Coal fly ash and farmyard manure amendments in dry-land paddy agriculture field: Effect on N-dynamics and paddy productivity

A field study was conducted at a dry-land agricultural farm during paddy crop season to assess the effect of fly ash (FA) and farmyard manure (FYM) amendments on the dynamics of inorganic-N (NH4+ and NO3-), N-mineralization and nitrification rates and paddy yields. Four treatments, each consisted of three replicates, were established in completely randomized block design. The treatments were: control, 50 t ha(-1) FA, 50 t ha(-1) FYM, and FA + FYM (each 50 t ha(-1)). The variations in soil physico-chemical properties due to treatments were statistically significant. Across different treatments, FA + FYM treated plot had significantly higher organic-C, total-N, total-P, water-holding capacity, but lower bulk density compared to control plot. The effect of various amendments and months was significant for soil inorganic-N (NH4+ and NO3-) concentrations, soil moisture (SM) content, N-mineralization and nitrification rates. Across various amendments and sampling months, inorganic-N, SM, N-mineralization and nitrification rates were greatest in FA + FYM treated plot in August month. An exponential positive relationship existed between gravimetric SM content and N-mineralization (R-2 = 0.865) and nitrification (R-2 = 0.633) rates. The SM content was negatively correlated with NH4+ (R-2 = 0.841) and NO3- (R-2 =0.920). The various selected paddy agronomic parameters and yields differed significantly due to treatments. The most effective treatment noted for paddy grain yield was the combination of FA + FYM (92% increase over control) followed by FYM and FA. Significant correlation was noted among soil physico-chemical properties (except soil pH) and paddy productivity. The results suggested that FA and FYM amendments enhance the rates of N-transformation processes, plant available-N and paddy productivity. Thus. FA and FYM can be used as potential amendments to enrich soil productivity and crop yields for dry tropical nutrient poor soils. (c) 2010 Elsevier B.V. All rights reserved.