Asian Journal of Soil Science and Plant Nutrition

The scarcity of irrigation water in Egypt requires addressing severe water scarcity, such as deficit irrigation and using organic amendments to improve water use efficiency in agriculture. A field experiment was conducted at El-Nubaria Agricultural Research Station in the summer of 2022 for maize and the winter of 2022/2023 for wheat to study the impact of organic amendments and irrigation regime on calcareous soil properties and productivity. The experiment involved a split-plot design with three replicates, irrigation regime was placed in main plots (50% (I₅₀), 75% (I₇₅), and 100% (I₁₀₀) of ETc) and organic amendments in subplots included five treatments: 1) 9.6 ton ha^-1 (B₁), 2) 14.4 ton ha^-1 (B₂) of biochar, 3) potassium humate at the rate of 1.5% (KH₁), 4) 3% (KH₂) and 5) compost (12 ton ha^-1). The obtained results indicated that compost, followed by B₂ (14.4 ton ha^-1), achieved the highest soil organic matter value. Applied I₁₀₀ had the highest soil available NPK and micronutrients, followed by I₇₅. Organic amendments significantly affected the soil availability of N, P, K, Fe, Mn and Zn. The maximum potassium content in grains was achieved using I₁₀₀, followed by I₇₅. The influence of organic amendments on field capacity and available water took the descending order: B₁> KH₁> compost. Water use efficiency was negatively impacted by increasing the amount of applied irrigation water. Applying I₁₀₀ resulted in a significant increment in wheat and maize grain yields, followed by I₇₅. The influence of organic amendments on wheat grain yield took the descending order: compost > potassium humate > biochar, while the effect on maize grain yield took the descending order: potassium humate > compost > biochar.