Effects of Nitrogen-reduction on the Soil profile Nutrient Distribution in Paddy Fields
A field experiment was used to investigate the effects of nitrogen-reduction on the accumulation and distribution of nutrients in paddy field profile.The results indicated that the content of organic matter,total nitrogen,total phosphorus,available nitrogen and phosphorus were decreased with the increase of the soil depth in T1(no nitrogen fertilizer added),T2(conventional fertilization level of local farmers)and T3(80 percentage conventional fertilization level of local farmers)treatments,respectively,while total potassium and available potassium were increased with the increase of the soil depth.Except for available nitrogen,phosphorus and potassium of the top layer soil(0～20 cm),the organic matter,total nitrogen,total phosphorus,total potassium,available nitrogen,phosphorus and potassium of 0～20 cm,20～40 cm,40～60 cm,60～80 cm,80～100 cm soil layer in the profile of 0～100 cm were increased in T3 treatment compared with T2 treatment.The marked increasing quantity of organic matter was mainly on the 3 soil layers at the depth of 0～60 cm,and nitrogen was mainly on the 2 soil layers at the depth of 0～40 cm,and potassium was mainly on the top layer soil(0～20 cm),while T3 and T2 treatment had no significant effect on phosphorus.These results demonstrated that T3 treatment increased the nutrient content that was concentrated primarily in the absorption region of crop.This is important to improve soil fertility and enhance the crop production.