Short-Term Soil Health Responses to Biochar and Irrigation in a Sandy Loam Soil

Abstract This study was conducted to determine how irrigation alters the effects of biochar on soil health parameters in a coarse texture soil for two consecutive growing seasons. Surface soil (0–15 cm) samples from a split-plot randomized block design (main plots, unirrigated and irrigated; subplots, 0 and 11.2 Mg ha − 1 biochar) taken after soybean ( Glycine max ) harvest in 2022 and 2023 were analyzed for electrical conductivity, pH, labile and total C, inorganic and total N, respiration rate, activities of four extracellular enzymes, and phospholipid fatty acid profiles. Yield was also measured. Neither biochar nor irrigation increased yield. Biochar increased pH and β-glucosidase activity but decreased phosphatase activity. Irrigation reduced organic C, respiration and activities of all enzymes except arylsulfatase. Principle component analysis showed that parameters related to organic C turnover were important without irrigation. Structural equation modeling for respiration rate found small positive effects of phosphatase activity and labile C with irrigation ( P < 0.10), but large positive effect of phosphatase without ( P < 0.01). An interrelationship of other enzymes and microbial biomass was important to respiration without irrigation, though not with irrigation. The effect of irrigation on soil health parameters in a coarse texture soil for two growing seasons was greater than the effect of biochar.