施氮量对土壤无机氮分布和微生物量氮含量及小麦产量的影响

Effects of nitrogen application rate on soil inorganic nitrogen distribution,microbial biomass nitrogen content and yield of wheat

在高肥力土壤条件下，研究了施氮量对土壤无机氮分布和微生物量氮含量及小麦产量的影响。结果表明，小麦生长期间，施氮处理0—100cm土层硝态氮积累量显著大于不施氮处理；当施氮量大于150kg／hm^2时，随施氮量增加，0—100cm土层硝态氮积累量显著增加；随小麦生育进程推进，施氮处理上层土壤硝态氮下移趋势明显，至小麦成熟时，施氮195～285kg／hm^2处理60—100cm土层硝态氮含量显著大于其它处理。小麦生长期间，0—100cm土层铵态氮积累量较为稳定，施氮处理间亦无显著差异。与不施氮肥相比，施氮提高小麦生长期间0—40cm土层土壤微生物量氮含量；当施氮量小于240kg／hm^2时，随施氮量增加，土壤微生物量氮含量增加。小麦的氮肥利用率随施氮量增加而降低；施氮105～195kg／hm^2，收获时小麦植株吸氮量、生物产量、子粒产量和子粒蛋白质含量提高；而施氮量大于240kg／hm^2时，小麦生育后期的氮素积累量降低，收获时植株吸氮量、生物产量和子粒蛋白质含量降低。说明本试验条件下，施氮105～150kg／hm^2可满足当季小麦氮素吸收利用，获得较高的子粒产量和蛋白质含量。继续增加施氮量，土壤微生物量氮含量增加，但土壤中残留大量硝态氮，易淋溶损失。

Nitrogen plays an important role in grain yield elevation. In order to obtain high grain yield and efficient nitrogen utilization and reduce the possible environmental effects, it is essential to determine the appropriate nitrogen application rate, especially on high fertile soil. A research was conducted to determine the effects of nitrogen application rate on soil in organic nitrogen distribution, microbial biomass nitrogen content, nitrogen uptake and utilization in wheat. The field experiments were carried out on a high fertile soil in Longkou, Shandong, during 2002—2003. Seven treatments （CK1, CK2, N1, N2, N3, N4, N5） with N application rate being 0, 0, 105, 150, 195, 240, 285 kg/ha was setup. Apart from CK1, 135 kg P2O5 and 105 kg K2O per ha was addressed before sowing for the other treatments. The content of nitrate, ammonium and microbial biomass nitrogen in soil, the nitrogen uptake of plant during wheat growing, and the grain yield and the protein content of wheat were analyzed. The results showed, during wheat growing, the amount of nitrate accumulation in 0—100 cm soil layers of treatments with nitrogen addition was dramatically larger than that without nitrogen addition. When nitrogen application rate was higher than 150 kg/ha, the amount of nitrate accumulation in 0— 100 cm soil layers increased significantly along with nitrogen addition increasing. Nitrate in upper soil layers with nitrogen treatments moved down obviously with the progression of growing; as the result, at maturity stage, the nitrate content in 60—-100 cm soil layers of treatments applied nitrogen at the rate of 195—285 kg/ha was dramatically higher than that of other treatments. During period of wheat growing, the amount of ammonium accumulated in 0—100 cm soil layers showed no obvious change, and no significant difference was found among treatments with nitrogen supplied. Compared with treatments no nitrogen applied, application of nitrogen increased the content of soil microbial biomass nitrogen in 0—-40 cm soil layers during wheat growing. With less than 240 kg/ha nitrogen applied, the content of soil microbial biomass nitrogen increased along with nitrogen addition increasing. With nitrogen addition increasing, nitrogen using efficiency of wheat decreased. Supply nitrogen at the rate of 105—195 kg/ha elevated the nitrogen uptake amount, biomass, grain yield and protein content of wheat at harvest. With more than 240 kg/ha nitrogen supplied, the nitrogen accumulation rate at later growing period, the nitrogen uptake rate at harvest, biomass and grain protein content decreased. The results indicated, nitrogen applied at the rate of 105—150 kg/ha could meet the need of wheat on the current growing season to obtain high grain yield and protein content. Applying more nitrogen would increase the content of soil microbial biomass nitrogen, but might result in large amount of nitrate residue in soil and suspected to leaching loss.