Uptake of nitrogen, phosphorus, potassium and sulphur by rice (Oryza sativa) and sunflower (Helianthus annuus)

Abstract

A field experiment was conducted during 1989-91 at Bangalore. There were 7 early rainy-season crop treatments
and a fallow. Among the treatments Sesbania rostrata green-manure-rice (Oryza sativa L.) -sunflower (Helianthus annuus) sequence'had the highest uptake'of N, P, K and S, followed by sunnhemp (Crotalaria juncea L.) rice-sunflower. The organic carbon content and available N, P and K status of the soil increased signitlcantly with Sesbania rostrata followed by sunnhemp green-manurt. Rice-sunfloWer sequence following fodder maize (Zea mays L.) had the lowest N, P, K and S uptake as well as the lowest organic carbon and available N, P, K and S status of soil at the end of second cycle of sequence crops, followed by fallow-rice-sunflower. Grain yield of rice and sunflower (4.47 and 0.78 tonnes/ ha) was significantly highest with S. rostrata green-manure, followed by sunnhemp, and the least with early rainy- season maize. Biomass yield also followed a similar trend.