“Effect of Adding NPK-Chitosan Fertilizer and Organic Matter On  Phosphorus and Potassium Content of Corn (Zea Mays L.)”. University of Thi-Qar Journal of Agricultural Research, vol. 13, no. 1, June 2024, pp. 146-52, https://doi.org/10.54174/utjagr.v13i1.310.