Soil Testing to Determine Nutrient Deficiencies
Date of publication : 5/13/2008
Source : Alberta Agriculture and Rural Development AgriNews
Nutrient deficiencies in the soil have a direct impact on crop growth and yield. The wide diversity of soil types and the variety of crops being grown result in very different fertilizer requirements across the province.
Nitrogen (N), phosphorous (P), potassium (K) and sulphur (S) are the four main nutrients that crops take from the soil and that need to be replaced with fertilizer. Soil testing is the most efficient way to check the nutrient levels in fields and make informed decisions about the nutrients and the amount of fertilizer is needed.
“Every year is a good year to soil test,” says Ross McKenzie, agronomy research scientist with Alberta Agriculture and Rural Development, Lethbridge. “It may not be necessary to soil test and sample all fields, but producers should pick representative fields and sample those fields year-after-year to get a sense of how nutrient levels vary.”
Farmers are encouraged to test at least some of their fields each year going into spring, particularly for N and S. These two nutrients can be quite variable from year to year, depending on the crops being grown and environmental conditions. Although P and K do not tend to vary much from year to year, when testing for N, the same extraction solution is used for P and K, so soil testing usually gives data on all three of those nutrients. A good soil testing regimen will provide information on N, P, K, S, soil pH and electro-conductivity (a measure of salt levels in soil).
“When it comes to fertilizer recommendations, it’s important to remember that labs, which do a very good job of analysis, are not in the business of making fertilizer recommendations,” says McKenzie. “While labs will give recommendations if asked, the recommendations will be general and won’t be based on crop value or fertilizer costs. Producers should take their test results and make the final fertilizer decisions themselves, based on their past experience or working with industry agronomists and fertilizer dealers.”
There are some new fertilizer products on the market. It is very important to know the benefits of the different fertilizers, the method being used to apply the fertilizer and the amount needed to give the best economical and agronomical results. It’s also important to remember that each crop has different nutrient needs.
An Alberta Agriculture and Rural Development computer program, AFFIRM (Alberta Farm Fertilizer Information Recommendation Manager) is a very effective tool that producers can download from the website. Producers input their soil test data values, the crop being grown, the area the field is in, the soil moisture conditions, the fertilizer price and the expected crop value. The program then provides evaluations to determine the optimum amount of fertilizer that is needed.
“Although fertilizer prices have gone up, crop values have gone up as well,” says McKenzie “An advantage of using this program is that it lets producers determine the upper limits of fertilizer needs for their intended crop from both an agronomic and an economic point of view.”
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