THE IMPACT OF FERTILIZER APPLICATION TECHNIQUES ON NITROGEN YIELD FROM 2 TILLAGE SYSTEMS

Simulated rainfall was used on experimental plots to study the effects of surface and subsurface fertilizer application methods on N yields from no-till and conventional tillage systems. Approximately 100 mm of simulated rainfall with an intensity of 50 mm h-1 was applied to 12 experimental field plots. Two fertilizer application methods, surface application and subsurface application, were investigated for no-till and conventional tillage systems. The no-till system was found to be very effective in reducing runoff and sediment losses. No-till reduced sediment loss and total runoff volume by 91-95% and 48-54%, respectively. Observed N yield was highest when fertilizer was surface applied in conventional tillage, and lowest when the fertilizer was incorporated in the no-till system. The effectiveness of no-till for N yield reduction ranged from 50% for NO3-N to 96% for TN(sed) compared with conventional tillage. Nitrogen yield in runoff from no-till plots was comparable to that from control plots (no fertilizer application) and significantly lower than that from conventional tillage plots. From the results of this study, it was concluded that compared with surface application, subsurface application of fertilizer is very effective for N yield reduction in runoff and is therefore recommended as an effective measure for controlling the nonpoint source pollution of surface waters.