Effects of biomass types and additions on soil infiltration characteristics and nutrient transport in fertilizer irrigation

Objective In order to explore the effects of different biomass additions and amounts on soil infiltration characteristics and nutrient transport in fertilizer irrigation, so as to provide a theoretical basis for improving fertilizer irrigation efficiency.

Method Biochar (BC), coffee grounds (CF) and bagasse (SC) were used as biomass additives, and four levels of addition were set including T₁ (0.5%), T₂ (1.0%), T₃ (1.5%), and T₄ (2.0%). The transport characteristics of fertilizer solution in different biomass-added soils and their nutrient distributions were measured. The effects of different biomass additions on soil structure were evaluated.

Result The inhibitory effects of three kinds of biomass on wetting front migration and soil cumulative infiltration were SC>CF>BC, and the inhibitory effects in each treatment group increased with increasing biomass addition. Compared with the CK group, the wetting front migration distances of SCT₄, CFT₄ and BCT₄ decreased by 38.33%, 37.00% and 34.00% respectively. The cumulative soil infiltration amounts of SCT₄, CFT₄ and BCT₄ decreased by 31.01%, 30.00% and 26.60% respectively. Compared with the CK group, the three kinds of biomass additions under the fertilizer irrigation improved the contents of three main inorganic nutrients in soil, and the soil fertility was improved with increasing biomass addition. The overall performance of soil nitrate nitrogen retention by the three kinds of biomass was BC>CF>SC. Among them, the soil nitrate nitrogen contents of BCT₄, CFT₄ and SCT₄ increased by 74.32%, 56.00% and 51.00% respectively. The overall performance of soil available phosphorus retention by the three kinds of biomass was CF>SC>BC. Among them, the soil available phosphorus contents of CFT₄, SCT₄ and BCT₄ increased by 140.70%, 139.20% and 30.25% respectively. The overall performance of soil available potassium retention by the three kinds of biomass was CF>BC>SC. Among them, CFT₄, BCT₄ and SCT₄ increased the soil available potassium contents by 143.87%, 126.85% and 104.03% respectively.

Conclusion All three kinds of biomass have inhibitory effects on the infiltration of fertilizer solution with biochar being the best. The three kinds of biomass all have interception effects on fertility, meanwhile, biochar has the best interception effect on nitrate nitrogen, and coffee grounds have the best interception effect on available phosphorus and available potassium.