Nutrient losses in runoff from conventional and no-till pearl millet on pre-wetted Ultisols fertilized with broiler litter

In the Southeastern Coastal Plain (USA) farmers with access to irrigation commonly water in herbicides following their preemergence application to improve efficacy of the herbicide. This practice increases near surface soil water content and may promote increased runoff during subsequent storm events. The objective of our study was to determine differences in P and N runoff from conventional tillage (CT) and no tillage (NT) systems when herbicides were watered into loamy sand Ultisols fertilized with broiler litter. Simulated rain with variable intensity was applied for 70 min with runoff samples collected every 5 min and analyzed for total P and N, PO43−, NH4+ and NO3−. Results indicated the no-tillage treatment lost significantly more PO43− and NH4+ than the conventional tillage treatment. However, total P and N and NO3− runoff losses were significantly less in the no-tillage treatment. The proportion of total P and N leached through NT residues was 5.6% and 22% of the P and N applied as broiler litter, and the proportion of total P and N in runoff was 0.8% and 1.2% of the P and N applied in broiler litter. Overall 3.4 times more N and 2.7 more P were lost in runoff from the CT treatments than for the NT treatments. Reduced tillage was found to reduce N and P losses when combined with watering-in of surface applied broiler litter.