Waste not, want not
Soil testing essential to cost-effective fertilizer use on the farm and in home gardens
April 10, 2006Contact Information:
Dr. Nathan Slaton, Department of Crop, Soils and Environmental Sciences
479-575-3910 / nslaton@uark.edu
Dr. Morteza Mozaffari, Soil Testing and Research Laboratory
870-295-2851 / mmozaff@uark.edu
Dr. Leo Espinoza, Cooperative Extension Service
501-671-2168 / lespinoza@uaex.edu
By Fred Miller, University of Arkansas Division of Agriculture
479-575-5647 / fmiller@uark.edu
Nathan Slaton, director of the Arkansas soil testing and research program, left, and Russ DeLong, program associate, compare the growth of wheat from a test plot where phosphorus was included in fertilizer applications with wheat from a control plot in which phosphorus was omitted. The plants receiving phosphorus are much taller and fuller.
FAYETTEVILLE, Ark. — High energy prices are dramatically driving up the cost of fertilizer, but a free test from the University of Arkansas Division of Agriculture can help farmers and gardeners get the most for their fertilizer dollars.
The key is to give plants the nutrients they need without overdoing it.
“One of my concerns is that some farmers are cutting down on fertilizer to save money,” said Morteza Mozaffari, director of the U of A’s Soil Testing and Research Lab at Marianna. “Cutting down on fertilizer can end up being more costly than putting too much on the field.”
Phosphorus and potassium are the most likely nutrients producers choose to cut. Mozaffari said cutting back on these nutrients may result in reduced yields. The cost of other inputs — water, pest and weed control — is wasted if yields are lost.
Mozaffari said U of A soil testing services are free to all Arkansas farmers and gardeners.
Nathan Slaton, director of the Arkansas soil testing and research program, said testing the soil and becoming familiar with how to interpret the results are the most important things producers can do to make sure they’re using the right amount of fertilizer. Then they should look at production guidelines, available from county extension offices, to learn the most effective application times and efficient fertilizer sources.
Slaton said the U of A Division of Agriculture has revised its fertilizer recommendations based on a change in philosophy for soil fertility.
“There are two schools of thought for how to approach fertilizer applications,” Slaton said. “You can fertilize the crop or fertilize the soil.”
Earlier recommendations were based on fertilizing the crop and on much lower yields than are produced now, he said. This approach uses the minimum amount of fertilizer needed to produce a growth response in the plants and can gradually deplete soil nutrients, reducing productivity. The revised recommendations are based on fertilizing the soil by adding higher rates of fertilizer that produce best the possible yield from the plants and also build up nutrients in the soil to optimal levels.
“This is also called building and maintenance,” Slaton said. “By storing up nutrients in the soil, future crops won’t have to rely so heavily on fertilizer applications.”
Once fertilizer has built up soil to a near optimal soil test level, producers simply add enough fertilizer to replace what the plants use.
“Research has shown that average yields from year to year are more consistent and a little higher for soil that has medium to optimum nutrient levels than for soil that is fertilized only for plant response,” Slaton said.
Soil samples can be submitted through county extension offices and the resulting fertilizer recommendations are based on best nutrient management practices developed from Division of Agriculture research.
“Much of the research is based in Arkansas, so the results match the conditions, climate, and cropping systems in our state,” Mozaffari said.
He said growers should make sure soil samples are representative of the whole field. A separate sample should be submitted for each different soil or for each area in which a different management system is used. For each area, samples should be taken from several locations and mixed together.
For home gardeners, Mozaffari said, it is important to fill the sample box all the way to the top in order to make sure there is a sufficient sample for complete analysis.
Sample boxes are available from county extension offices, Mozaffari said. Once filled, return the samples to the extension office, which will send them to the soil testing lab. Results will be returned to the extension office for distribution.