Data from: Surface and subsurface phosphorus discharge from a clay soil in a 9-year study comparing no-till and plowing

No-till as a water protection measure is highly efficient in controlling erosion and particulate phosphorus (PP) loss, but tends to increase dissolved reactive P (DRP) concentrations in runoff water. In a 9-year field study on a clay soil in SW Finland, the effects of no-till and autumn plowing on surface runoff and subsurface drainage water quality were compared. The site had 2% slope and was under spring cereal cropping, with approximately replacement fertilizer P rates. Vertical stratification of soil test P that had developed during a preceding 6-year grass ley was undone by plowing, but continued to develop under no-till. During the 9-yr study period, no-till soil had 27% lower cumulative total P losses than plowed soil (10.0 vs. 13.7 kg TP ha-1). Concentrations and losses of PP were clearly lower under no-till than plowing (5.6 vs. 12.3 kg PP ha-1), but DRP loss showed the opposite trend (4.3 vs. 1.4 kg DRP ha-1). There was an increasing trend in subsurface drainflow DRP concentration under no-till, possibly because of development of a conductive pore structure from soil surface to drain depth. The potential benefit of no-till in water protection depends on how much of the PP transported to water is transformed into a bioavailable form and used by aquatic organisms. The beneficial effect of no-till in controlling P induced eutrophication at the study site would only be realized if the bioavailable share of PP exceeds 43%. Otherwise no-till would not be an efficient eutrophication control measure at this site