不同肥源对萝卜硝酸盐累积分布和同化的影响

采用田间试验研究了牛粪、化肥单施和配施对萝卜产量,菜体硝酸盐累积、分布、同化,及土壤硝态氮含量变化的影响。结果表明,牛粪、化肥单施和配施,萝卜产量动态变化依次为FOM(1/2化肥+1/2牛粪)、OM(牛粪)F(化肥)CK(无肥),叶部和肉质根硝酸盐含量高低依次为FFOMCKOM,粗蛋白累积量依次为FFOMCKOM,土壤硝态氮含量动态变化依次为FFOMOMCK。综合各因素总体以化肥配施牛粪最为适中,若重点考虑食用安全和土壤硝态氮累积环境效应,则以单施牛粪表现为最佳,各处理引起硝酸盐富集和土壤硝态氮残留的风险依次为化肥(1/2化肥+1/2牛粪)牛粪。萝卜硝酸盐含量分布表现为叶部生长旺盛期叶部硝酸盐含量高于肉质根,肉质根生长旺盛期地下部将贮存更多的硝酸盐。在地上部,当植株硝酸盐富集时,硝酸盐累积在内叶和叶柄中;当植株生长处于养分"饥饿"状态时,硝酸盐释放到外叶和叶片中。因此,菜地连续施用有机肥,不仅可减少蔬菜对硝酸盐的富集,且可维持后期蔬菜产量。

Effect of different fertilizer on accumulation, distribution and assimilation of nitrate in radish

Radish is one of the most consumed vegetables,which is also a nitrate-rich root vegetable. Numerous studies have reported that fertilization was one of the major factors influenced nitrate content in vegetables, especially in radish. However, few researches on the influence of fertilization on nitrate accumulation, distribution and assimilation in vegetables have been carried out. Therefore, Experiments of radish cultivation were adopted to comprehensively investigate the effects of continuous application of organic and inorganic fertilizers on the radish yield, the soil nitrate dynamics, and the absorption, distribution and assimilation of nitrates in vegetable tissue. The radish biomass was declined in the order of half chemical fertilizer plus half organic manure(FOM)>organic manure(OM)>chemical fertilizer(F)>no fertilizer(control, CK). Among them, there were no significant differences between FOM and OM treatments. The nitrate concentrations in leaves and roots were decreased following by F>FOM>CK>OM. And the content of crude protein in radish is in the same order with the nitrate concentration in leaves. Considering all these factors, including radish production, the nitrate accumulations in vegetable and soil, the most moderate fertilization was organic manure plus chemical fertilizer. If considering food safety of vegetables nitrate accumulation and environmental effect of soil nitrate, the single application of organic manure was the best after applying for several seasons. The risk of the nitrate accumulation of radish and the nitrate nitrogen residue of soil were followed by F>FOM>OM. The nitrate contents in leaves and root both showed a decreasing trend over time. In the vigorous growth stage of leaves, the nitrate contents in the aboveground parts were higher than those in the underground parts. While in the roots growth period, more nitrates were stored in roots. When chemical fertilizer was applied alone (F), higher nitrate content was absorbed by plant, more enriched nitrates were stored in petiole and inner leaves. When cow manure was single fertilized (OM), low nitrate nutrition was offered in the whole growth period, the accumulative nitrate in vegetables tissues were released to the mesophyll and outer leaves to maintain the normal growth of radish. Therefore, continuous application of organic fertilizer, not only decreased the nitrate content in vegetables, but also increased the vegetable yield in the latter seasons.