Abstract:

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 NO3--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 <42mg?kg-1, 42~97 mg?kg-1, 97~164mg?kg-1, 164~194mg?kg-1, and >194 mg?kg-1 when soil fertility were classified as very low, low, medium, high and very high, respectively. Meanwhile, conversion model of alkali hydrolysable N to dissociative NO3- is stimulated by liner equation, it was y = 0.4012x - 1.3695; alkali hydrolysable N to inorganic N is 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 NO3- were: ＜11mg?kg-1, 11~34mg?kg-1, 34~66mg?kg-1, 66~82mg?kg-1 and >82mg?kg-1; abundance and deficiency index values of inorganic N were: ＜17mg?kg-1, 17~46mg?kg-1, 46~86mg?kg-1, 86~105 mg?kg-1 and > 105mg?kg-1, respectively, when soil fertility are classified as very low, low, medium, high and very high.