地表覆盖对旱作玉米农田土壤氮素矿化的影响
Effect of surface mulching on soil nitrogen mineralization in dry farmland

采用树脂芯方法研究了黄土高原旱作农田秸秆覆盖和地膜覆盖对0~20 cm土层土壤氮素净矿化的影响。结果表明：不覆盖（对照）、秸秆覆盖和地膜覆盖3个处理在玉米生育前期（播前~六叶期）表现为土壤氮素净固持，净固持量分别为53.7、52.7、56.7 mg·kg-1，六叶期之后表现为氮素净矿化，净矿化量分别为26.3、31.8、13.7 mg·kg-1；综合两个生育阶段从全生育期看，3个处理土壤氮素矿化均表现为净固持，矿质氮净固持量分别为27.4，20.9 mg·kg-1和43.0 mg·kg-1。从不同覆盖处理看，秸秆覆盖会显著增加土壤氮素净矿化量和氮净矿化速率，地膜覆盖虽然有利于增加土壤温度和水分含量，但并没有显著改变土壤氮净矿化量和氮净矿化速率，这一结果间接证明地膜覆盖并不会显著影响土壤有机质矿化。研究还发现，在本试验条件下当田间土壤温度在22℃~25℃、土壤含水量在20%左右时有利于土壤氮素矿化，该条件下净矿化速率较高，且干湿交替有利于矿化。
The effect of straw mulching and plastic mulch on soil net N mineralization in dryland croplands of Loess Plateau was studied by resin core technique method. The results showed the net immobilization of the soil mineral N with three treatments of bare ploughing , straw mulching and plastic mulching was 27.4, 20.9, 43.1 mg·kg-1 in the first two periods of maize (PT~V6 stages ). And the net mineralization was 26.3, 31.8 mg·kg-1 and 13.7 mg·kg-1 at the rest of maize stages. The three treatments of 0~20 cm soil layer showed a net soil retention combined the two stages and the net immobilization were 27.4, 20.9, 43.0 mg·kg-1 at all culture stages. In addition, straw mulching significantly increased the soil net N mineralization and net N mineralization rate and plastic film mulching increased soil surface temperature and water content, but it did not influence the net N mineralization and net N mineralization rate, implying that plastic mulching should not affect soil organic matter mineralization. The study also revealed that when the soil temperature was between 22℃ and 25℃ and the soil moisture content was about 20%, the soil nitrogen mineralization rate reached a maximum, indicating the promoting effect of dry\|wet alternation on mineralization.