How best to utilize your fertilizer dollars

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cattle in pasture

It is no secret that the cost to fertilize pastures this year will be much greater than past years. The significant price increases in nitrogen, phosphorus and potassium have many farmers wondering what management steps to follow. 

Why

There are several reasons fertilizer prices have increased. A University of Illinois Farmdoc assessment in October of last year identified the following as reasons for increased prices: Hurricane Ida in September leading to supply disruptions, increasing natural gas prices, the correlation between grain prices and fertilizer costs and general supply chain issues associated with COVID. 

In addition to these factors, Barry Ward, of Ohio State University Extension, has discussed these additional concerns: China halting phosphate and UAN fertilizer exports, potash shipping issues, countervailing duties and geo-political tensions. 

Will fertilizer prices decline in the next few months? It’s impossible to say what prices will do. While the increase in prices seems to have slowed, most indications are that we will not experience significant price declines for some time. 

Back to basics

Soil sampling is always important, but is even more critical this year given the current pricing scenario. If you don’t have current (within the last three years) soil samples, it is important to get them collected as soon as conditions allow. Taking a good quality sample is important — the results you receive from the testing lab are only as good as the quality of the sample submitted. 

When sampling soil for analysis, the individual samples you select are combined to make one composite sample that represents the entire field. To demonstrate the importance of proper sampling technique, consider that a one-inch diameter soil probe represents 0.6 inches of soil, and there are six million inches of soil in one acre. 

When taking soil samples, consider field slope, wet areas and variation in soil type. If there are distinct differences in yield due to these or other factors, sample them separately. It is recommended that samples represent no more than 25 acres. 

Soil sample report

The report you receive from the testing lab will contain a great deal of information and often provides recommendations. I encourage you to look closely at the pH value provided in your report. Why? Because it is critically important that soil pH be in the appropriate range so plants can most efficiently use the nutrients applied. 

Depending upon the crop, the desired pH should be between 6.2 and 6.8. Grasses will generally do well at more acid pH (6.2), but to maintain legumes in the pasture, a soil pH closer to neutral (6.8) is desired. 

Lime is applied to adjust soil pH by neutralizing acidity. Agricultural limestone is the common agricultural liming material used, but other products include burned lime, hydrated lime, carbonate lime, pulverized agricultural slag and more. 

The two factors that greatly influence agricultural lime quality are Total Neutralizing Power (TNP) and fineness of the grindings. If a state requires Effective Neutralizing Power (ENP) as a component of the lime analysis, an individual does not have to be concerned with TNP and fineness of grind, since the ENP value already includes TNP and grind fineness as well moisture content. 

Moisture content is generally not an issue unless using certain byproducts such as wastewater treatment lime. If ENP is not required for a state’s lime analysis, then TNP and grind size must be considered. The TNP is a measure of the ability of a liming material to raise the pH. 

Pure calcium carbonate has a neutralizing power of 100. All other liming materials are compared on a percentage basis with pure calcium carbonate. The TNP of a liming material is affected by percentage of calcium, percentage of magnesium and impurities, such as silt and clay. Regardless of the type of liming material you use, be certain to obtain a TNP analysis of the product. 

Also, check in-state publications on grind size since each state may have different percent passing a certain mesh size in defining a grade. 

When the choice is between an investment in lime or fertilizer, it is recommended lime be purchased and applied to correct soil pH before purchasing fertilizer. Having soil pH properly adjusted allows for nutrients to be efficiently used by plants. 

Establishing a new pasture or maintaining an existing one will be much more expensive this year. Consult with your local extension educator about soil sampling, interpreting test results and determining how best to utilize your fertilizer dollars. 

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