EFFECTS OF LIMING AN ACID SOIL AMENDED WITH SEWAGE SLUDGE ENRICHED WITH CD, CU, NI, AND ZN ON YIELD AND CD CONTENT OF WHEAT-GRAIN

An acid soil (pH 5.2) was treated ± lime and 1% sewage sludge enriched with three concentrations each of Cd, Zn, Cu, and Ni in a 34 complete factorial design experiment (81 treatments ± lime). These treated soils were placed in pots and cropped with wheat (Triticum aestivum L.). Analysis of variance revealed significant main effects on grain yield from all metal additions to the acid soil and from Cd and Cu only in the limed soil. Significant main effects on the concentration of Cd in grain occurred with all metals added in the limed soil, but only from Cd, Zn, and Ni on the acid soil. Significant multiple metal interactions occurred in all cases. Multiple regression equations were developed for estimating grain yield and Cd content from soil metal additions and saturation extract metal content. Grain Cd concentrations were highly correlated with soil metal additions (R2 = 0.978 and 0.988 for limed and unlimed soils, respectively) and saturation extract metals (R2 = 0.879 and 0.950 for limed and unlimed soils). The best fit equations were used to calculate metal equivalent values for soil metals added (SME) which were then used to develop regression equations and graphs relating grain yield to SME.