Runoff Losses of Sediment and Phosphorus from No‐Till and Cultivated Soils Receiving Dairy Manure

Managing manure in no‐till systems is a water quality concern because surface application of manure can enrich runoff with dissolved phosphorus (P), and incorporation by tillage increases particulate P loss. This study compared runoff from well‐drained and somewhat poorly drained soils under corn ( Zea mays , L.) production that had been in no‐till for more than 10 yr. Dairy cattle ( Bos taurus L.) manure was broadcast into a fall planted cover crop before no‐till corn planting or incorporated by chisel/disk tillage in the absence of a cover crop. Rainfall simulations (60 mm h −1 ) were performed after planting, mid‐season, and post‐harvest in 2007 and 2008. In both years and on both soils, no‐till yielded significantly less sediment than did chisel/disking. Relative effects of tillage on runoff and P loss differed with soil. On the well‐drained soil, runoff depths from no‐till were much lower than with chisel/disking, producing significantly lower total P loads (22–50% less). On the somewhat poorly drained soil, there was little to no reduction in runoff depth with no‐till, and total P loads were significantly greater than with chisel/disking (40–47% greater). Particulate P losses outweighed dissolved P losses as the major concern on the well‐drained soil, whereas dissolved P from surface applied manure was more important on the somewhat poorly drained soil. This study confirms the benefit of no‐till to erosion and total P runoff control on well‐drained soils but highlights trade‐offs in no‐till management on somewhat poorly drained soils where the absence of manure incorporation can exacerbate total P losses.