Strategic tillage of no-till decreased surface and subsurface losses of dissolved phosphorus

No-till is a cultivation practice in which plant seeds are applied in soil without completely breaking up the surface of agricultural fields as, e.g., in plowing. When growing annual crops, no-till is considered the most effective way of controlling erosion and associated nutrient losses to surface waters. The downside of long-term no-till, especially in soils with modest inherent erosion, is phosphorus (P) enrichment of the uppermost soil surface layer that causes an increase in dissolved P loss, i.e., the most potent fraction of P losses causing eutrophication of surface waters. As a remedy to dissolved P losses, occasional tillage, also termed strategic tillage, of long-term no-till fields has been suggested. We made strategic tillage of clay soil that has been under no-till management for a decade and measured surface and subsurface P losses during the following 4 yr. The study was made on a field, divided into four 0.5-ha plots, in SW Finland. Surface and subsurface (tile drainage) waters are collected and sampled for analyses flow-propositionally. These supplemental data contain a description of the field site and quarter-year sums of surface and subsurface discharges of water, dissolved P, particulate P, and total P. Also, the outcomes of statistical testing of the data are included. We found that strategic tillage effectively (by about 60%) decreased the losses of dissolved P via surface and subsurface discharge pathways. When the strategic tillage was done in summer and a new crop was sown a week later, erosion-associated particulate P losses only increased by about 10%. At the study site, strategic tillage was preferred over continuous no-till and annual plowing when searching for the least water eutrophication-fuelling tillage methods.

Methods
The data are from a 2-ha field in SW Finland where surface and subsurface discharges are measured and sampled. In the field, three tillage options were applied: annual plowing, continuous no-till, and no-till that was plowed one time in the summer of 2018. Included in the data are discharge water volumes and P losses via surface and subsurface pathways during four years. The data are calculated as quarter-year sums from Aug 2018 to Aug 2022.