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Title: Use of the Nitrogen Index to assess nitrate leaching and water drainage from plastic-mulched horticultural cropping systems of Florida

Author
item MARCHI, E.C.S. - University Of Florida
item ZOTARELLI, L. - University Of Florida
item Delgado, Jorge
item ROWLAND, DIANE - University Of Florida
item MARCHIE, GIULIANO - Embrapa

Submitted to: International Soil and Water Conservation Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2016
Publication Date: 1/3/2016
Citation: Marchi, E., Zotarelli, L., Delgado, J.A., Rowland, D., Marchie, G. 2016. Use of the Nitrogen Index to assess nitrate leaching and water drainage from plastic-mulched horticultural cropping systems of Florida. International Soil and Water Conservation Research. 4(4):237-244. doi:10.1016/j.iswcr.2016.12.001.

Interpretive Summary: The Nitrogen Index tool was calibrated and validated for Florida’s environmental conditions through adjusted k and WC constants. These constants were adjusted by varying their values in a system where data from zucchini was compiled from published data. The adjusted program was validated using compiled data for tomato and green pepper grown during 2005 to 2007. The scenario of using a cover crop after removing vegetable crops and plastic mulching showed that the use of cover crops may reduce N leaching and increase N use efficiency in these vegetables systems in Florida. Thus, the Nitrogen Index tool can be used to assess and improve local management practices under several crops and environmental conditions.

Technical Abstract: Water quality in Florida is significantly impacted by nitrogen (N) losses from agriculture in a large part of the state, where there is a close interaction between surface water and groundwater that has a high water table. Horticultural crops are planted across large areas of Florida, including areas with potentially highly vulnerable groundwater aquifers, where vegetable crops are grown on coarse, sandier soils over groundwater aquifers with high water tables. Nitrogen losses from these vegetable systems can negatively impact groundwater and can also result in economic losses. There are new tools such as the Nitrogen Index that are able to quickly assess N use efficiency and losses from agricultural systems, provide technical information to growers and policymakers about the effects of current crop management practices on N use efficiency, and highlight N loss pathways. The N-Index is a tool that provides information about N losses tied to agricultural management practices with a great level of confidence. However, the current version of the N-Index has not been calibrated to be used in plastic mulch systems of Florida. The aim of this work was to determine N-Index model parameters and to validate predicted values generated by the program in horticultural systems of Florida. Additionally, a hypothetical scenario was developed to assess N losses from vegetable production systems with cover crops. This study found that the N Index tool accurately identified and ranked the risk of nitrogen losses in the evaluated systems.