The Study On Fertility Properties Of Several Vegetable Soils And Controlling Techniques For Nitrate Pollution Of Pakchoi In Changsha, Hunan Province

To set up effective techniques for control nitrate content in vegetables, this paper is an attempt to study the local conditions and fertility properties of the type vegetable garden soils of 6 chief bases in the suburb of Changsha by field investigation and sampling and laboratory analysis; field plot experiments were conducted in red garden soil and alluvial garden soil to examine the effect of applying dicyandiamide , rare earth element fertilizer or micronutrient fertilizer(Cu, Zn, B, Mo, Mn) plus reasonable combined application of N, P, K and organo-inorganic fertilizers on the yield and nitrate content of vegetable as well as the ability of absorption of nutriment and other qualities in leafy vegetable. The results show that:â‘ The vegetable garden soils are developed from the alluvial deposit in the alluvial terrance and quarternary red clay in the hilly valley and are located in the lower smooth terrain. The soil texture ranges from lightly loamy to heavily loamy, and is suitable for crop growth. The nutrient status of the vegetable garden soils in the suburb of Changsha was good on the whole, the contents of organic matter, nitrogen, phosphorus and potassium were all at very high level, and especially the content of phosphorus was much higher than that of the other cultivated soils. Of them the vegetable garden soils developed from river alluvium has much higher nutrient contents than the reddish vegetable soil developed from quaternary red clay.â‘¡It was evidence that P was abundant in the tested soil and the contents of the total P and the available P were far more than other tillage soils. The contents of the total P in the vegetable garden soils developed from river alluvium was evidently more than that of the reddish vegetable soil developed from quaternary red clay. The longer age of the vegetable soil, the higher contents of soil available P. Inorganic phosphorus was the main form which accounts for 86.8 % of the total P in tested soil, and the organic P was only 13.2 % in average. The contents of the inorganic P in the vegetable garden soils developed from river alluvium was also evidently more than the reddish vegetable soil developed from quaternary red clay. In the inorganic P forms, the Ca2-P,Ca8-P,Al-P,Fe-P,O-P and Ca10-P were taking 8.6, 7.3, 17.4, 34.1, 21.2 , 11.4 percents of the total P, respectively. Fe-P was the main form of the inorganic P and followed by Fe-P and O-P. According to the correlation analysis, the available P was markedly positive correlated with the Ca2-P,Ca8-P,Al-P,Fe-P(the R value were 0.969, 0.773, 0.752, 0.546, respectively), while the relativity was not good with O-P and Ca10-P.Therefore it indicated that the Ca2-P,Ca8-P,Al-P,Fe-P were importance resources of the effective P. In the organic P forms, Moderately labile organic phosphorus (MLOP) was the...