Impact of no-tillage on water purification and retention functions of soil

Abstract

There are still uncertainties regarding the long-term impact of no-tillage farming practices on separate soil functions in the United Kingdom. This paper aimed to evaluate the chemical and physical processes in two different agricultural soils under no-tillage and conventional management practices to determine their impact on water related soil functions at field scale in the United Kingdom. The field-scale monitoring compares two neighboring farms with similar soil and topographic characteristics—one of the farms implemented no-tillage practices in 2013, while the second farm is under conventional soil management with moldboard plowing. Two soil types were evaluated under each farming practice: (1) a free-draining porous limestone, and (2) a lime-rich loamy soil with high silt and clay content. Field monitoring was undertaken over a two-year period and included nutrient analysis of surface and subsurface soil samples, bulk density, soil moisture, infiltration capacity, surface runoff, and analysis of phosphorus (P) and suspended solids in watercourses in close proximity to the test fields. The conversion to no-tillage changed the soil structure, leading to a higher bulk density and soil organic matter content and thereby increasing the soil moisture levels. These changes impacted the denitrification rates, reducing the soil nitrate (NO₃) levels. The increased plant material cover under no-tillage increased the levels of soil phosphate (PO₄^3–) and PO₄^3– leaching. The extent to which soil functions were altered by farming practice was influenced by the soil type, with the free-draining porous limestone providing greater benefits under no-tillage in this study. The importance of including soils of different characteristics, texture, and mineralogy in the assessment and monitoring of farming practice is emphasized, and additionally the between field and in-field spatial variability (both across the field and with depth) highlighted the importance of a robust sampling strategy that encompasses a large enough sample to effectively reveal the impact of the farming practice.