Connecting the soil health-water quality nexus under surface-irrigated conservation tillage.

Abstract

Intense tillage degrades soil health, worsens soil structure, and accelerates nutrient and sediment transport to vulnerable water bodies. Unfortunately, few studies have measured both soil health and water quality under conservation tillage, particularly in semi-arid furrow-irrigated fields, limiting our understanding of tillage impacts in these systems. To address this research gap, we investigated the impact of three tillage types (conventional tillage [CT], strip tillage [ST], and minimum tillage [MT]) on soil health and water quality on large research plots. Specifically, we measured 10 soil health indicators under the Soil Management Assessment Framework, soil organic C fractionations, and six edge-of-field runoff water quality indicators over 2 years. Edge-of-field water quality was improved in ST and MT plots as compared to CT, with reductions in mean concentrations for particulate constituents (sediment and total Kjeldahl N) approaching approximately 50% or greater. Additionally, indicators of physical soil health (bulk density and water-stable aggregates) and biological soil health (microbial biomass C, soil organic C, potentially mineralizable N, and particulate organic matter C) correlated to decreased concentrations of water quality pollutants. This trend was most pronounced for particulate constituents (e.g., sediment, total Kjeldahl N), which were correlated to indicators of aggregate stability. Furthermore, the lack of difference between ST and MT plots with regards to water quality, soil health, and crop yield indicated that there was little difference between ST and MT. In semi-arid furrow-irrigated fields, we suggest utilizing reduced tillage practices to limit offsite sediment loss, nutrient transport, and environmental degradation.