AM fungi lead to fertilizer phosphorus economy and enhanced system productivity and profitability in okra (Abelmoschus esculentus L.)-pea (Pisum sativum L.) cropping system in Himalayan acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, Himachal Pradesh, India, during 2009-2011 to economize inorganic phosphorus (P) and enhance profitability of okra (Abelmoschus esculentus)-pea (Pisum sativum) cropping system through arbuscular mycorrhizal fungi (AMF). A field experiment was replicated thrice in a randomized block design comprising 14 treatments involving AMF (Glomus mosseae) at varying inorganic P (50%, 75%, and 100% of recommended soil test-based P dose) and irrigation regimes (40% and 80% available water capacity] in a Himalayan acid Alfisol. In okra, AMF inoculation at varying P and irrigation regimes registered higher P response ratio (PRR), net returns (10-18%), and benefit:cost (B:C) ratio (17-49%) compared to generalized recommended P dose (GRD) and their non-AMF counterparts. Similarly in pea, AMF inoculation at varying P and irrigation regimes again registered higher PRR, net returns (14-23%), and B:C ratio (10-58%) compared to GRD and non-AMF counterparts. Higher system productivity (7-16%) and profitability in terms of net returns (9-23%) and B:C ratio (10-54%) were also registered in AMF-imbedded treatments compared to non-AMF counterparts. Further, AMF + 75% soil test-based P dose at either of these irrigation regimes registered statistically similar okra-pea system productivity and profitability as that obtained under 100% soil test-based P dose at either of two irrigation regimes, thus indicating an economy of soil test-based applied P dose by about 25%. Overall, the current study suggests that practice of AMF inoculation has great potential in enhancing system productivity and profitability besides cutting down about 25% inorganic P requirement in okra-pea production system in the Himalayan acid Alfisol.