水稻土模拟土柱中肥料氮素的迁移转化特征

为了明确肥料氮素在模拟土柱中的迁移转化特征,通过布置室内模拟土柱试验,研究了3倍常规施肥水平下(360 mg·kg-1)水稻土中矿质氮的变化.结果表明:不同处理、不同土层间NH4+-N和NO3--N含量差异显著.不施肥对照在整个培养期间养分含量变化不大,不同土层间亦没有显著性差异.施用尿素和硫铵后,土壤NH4+-N和NO3 --N含量显著提高,尤其是0 ～ 50 mm土层内,分别达到186.0 ～2882.1 mg· kg-1和268.7 ～351.5 mg· kg-1,分别相当于对照的4.8 ～242倍和5.7～316倍,50 mm以下各土层与对照处理相似,表明肥料氮素的迁移转化主要发生在0 ～ 50 mm土层内,并且在培养的前14 d变化最大.整个培养期间不同土层内,硫铵处理不同矿质态氮含量是尿素处理的0.7 ～2.0倍,硝化率是尿素处理的0.9～1.4倍,表明硫铵在水稻土中的转化效率略高于尿素.

Translocation and transformation characteristics of fertilizer nitrogen in paddy soil: a study with simulated soil column

Aimed to understand the translocation and transformation characteristics of applied fertilizer nitrogen in paddy soil, a simulated soil column experiment was conducted in laboratory to study the variations of soil mineral nitrogen along the profile under the application of 360 mg x kg(-1) (3 folds of conventional application rate) of urea- and ammonium sulfate nitrogen. In the experimental period, the soil NH4(+)-N and NO3(-)-N contents in the control (no fertilization) had less change, and no significant differences among different soil layers. Applying urea- and ammonium sulfate nitrogen resulted in a significant increase of soil NH4(+)-N and NO3(-)-N in 0-50 mm layer, being 186.0-2882.1 mg x kg(-1) and 268.7-351.5 mg x kg(-1), and 4.8-242 times and 5.7-316 times of those in CK, respectively. However, the NH4(+)-N and NO3(-)-N contents below 50 mm soil depth were similar to those in CK, indicating that the translocation and transformation of applied fertilizer nitrogen mainly occurred in 0-50 mm soil layer. The translocation of fertilizer nitrogen mostly occurred in the first 14 days after fertilization. In the whole experimental period, the NH4(+)-N and NO3(-)-N contents in each soil layer under the application of ammonium sulfate were 0.7-2.0 times of those under the application of urea, and the nitrification rate was 0.9-1.4 times of that, suggesting the higher transformation rate of applied ammonium sulfate in paddy soil, as compared with applied urea.