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United States Department of Agriculture

Agricultural Research Service

Title: INVERSE AND DIRECT MODELING ASSESSMENT OF SOIL FLOW AND LEACHING CHANGES INTRODUCED BY A SUMMER COVER CROP IN SOUTH FLORIDA

Authors
item Ritter, A - ICIA, SPAIN
item Munoz-Carpena, R - UNIV. OF FLORIDA
item Bosch, David
item Schaffer, B - UNIV. OF FLORIDA
item Potter, Thomas

Submitted to: Methods of Soil Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2005
Publication Date: December 15, 2005
Citation: Ritter, A., Munoz-Carpena, R., Bosch, D.D., Schaffer, B., Potter, T.L. 2005. Inverse and direct modeling assessment of soil flow and leaching changes introduced by a summer cover crop in South Florida. Estudios de la Zona no Saturada del Suelo 7:281-287.

Interpretive Summary: This study was designed to measure impacts of sweet corn (Zea mays L.) production under South Florida’s subtropical conditions on groundwater quality and to determine the extent to which these impacts may be reduced by using a leguminous sunn-hemp (Crotalaria juncea) summer cover crop. Water and nitrogen inputs and outputs were measured during three growing seasons in an experimental field divided into six plots. Three plots included the sunn-hemp summer cover (CC plots) while the other three were kept fallow (NC plots). Sweet corn was grown in all plots in the winter with identical management in all plots during the growing seasons. A numerical model (WAVE) was used to simulate water and agrochemicals movement in the soil during the last two seasons (2001-2002 and 2002-2003). This study indicates that although the cover crop resulted in an improvement in the soil physical conditions and subsequent enhanced crop evapotranspiration and soil drainage reduction, it can also result in net increases of N loadings towards the aquifer. The use of this summer leguminous cover crop should be coupled with a reduction in the winter crop N fertilization to account for the net increase in soil N content.

Technical Abstract: This study was designed to measure impacts of sweet corn (Zea mays L.) production under South Florida’s subtropical conditions on groundwater quality and to determine the extent to which these impacts may be reduced by use of the leguminous summer cover crop sunn-hemp (Crotalaria juncea) as a potential best management practice. Water and nitrogen inputs and outputs were measured during three corn seasons in an experimental field divided in six plots. Three plots were rotated with sunn-hemp in the summers, before the winter corn seasons (CC plots), while the other three were kept fallow (NC plots). Crop management was identical in all plots during the winter seasons. A numerical model (WAVE) for describing water and agrochemicals movement in the soil was used to simulate water and nitrogen balances during the last two seasons. Soil moisture data at three depths continuously measured during the two corn seasons were used to calibrate the hydrodynamic component of WAVE. Model performance was successfully tested, yielding coefficients of efficiency of 0.85 and 0.91 for CC and NC plots, respectively. The parameters involved in the N balance were obtained by direct methods. This study indicates that although the sunn-hemp cover crop resulted in an improvement in the soil physical conditions and subsequent enhanced crop evapotranspiration and soil drainage reduction, it can also result in net increases of N leaching loadings towards the shallow aquifer. The use of this summer leguminous cover crop must be coupled with a reduction in the winter crop N fertilization to account for the net increase in soil N content.

Last Modified: 9/1/2014
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