华南主要露地蔬菜土壤的供氮指标

Study on Nitrogen Supply Index of Main Open Field Vegetables in South China

依托测土配方施肥田间试验的数据,开展露地蔬菜土壤供氮指标研究,旨为华南菜田土壤养分丰缺指标体系建设提供参考。以蔬菜不施氮肥处理与完全施肥处理的相对产量的50%、75%、90%和95%为指标,建立华南菜田土壤碱解氮丰缺指标,根据土壤碱解氮含量划分的极缺、缺、中等、高和极高5级水平的土壤供氮指标分别为小于42、42-97、97-164、164-194mg/kg和大于194mg/kg。针对目前逐渐采用土壤硝态氮作为土壤供氮指标的需求,建立了碱解氮-硝态氮和碱解氮-无机氮的转换方程,分别为：y硝态氮=0.4012x碱解氮-1.3695和y无机氮=0.4955x碱解氮＋2.0736,二者均达到极显著水平。由该方程计算得出,当蔬菜相对产量为50%、75%、90%和95%时,并对所建立的丰缺指标进行不同形态氮的指标值转换。土壤硝态氮的丰缺指标转换值为：11、34、66mg/kg和82mg/kg;无机氮的丰缺指标转换值为：17、46、86mg/kg和105mg/kg。

This paper was aimed to introduce our investigative study on establishing soil alkali hydrolysable N abundance and deficiency indices of vegetable-producing areas in southern China. In addition, inorganic N and dissociative NO 3--N were also transformed to abundance and deficiency index values. For this purpose, experiments of soil testing and fertilizer recommendation were conducted in vegetable-producing areas of southern China during 2007 to 2009. Soil alkali hydrolysable N were classified as very low（ 〈50% relative yield）, low（50%-75% relative yield）, medium （75%-90% relative yield）, high （90%-95% relative yield） and very high （〉 95% relative yield） based on the relative yields. Abundance and deficiency indices of soil alkali hydrolysable N were simulated by the models of logarithmic equation. The results indicated that soil alkali hydrolysable N indices were〈 42 mg/kg, 42-97 mg/kg, 97-164 mg/kg, 164-194 mg/kg, and〉 194 mg/kg when soil fertility were classified as very low, low, medium, high and very high, respectively. Meanwhile, conversion model of alkali hydrolysable N to dissociative NO 3-was stimulated by liner equation, it was y=0.4012x-1.3695; alkali hydrolysable N to inorganic N was also stimulated by liner equation, which was y=0.4955x＋2.0736, both of them shown strong significant correlations. Transformed by these models, abundance and deficiency index values of dissociative NO 3-were： 〈11 mg/kg, 11-34 mg/kg, 34-66 mg/kg, 66-82 mg/kg and〉 82 mg/kg;abundance and deficiency index values of inorganic N were：〈 17 mg/kg, 17-46 mg/kg, 46-86 mg/kg, 86-105 mg/kg and〉 105 mg/kg, respectively, when soil fertility are classified as very low, low, medium, high and very high.