LONG TERM EFFECT OF INTEGRATED NUTRIENT MANAGEMENT ON POOLS OF NITROGEN IN RHIZOSPHERE AND NON RHIZOSPHERE SOILS

Management practices can have significant implications for both soil quality and soil fertility. The observation on different pools of nitrogen in rhizosphere and non-rhizosphere in the long term are limited. Here we present the results on different pools of nitrogen in soil from long term integrated nutrient management practices under finger millet – groundnut cropping system, that has been in operation for more than 42 years. Organic manures - farmyard manure, maize residue and mineral fertilizers had been applied repeatedly for 42 years with finger millet – finger millet mono-cropping and finger millet- groundnut cropping system. The results indicated that all the nitrogen fractions were found to be higher in non-rhizosphere soil except total nitrogen and ammonical nitrogen fractions. The combined application of FYM @ 10 t ha -1 and mineral fertilizer 100% RDF in finger millet – groundnut cropping system recorded significantly higher total nitrogen (R-969.20 mg kg -1 ; NR-956.93 mg kg -1 ), nitrate nitrogen (R-84.00 mg kg -1 ; NR-85.40 mg kg -1 ), Ammonical N (R-109.20 mg kg -1 ; NR-106.30 mg kg -1 ) and organic nitrogen fractions in both rhizosphere and non-rhizosphere soil. The total nitrogen was found to be significantly and positively correlated with organic carbon (r = 0.718**, r = 0.831**), available nitrogen (r = 0.912**, r = 0.915**), MBN (r = 0.912**, r = 0.914**) and urease (r = 0.809**, r = 0.820**) in case of both rhizosphere and non-rhizosphere soil. All the nitrogen fractions were significantly and positively correlated with each other indicating the existence of dynamic equilibrium.