施肥对设施菜地土壤硝态氮累积及pH的影响

在甘肃武威市设施栽培条件下,通过田间小区试验研究了不同施肥量及肥料种类（化肥、有机肥、有机＋无机）对设施土壤硝态氮累积、硝态氮在土壤剖面运移及土壤pH值变化的影响。结果表明：施氮量和肥料种类对土壤硝态氮的累积和淋溶均有较大的影响,随施氮量的增加,土壤剖面硝态氮累积量增加,其中对0～20cm土层硝态氮累积量的影响最为显著;在同等施氮量时,单施无机肥处理（NPK）、有机无机肥减半配施处理（1/2MNPK）、单施有机肥处理（M）,在40～150cm土层硝态氮的累积量分别为267.33、211.94、125.72kg.hm-2,表明只施用化肥较有机肥、有机肥与化肥配施更易造成土壤硝态氮淋溶并在深层累积。将农户习惯施肥量（MNPK）减半后施用（1/2MNPK）对蔬菜产量没有影响,并且显著减少了硝态氮在土壤中的累积,表明当地农户设施栽培肥料施用量过高,不仅造成肥料利用率低,栽培成本高,还可能给地下水位较浅的地区带来环境污染的风险。此外,土壤硝态氮含量与pH值呈极显著负相关关系,表明硝态氮在土壤中大量累积会造成土壤pH值的下降。

Effects of Fertilization on NO3-N Accumulation in Greenhouse Soils

A field plot experiment was conducted in Wuwei City, Gansu Province to study the effects of different application rates and types of fertilizer（ chemical fertilizer, manure, and chemical fertilizer ＋ manure ） on NO3-N accumulation and leaching in greenhouse soil profiles, and on soil pH change. Obtained results showed that NO3-N accumulation and leaching in greenhouse soils were affected by the application rates and types of fertilizer. Nitrate content in soil profile increased with N fertilizer application rates, especially in 0-20 cm soil layer. NO3-N ac- cumulation in 40-150 cm soil layers of NPK, 1/2MNPK, and M treatments with the equal level of N application, were 267.33 kg.hm6-2, 211.94 kg. hm^-2, and 125.72 kg.hm^-2, respectively. It indicated that chemical fertilizer application could easily result to the leaching and accumu- lation of NO3-N in deeper soil layers by contrast with the manure or fertilizer ＋ manure application. Furthermore, no effect on vegetable yield and significant decrease in NO3-N accumulation in greenhouse soils were obtained by halving fertilizer application amount in local farmers＇ practice. It could be inferred that the high application of fertilizer in greenhouse soils in Wuwei City might lead to the lower utilized coeffi- cient of fertilizer, high cost of production and the possible environmental pollution in some areas with shallow ground water. In addition, the significantly negative correlation between NO3-N content and soil pH was observed. The substantial accumulation of NO3-N in soils might be responsible for the decrease of pH.