IMPLEMENTING A WEB SITE, WIRELESS DATA NETWORK AND SQL DATABASE FOR NITRATE BMP VERIFICATION IN CITRUS

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1 IMPLEMENTING A WEB SITE, WIRELESS DATA NETWORK AND SQL DATABASE FOR NITRATE BMP VERIFICATION IN CITRUS L. J. Waldo 1 and A.W. Schumann 1 ABSTRACT A Best Management Practices (BMP) verification web site was created to serve as an information resource for citrus grower cooperators and the general public on the topic of citrus nitrate BMPs located in Florida's Lake Wales Ridge region. The objective of the study is to verify whether the current BMPs for Ridge Citrus are effective at reducing nitrate contamination of groundwater and maintaining nitrate concentrations at safe levels. The web site includes background information about the BMP verification study, and also serves as an up to date source for current weather and soil conditions in nine citrus grove locations. Each location has a solar/battery powered data logger, which measures the weather (temperature and rainfall), soil water content (at 25, 60, and 150 cm depths), and irrigation run times (irrigation water pressure, duration, and interval). A cellular phone connected to the data logger communicates with the web server in the laboratory, which collects data from all data loggers every six hours and appends it to a database. Structured Query Language (SQL) commands embedded in Common Gateway Interface (CGI) scripts are used to filter, sort and average the data by grove location for presentation to the internet as summary graphs and tables. The current rate of data collection is 864 database records per day or 315,360 per year. Other information which is manually added to the web site includes groundwater monitoring well data, vacuum lysimeter soil nitrate concentrations, and leaf nutrient concentrations. These data, along with the horticultural history of each site, are used to assess whether the current BMPs for Ridge Citrus are sufficiently protecting the groundwater from nitrate contamination KEYWORDS. BMP, nitrate, groundwater, SQL database, data logger, citrus, web INTRODUCTION The Nitrogen Best Management Practices (N BMPs) rule for Florida 'Ridge' Citrus in Florida's Lake Wales Ridge region was implemented in 2002 (FDACS, 2002a). It is currently an incentive based program, which contains fertilization and irrigation guidelines for citrus that was developed from citrus research done since the early 1990s. The citrus research aimed at the development of the nitrogen BMPs was initiated in 1993 with the support of the Florida Department of Environmental Protection (FDEP), Southwest Florida Water Management District (SWFWMD), Florida Department of Agriculture and Consumer Services (FDACS), and the University of Florida Institute of Food and Agricultural Sciences (UF IFAS) (Schumann, 2003). Before the BMPs were implemented, citrus growers followed interim measures, which were primarily horticultural practices consistent with the fertilizer recommendations published by the University of Florida (UF) or the Florida Agricultural and Mechanical University (FAMU), modified by the Department of Agriculture and Consumer Services (DACS), to reflect public input (FDACS, 2002b). The purpose of the Ridge Citrus N BMP is to minimize the risk of leaching nitrates from fertilizers to ground water (FDACS, 2002a). It was designed to protect the quality of water reaching the surficial aquifer and to improve water quality degraded from past practices. Because of the nitrate ion's exceptional ability to leach from root zones into groundwater on Ridge sites, 1 University of Florida, Citrus Research and Education Center, 700 Experiment Station Rd., Lake Alfred, FL

