不同水稻栽培模式下小麦秸秆腐解特征及对土壤生物学特性和养分状况的影响

Decomposition characteristics of wheat straw and effects on soil biological properties and nutrient status under different rice cultivation

采用尼龙网袋法于2007—2008年连续2a在水稻常规栽培和节水灌溉栽培模式下,研究小麦秸秆腐解特征、养分释放规律及对土壤微生物数量、酶活性和养分状况的影响。结果表明:秸秆还田后,在0—30d腐解较快,后期腐解速率逐渐变慢。90d时累计腐解率达到了48.9%—61.3%。秸秆中养分释放速率表现为K>P>N≈C。节水栽培模式下小麦秸秆还田腐解率和养分释放率均显著高于常规栽培。秸秆还田后,土壤微生物数量以及土壤脲酶、碱性磷酸酶和蔗糖酶活性均呈现"前期迅速增加,中期急剧减少,后期缓慢减少"的变化特征,而纤维素酶活性呈现"前期剧升、中期缓增、后期骤降"的变化趋势。小麦秸秆在节水栽培模式下还田土壤微生物数量和酶活性均显著高于常规栽培。适当增加秸秆用量可以提高微生物数量和酶活性,用量过高对细菌和放线菌数量有负效应。秸秆还田可显著提高土壤有机碳和养分含量。土壤有机碳、全氮、碱解氮和速效磷含量在整个试验期间均呈增加趋势。速效钾含量在秸秆还田30 d时达到最高,而后则逐渐降低。节水栽培模式下秸秆还田后土壤有机碳和养分含量的提高效应显著高于常规栽培。提高秸秆用量对土壤养分含量有显著的正效应。

The decomposition characteristics of wheat straws and their effects on soil biological properties and nutrient status under different rice cultivation were studied in the 2007 and 2008 growth seasons,respectively.Wheat straws were wrapped in net nylon bags and embedded into the soil under conventional cultivation and a water-saving cultivation model.The rate of straw decomposition was greatest within the first 30 days and then decreased until the end of the experiment.Straw decomposition under the water-saving cultivation model was faster than straw decomposition under conventional cultivation,and the wheat straw cumulative decomposition rates were 48.9%—61.3%.The sequence of nutrient release rates were KPN≈C.The effect of the cultivation model and incorporation method on N,P and C release patterns followed almost the same trend as the decomposition of straw.Soil microbial biomass increased rapidly in the early growth stage after wheat straw was returned to the field,but decreased significantly in the middle growth stage and reduced slowly in the late growth stage.Urease,alkaline phosphatase and sucrase activities in the soil followed the same pattern as the microbial biomass after straw mulching.However,cellulase activity was different in that it increased rapidly in the early growth stage,improved slowly in the middle growth stage and decreased rapidly in the late growth stage.Microbial numbers and enzyme activities under the water-saving cultivation model were significantly higher than under conventional cultivation.Increasing the amount of wheat straw could improve microbial numbers and enzyme activities,but excessive straw would have a negative effect on bacterial and actinomycete numbers. The results also showed that soil nutrient contents could be improved noticeably by returning straw to the field.After straw mulching,organic carbon,total nitrogen,alkali-hydro nitrogen,and available phosphorus contents increased throughout the whole trial period.The available potassium content was highest after 30 days of straw mulching,and then decreased gradually.Nutrient contents under the water-saving cultivation model were higher than under conventional cultivation.Increasing the amount of straw had a positive effect on soil nutrient contents.