GIS/GPS/Remote Sensing
GeoTechnology Use Grows in California's Ag Community
Farmers are using GIS, GPS and remote sensing technologies in increasing numbers to improve financial returns, boost land productivity and ease compliance reporting.
By Laura Lang

When todayÕs farmer looks into a cloud-filled sky, heÕs probably got more on his mind than bringing the cows in. ItÕs just as likely, heÕs wondering how cloud cover will impact imagery being captured by remote sensing or aerial photography, or how an incoming storm will affect a GPS survey crew heÕs scheduled.
      Farming has become big business in the U.S., and like other business ventures itÕs undergone its share of automation. Starting about three years ago in the MidwestÕs corn-and-wheat growing regions, and now progressing throughout the nation, AmericaÕs farmers are using GIS, GPS and remote sensing technologies in increasing numbers to improve financial returns, boost land productivity and ease compliance reporting.
      According to Don Gordon, a senior GIS analyst at VESTRA Resources Inc. (Redding, Calif.), using commercial GIS packages lets farm managers view information collected from a wide variety of sources, including GPS surveys, aerial photography, satellite imagery, and point data collected in the field. The GIS software is then used to analyze the data, providing a scientific barometer of crop health and maturity, which in turn points to recommended treatments, planting times and harvest cycles.

Family Roots
About two years ago, VESTRA began using GIS-based technologies for high-tech farming on the 2,400-acre Gordon Family Ranch (GFR), located in southeastern Napa County in Northern California. About 2,200 acres of GFRÕs land is rangeland where cattle graze. The remaining 200 acres is used to grow grapes.
      The farmÕs manager, Don Gordon Sr., maintains data about the fields with an Excel spreadsheet. Basemap data including road boundaries, topographic data, and hydrographic features were input by VESTRA using USGS 7.5 minute quad maps. The company then built the GIS data with ARC/INFO Version 7.04 and viewed using ArcView 2.1 GIS software (ESRI, Redlands, Calif.) running on PC and Macintosh computers. Attribute data about the crops can be accessed directly from GordonÕs spreadsheet package. ÒThis makes it fast for me to check on all kinds of data,Ó explains the senior Gordon. ÒI just point to the location I want to check and click on the information layer to retrieve, such as soils or vineyard block.Ó
      Once the basemap data were created, panchromatic aerial photography (1:12,000) was acquired of the ranch so VESTRA could create a digital orthophoto, a position-corrected image readable by the GIS, to update features in and around the ranch on the GIS vector maps. Field boundaries and vineyard rows were derived from the orthophoto and used to build the crop database which is used by Don Gordon Sr. to track information on rootstocks (the underground parts of plants), plant dates, tonnage and other data that can be linked with individual vineyard blocks. The system is not only easier than tracking these attributes by hand, says Gordon, it gives him a more complete record that can be used for many purposes. ÒThe data is used in different ways throughout the year as we plant, fertilize, and harvest crops; prepare reports for state and federal regulatory agencies, and maintain data on experimental rootstock plantings.Ó
       For example, prior to harvesting and pruning, the GIS was used to map crop maturity and assign field crews. By utilizing ArcViewÕs ODBC capabilities, re-entry maps are generated and posted at fields treated with specific pesticides or herbicides. This information is maintained in a crop protectant tracking database. Field crews are scheduled each day with a map showing what fields are off-limits and where the work is to be performed for the day. In this manner, the GIS helps reduce misunderstandings about the location of work to be done and helps to coordinate and schedule work, Gordon says.
      Since parts of a vineyard can ripen at different times, sugar samples from the crops are used to create GIS harvest scheduling maps. Crews and equipment are sent to locations where the grapes are ready so they donÕt have to stop and relocate when they come on blocks of unripened grapes.
      Stratified soil samples were collected so the GIS could generate a soil nutrient gradient model. This map interpolated soil nutrients to show distribution and concentration gradients that were occurring in the vineyard. These maps were used as new areas were planted, since they showed key nutrients and critical high and low values for each vineyard block. For blocks with high soil acidity levels, for example, lime was added before planting to bring up the pH values closer to neutral.
      The system was also used to define which areas needed specific treatments, saving the farmers from having to apply soil treatments to the entire vineyard. Furthermore, the selection of rootstock and variety can be fine-tuned to the soils and microcl mate of the vineyard block to ensure that only the best wine grapes are produced. Currently, Gordon says, the system is being used to track costs, such as labor and tractor expenses at the ranch.
      During the course of the year, he plans to use the GIS to analyze bunch weights, soil moistures, and leaf area of the vines to determine when and where to perform specific viticultural treatments. By limiting, focusing, and timing the application of inputs such as water, fertilizers, and pesticides, cost savings and increased efficiency of resources can be achieved.
      Four-band multispectral digital imagery, flown by Positive Systems Inc. (Whitefish, Mont.), was captured at the end of June 1996. This imagery is currently being processed by Dr. Shlemon Youkhana at VESTRA to produce a normalized difference vegetation index or NDVI. This data will be tied back to the GIS and overlaid with soils and yields to determine the overall health and productivity of the vineyard. The information will be important for planning replanting costs and identifying potential problem areas early.
      As a next step, Gordon will be using a Trimble Pathfinder Pro XL GPS receiver to collect data points around the ranch to expand the overall accuracy of the GIS database. ÒGPS not only improves our accuracy but it also helps us pinpoint permanent sample sites, such as pest traps,Ó states VESTRAÕs Gordon.