2 and the danger it poses to human health (Methemoglobinemia), nitrogen has been the main focus for the nutrient BMPs in the Ridge citrus production area. Some of the soil series classifications on the Ridge include Adamsville, Archbold, Astatula, Broward, Canaveral, Candler, Dade, Fort Meade, Gainesville, Lake, Neilhurst, Palm Beach, Paola, Satellite, St. Augustine, St. Lucie, and Tavares (FDACS, 2002b). The National Pesticide Survey, published in 1990, and conducted by the U.S. Environmental Protection Agency (EPA), found widespread nitrate contamination in drinking water wells. Approximately 55% of all wells were found to contain levels of nitrates above the background levels. In 1.2% of urban and 2.4% of rural drinking wells the nitrate N concentrations were above the Maximum Contaminant Level (MCL) of 10 mg/l (Graham et al., 2000). The survey also showed a consistent pattern of drinking water well contamination in areas with higher fertilizer sales and higher crop monetary values, which indicates that agricultural practices may be an important contributor to the nitrate problem (Graham et al., 2000). In the predominantly agricultural regions of Florida the frequency of drinking water wells contaminated by nitrates exceeded the national frequency found in the EPA survey. As a result of the survey, FDACS formed a multi agency nitrate study committee in October of 1992 (Graham et al., 2000). The agencies involved in this committee included FDACS, FDEP, UF IFAS, and SWFWMD. The committee recommended that a long term research project should be initiated to evaluate the impacts of alternative citrus nutrient and water management practices on groundwater quality beneath the vulnerable sandy soils in the Ridge citrus region of central Florida. That project, which was concluded in 2000 (Graham et al., 2000), laid much of the foundation for the currently implemented Ridge N BMP (FDACS 2002a). The objectives of the current study are (1) to verify whether the implemented BMPs for Ridge Citrus are effective at reducing nitrate contamination of groundwater and maintaining nitrate concentrations at safe levels, and (2) establish an on line information resource base and sensor network to provide feedback and assistance to grower cooperators signed up with the N BMP. SITE SELECTION AND WIRELESS DATA NETWORK SETUP Site selection for the Ridge Citrus N BMP Verification project began in In order to be selected for this study the grove had to meet several requirements. It had to be representative of a typical Ridge grove, have a shallow water table (for monitoring well purposes, depths of less than 7.6 m are preferable), and the grower had to be part of or willing to enroll in the BMP program. Nine sites were selected for this study; four in Polk County, and five in Highlands County, Florida. Eight of the nine sites have a water table less than 6.7 m deep, while the water table at the 9th site is m deep. Soil series are either Astatula, Candler, or Tavares, which are all typical of the Lake Wales Ridge region. Each site has a data logger station which logs both weather data and current soil moisture conditions (Figure1 and Figure 2). The data stations consist of a solar/battery powered data logger, rain gauge, temperature probe, pressure sensor, and three soil moisture probes. The data logger is an eleven channel XR5 data logger (Pace Scientific, Inc., Mooresville, NC), having 8 analog inputs, 3 pulse inputs, adjustable sensor excitation, detachable 20 position screw terminal block, status indicators and a RS 232 serial data communication port. The rain gauge used in this study is a RainWise digital electronic rain gauge (Spectrum Technologies, Inc. East Plainfield, Ill). It is installed at the top of the data station's 3 m high support pole and measures rainfall with a tipping bucket mechanism in 0.25 mm increments. Connection of the rain gauge to the data logger is via one of the pulse input channels. The LM35 temperature sensor (National Semiconductors, Santa Clara, CA) is connected to the data logger's analog input channel and measures the air temperature in degrees Celsius. The pressure transducer (Measurement Specialties, Inc., Hampton, VA) is connected to an analog input channel and senses the water pressure in the micro jet irrigation system under the tree canopy. Three AquaPro Direct Burial Moisture Sensors (Figure 3) (Aquapro Sensors, Ducor, CA) were installed in each site at a depth of 25, 60, and 150 cm below the soil surface, under the tree canopy and within the range of the micro jet irrigation nozzle. The probes were fitted with a 12.7 mm diameter PVC pipe for easy installation at the three depths and for removal if maintenance or 2

3 reinstallation is necessary. The capacitance type probes measure the volumetric water content (θ v ) of the soil and output an analog voltage (0 5 V) to the data logger. The resulting data can be used to monitor the soil moisture response to rainfall and irrigation events, schedule irrigation, and monitor leaching events. Each site also has a CDMA Motorola V120 cellular phone (Motorola Inc., Schaumberg, Ill) connected to the data logger, which communicates wirelessly with the web server in the laboratory. Figure 4 shows the integration of the components of the N BMP verification wireless network and web site. Each grove site also includes two vacuum lysimeters for soil leachate collection and analysis of nitrates, and five seven channel, multi level groundwater monitoring wells that are sampled quarterly and analyzed for nitrates. Figure 1. Data station enclosure containing the data logger, battery, and cellular phone for wireless data downloads. Figure 2. Data station at one of the sites used in this study. The rain gauge is at the top of the pole with the solar panel. White PVC tubes in the ground contain the vacuum lysimeters. Figure 3. AquaPro, Direct Burial Moisture Sensor. Each site has 3 moisture sensors installed (at 25, 60, and 150 cm depths). RIDGE CITRUS NITRATE BMP VERIFICATION WEB SITE The Ridge Citrus Nitrate BMP Verification Web Site was created to serve as a dynamic information resource for citrus grower cooperators and the general public. The main goal was to provide up to date data and results to the grower cooperators. The main web page structure was created using Microsoft Office FrontPage 2003 (Microsoft Corporation, Redmond, WA). The 3

