Nutrient Dynamics of Different Seed Sources of Pongamia Pinnata Based Agroforestry System in Transitional Zone of Karnataka

Abstract

The investigation was aimed at analyzing nutrient status in different seed sources of Pongamia based agroforestry system in transitional zone of Karnataka. From the present study MTP-II source had a tight (conservative) nutrient cycling whereas RAK-89 source recycled nutrients more efficiently. In case of tight cycling, net production per unit of nutrient uptake or requirement (uptake + retranslocation) is reduced. Conversely, loose cycle produced greater biomass per unit of nutrient uptake or demand (RAK-89). As such the greater demand of nitrogen particularly for RAK-89 source which is deficient in soil may be limiting factor for its optimum production. Nutrient cycling of Pongamia studied herewith varied significantly with nutrients. Nitrogen demand (uptake and retranslocation) was 30 per cent more from the MTP-II Pongamia source for the annual net primary production. The trees having higher nitrogen concentration in their foliage (RAK-89) reabsorbed greater nitrogen prior to senescence to meet out the next year’s growth demand. Nitrogen demand for annual productions accomplished both from uptake and by retranslocaiton.

Key words: Nutrient uptake, retranslocation, intercrops, agroforestry system