Experimental Evidence for the Safety Net Hypothesis in a
Pecan-Cotton Alley Cropping System in the Southern United States. (A08-allen315295-oral)
Authors:
S.C. Allen* - CSTAF, University of Florida S. Jose - University of Florida
P.K. Nair - University of Florida B.J. Brecke - University of Florida C.L. Ramsey - University of Florida
Abstract:
Excessive application of nitrogen fertilizer in commercial agriculture can result in leaching of nitrate (NO3-N) into surface and subsurface drainage water. Temperate alley cropping is considered to hold potential for mitigating leaching problems because deep roots of trees may serve as a ‘safety net’ for capturing the N that is leached below the crop rooting zone. This hypothesis was tested in a pecan (Carya illinoensis K. Koch)-cotton (Gossypium hirsutum L.) alley cropping system in northwestern Florida from June 2001 to August 2002. Nutrient leaching was quantified from lysimeter water samples collected at 0.3 and 0.9 m depths at specific locations in alleys of barrier (tree roots excluded) and non-barrier (tree roots included) plots. Seasonal nitrate losses for both growing seasons were
significantly lower in non-barrier treatment compared to barrier treatment at 0.9 m depth. Cumulative amounts of nitrate leached during the study period were 122 and 46 kg ha-1 for 0.3 and 0.9 m depths, respectively, in barrier treatment, compared to 64 and 13 kg ha-1 for respective depths in non-barrier treatment, representing a significant reduction in total nitrate leached at both depths. Results indicate that tree roots play a significant role in alleviating nitrate leaching through their safety net role in temperate alley cropping systems.
Speaker Information: Samuel Allen, CSTAF, University of Florida, PO Box 110831, Bldg 191, Mowry Rd, Gainesville, FL 32611-0831; Phone: (352) 846-3496; E-mail: [email protected]
Session Information: Thursday, November 6, 2003, 7:25 AM-11:40 AM Presentation Start: 7:30 AM
Keywords: temperate alley cropping; nitrate leaching; safety net; nutrient capture