Effects of phosphogypsum and water treatment residual application on key chemical and biological properties of clay soil and maize yield

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 of PG and WTR applied 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+PG at 5.0 t ha−1 (NF+PG5); NF+PG at 10.0 t ha−1 (NF+PG10); NF+WTR at 5.0 t ha−1 (NF+WTR5); and NF+WTR at 10.0 t ha−1 (NF+WTR10). The results revealed that the soil microbial biomass carbon (MBC), CO2 evolution and dehydrogenase activity (DHA) increased significantly with the addition of PG or WTR. The application of PG with NF at 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 of NF+PG at the rates of 10 and 5 t ha−1 and F+WTR at 10 and 5 t ha−1 increased DHA by 1.70, 1.60, 1.40 and 1.20 times, respectively, compared to the NF treatment. It can be concluded that application of PG and WTR with the recommended application rates would help in improving the properties of heavy clay soils.