长期棉花连作对北疆棉区土壤生物活性与酶学性状的影响

以长期连作棉田为研究对象,通过对5-15年连作棉田土壤理化性质和生物学性状的测定,揭示北疆长期连作对土壤主要肥力性质、土壤酶活性、微生物量碳氮以及土壤呼吸的影响。结果表明：长期棉花（Gossypium spp）连作对土壤肥力性状影响显著,表层土壤（0-20cm）肥力明显高于亚表层（20-40cm）。长期棉花连作对土壤酶活性、微生物量碳氮、土壤呼吸等生物活性有显著影响,脲酶、碱性磷酸酶、β-葡萄糖苷酶、纤维素酶和多酚氧化酶均随棉花连作年限增加而下降,棉花/苜蓿（Medicago sativa Linn）轮作（CtR-AR）处理各酶酶活性均高于棉花连作处理。微生物量碳（MBC）随棉花连作年限逐渐下降,而微生物量氮（MBN）随不同棉花连作年限并无一致性变化。不同棉花连作年限处理之间的呼吸商（q（CO2））有很大的差异,15年棉花连作非病区（CtN15）土壤呼吸商最高为19.00g？mg-1？h-1,CtR-AR处理的呼吸商最低为13.64g？mg-1？h-1。土壤微生物商随棉花连作年限延长呈现下降趋势,CtN15处理出现最低值,为0.81%。随棉花连作年限增加,土壤微生物活性降低,不利于土壤健康持续利用。

Effects of long-term cotton monocropping on soil biological characteristics and enzyme activities in Northern Xinjiang

The objective of the present paper is to investigate the effects of long-term cotton monocropping on soil nutrients status and soil biological characteristics in the oasis cropland of northern Xinjiang.Biological characteristics tested included soil enzyme activities,microbial biomass C（MBC）,microbial biomass N（MBN）and soil respiration as well.Long-term cotton monocropping significantly influenced soil available N,available P and soil available K as well,and caused soil available K content to decrease sharply,especially in top-surface soil.Furthermore,soil nutritional status of N,P,and K content were much higher in top-surface layer（0-20 cm）than in subsurface layer（20-40 cm）.Soil pH value was significantly higher in subsurface layer than in top-surface layer.Long-term cotton monocropping also significantly influenced soil biological characteristics including main enzymes activities,MBC,MBN and soil respiration.Soil enzymes activities were substantially higher in the treatment with alfalfa-maize rotation（CTR-AR）.The activities of urease,alkaline phosphomonoesterases,β-glucosidase,cellulase and polyphenol oxidase were signifi-cantly decreased with prolonging of cotton monocropping（5-10-15years）.MBC content decreased with prolonging of cotton monocropping（5-15 years）but no consistent effect of cotton monocropping on MBN content was found.MBC/MBN ratio was higher in cotton wilting plot than in non-wilting plot with lowest value of 4.72 observed in cotton monocropping for 15 years（CTN15）.With prolonging of cotton monocropping,the accumulative values of soil respiration were decreased during incubation time（120 hour）.The soil respiration quotient varied significantly among different durations of cotton monocropping.Soil respiration quotient（q（CO2））was highest in cotton monocropping for 15 years（CTN15）and was lowest in rotation with alfalfa following cotton monocropping for 5 years（CtR-AR）.The soil microbial quotient as well as the soil microbial activities decreased with prolonging of continuous cotton monocropping.Therefore,long-term cotton monocropping has negative effects on soil biological activity,and is not a good cultivation model for sustainable agriculture in Northern Xinjiang.