4 Home page divides the web site into background information, study objectives, project results, maps, soil profiles, a photo gallery, references, and links. The Project Results ( page is where the bulk of the data is located. This page has two sub pages, the Chemical Analysis page, which contains the manually collected field data, and the Data Logger page, which contains the real time automatically downloaded data. internet data logger Stations 2 9 data logger station 1 temperature sensor rain gauge web server wireless link data logger modem cellular phone pressure sensor moisture sensors Figure 4. Block diagram of the wireless data logger network and its integration with sensors and the N BMP Verification Website on the internet. Chemical Analysis Results The Chemical analysis page includes the results of all the field and lab analyses. These results include the lysimeter data, multi level monitoring well results, annual leaf nutrient analysis, water budget tables, and current fertilization and yield records from each site. The ceramic collection cups of the lysimeters at each site are installed 150 cm below the soil surface and collect water and nitrate that has leached past the root zone. Lysimeter samples are collected every ten to fourteen days and are analyzed using a Flow Solution 3000 rapid flow analyzer (OI Analytical, College Station, TX). Leaves are sampled annually in July and are analyzed by the Waters Agricultural Lab, Inc., Camilla, GA) for both macro and micronutrients. The monitoring well sample results come from the five, seven channel monitoring wells that were installed at each site. These wells were installed below the water table by Jim Stidham and Associates, Inc. (JSA), Tallahassee, FL, in August and November of Quarterly samples are taken by JSA from these wells and analyzed for nitrate N concentrations. Other data from each site that can be found on this page includes yield history, fertilization history, and water budget tables. Data on the Chemical Analysis 4

5 page is arranged into various tables and graphs and can be found at Using the web site to display these data to the grower in an anonymous fashion is very beneficial; growers receive the results from their site's samples as soon as analyses are completed and uploaded to the web site. Growers can immediately compare their results with those from other sites; results are identified only by a confidential site number 1 9. Data Logger Results The Data Logger page of the web site contains all real time data collected from the remote data station. A desktop server computer in the lab is equipped with a Windows program that automatically dials the nine sites in succession with a modem and connects with the data logger (Figure 4). It then downloads the data packets from each data logger in the field and appends them into a Microsoft Access database. These data are downloaded four times a day, usually six hours apart, unless air temperatures drop below 4.5 o C, when the downloads occur every hour until temperatures rise again above 4.5 o C. Since each data logger collects sensor data at 15 min intervals, there are 864 database records being added daily, and 315,360 records added yearly. Once the data records are stored in the database, Structured Query Language (SQL) commands embedded in Common Gateway Interface (CGI) scripts are used to filter, sort and average the data from the database by grove location and time interval for presentation to the BMP Verification Web Site as summary graphs and tables (Figure 4). Delphi 5.0 (Borland, Cupertino, CA) was used to embed the SQL commands in CGI scripts for deployment on the web site. An example SQL statement would be " SELECT [Log_data].[Station#] AS [Station#],[Log_data].[Date] AS [Date], Sum([Log_data].[Rain])/25.4 AS Rain, avg([log_data].[d8])*9/5+32 AS Tmean, min([log_data].[d8])*9/5+32 AS Tmin, max([log_data].[d8])*9/5+32 AS Tmax FROM Log_data GROUP BY [Log_data].[Date], [Log_data].[Station#] HAVING (((Log_data.[Station#])<10)) ORDER BY [Log_data].[Station#], [Log_data].[Date] desc')". This statement extracts the daily average, maximum, and minimum temperatures, and total daily rainfall data for one remote data station from the main database, to be presented in a summary table on the website. Each grove site number has a drop down box containing graphs and tables of the data logged at the data station. The graphs and tables included in the drop down box are: Two week graph of 15 min data Two week table of 15 min data Daily weather table, aggregated by day Monthly weather table, aggregated by month Irrigation table Ten day weather forecast from Weather.com The two week graph and two week table both include all the data collected by the data logger at that site from the previous two weeks. Data included in this graph and table are rainfall in millimeters, irrigation pressure in pounds per square inch, air temperature in degrees Celsius, and the volumetric water content (%) of the soil at the three depths. The graph also contains the soil water depletion set point, which is 25% of available soil water for February through June, and 50% for July through January. Figure 5 is an example of one of the two week graphs that can be found on the web site. The daily weather table displays the rainfall in inches and the mean, maximum, and minimum temperatures in degrees Fahrenheit for the day. The monthly weather table contains the monthly totals of rainfall in inches at the site, as well as, the mean, maximum, and minimum temperature at that site for the month. The irrigation table summarizes the data collected by the irrigation water pressure sensor. These data include the pressure in pounds per square inch of the irrigation water being applied at the sprinkler nozzle, the duration of the irrigation event in hours, and the interval between applications in days. It also contains a column that displays when the event was an overnight irrigation application, which is used by growers for 5

