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, 50tha⁻¹ FA, 50tha⁻¹ FYM, and FA+FYM (each 50tha⁻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 (R²=0.865) and nitrification (R²=0.633) rates. The SM content was negatively correlated with NH₄ ⁺ (R²=0.841) and NO₃ ⁻ (R²=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.