添加尿素和秸秆对三熟制水旱轮作土壤各形态氮素的影响

Effects of Urea and Straw on Soil Different Nitrogen Forms Under Paddy-Upland Rotation of Triple Cropping System

添加不同外源氮对土壤中不同形态氮素的转化具有十分重要的影响。选取长期耕作土壤,设置对照、添加尿素N 150 kg/hm^2(U150)、添加秸秆(相当于添加N 38 kg/hm^2,Straw)、添加尿素N 150 kg/hm^2+秸秆(相当于添加N188 kg/hm^2,U150+Straw)和添加尿素N 188 kg/hm^2(U188)5个处理进行室内培养试验,研究了添加不同外源氮对土壤铵态氮、硝态氮、可溶性有机氮、微生物生物量氮含量的影响。结果表明,土壤铵态氮随着培养时间的延长表现为先增后减的趋势,添加尿素的两个处理其土壤铵态氮较Straw、U150+Straw处理能够更快地达到峰值;而土壤硝态氮则表现为逐步增加的趋势。添加尿素处理能够显著提高土壤矿质氮的含量,在添加等量氮素的条件下,U188处理矿质氮含量在培养期间始终高于U150+Straw处理;此外,U150+Straw处理矿质氮含量在培养前期均低于U150处理,至培养30天后其含量略高于U150处理。与对照相比,培养结束时添加不同外源氮素处理的土壤矿质氮含量能够提高169.61%~496.75%。对于微生物生物量氮和可溶性有机氮而言,添加不同外源氮素分别在培养10天和30天达到峰值,此后逐渐降低。不同处理而言,添加秸秆+尿素、添加秸秆处理的微生物生物量氮和可溶性有机氮含量在培养前期明显高于仅添加尿素的两个处理,说明添加有机物料氮源主要有益于提高土壤有机态的氮素含量。

Adding different exogenous nitrogen （N） sources is essential for soil N transformation. In this study, soil under long-term cultivation was selected to conduct the indoor incubation experiment, in which five treatments were designed in order to analyze the effects of adding different exogenous N sources on soil ammonium N （NH4）, nitrate N （NO3）, dissolved organic N （DON）, and microbial biomass N （MBN）, the designed treatments were as follows： 1） control（CK）, 2） adding Urea at N 150 kg/hm2 （Uls0）, 3） adding rice straw （equal to adding N 38 kg/hm2, Straw）, 4） adding urea and straw （equal to adding N 188 kg/hm2, U150＋Straw）, and 5） adding urea at N 188 kg/hm2 （U188）. The results showed that soil NH4 increased first and then decreased during the incubation period, soil NH4 of treatments adding with urea reached the peak value more rapidly than those adding with straw. Soil NO3 content increased with time. Total mineral N of Ul88 treatment was higher than that of Uls0＋Straw treatment during the period of incubation. Compared with U150 treatment, soil mineral N content was lower in U150＋Straw treatment but became a little higher after 30 days of incubation. Compared with CK, adding different exogenous N source increased soil mineral N by 169.61% - 496.75% at the end of incubation. MBN and DON of treatments with adding different exogenous N sources reached maximum values at 10 days or 30 days after incubation and then decreased with time. MBN and DON of treatments with adding straw and/or straw＋urea were higher than those with adding urea only during the prior stage of incubation. The results demonstrated that adding exogenous N sources of organic material mainly increased soil organic N.