青海高原小麦秸秆-毛叶苕子混合腐解特征

Characteristics of mixed decay of wheat straw-hairy vetch on the Qinghai plateau

【目的】研究小麦秸秆、毛叶苕子及二者混合物料在耕层土壤还田后的腐解和养分释放规律,以期为青海高原有机物料还田提供理论依据和技术指导。【方法】将毛叶苕子(G)、麦秆(S)和麦秆+毛叶苕子混合(G+S)3种有机物料自然风干后,切成2 cm长,放入尼龙网袋,埋入20 cm深土壤中自然腐解,地表撂荒。在埋入土壤后的第7、14、28、42、72、117、162天取样,测定相关指标。【结果】各处理干物质累积腐解率和养分释放率随腐解进程的推进而逐渐升高,升高趋势表现为前期快后期慢,试验结束时均表现为G>G+S>S,3种有机物料的累积腐解率分别为81.93%(G)、51.65%(S)、64.17%(G+S),碳素累积释放率分别为85.30%(G)、46.66%(S)、62.77%(G+S),氮素累积释放率分别为88.29%(G)、31.83%(S)、66.78%(G+S),磷素累积释放率分别为71.30%(G)、62.66%(S)、68.24%(G+S),钾素累积释放率分别为98.24%(G)、94.62%(S)、97.40%(G+S)。各处理的快速腐解期均为0~42天,各养分的快速释放期不同,碳是在0~7天,氮是在0~28天,磷是在0~14天,钾是在0~42天。通过双库指数衰减模型模拟发现,G、S、G+S处理易分解干物质量,分别占总质量的79.25%、53.62%、64.16%,各处理碳、氮、磷和钾的易分解比例均以G处理最高,钾的易分解比例以S处理最高。G+S处理的实测值(OBS)相较于预测值(EXP)提高了干物质量、碳、氮、磷和钾的易分解部分比例,分别提高了1.47%、6.02%、22.77%、5.41%和0.20%,并增加了碳、氮的平均周转天数,降低了磷、钾的平均周转天数。【结论】毛叶苕子、麦秆的累积腐解率分别为81.93%(G)、51.65%(S),二者混合后可达64.17%,毛叶苕子中的碳、氮、磷和钾的累积释放率高于麦秆。毛叶苕子中易分解部分的比例为79.25%,且碳、氮、磷和钾在易分解部分中的比例高于麦秆。毛叶苕子与麦秆混合后,调节了易分解部分比例以及其中的碳、氮、磷和钾含量,增加了碳、氮的平均周转天数,降低了磷、钾的平均周转天数,更有利于后茬作物对养分的利用。

【Objectives】Study the decomposition and nutrient release patterns of wheat straw and hairy vetch(Vicia sativa)seperately and both of them in farmland will provide theoretical and technical guidance for the management of organic materials returning to the field in Qinghai plateau.【Methods】The tested wheat straw and hairy vetch were naturally dried and cut into 2 cm long,single wheat straw(S),single hairy vetch(G),and wheat straw and hairy vetch together(G+S)were loaded into nylon mesh bags,and buried into 20 cm deep in soil for decomposition.At the 7,14,28,42,72,117,and 162 days of burying,sample bags were dig out for measurement of required indexes.【Results】The dry matter decay rate and nutrient release rate in all the three treatments were fast in early stage and slow in later stage,and the cumulative decomposition rates were 81.93%for G treatment,51.65%for S treatment,and 64.17%for G+S treatment.The cumulative nutrient release rate in G,S,and G+S treatments were 85.30%,46.66%and 62.77%for C;88.29%,31.83%and 66.78%for N;71.30%,62.66%and 68.24%for P;98.24%,94.62%and 97.40%for K.The rapid decay period was less than 42 days,and the rapid release period for each nutrient varied from 0-7 days for C,0-28 days for N,0-14 days for P,and 0-42 days for K.Simulation by the bi-pool exponential decay model revealed that the proportions of easily decomposed fraction in total weight in G,S and G+S treatments were about 79.25%,53.62%,and 64.16%,respectively.The proportions of easily decomposed C,N,P were all the highest in hairy vetch treatment,and K is the highest in wheat straw treatment.The G+S treatment increased the proportion of dry matter mass,C,N,P,and K in the easily decomposable fraction compared to the predicted values in all cases,increasing dry matter mass by 1.47%,C by 6.02%,N by 22.77%,P by 5.41%,and K by 0.20%,increasing the average turnover days of C and N,and decreasing the average turnover days of P and K.【Conclusions】The cumulative decomposition rate of hairy vetch and straw were 81.93%and 51.65%,and it was 64.17%for their mixtures.Therefore,hairy vetch had higher release ratio than wheat straw in dry matter,C,N,P and K.In addition,the C,N,P and K had higher proportion in the easily decomposed part of hairy vetch than in wheat straws.The mixture of hairy vetch and wheat straw adjusted the nutrient proportion in the easily decomposed parts,and increased the average turnover days of C and N but decreased those of P and K,which was favorable to the use of subsequent crops.