温度和湿度对紫花苜蓿土壤氮矿化的影响

为确定温度和水分对土壤氮矿化特征的影响,以取自甘肃庆阳黄土高原4年龄(4a)和8年龄(8a)紫花苜蓿草地0~10cm土壤为对象,在不同的温度(5,15和25℃)和水分(30%,50%和70%田间持水量)组合下进行了室内培养。结果表明温度是影响黄土高原紫花苜蓿草地土壤净氮矿化速率的主效因素,培养14d后净硝化率和净矿化率最大值均出现在25℃/70FC下,分别为0.481μg/(g·d)(4a)和0.942μg/(g·d)(8a),0.293μg/(g·d)(4a)和0.632μg/(g·d)(8a);在5℃/30FC下4a土壤的净氮固持率最大,为0.232μg/(g·d),8a土壤则在5℃/70FC下净氮固持率最大,为0.127μg/(g·d);8a苜蓿土壤培养后微生物碳含量显著高于4a苜蓿土壤,在15℃/50FC的组合下8a土壤是4a的1.44倍。土壤有机质含量不同是导致2个年龄苜蓿土壤净硝化率、净矿化率和微生物生物量碳差异的主要原因。

Effects of temperature and moisture on soil nitrogen mineralization of lucerne stands

The effects of temperature and moisture on nitrogen mineralization in the 0-10 cm soil layer from four years (4 a) and eight years(8 a) old lucerne stands in the Loess Plateau were determined by an incubation experiment with combinations of three temperature levels (5℃, 15℃, and 25℃) and three moistures levels (30%, 50%, and 70% of field capacity). Temperature was the dominant factor affecting net mineralization in the 0-10 cm soil layer from lucerne stands in the Loess Plateau. The highest net nitrification rates were 0.481 μg/(g·d)(4 a), 0.942 μg/(g·d)(8 a) with net mineralization rates of 0.293 μg/(g·d)(4 a), 0.632 μg/(g·d)(8 a), which were in the 25℃/70FC treatment after 14 days incubation. The highest nitrogen immobilization rate (0.232 μg/g·d) in soil from 4 a lucerne stands was in the 5℃/30FC treatment while it was 0.127 μg/(g·d) in the 5℃/70FC treatment for the 8 a stands. Microbial biomass carbon content in the 0-10 cm soil layer from 8 a lucerne stands was 1.44 times higher than that in the 4 a stands under 25℃/70FC condition. The differences of nitrogen mineralization rate and organic microbial C between two ages of lucerne soil are due to the difference of soil organic C content from the two soils.