适量施肥提高土壤残留硝态氮利用率及菠菜产量

Appropriate nitrogen fertilizer amount increases use efficiency of residual nitrate in vegetable field and raises spinach yield

针对菜地耕层土壤硝态氮残留量较高和当季肥料氮利用率低的问题,该研究通过田间注射外源标记氮(15N)微区试验,在土体15 cm(N15)和30 cm(N30)设置标记点,同时设置不施氮肥(N0)、传统施氮量(N1)、传统施氮量的70%(N2)和传统施氮量的40%(N3)4个施氮处理,研究土壤耕层残留硝态氮对菠菜产量及当季氮肥利用率的影响。结果表明:土体15和30 cm标记处理下传统施氮量70%和40%处理,与传统施氮处理的菠菜产量相比较均未达到显著差异(p>0.05),但菠菜对标记氮的利用率随施氮量降低而提高,N3N15处理残留氮利用率为22.7%,分别是N1N15、N2N15处理的2.1倍、1.3倍;N3N30处理残留氮利用率为27.5%,分别是N1N30、N2N30处理的3.8和2.2倍。无论是有标记处理还是无标记处理,肥料氮利用率均随施氮量的增加而降低,15 cm标记处理中,N3处理当季氮肥利用率为45%,是N1处理的3.5倍,N2处理的3.4倍;30 cm标记处理中,N3处理当季氮肥利用率为43.8%,是N1处理的4.2倍,N2处理的3.7倍。说明氮肥施用量降低到传统施氮量的40%,不会明显降低菠菜产量,土壤中残留氮素却得到了充分的利用,明显提高当季氮肥利用率,为蔬菜生产中合理降低氮肥施用,减少无机氮素残留提供理论依据。

Nitrogen fertilizer is often largely used for vegetative production and thus the high amount of nitrate is left in soils. It is important to understand the utilization rate of the residual fertilizer for lowering its negative influence on ecosystem since the nitrate is easy to leach with rainfall and irrigation water. The purpose of this study was to investigate the effects of residual nitrate in topsoil layer on spinach yield and its utilization rate and nitrogen fertilizer use efficiency. The experiment was conducted in the Experimental station of Anhui Agricultural University in 2007. The experiment design included 4 nitrogen fertilizer application rates （no fertilizer N0, traditional fertilizer amount N1, 70% of the traditional fertilizer amount N2, and 40% of traditional fertilizer amount N3） and 3 15N labeled NO3-N treatments （no 15N, 15N in 15 cm depth, and 15N in 30 cm depth） with 3 replicates for each treatment. The labeled NO3-N was injected in 15 cm and 30 cm soil depth of the micro-plots of each nitrogen fertilizaer treatment plot. T Soil samples were collected in 0-60 cm depth every 10 cm at 5 and 10 cm away from the labeled point after spinach harvest. The results showed that compared with the N0, the spinach yield was not significantly different from that in the traditional amount treatment N1 when the nitrogen fertilizer application amount was decreased to 40% traditional amount （p〉0.05）. Under different nitrogen fertilization treatment, the residual 15N in soil profile moved downward but with the moving depth for the 30 cm labeled 15N treatment higher than that for the 15 cm labeled 15N treatment （p〈0.05）. The 15N abundance was higher （p〈0.05） at the 5 cm horizontal distance away from the labeling points than that at the 10 cm horizontal distance away from the labeling points. As the nitrogen fertilizer amount increased, the residual nitrogen utilization rate decreased. In the 15 cm labeled 15N plots, the residual nitrogen utilization rate in the N3 treatment was as 2.1 and 1.3 times as that in the N1 and N2 treatment. In the 30 cm labeled 15N plots, the residual nitrogen utilization rate in the N3 treatment was as 3.8 and 2.2 times as that in the N1 and N2 treatment. The utilization rate of in-season nitrogen fertilizer decreased with increasing nitrogen fertilizer amounts. When the nitrogen amount was decreased to 40%traditional nitrogen amount, the utilization rate of in-season nitrogen fertilizer could reach 45%（15 cm labeled 15N treatment） and 43.8%（30 cm labeled 15N treatment）. This study suggested the nitrogen fertilizer reduced to 40%traditional nitrogen amount can greatly improve the utilization rate of redisual nitrogen in soil and the in-season fertilizer efficiency while keeping the spinach yield. The results can help with reasonable application of nitrogen fertilizer in vegetables.