冬小麦-夏玉米轮作体系中不同施氮水平对玉米生长及其根际土壤氮的影响

在河北衡水潮土上进行田间试验,以当地习惯高氮用量(小麦季施N 300 kg/hm2,玉米季施N 240 kg/hm2)为对照,研究冬小麦-夏玉米轮作体系中减少氮肥用量对玉米季植株生长、氮素吸收及根际土壤中无机氮与微生物量氮的影响。结果表明,两季作物氮肥施用量减少25%和40%,对玉米产量、生物量及植株体内氮累积量未产生明显影响,氮肥利用率提高。不同氮肥施用量对根际和非根际土壤铵态氮含量的影响不显著;减少氮肥施用量,对玉米根际土壤硝态氮含量也没有明显影响。在玉米苗期、抽雄期和成熟期,习惯高施氮量处理的非根际土壤硝态氮含量较高,其中抽雄期,非根际土壤硝态氮含量较氮肥减施40%用量处理高出近一倍,但非根际土壤微生物量氮水平含量明显降低。氮肥减施未影响根际土壤微生物量碳、氮含量,反而增加了非根际土壤微生物量碳、氮水平。在高肥力的潮土上,冬小麦/夏玉米轮作体系中适当减施氮肥并未影响玉米根际土壤氮素水平,可保证玉米稳产,实现减氮增效。

Plant nitrogen utilization and soil nitrogen status in rhizosphere of maize as affected by various nitrogen rates in wheat-maize rotation system

A field experiment was conducted on fluvo-aquic soil (aquic inceptisol) in Hengshui of Hebei province. The objective was to investigate the effects of different nitrogen rates on inorganic nitrogen and microbial biomass nitrogen in rhizosphere and non-rhizosphere soils, and nitrogen utilization by maize plants under the rotation system of winter wheat and summer maize. The results showed that in comparison to farmers' conventional N fertilization (300 kg/ha for winter wheat and 240 kg/ha for maize), reducing nitrogen application rates by 25% and 40% in the rotation system of winter wheat and summer maize did not significantly affect total biomass and total nitrogen accumulation of summer maize, but improved nitrogen use efficiency for maize plants. The soil NH⁺₄-N contents presented no significant difference among various nitrogen application rates. The NO^-₃-N contents in rhizosphere soils did not significantly decreased with N application reduction, but decreased in non-rhizosphere soils. Especially in tasseling stage, the NO^-₃-N contents in non-rhizosphere soils under conventional N rate were one times higher than that under 60% of conventional N rate. The concentrations of microbial biomass carbon and nitrogen in rhizosphere soils did not change under the treatments of different nitrogen application rates. However, the levels of microbial biomass carbon and nitrogen in non-rhizosphere soils were increased when reducing N application rates by 40%. It is suggested that in those area with excessive nitrogen application in the rotation system of winter wheat and summer maize, nitrogen application should be reduced to an appropriate rate.