Potato peel and Date palm waste char: Production techniques and their effects on soil properties and plant growth

In arid regions such as the United Arab Emirates, where 80 % of the land consists of deserts, sandy soils pose significant agricultural challenges due to their low organic carbon content, poor water retention capacity, and high nutrient leaching. This study investigates the potential of potato peel (PP) waste and palm waste (PW) chars, produced through microwave pyrolysis, conventional pyrolysis and microwave hydrothermal carbonisation, to improve soil properties, nutrient retention, and plant growth in sandy soil. Three wheat-pot experiments were conducted under controlled conditions over 12 weeks.
Char characterisation revealed that production temperature and feedstock composition significantly influenced biochar physiochemical properties. The initial lab experiments revealed that higher pyrolysis temperatures reduced biochar yield but increased surface area and porosity. Chars with high cationic exchange capacity (CEC), particularly potato peel biochars produced via conventional (PP-CB) and microwave pyrolysis (PP-PB), and palm waste biochar produced via conventional pyrolysis (PW-CB), significantly reduced water leaching and leaching of nutrient, including calcium (p < 0.05), magnesium (p < 0.05), and nitrate (p < 0.05), while enhancing plant growth. In contrast, chars produced via hydrothermal carbonization (PP-MWH and PW-MWH) were hydrophobic, leading to increase leachate volumes and nutrient losses. Despite PP-CB exhibiting high CEC, excessive potassium leaching (p < 0.05) was observed, leading to nutrient imbalances and inhibited root development.
Plant growth analysis showed that char amended soils generally improved biomass yield and nutrient uptake, except for hydrothermal chars and PP-CB. Leaf number remained similar across treatments during the initial stages but increased significantly from weeks 6 to 12 (p < 0.05).
This study compares the effectiveness of different char produced from different feedstocks and production methods on char properties, soil leachate, nutrient retention, and dissolved organic carbon leaching. These findings suggest that PP-PB, PW-CB are the most effective treatments for improving soil fertility and crop productivity in arid environments.