Quantitative estimation of fertilizer requirement for maize and chickpea in the alluvial soil of the Indo-Gangetic plains

A field experiment was conducted in maize-chickpea cropping system with integrated use of biogas spent slurry and fertilizer to estimate the fertilizer requirement for specific yield targets of maize and chickpea. Grain yields of maize and chickpea increased by application of biogas slurry up to 10 t ha⁻¹. Responses to N, P and K application could be obtained up to 150, 44 and 125 kg ha⁻¹ and 20, 26 and 21 kg ha⁻¹ in maize and chickpea, respectively. The required N, P, and K accumulation in the plant for 1 tonne grain yield was 26.6, 4.5 and 25.3 kg in maize and 46.1, 3.9 and 41.1 kg in chickpea. This suggested N:P:K ratios in maize and chickpea to be 5.9:1:5.6 and 10.8:1:10.5, respectively. In maize the average N, P and K supply from soil was 19, 36 and 18% of KMnO₄-N, Olsen P and NH₄OAc-K, respectively, while the values in chickpea were 25, 27 and 17%, respectively. Quantitative relationships of fertilizer N, P and K requirement, soil nutrient status and recovery efficiency of added nutrient to achieve a target yield of maize and chickpea were derived from the experiment. The adjustment equations for estimating NPK requirement for maize and chickpea with and without manure application have been developed for fertilizer recommendation in the alluvial soils of Indo-Gangetic plains.