial characteristics to different nitrogen and phosphorus treatments in oat and common vetch within different planting configurations. In this experiment in an alpine region， monocultures of oats （Avena sativa） or common vetch （Vicia sativa） and plots of oats mix-cropped with vetch in a 1∶1 seeding ratio were established， and four different nutrient addition treatments were applied： Nitrogen only， phosphorus only， nitrogen and phosphorus and zero added nutrients. Variation in soil microbial biomass carbon， nitrogen and phosphorus and their stoichiometric ratios， together with extracellular soil enzyme activities were the main focus of measurements. It was found that： 1） N only and P only had negative effects on soil microbial biomass in oat monocultures； P fertilizer application and combined nitrogen and phosphorus application had a positive effect on soil microbial biomass in vetch monocultures； Application of N fertilizer only resulted in increased soil microbial biomass carbon only in the mixed oat-vetch sowings， while the combined application of nitrogen and phosphorus decreased the microbial biomass carbon and microbial biomass nitrogen. 2） Added N only increased the activity of β-1，4-glucosidase （BG）， while added P only increased the activity of acid phosphatase （AP）. However， β-N-acetylglucosaminidase （NAG） and AP enzyme activities were increased in oat plots indicating that soil microorganisms can increase the nutrient acquisition ability by increasing the enzyme activities obtained by C， N and P. 3） For soils in this experiment， the soil microbial biomass （SMB） C∶N was lower than the national average， while the SMB N∶P was higher than the national average， and the soil N∶P enzyme activity ratio was greater than 1， indicating that the nitrogen availability restriction to soil microbial activity was greater than the phosphorus limitation at the test site. Therefore， in this experiment， the single application of nitrogen fertilizer inhibited the growth of soil microorganisms in the oat monoculture plots， but was beneficial to the growth of soil microorganisms in the mixed oat-vetch plots. Stoichiometric ratios indicate that microorganisms respond to changes in soil nutrient conditions by adjusting the nutrient content of the microbial biomass and the content of secreted extracellular enzymes.