ON-FARM PRODUCTION OF VERMICULITE BASED INDIGENOUS AM FUNGUS INOCULUM FOR IMPROVED PHOSPHORUS NUTRITION IN UPLAND RICENeha Nancy Toppo, N.N. Jambhulkar, Mukesh Nitin, A.K. Srivastava and Dipankar Maiti
Rice production in the upland ecology is severely impeded due to low phosphorus (P) acquisition from soil and chemical P fertilizers fixing in soil soon after application. Arbuscular mycorrhizal (AM) technology appears to be a useful option to address this constraint. On-farm developed soil-root based mass-inoculum (MI) produced by multiplying nucleus inoculum (NI) containing indigenous arbuscular mycorrhizal consortium prepared on sterilized substrate was reported to enhance P-acquisition in upland rice with concomitant increase in yield in a sustainable and cost-effective way. Efficiency of MI largely depends upon the substrate utilized for NI. In the present study, a more effective substrate combination for NI (Vermiculite:Soil:Farm Yard Manure or V:So:FYM) fortified with Hoagland nutrient solution (10 ml per 50g substrate per week for 4 weeks) for encouraging further root proliferation and AMF multiplication was identified. Improved MI produced by multiplying V: So: FYM based NI added at 0.5 t ha-1 resulted in significantly higher P-uptake (46.7% to 48.7%) and grain yield (21.4% to 25%) compared to control plots (no inoculum application). The resultant advantages of applying improved MI (0.5 t ha-1) were comparable to that obtained from application of traditionally produced MI at 1.25 to 1.50 t ha-1. The improved MI is thus recommended to replace the traditional MI. Further, as a decision-making tool under precision farming system where inoculum application is based on site/system specific precise dose requirements to avoid excess or less application, mathematical models were developed for differentially AM-responsive rice varieties to determine AM-inoculum requirement under known soil P and inherent AMF status for targeted P-uptake in rice.
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