Abstract
The reuse of phosphogypsum (PG) and water treatment residual (WTR) waste for agricultural purposes is a possible option to improve the soil properties and increase the crop yield. The present study was conducted during the 2014 growing season in order to determine the impacts ofPGandWTRapplied to the heavy clay soils (which contain more than 50% clay particles) at rates of 5 and 10 t ha(-1)with the recommended nitrogen fertilizer (NF) on the key soil properties and maize yield. A field experiment was conducted as a randomized complete block design with five treatments and three replications. The treatments were as follows: recommended nitrogen fertilizer (NF);NF+PGat 5.0 t ha(-1)(NF+PG5);NF+PGat 10.0 t ha(-1)(NF+PG10);NF+WTRat 5.0 t ha(-1)(NF+WTR5); andNF+WTRat 10.0 t ha(-1)(NF+WTR10). The results revealed that the soil microbial biomass carbon (MBC),CO(2)evolution and dehydrogenase activity (DHA) increased significantly with the addition ofPGorWTR. The application ofPGwithNFat the rate of 10 t ha(-1)recorded the highest microbial activity, soil available nutrients, grain yield and yield component of maize plants compared to the other treatments. Additions ofNF+PGat the rates of 10 and 5 t ha(-1)and F+WTRat 10 and 5 t ha(-1)increasedDHAby 1.70, 1.60, 1.40 and 1.20 times, respectively, compared to theNFtreatment. It can be concluded that application ofPGandWTRwith the recommended application rates would help in improving the properties of heavy clay soils.