Predicting grain yields of maize in soil amended with organic wastes using modified productivity index was studied for three cropping seasons. Soil samples for determination of productivity index and individual productivity indicators for prediction of grain yields of maize were collected from 0 15, 15-30, 30-45, and 45-60 cm depths. Ascribed sufficiency value was assigned to each productivity indicator of bulk density, available water capacity (AWC) pH and depth of rooting zone (DRZ) which were used to calculate productivity index (PI) for each amendment. Highest predictions of grain yields of maize were obtained for sawdust PI=0.39 and grain yield of maize-2.30 t ha-1 in 2013 and burnt rice mill waste PI=0.39 and grain yield of maize=2.30 t ha-1 and PI=0.37 and grain yield of maize=2.25 t ha-1 in 2014 and 2015 cropping seasons, respectively. The prediction of organic wastes for grain yields of maize is as follows BRMW>SD>URMW>C. Calculated productivity index (CPI) predicted highly significant (r=0.92 and r2=0.84) grain yields of maize. Bulk density more than AWC and pH predicted highly significant (r=0.95 and r2 = 0.89) grain yield of maize.
Key words: Amended, grain yields of maize, organic wastes, predicting, productivity index.