Biochar, Bentonite and Potassium Humate Effects on Saline Soil Properties and Nitrogen Loss

Aim: In order to study the effect of biochar, bentonite and potassium humate on saline soil characteristics, barley growth and nitrogen loss, a column experiment was conducted. Addition of the above mention materials was hypothesized to improve the characteristics of saline soil and decrease nitrogen loss in the leachate solution.

Place and Duration of Study: Farm of Soils and Water Department, Faculty of Agriculture, Al-Azhar University, Cairo, Egypt during the winter season of 2019.

Methodology: Biochar and bentonite were added with rates 0, 5 and 10 g.kg-1; and the rates of potassium humate were 0, 5 and 10 mg.kg-1. Excess irrigations were implemented three times (on 12th, 24th, 36th days) during growing season. Leachate solution was collected after each excess irrigation from each column to determine nitrogen loss.

Results: Main results show that total organic carbon and soil porosity were increased by increasing the addition rates of the studied materials, especially at the high rates of biochar and bentonite. Also, the availability of water significantly increased. Addition of biochar and bentonite gave the highest decreasing in leachate solution volume. Nitrogen loss was decreased significantly at the highest rates of the studied materials, where the decrement percentage in leachate solution reached at 36.07%, 35.82 and 23.81 at the highest rates of biochar, bentonite and potassium humate, respectively. That led to increasing the retention of available nitrogen in saline soil. Fresh and dry weights of barley plants were increased significantly by increasing the addition rates of all amended materials. Macronutrients (NPK) content and uptake were increased significantly by increasing the addition rates of the studied materials.

Conclusion: Research results proved that changes in soil properties caused a significant increase in barley growth and nutrients uptake. Addition of biochar and bentonite were the best option for improving saline soil properties, barley growth and nutrients uptake and reduce nitrogen loss by improving nitrogen retention and decreasing the leachate volume.