Effect of Organic and Inorganic Fertilizer Combination on Rice Productivity and Soil Fertility

Although the common understanding that applying only chemical fertilizer in long duration will cause the deterioration of soil fertility and decrease crop yield has been reached, few data on long-term observation in fixed location were reported.Our studies in continuously seven cropping seasons showed that, the yield-maintaining rates of urea-broadcasting, urea+azolla, urea+ricestraw treatments are 81.6-89.0%, 100.5-102.6%and 101.1 - 101.7% respectively.Combining application of inorganic fertilizer with organic manure tends to enhance rice grain yield.When calculating on the input of each kg pure nitrogen, the economical benefits of applying azolla and ricestraw were increased 1.10-1.28 and 0.80 - 0.96 folds respectively.Furthermore, the input/output ratio of nitrogen application was increased 8.0 - 9.0%,maximal-ly, 22.6%.Applying inorganic N with azolla and ricestraw caused the increase of soil total N (0.019 -0.049%), O.M.(0.08-0.66% ), decrease of soil B.D (0.0450 - 0.120g/cm3), specific gravity (0.015 - 0.030g/cm3), dispersive coefficient (0.68 - 4.53%), also the increase of physical clay content ( 0.01mm, 1.77-5.79%) .The soil microecological environment was improved.