Assessment of soil properties and carbon sequestration under fodder crop based systems

Abstract

The present investigation was carried out for assessment of soil physico-chemical and biological properties, distribution of different forms of soil carbon and contribution of different forms of soil carbon on soil aggregation under different fodder crop based system. Soil samples were collected from twenty three crop situations of three locations of Jorhat and Golaghat districts of Assam including virgin soils. Samples were collected as bulk soil samples, large core samples and mini core samples from 0 20, 20-40, 40-60, 60-80 and 80-100 cm soil depth from each plot under fodder crop and virgin soil. newlineIt was observed that soil physico- chemical and microbiological properties were greatly improved by continuous cultivation of fodder crops. The pH of soils under fodder crops down the depth were higher than those in virgin soils making these soils less acidic in reaction. Continuous cultivation of fodder crops increased the per cent organic carbon content of soil and it is high in case of napier than other fodder crops. Available nitrogen, phosphorus, potassium, calcium and magnesium contents increased due to continuous cultivation of fodder crops and continuous cultivation of napier grass as well as setaria showed high range of these nutrients than other fodder crops. Continuous cultivation of fodder crops increased hydraulic conductivity of soils and six years continuous cultivation of napier showed highest range of hydraulic conductivity of 0.119 cm sec-1 to 0.001 cm sec-1 with a mean value of 0.028 cm sec-1. Bulk density decreased due to continuous cultivation of fodder crops and continuous cultivation of setaria for six years showed lowest bulk density ranged from 0.93 Mg m-3 to 1.05 Mg m-3 with a mean value of 1.00 Mg m-3. Per cent available water content increased due to continuous cultivation of fodder crops and fourteen years continuous cultivation of napier showed highest range of available water content of 13.37% to 6.79% with a mean of 10.59%. Continuous cultivation of napier, setaria and congosignal showed higher soil aggregation and mean weight diameter than other fodder crops and virgin soil. newlineThe microbial biomass carbon, phosphomonoesterase activity and dehydrogenase activity of fodder crops was much higher than the virgin soils. The highest microbial biomass carbon range was found in case of fourteen years continuous cultivation of napier (769.3 and#956;gm gm-1 to 96.6 and#956;gm gm-1 with a mean of 388.3 and#956;gm gm-1). Six years continuous cultivation of maize showed highest phosphomonoesterase activity (336.5 and#956;gmgm-1hr-1 to 210.1 and#956;gmgm-1hr-1 with a mean of 249.0 and#956;gmgm-1hr-1) and five years continuous cultivation of hybrid napier showed highest dehydrogenase activity (22.94 and#956;gmgm-1hr-1to 5.69 and#956;gmgm-1hr-1with a mean of 15.82 and#956;gmgm-1hr-1). newlineThe highest total organic carbon content wasfound in case of continuous cultivation of napier followed by continuous cultivation of setaria and it was higher in 20-40 cm layer of soil than in 0-20 cm layer. Six years continuous cultivation of napier showed highest range of soil carbon stock of 37.01 t ha-1 to 24.64 t ha-1 with a mean of 31.46 t ha-1. The oxidisable organic carbon decreased with the increase in soil depth down the profile anddue to high vegetative growth, continuous cultivation of napier or hybrid napier showed high oxidisable organic carbon in soils. Highest hot water extractable organic carbon was found in continuous cultivation of hybrid napier followed by setaria.