Compounding with humic acid improved nutrient uniformity in drip fertigation system using brackish water: The perspective of emitter clogging

Brackish water drip irrigation (BWDI) is an effective application to overcome the water scarcity issues and achieve sustainable agriculture development. However, emitter clogging and soil salinization is inevitable issue in BWDI, eventually threatening the environmental pollution and sustainable application of drip irrigation systems. Therefore, this study experimentally assessed the anti-clogging efficacy of compounding appropriate types of humic acid (HA) with conventional fertilizer in BWDI systems (BWDIs). Humic acid nitrogen (HAN), humic acid phosphate (HAP), humic acid potassium (HAK), were compounded with conventional fertilizers. Our results revealed, compared with conventional fertilizer (CK) the HA treatments indirectly affected the precipitates and particulate fouling by absorbing the active functional groups, and directly decreased the pH, calcium and magnesium contents in brackish irrigation water. Accordingly, HA compound fertilizer significantly reduced the fouling content of drip irrigation system, and the anti-clogging effect became better with the increase of HA application. Thus, based on better anti-clogging performance and minimum fertilizer costs, our results suggested, the HAN+HAK integrated fertigation could be an effective selection for BWDIs, which significantly enhanced the average discharge ratio and Christiansen coefficient of nutrient uniformity in BWDIs by 16.0% and 19.0% respectively. These results might provide a new guideline for the successful application of HA compound fertilizer in BWDIs, to increase the drip irrigation anti-clogging ability and overcome the agricultural non-point source pollution issues.