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United States Department of Agriculture

Agricultural Research Service

Title: Nitrogen and phosphorus losses from variable and constant intensity rainfall simulations on loamy sand under conventional and strip tillage systems

Authors
item Franklin, Dorcas
item Truman, Clinton
item Potter, Thomas
item Bosch, David
item Strickland, Timothy

Submitted to: Southern Association of Agricultural Scientists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 8, 2007
Publication Date: January 8, 2007
Citation: Franklin, D.H., Truman, C.C., Potter, T.L., Bosch, D.D., Strickland, T.C. 2007. Nitrogen and phosphorus losses from variable and constant intensity rainfall simulations on loamy sand under conventional and strip tillage systems [abstract]. Southern Branch American Society of Agronomy 2007, February 4-6, 2007, Mobile, Alabama. CD-ROM.

Technical Abstract: Nitrogen and phosphorus loss in runoff for different tillage systems must be better quantified to evaluate nutrient management strategies for best nutrient use efficiency and calibration of current nutrient transport risk assessment tools. 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 (both of which averaged at the end of the rainfall event to be 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. 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 DRP and NO3-N than conventional tillage systems, but only a fraction of the total N (33%) and total P (11%) lost through over land flow from conventional tillage systems. These results also 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.

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