Effect of sunflower stover and nutrients management on soil biological properties and available nitrogen and phosphorus at different stage of pigeonpea growth under pigeonpea-sunflower cropping system

A fixed plot field experiment was carried out during 2008-09 and 2009-10 at New Delhi, India to study the “effects of sunflower stover, nitrogen and phosphorus management on soil health under pigeonpea-sunflower cropping system’’. Kharif season experiment in the first year was laid out in split-plot design, assigning sunflower stover incorporation (8 t/ha) and no stover incorporation (control) to main plots and combination of P levels and bio-fertilizers {control, 15 kg P/ha, 15 kg P/ha + phosphate solubilizing bacteria (PSB), and 30 kg P/ha} to sub-plots. The spring season experiment of both years was laid out in split-split plot design in which NP doses to sunflower crop {control, 50% recommended dose (RD) of NP, and recommended dose (RD) of NP (80 kg N + 15 kg P/ha} were applied in sub-sub plots. Kharif season experiment in the second year was laid out in split-split plot design to investigate the residual effect of NP doses applied to spring season crop in sub-sub plots. Treatments were replicated thrice during both years. Results reveal that the sunflower stover incorporation resulted in better soil biological properties in terms of dehydrogenase activity, alkaline phosphatase activity and microbial biomass carbon (MBC). Available soil NH4-N and NO3-N, available P initially reduced due to sunflower stover incorporation but at latter stages, these nutrients in soil increased. Among the various P levels, application of 30 kg P/ha recorded maximum values of soil dehydrogenase, MBC and available P, NH4-N and lowest values of alkaline phosphatase and NO3-N. With respect to the residual effect of nitrogen and phosphorus applied to sunflower, among the various levels of N and P, recommended dose (RD) of N and P resulted in better soil biological properties under study and higher values of available N and P.   Key words: Available nutrients, biological properties, cropping system, nutrients management, sunflower stover management.