不同施肥处理对玉米秸秆碳氮比及其矿化特性的影响

Effects of fertilization on carbon/nitrogen ratio of maize straw and its mineralization in soil

以两个长期定位试验不同施肥处理玉米秸秆为对象,采用室内培养试验研究了其碳、氮养分在土壤中的矿化特性.结果表明:与未施肥处理相比,施用化肥(NPK)或化肥与有机肥配施(MNPK)处理明显增加了玉米秸秆的氮素含量,降低了其C/N.不同处理秸秆碳、氮矿化量和被微生物固持的碳、氮量因培养时期不同而异,NPK、MNPK和240kg N·hm-2处理秸秆在培养期间碳的矿化率显著高于相应不施肥处理;60d培养期结束后,NPK处理秸秆的有机碳矿化量最大,占加入总有机碳的13.24%.各施肥处理玉米秸秆施入土壤后引起的土壤矿质氮固持量均较不施肥秸秆低,其中MNPK处理最低.施用秸秆增加了土壤微生物的代谢熵(qCO2),但不同处理间qCO2的差异较小;各处理土壤微生物生物量碳、氮含量因培养时期不同而异.因此,生产中利用秸秆时应考虑不同施肥处理秸秆养分含量的差异.

Maize straws were collected from different treatments of two long-term fertilization studies, their carbon （C） / nitrogen （N） ratios were determined, and their C and N mineralization rates in soil were compared in an aerobic incubation test. The results showed that comparing with no fertilization, applying chemical fertilizers （NPK） or chemical fertilizers plus manure （MNPK） increased the N content and decreased the C/N ratio of maize straw. The amounts of mineralized and immobilized C and N of the straws from different fertilization treatments differed with incubation time. The straws from treatments NPK, MNPK, and N240 had significantly higher C mineralization rates than that from the treatment without fertilization. After incubation for 60 days, the straw from treatment NPK had the highest C mineralization rate （ 13.24% of added organic C）, and the immobilized N from the straws of fertilized plots, especially of MNPK plot, was lesser, compared to unfertilized plots. Adding maize straw into soil increased the metabolic quotient （qCO2） of soil microorganisms, but the difference among the treatments was not significant. During incubation, the amounts of soil microbial biomass C and N from different treatments differed with time. Therefore, in agricultural practices, the differences in the nutrient contents of straw due to different fertilization should be considered when the straw was to be added into soil.