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

Authors: TRIMARCO, TAD - Colorado State University; Harmel, Robert; WARDEL, ERIK - Colorado State University; BUCHANAN, CASSIDY - Colorado State University; BROWN, ANSLEY - Colorado State University; DELEON, EMMANUEL - Colorado State University; IPPOLITO, JAMES - Colorado State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Intense tillage on farmland damages soil health, destroying soil structure and accelerating nutrient and sediment transport to vulnerable water bodies. Despite this, few studies have measured both soil health and water quality in response to 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, strip, and minimum) on soil health and water quality on large research plots. Specifically, we measured ten soil health indicators under the Soil Management Assessment Framework, soil organic C fractionations, and six edge-of-field runoff water quality indicators over two years. Results suggested that edge-of-field water quality was improved in strip till and minimum till plots as compared to conventional till. Additionally, indicators of physical soil health and biological soil health correlated to decreased concentrations of water quality pollutants. This trend was most pronounced for runoff particulates, indicating that resistance to erosion in conservation tillage is the most important factor in sediment and particulate N runoff. Furthermore, the lack of difference with regards to water quality, soil health, and crop yield indicates that there is little difference between strip till and minimum till. We suggest minimizing tillage to minimize inputs with additional tillage as necessary to meet agronomic needs.

Technical Abstract: Intense tillage on farmland damages soil health, destroying soil structure and accelerating nutrient and sediment transport to vulnerable water bodies. Despite this, few studies have measured both soil health and water quality in response to 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 [CT], strip [ST], and minimum [MT]) on soil health and water quality on large research plots. Specifically, we measured ten soil health indicators under the Soil Management Assessment Framework, soil organic C fractionations, and six edge-of-field runoff water quality indicators over two years. Results suggested that edge-of-field water quality was improved in ST and MT tillage plots as compared to CT. Additionally, indicators of physical soil health (bulk density, 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, indicating that aggregate resistance to erosion in conservation tillage is the most important factor in sediment and particulate N runoff. Furthermore, the lack of difference between ST and MT plots with regards to water quality, soil health, and crop yield indicates that there is little difference between ST and MT. We suggest minimizing tillage to minimize inputs with additional tillage as necessary to meet agronomic needs.