Abstract
Sandy soil covers a significant portion of Egypt's total land area, representing a crucial agricultural resource for future food security and economic growth. This research adopts the hypothesis of maximizing the utilization of secondary products for soil improvement to reduce ecosystem pollution. The study focuses on assessing the impact of combining phosphogypsum and modified biochar as environmentally friendly soil amendments on loamy sand soil quality parameters such as soil organic carbon, cation exchange capacity, nutrient levels, and wheat yield. The treatments were T(1): the recommended NPK fertilizer (control); T(2): 2.5 kg phosphogypsum m(-2) soil; T(3): 2.5 kg rice straw biochar m(-2) soil; T(4): 2.5 kg cotton stalk biochar m(-2) soil; T(5): 2.5 kg rice-straw-modified biochar m(-2) soil; T(6): 2.5 kg cotton-stalk-modified biochar m(-2) soil; and T(7) to T(10): mixed phosphogypsum and biochar treatments. The results revealed that the combined use of phosphogypsum and modified cotton stalk biochar (T(10)) significantly enhanced soil organic carbon (SOC) by 73.66% and 99.46% in both seasons, the soil available N both seasons by 130.12 and 161.45%, the available P by 89.49% and 102.02%, and the available K by 39.84 and 70.45% when compared to the control treatment. Additionally, this treatment led to the highest grain yield of wheat (2.72 and 2.92 Mg ha(-1)), along with a significant increase in straw yield (52.69% and 59.32%) compared to the control treatment. Overall, the findings suggest that the combined use of phosphogypsum and modified biochar, particularly cotton-stalk biochar, holds promise for improving loamy sand-soil quality and wheat productivity.