Soil Quality Improvement through Conversion to Sprinkler Irrigation

Core Ideas Long‐term furrow irrigation has caused soil erosional losses. Sprinkler irrigation is considered a water conservation practice. Conversion from furrow to sprinkler irrigation improves soil quality in degraded field areas. Conversion from furrow to sprinkler irrigation is a recommended conservation practice for improved water‐use efficiency (and erosion control), but effects on soil quality indicators are unknown. Several soil quality indicators were therefore quantified within a northwestern United States Conservation Effects Assessment Project (CEAP) watershed after changing from long‐term furrow to sprinkler irrigation. Four on‐farm sites were identified where producers were growing irrigated barley (Hordecum vulgare L.) using both irrigation practices. Climate, soil type, and management were similar between sites. Soil samples were collected from the upper and lower ends of furrow irrigated fields at three in‐field positions (bed, shoulder, and furrow); fields converted to sprinkler irrigation were sampled where the upper and lower ends were when the field was furrow irrigated. Soil quality indices (physical, chemical, biological, nutrient, and overall) were computed using the Soil Management Assessment Framework (SMAF). Regardless of in‐field position, furrow irrigated field bottoms had higher soil quality index scores than field tops because of long‐term erosional deposition. Within sprinkler irrigated fields, soil quality indices for field tops and bottoms showed minimal differences. Overall, when all sampling locations and in‐field positions were combined, soil quality was similar for both irrigation methods. However, as compared with furrow irrigation, sprinkler irrigation had greater soil quality indices in the field tops, suggesting that sprinkler irrigation improved soil quality of historically eroded furrow irrigated fields.