| authors: | Harrison, C.B. ; Graham, W. ; Lamb, S.T. ; Alva, A. |
| title: | Impact of Alternative Citrus Management Practices on Ground Water Nitrate in the Central Florida Ridge: II Numerical Modeling |
| year: | 1999 |
| source: | Amer. Soc. Of Agri. Eng. 42:1669-1678 |
| URL: | Please log in to access the document. |
| abstract: | Long-term impacts of alternative citrus nitrogen and water management practices implemented at grower cooperator sites on the Central Florida Ridge were modeled using the nitrogen component of the Leaching Estimation and Chemistry Model (LEACHN). A bromide tracer test was conducted at one representative cooperator site to parameterize and validate the model. Following validation, 50-year simulations of the historic management practices at each site were conducted. These simulations confirmed field observations that groundwater nitrate-nitrogen concentrations below mature citrus groves that receive 246 kg/ha/yr nitrogen (N) as three split applications of dry soluble fertilizer can be expected to exceed the Environmental Protection Agency's (EPA's) Maximum Contaminant Level (MCL) of 10 mg/L a majority of the time. Fifty-year simulations of alternative nitrogen and water management practices implemented in the field study predicted that in all cases reducing the rate and increasing the frequency of N application, and improving irrigation management, will increase N uptake by plants and reduce average groundwater nitrate-nitrogen concentrations to within EPA standards. Modeling results support conclusions of the field study that showed that, of the appling 180 kg N/ha/year as slow released/dry soluble BMP should be the least effective at reducing groundwater nitrate-nitrogen concentrations. Modeling results furthering suggest that, to maintain the average groundwater nitrate-nitrogen concentrations below the EPA MCL in this region, the N rate should not exceed 172 kg/ha/year if the fertilizer is to be slow release/dry soluble fertilizer; or 231 kg/ha/yr if the N is to be applied in 18 split fertigation applications. If 64 kg N/ha/yr is applied as foliar spray, modeling resulting suggest that an additional 187 kg/ha/year may be applied in 18 split fertigation applications (for a total N application rate of 251 kg/ha/yr) while maintaining the average concentration of the leachate below the EPA MCL. |
| keywords: | Citrus, Best management practices, ground water quality, modeling, nitrate-nitrogen |
