Impact of Agro-forestry Systems on Nutritional Status and Biological Activity on Rainfed Red Sandy Loam Soils

Different agroforestry systems and tree systems (15 years old) were studied for their microbial buildup in red sandy loam soil at Agroforestry Research Unit of Acharya N.G. Ranga Agricultural University, Hyderabad. Significant differences were observed in the nature of microbial population viz., bacteria, actinomycetes and fungi. Agri-silvi-horti system harboured more number of bacteria than other systems, signifying that multi-component systems have a role to play in microbial proliferation. In Eucalyptus plantation, the population of fungi was less comparative to bacteria and actinomycetes. The presence of allelochemicals and reduction in pH might be the reason for such situation. There was significant correlation between microbes and various soil chemical parameters. C:N and C:P ratios were calculated and it was found that tree leaves with fast decomposition rate showed higher ratios than those with slow decomposition such as in teak. Significant differences were also observed in physio-chemical properties of soils between agroforestry and tree systems studied. It was found that organic carbon is a principle component which can cause significant improvement or otherwise of microbial population build up in soils of light textured nature.