Phosphorus fixing capacity of the Oxic Rhodustalf—alfisol soil in the Chotanagpur plateau region of Eastern India

The P-fixing capacity of a soil governs the P-nutrition of crop plants. P-nutrition of the crop plant is more a soil problem and a higher dose of phosphatic fertilizer is necessary for soils having high P-fixing capacity. The phenomenon of P-fixation and the great variation in the P-fixing capacity of different soils has thus important bearing on crop response to P-application. The eastern plateau region of India with acid lateritic soil is chronically deficient in available phosphorus resulting in very low productivity. An experiment was thus carried out to estimate the P-fixing capacity of soil collected from two depths, 0 - 20 cm and 20 - 50 cm, from the Agricultural experimental farm of Indian Statistical Institute, situated at Giridih, Jharkhand, in the eastern India. The soil was acidic in reaction (pH-5.4) with presence of Fe (1.60%) and Al (17.2%). The P-fixing capacity of the soil was estimated to be 59.60% and 64.94% for the surface and the subsurface soil respectively showing lower P-fixing capacity of the surface soil as compared to the subsurface soil which may be due to presence of more organic matter in the surface soil as organic molecules released on decomposition of organic matter complexes with Fe and Al in the soil thereby blocking the P-fixing sites in the soil.

Short-term application of biochar increases the amount of fertilizer required to obtain potential yield and reduces marginal agronomic efficiency in high phosphorus-fixing soils

There is little understanding as to whether the addition of biochar requires less fertilizer to obtain the potential yield.Furthermore,the additional yield ascribed to the non-nutrient effects of biochar is ambiguously quantified.Therefore,this study is aimed to elucidate the influence of biochar application rate and production temperature on(i)marginal agronomic efficiency(AELN),(ii)potential yield(Yopt),(iii)the amount of mineral fertilizer required to obtain the potential yield(Fopt);and(iv)nutrient use efficiency.AELN,Yopt and Fopt were calculated after fitting the yield response at different levels of mineral fertilizer with a second-degree polynomial.Application of biochar reduced marginal agronomic efficiency,implying that the plant utilized the applied nutrient more efficiently without biochar at a low dose of mineral fertilizer.Biochar increased potential yield but required more mineral fertilizer to obtain the optimum yield.The non-nutrient associated effect of biochar reached to 39% and is mainly attributed to its liming effect.The effect of biochar on AELN,Yopt,Fopt,fertilizer use efficiency and soil pH were more pronounced at the higher application rate.Addition of biochar,however,increased soil Mehlich-P and carbon content,irrespective of production temperature and application rate.This study demonstrated that the short-term effect of biochar application on fertilizer utilization should be examined with caution in low-input cropping systems because the biochar effects were dependent on fertilizer level,biochar application rate,production temperature and their interactions.Further manipulative experiments are recommended to identify the mechanisms that explain the non-nutrient effect of biochar on yield.