Can application of liquid dairy manure onto no-tillage oxisols reduce runoff, sediment, phosphorus, and nitrogen losses over 9 years of natural rainfall?

The objective of this study was to explore the effects of long-term (9 years) application of liquid dairy manure (LDM) on runoff, sediment, phosphorus, and nitrogen losses in two Oxisols with sandy clay loam or clayey textures under no-tillage and natural rainfall. Treatments were LDM rates of 0, 60, 120, and 180 m(3) ha(-1) year(-1) randomized in a complete block design with four replications. Manure was applied onto a mulch cover and split into winter application, after black oat or wheat sowing, and summer application, after soybean or maize sowing. Runoff was sampled and analysed after each rainfall event for 9 years. Rainfall events which led to runoff were separated into three classes: <35 mm day(-1), 35-50 mm day(-1), and >50 mm day(-1). Application of LDM increased the concentration of nutrients in the runoff, but overall reduced the runoff volume and therefore losses of sediment, dissolved reactive phosphorus, ammonium, and nitrate by on average 34% in the sandy clay loam soil and 56% in the clayey soil, at the most effective rate of 120 m(3) ha(-1) year(-1) Effects of LDM application on reducing runoff was also more evident in summer season and for rainfall events <35 mm day(-1). In practical terms, we would recommend application of LDM up to rate of 120 m(3) ha(-1) year(-1 )to promote agronomic and environmental benefits. Although LDM applied in no-tillage system reduced water, sediment, and nutrients losses, complementary practices must be adopted to prevent the surface runoff from reaching the aquatic system.

Automated summary

The long-term application of liquid dairy manure (LDM) had varying effects on runoff, sediment, and nutrient losses in two Oxisols with different textures. Increasing the LDM rate up to 120 m(3) ha(-1) year(-1) was found to be effective in reducing losses and runoff, especially during the summer season and for rainfall events <35 mm day(-1). Complementary practices should be adopted to prevent surface runoff from reaching aquatic systems.