J. Singh , I. P. Bora , A. Baruah , M. Hussain

Abstract

The present study highlights the changes of physico-chemical properties of soil during different phases of shifting cultivation and also in fallow lands of different ages. Burning resulted significant increase in soil pH, which decreased soil acidity and acidity increased as the fallow progressed. The percentage of sand increased while the clay percentage decreased after burning the sites. A drastic reduction in moisture content was recorded due to burning operation. Gradual decrease in conductivity was observed at the time of cropping and harvesting period, which increased with the fallow age. Jhuming caused appreciable change in organic matter content resulting nutrient imbalance in soil. Burning of the debris after slashing the forest leads to the depletion of organic carbon and nitrogen content in soil. However, the recovery of nitrogen in cropping phases is quite fast in comparison to carbon. Highest value of carbon content was noticed in winter season while nitrogen showed its highest value during the monsoon. Exchangeable Ca, Mg, K and available P increased just after burning and thereafter a gradual decrease was noticed in cropping phases. As the fallow progressed the value increased gradually. Nutrient status of soil was recorded significantly higher in natural forest than in the fallow lands and in all cases the value was inversely proportional to depth.

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I. P. Bora , A. Baruah , J. Singh

Abstract

A pot experiment was conducted by using isolated inoculants of Rhizobium and Rhizobium + recommended dosages of fertilizers at different levels of N to evaluate their individual and combined effects on symbiotic traits and growth and biomass production of Albizia procera. Seven strains of Rhizobium were isolated from Albizia procera seedlings. Among them Ab(l)100, Ab(m) 98 and Ab(l) 32 were found to be efficient, having positive effect on growth, nodulation and biomass production. Nodulation was recorded maximum in Ab(l)32 inoculated seedling, being 69.82% higher than control (uninoculated ones). The combined effect of Rhizobium inoculation along with application different levels of N dosages of fertilizer showed significant increase in growth, nodulation and biomass production at low level of urea-amended soil (20 kg /h). Nodulation was found to be suppressed in medium level urea (40 kg/h) application although there was a significant increase of growth and biomass production of plant. However an exception was noticed in Ab(m)98 inoculated seedlings where in significantly high value of nodulation was recorded when medium level urea was applied to soil. Stunted growth and poor nodulation was observed when high level urea (60 kg /h) was applied to soil.

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