Growth Path
What started as an experiment with one employeeÕs family farm has blossomed into a promising new business area for VESTRA, reports Dean Angelides, vice president. Several farms in Northern CaliforniaÑincluding Mondavi Vineyards (winegrapes), Deaver Vineyards (winegrapes), Bowles Farming Co. (cotton and alfalfa), San Juan Ranching Company/Rio Bravo Ranch (citrus, melons, cotton, tomatoes and cattle), and Mohr-Fry Ranches (cherries, vegetables, and winegrapes)Ñhave expressed interest in using GIS-related technologies, he says.
      One project already underway is for R.H. Phillips, a leader in innovative viticultural practices. The company manages about 3,000 acres in Yolo County, and is rapidly expanding to develop new vineyards in the region. ArcView GIS software is helping R.H. PhillipÕs research viticulturalist, Rick Tracy, determine that he can better manage larger tracts of land than he could handle without the automation.
      VESTRA has captured base GIS data from quad maps and integrated soils data from Yolo County. Image acquisition is planned for next year to create a digital orthophoto to enhance use of the GIS data. R.H. Phillips is planning to use ArcView GIS to help integrate a variety of data. Data from weather stations, neutron probes (a soil moisture-measuring instrument), pruning weights, sugar samples, bunch weights, and insect population surveys will be used to monitor and evaluate the health and productivity of the vineyards.
      Furthermore, because R.H. Phillips harvests at night, it is critical that the grapes are ready to harvest. The GIS is expected to save substantial amount of money by producing maps that show where and when to pick crops as the logistics of moving crews and equipment at night is very tedious and time consuming.
      Like R. H. Phillips, most farmers could benefit from enhanced soil analysis, nutrient modeling and other analytical capabilities provided by GIS. They will benefit from the first forays into the field, which have already shown the most efficient ways to combine these technologies. For example, VESTRA has found that aerial imagery excels in revealing differentiation among permanent crops like vineyards and orchards, while 10- to 30-meter resolution satellite imagery is cost effective for determining general growth patterns, especially for large acreages. ÒVESTRA has found that it takes a mix of these technologies to best fulfill a particular farmerÕs needs,Ó says Angelides. GFR and the other properties offered enough variety and acreage to thoroughly test how well these technologies could be used with GPS and GIS, he says.
      In California, where nearly 29.7 million acres are devoted to agriculture production, the technologies could improve management of diversified crops, from grapes and cotton to almonds, oranges, wheat, lettuce and strawberries. Advises VESTRAÕs Gordon: ÒOnce the basemap data in place, the farm managers need only capture real-time data, like weather data or soil sampling, as itÕs needed to create current crop analysis, treatment and harvest maps.Ó As more data is compiled and used, through informal consortiums or farming associations, new tools will emerge, particularly for collecting shared data, he predicts.
      In CaliforniaÕs central San Joaquin Valley, a group of commodity growers including Sunkist Growers Inc. (Lindsay, Calif.) has discussed the need to share data resources collected for their region. ÒA satellite image, for example, is the same for an orange grove as it is for a cotton grove, so why buy two if you can share the costs or that data?Ó explains SunkistÕs Chris Stambach, supervisor of SunkistÕs Crop Estimating Group.
      As the desktop tools for GIS farming are tested and fine- tuned, VESTRA thinks more farmers in California and around the U.S. will make the leap from faith-farming to fact farming, using scientifically controlled agricultural practices.
      With more than $22 billion at stake in California crop production, GIS, GPS and remote sensing can offer a small measure of security to whatÕs always been considered a risky business. For the farmer, itÕs one less worry on his mind.

About the Author:
Laura Lang is a freelance writer based in Ramona, California. Her writing has appeared in national and international publications.

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