冻融交替对农田棕壤氮素转化过程的调控效应

Regulation Effects of Freezing-Thawing Cycle on Farmland Brown Soil Nitrogen Transformation Process

通过室内培养模拟试验,研究了农田棕壤可溶性氮(可溶性无机氮,DIN;可溶性有机氮,DON;可溶性全氮,DTN)含量、微生物生物量氮(MBN)含量和净氮矿化速率(NNMR)对不同冻融温度和冻融频数的响应。结果表明:冻结温度和冻融频数是影响农田棕壤氮素转化过程的主要因子。随着冻结温度降低,土壤NO3–-N、NH4+-N、DIN、DON、DTN和NNMR均显著增加,而MBN先降低后增加。随着冻融频数增加,土壤NO3–-N、NH4+-N、DIN和DTN均显著增加,这与NNMR的变化趋势正好相反;MBN则呈现降低–增加–降低的变化趋势,这与DON的变化正好相反。可见,冻融交替显著促进非生长季农田棕壤的氮素转化,增加土壤无机氮含量,提高土壤供氮能力。

With a laboratory simulation experiment, the responses of soil dissolved nitrogen （Dissolved inorganic nitrogen, DIN; Dissolved organic nitrogen, DON; Dissolved total nitrogen, DTN） content, microbial biomass nitrogen （MBN） content and net nitrogen mineralization rate （NNMR） to different freezing-thawing temperatures and freezing-thawing frequencies were studied in a farmland brown soil. The results showed that freezing temperature and freezing-thawing frequency were the major factors affecting N transformation process of farmland brown soil. With freezing temperature decreasing, NO3--N, NH4＋-N, DIN, DON, DTN and NNMR all significantly increased, but MBN first decreased then increased. With freezing-thawing frequency increasing, NO^-N, NH4＋-N, DIN and DTN all significantly increased being contrary to the changes of NNMR, and MBN showed a trend of decrease-increase-decrease being contrary to the changes of DON. Therefore, it was preliminarily concluded that freezing-thawing cycle significantly promoted N transformation of farmland brown soil during no growth season, and further increased soil DIN content and soil N supply capacity.