露地栽培条件下大白菜氮肥投入阈值研究

通过田间试验,研究了不同施氮量对大白菜产量、氮肥利用率、硝态氮残留量的影响。结果表明,施氮对大白菜有显著的增产作用,但随着施氮量的增加产量变化不大,产量对施氮量的反应呈平台模式。氮肥利用率在3.3%-12.6%,并且随施氮量的增加呈先增加后降低的趋势,在施氮量为656.4 kg/hm^2（纯氮300 kg/hm^2＋有机肥12 000 kg/hm^2）时,氮肥利用率和作物产量最高。合理控制氮肥用量会促进作物对土壤氮素的吸收。施氮可明显提高0-180 cm剖面土壤NO3--N的累积量,残留的NO3--N的分布随施氮量的增加而显著增加,并且随施氮量的增加残留深度下移,表现出明显的底层累积。各处理土壤氮均集中在0-100 cm土层中,100 cm土层以下,各处理氮含量渐趋一致。综合不同施氮量对大白菜产量以及环境指标的影响,在本试验肥力水平下,大白菜氮肥投入阈值为656.4 kg/hm^2（纯氮300 kg/hm^2＋有机肥12 000 kg/hm^2）时,能够兼顾作物高产与环境安全。

Study on Nitrogen Threshold of Chinese Cabbage in Open Field

In order to provide evidence for reasonable use of nitrogen fertilizer,a field trial was carried out to examine the effects of the yield and the environmental effects of the chinese cabbage under open field cultivation during 2011 — 2012. The results showed that the yield of chinese cabbage was highest at 656.4 kg/hm^2（N 300 kg/hm^2＋organic manure 12 000 kg/hm^2）. The nitrogen uptake by chinese cabbage increased with increasing N rate. With N application of 656.4 kg/hm^2（N 300 kg/hm^2＋organic manure 12 000 kg/hm^2）,the nitrogen uptaked was the highest. With N fertilizer rate increasing,the content of NO3--N in soil layers increased dramatically. With more than 656.4 kg/hm^2（N 300 kg/hm^2＋organic manure 12 000 kg/hm^2）was supplied,soil NO3--N moved down obviously. N fertilizer residual amount increased with increased N fertilizer rate. The nitrogen use efficiency ranged from 3.3% to 12.6% under different rates of N fertilization. At the rate of 656.4 kgN/hm^2（N 300 kg/hm^2＋organic manure 12 000 kg/hm^2）could meet the chinese cabbage demand.These results suggest that the N application rates of 656.4 kg/hm^2（N 300 kg/hm^2＋organic manure 12 000 kg/hm^2）,would be optimal for the yield of chinese cabbage and a reduction in the risk of nitrate release into environment.