Long-Term Effect of Phosphate Rocks for Rice-Groundnut Cropping System

A field experiment was conducted for five years in the Central Research Station of Orissa University of Agriculture and Technology, Bhubaneswar, Orissa during 1994-1995 in order to study the long-term effects of phosphate rocks for rice-groundnut cropping system. Rice variety Lalat and groundnut variety ICGS 11 were taken as the test crop. Altogether there were ten treatments including control. The soil of the experimental site was sandy to sandy clay loam (Fluventic Ustochrept) having pH 5.6, low organic carbon, medium available ‘P’, (Olsen and Bray) and low CEC. Three rock phosphates (water insoluble) namely Yousouffia, Gafssa and Tebessa (YRP, GRP, and TRP) imported from Morocco along with one indigenous i.e. Mussoorie rock phosphate (MRP) were applied @ 250 kg and 500 kg P₂O₅ ha^-1 once before planting of rice was compared with water soluble form of fertilizer i.e. DAP was applied @ 50 kg ha^-1 to each crop on each seasons for five years. Application of rock phosphate increased the yield of rice and groundnut over control and DAP. Application of 500 kg P₂O₅ ha^-1 from rock phosphate source produced significantly higher yield over 250 kg P₂O₅ ha^-1 but reverse trend was marked in case of apparent ‘P’ recovery (APR), agronomic efficiency (AE) and production efficiency (PE). Available ‘P’ status showed an increasing trend from the initiation of the experiment till the end of the experiment. The sustainable yield index (SYI) indicated almost all the treatments to be recommendable excepting control in case of groundnut.