Dorcas Franklin1, Clinton Truman2, David Bosch3, Thomas Potter4, and Timothy Strickland4. (1) USDA-ARS, 1420 Experiment Station Rd, Watkinsville, GA 30677, (2) Southeast Watershed Res. Lab., "Po Box 748, 2375 Rainwater Rd.", Tifton, GA 31793, United States of America, (3) USDA-ARS-SEWRL, PO Box 748 Rainwater Road, PO Box 748 Rainwater Road, Tifton, GA 31793, United States of America, (4) USDA ARS, 817 Gornto Rd., 817 Gornto Rd., Tifton, GA 31602
Nitrogen and phosphorus loss in runoff for different tillage systems must be better determined to adjust nutrient management strategies for best nutrient use efficiency and to calibrate current risk assessment tools for nutrient contamination. Our objective was to quantify and compare effects of constant (Ic) and variable (Iv) rainfall intensity patterns on inorganic nitrogen (N) and phosphorus (P) losses from a Tifton loamy sand (Plinthic Kandiudult) cropped to cotton (Gossypium hirsutum L.) and managed under conventional (CT) or strip-till (ST) systems. We simulated rainfall at a constant intensity and a variable intensity pattern (57 mm h-1) and collected runoff continuously at 5 min intervals for 70 min. We found that CT treatments lost significantly greater amounts of TKN and TKP than ST treatments and in contrast, ST treatments lost significantly greater amounts of DRP and NO3-N than CT treatments. For cumulative runoff at 70 min, no significant differences in total losses were evident for TKN or TKP from either rainfall intensity pattern. In contrast, total cumulative losses of dissolved reactive P (DRP) and NO3-N were greatest for ST-Ic, followed by ST-Iv, CT-Ic, and CT-Iv in diminishing order (69 g DRP ha-1 and 361 g NO3-N ha-1 ; 37 g DRP ha-1 and 133 g NO3-N ha-1; 3 g DRP ha-1 and 58 g NO3-N ha-1; 1 g DRP ha-1 and 49 g NO3-N ha-1). These results indicate that strip tillage systems may be losing more soluble fractions than conventional tillage systems, but only a fraction the total N (33%) and total P (11%) lost through over land flow from conventional tillage systems. These results indicate that constant-rate rainfall simulations may over estimate the amount of dissolved nutrients lost to the environment in overland flow from cropping systems in loamy sand soils.
See more of Soils--Environmental
See more of The 2007 SAAS Convention
