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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #192618
Title: Summer cover crop impacts on soil percolation and nitrogen leaching from a winter corn field

Author
item MUNOZ-CARPENA, R - UNIV OF FLORIDA
item RITTER, A - ICIA, SPAIN
item Bosch, David
item SCHAFFER, B - UNIV OF FLORIDA
item Potter, Thomas

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2007
Publication Date: 5/1/2008
Citation: Munoz-Carpena, R., Ritter, A., Bosch, D.D., Schaffer, B.A., Potter, T.L. 2008. Summer cover crop impacts on soil percolation and nitrogen leaching from a winter corn field. Agricultural Water Management. 95(6):633-644.

Interpretive Summary: The South Florida Miami-Dade area is an important agricultural region undergoing significant land-use changes. Agriculture in the region competes for land and water resources with the restoration efforts and Miami’s urban sprawl. Understanding regional water quality interactions is critical to reducing a potentially negative impact to agriculture. 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 in an experimental field divided in six plots in which sweet corn was grown. Three plots included a sunn-hemp summer cover while the other three were kept fallow. A numerical model (WAVE) was used to simulate water and nitrogen balances. 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 of them 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 both types of 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 in both types of plots during the last two seasons (2001-2002 and 2002-2003). 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. Several measured components of the nitrogen balance (corn yields and estimated nitrogen uptake, measured soil organic nitrogen at the end of the simulation) were used to assess the quality of the nitrogen simulation results. 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.