by Greg Clark MSc, Agronomy Researcher
Did you experience any of the below problems in 2019 including poor plant growth and response from applied fertilizers, nutrient deficiencies in crops, difficult to control weeds, insignificant forage quality, abnormal plant growth in fields?
To help solve or understand these problems, testing the soil for a nutrient profile must be completed. Comprehending soil is imperative for productive crop production. Soil testing can determine a shortage of plant nutrients that are significant for optimum growth. Nitrogen, phosphorus, or potassium (K) levels may be restricting plant growth, along with a lack of other essential plant macronutrients (calcium, magnesium, and sulfur) and micronutrients (chloride, iron, boron, manganese, zinc, copper, and molybdenum).
Soil tests can also reveal the organic matter, soluble salts, pH, element toxicities, and soil texture. Soil testing also identifies limiting factors in the soil such as pH (low pH or high pH), low organic matter, and excess levels of specific nutrients.
When and How to Test Soil?
“In the Spring or Fall is the best time for soils to be tested because K test results are most reliable then. Results of the K test tend to be cyclic, with low levels in late summer and early fall and high levels in late January and early February. Phosphorus and pH levels are typically not seasonally affected in most soils in Illinois. In coarse-textured (sandy) soils with low buffer capacity, pH levels can increase as much as one unit under wet conditions” .
- Soil probe/tube.
- Scrape away crop residue.
- Sample the soil from the surface down to seven inches or if testing for nitrate-nitrogen, then sample from twelve to twenty-four inches.
- Be sure the sample is a reliable representative of the entire field.
- Collecting multiple soil samples should be done from any given area.
- Composite into one sample to minimize the cost of analysis.
Sampling every four years is suggested when soils are at an optimum balance of fertility. Once maintenance levels are not being applied in cropping systems that remove large quantities of nutrients, such as corn silage or forages, soil testing should be done every other year.
Soil test reports can only be as accurate as the sample sent in for analysis. To enhance the uniformity of the results, collect samples at the same time of year. Sampling done within a few months of lime or fertilizer treatment will be more variable than after a year.
QLF Regional Sales Agronomist can provide recommendations for soil treatments based on the results of the analyses. Make sure to plan early since laboratories will get busy during the soil sampling season, thus ensuring timely results, and allow time for implementation of Liquid Carbon-Based Fertilizers (L-CBF) recommendations and corrective measures.
¹ Fernández, Fabián G. and Robert G. Hoeft, Illinois Agronomy Handbook: Chapter 8: Managing Soil pH and Crop Nutrients. Publication Plus, University of Illinois: 2010. Extension Book Search. Web. 13 August. 2019.