6 frost protection on very cold nights. The ten day weather forecast is specific to the postal zip code where the site is located and is presented in the web site for quick access of rainfall and temperature predictions. At the bottom of the page there is also a link to view a four day daily weather summary table containing all nine sites. This is for quick reference and comparison of the weather conditions at all nine sites. All of the data presented on this page are located at Figure 5. A sample two week graph that can be found on the BMP web page; this graph is displaying data that has been filtered out of the main database where all data from the nine sites is stored. CONCLUSION The purpose of the Ridge Citrus Nitrogen BMP Verification study is to monitor whether the Ridge Citrus N BMP rules are effective when implemented by growers. The BMP web site was created to serve as an information repository and on line source for the grower cooperators as well as researchers and the general public. The downloaded data from the field data logger stations are immediately made available on line to help the grower make informed decisions about irrigation scheduling as well as planning ahead for future fertilizer applications. The automated system gives the grower feedback as up to date real time data every six hours and helps to make decisions about when to run the irrigation system based on the soil water content in the rootzone and below the root zone. During the winter months, the grower can monitor the grove s air temperature and decide whether to irrigate the grove for freeze protection. Real time data makes it easier for the growers to follow good fertilization and irrigation practices. Efficient management of the irrigation system will minimize the amount of nitrates leached from fertilizer into the aquifer, which is the main goal of the Nitrate BMPs. Other data compiled and summarized on the web site which are not real time, such as nitrate analyses from the seven channel multi level monitoring wells, leaf nutrient analysis, and lysimeter sampling, also guide the growers to make educated decisions about their management practices. The web site plays a key role in the verification of the BMPs in that it serves as an information resource for growers and researchers, allows monitoring of the grower s management practices, and provides an efficient and user friendly report of results to the growers. 6

7 ACKNOWLEDGEMENTS This research was supported by the Florida Agricultural Experiment Station and a grant from the Florida Department of Agriculture and Consumer Services. Mention of trade names and commercial products is solely for purpose of providing specific information and does not imply recommendation by the University of Florida or its cooperators. The authors would like to thank the citrus growers for allowing this study to be conducted in their groves, Adair Wheaton for much of the planning and initiation of the project, Marjie Cody for assisting with sample collection and analysis, and the sampling team of Jim Stidham and Associates for operating the groundwater monitoring wells. REFERENCES 1. Florida Department of Agriculture and Consumer Services Office of Agricultural Water Policy. 2002a. Nitrogen Best Management Practices (BMPs) for Florida Ridge Citrus. Available at Accessed 06 June Florida Department of Agriculture and Consumer Services Office of Agricultural Water Policy. 2002b. 5E Procedures for Landowners and Leaseholders to Submit the Notice of Intent to Implement Nitrogen Best Management Practices (BMPs). Available at Accessed 06 June Graham, W. and T.A. Wheaton Ridge Citrus Water Quality Project, Annual Progress Report ( ) for FDACS, SWFWMD, and FDEP. Sept Schumann, A.W Nutrient BMPs for the Ridge Citrus Production Region. Nutrient Management for Optimum Citrus Tree Growth and Yield short course. 29 Oct Available at Accessed 06 June