Precision Fertilizer Placement
By Sterling Allen for Agri-Times NW
Published May 16, 2008
Reprinted with permission
The increasing cost of fertilizer prices ratcheting upward, with N costs exceeding 60 cents/lb is bringing a shock wave through the agricultural community.
Monitoring soil nutrients and measuring the natural soil variability is a reality that farmers will be researching and measuring more in the future.
Larry Coppock & Associates is launching a variable rate fertility mapping analysis service to help farmers to become efficient on operating a site–specific farm management program.
Coppock will work with the grower and develop management zones. These zones can be created using yield, electrical conductivity (EC), topography, soil survey, infrared photo, weeds, insects, diseases or probably any criteria that impacts crop performance. To make it useable, allowing just three zones of difference keeps the map from being cluttered.
Coppock will soil test the field management zones, marking each location on the GPS unit. This will allow subsequent future soil samples to be taken from the exact location which will allow the farmer the accuracy of calculating if the soil nutrients are trending.
Using the soil sample date, Coppock will then prepare a field map, showing different nutrient zones, and allowing the farmer to utilize variable rate fertilizer application to efficiently apply nitrogen
Yield potential, nutrient requirements and management practices vary within fields whose margins are delineated largely on survey boundaries rather than production potential.
Pacific Northwest cropland fields have contrasting areas with distinctive soil properties, production potential and limitations. If these areas can be delineated for management purposes, then knowledge of these distinct conditions can be used to develop special production strategies.
Site-specific detection of residual soil N levels and the levels of other plant nutrients have been studied during the last twelve years at North Dakota State University under the direction of Dr. Dave Frazen, extension soil scientist.
The NDSU research results support the general use of a “zone” approach to soil sampling that could easily be adopted by most growers. Topography is important in analyzing soils. Zone sampling provides at least the same level of delineation accuracy as one-sample-per-acre grid sampling.
Commercial samplers have been very successful in their use of the zone approach for soil sampling. Those who are using more than one zone delineation method might find that the stability of their zones is better from year to year than if just one method were used.
‘There is increasing farmer interest in mapping fields for variability rate fertilization in North Dakota,” said Frazen. “The most important analysis in the soil sample is the residual soil nitrate readings.”
Consultants have been providing a mapping and soil analysis service for growers throughout the state, said Frazen.
Washington State University scientists mapping soil organic matter have found greater variation within fields than between fields. This is why site specific soil sampling can be so productive. Mulla at WSU developed variable rate fertilizer recommendations that resulted in purchasing $11.20/A less fertilizer product at St. John and $31.77/A less product at Colfax.
The Umatilla County SWCD is promoting to farmers a precision nutrient management program sign up for cost share funding, said Loren Unruh, director.
“The program plan is for farmers to try new farming methods and a goal of efficiently use nitrogen,” said Unruh.
Coppock can be contacted at (541) 566-3776 for more information about his services.