Effect of Biochar, Hydrogel and Soil Liming on Nutrient Leaching in a Coarse-Textured Soil

Nutrient leaching from agricultural fields can degrade soil fertility and groundwater quality, especially in coarse-textured soils. Amending soils with biochar, lime, hydrogel, or their combinations may reduce leaching, but the effects of single versus combined amendments remain unclear. A three-year pot experiment under field conditions was conducted on a loamy sand soil to enhance water and nutrient retention capacity of this soil. Soil samples were mixed with all possible combinations of 1% biochar (B), l% lime (L), and 0.5% hydrogel (H), i.e., BL, BH, HL, and BHL. The amendments were arranged in a randomized complete block design with four blocks. The results showed that compared to control, amendments B, H, BH, HL, and BHL significantly decreased (p ≤ 0.05) nitrate-N leaching per unit biomass by 58%-88%, and L, H, BH, HL, BHL significantly reduced (p ≤ 0.05) orthophosphate-P leaching per unit biomass by 34%-98%. Compared to control, the marketable yield significantly increased (p ≤ 0.05) by 24%-38% under BH, HL, and BHL in 2019, and by 17%-52% under amendments B, L, H, BL, BH, HL, and BHL in 2020. These results were not seen in the first year due to soil conditioning for biochar and lime. Amendments H, BH, HL, and BHL show potential to improve water use efficiency, reduce nutrient leaching, and support sustainable crop production.