Influence of organic nutrient management on Basmati rice (Oryza sativa)– wheat (Triticum aestivum)–greengrsam (Vigna radiata) cropping system

In a field experiment conducted at New Delhi during 2003–2009, different organic sources of nutrients such as multani mitti based blue green algae (BGA) @ 2.0 kg/ha, Azolla @ 1.0 tonne/ha, vermicompost (VC) @ 5.0 tonne/ha and farm yard manure (FYM) @ 5.0 tonne/ha were tested alone or in combinations to find out suitable organic sources of nutrient supply for sustaining the productivity of Basmati rice (Oryza sativa L.)–wheat [Triticum aestivum (L.) emend. Fiori & Paol.]–greengram [Vigna radiata (L.) R. Wilczek] cropping systems. In wheat crop Azotobacter replaced Azolla, but other treatments remained same. Greengram was taken up on residual soil fertility and biomass of this crop was incorporated after picking the pods. Results revealed a significant enhancement in grain yield of rice over absolute control due to the application of different organic sources of nutrient applied alone or in combinations. Grain yield over 4.0 t/ha of Basmati rice (‘Pusa Basmati 1’) was obtained with the combined application of four (Azolla, BGA, FYM and VC) organic sources of nutrients. Grain yield of wheat was lower than 4 t/ha during first four years even with the combined application of four organic sources of nutrients, but, fourth year onward wheat yield level crossed 4.0 t/ha level with four organic sources of nutrient. A significant increase in uptake of iron, zinc and manganese in the grains of rice, wheat and greengram was recorded when two or more organic sources of nutrient were applied together compared to control. Total uptake of Fe, Zn, Mn and Cu in rice-wheat-greengram cropping system ranged between 177.0.1 to 414.7, 175.0 to 381.0, 177.3 to 420.2 and 71.2 to 181.0 g/ha, respectively. Microbial (actinomycetes, bacteria, fungi and BGA) population was enhanced due to the application of four sources of organic nutrients as compared to absolute control that resulted in a notable enhancement in dehydrogenase enzyme activity. Sustainability yield index (SYI) data indicated that rice-wheat-greengram system (0.93) was most sustainable followed by greengram (0.85), wheat (0.82) and rice (0.81) crop under integrated use of organic sources of nutrients.