Carryover Effect of Biochar and Cow Dung Manure on the Productivity of Green Gram (Vigna radiata L.) in Typic haplustalf

In cereals based legume cropping system more importance and intensification are given to first crop (cereals) as compared to succeeding crops. Hence, succeeding crops yield got reduced due to grown in low fertile soils. Productivity of green gram have declined or stagnated in recent years though we grew high yield varieties, due to grown in marginal lands with low nutrient and moisture. Biochar is organic substance that highly persists in soils with very little biological decomposition and helps to store nutrients and moisture for succeeding crop. The present investigation was felt necessary to get utilize the residual soil nutrients and moisture from the preceding biochar applied upland rice field for sustainable yield of green gram crop.

The present investigation was conducted during kharif season 2018. The study was conducted in randomized black design with sixteen treatments consisting of four levels of coconut shell biochar (CSB) at 2, 4, 6 and 8 t ha^-1 and two levels of cow dung manure (CDM) at 5 and 10 t ha^-1 with applied alone and in combinations with three replications (applied for previous upland rice crop). The recommended dose of NPK fertilizer (20:50:50 kg ha^-1) for green gram was common except absolute control.

The study results indicated that, residual effect of previously applied biochar and cow dung manure had a significant effect on succeeding green gram crop productivity in acid sandy loam soils due to its liming effect on improving soil properties and nutrient availability. Especially, combination of coconut shell biochar (CSB at 8 t ha^-1) and cow dung manure (CDM at 10 t ha^-1) with recommended NPK fertilizers.