Tennessee is suffering from a sharp decline in its potassium balance trend, which has led to an alarming 14 percent increase in the percentage of soils testing below the critical level for potassium.

The eKonomics nutrient balance analysis is the industry’s first to annually assess state-by-state nutrient removal records, fertilizer consumption information, and manure data. Findings reveal that a large percentage of soils are becoming depleted of nutrients at an alarming rate, causing many areas to fall below the critical level for potassium and phosphorus. Is your farm among them?

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43 percent of Tennessee farm fields are critically deficient in two key soil nutrients, which is decreasing both crop yields and farmer income throughout the state.

These are the findings of the International Plant Nutrition Institute (IPNI), which recently collected more than four million soil samples from farms across North America – including 152,800 in Tennessee – and had them analyzed by both public and private laboratories.

“This landmark study shows that 43 percent of Tennessee farms are critically deficient in potassium, while 58 percent are critically deficient in phosphorus,” said Dr. Robert Mullen, Director of Agronomy at Nutrien.

Nutrient Balance Data



The “critically below” figure for potassium has risen significantly in the last five years, while the phosphorus figure has gotten slightly better. Historically though, potassium nutrient balances in the state are down by a staggering 798 percent since 1975, and phosphate nutrient balances are down 106 percent in that time period.

Farmers are leaving thousands of dollars in the field

Given the importance of potassium and phosphorus to crop health and yields, these figures should paint a sobering picture for Tennessee farmers.

“Under current conditions, 43 percent of Tennessee farmers are losing money because they are potassium deficient and more than half are losing out by shorting the soil of phosphorus,” Mullen said. “When times get tough and crop prices are down, the natural tendency is to pull back on your phosphorus and potassium applications, but more often than not, cutting back on crop nutrients means cutting back on profits.”

The problem of this practice, experts say, is that it leaves a lot of potential yield and profit lying dormant in the field.

Mullen uses the eKonomics ROI calculator to illustrate his point. “Let’s say you’re growing 58-cent cotton on 190 acres with a yield potential of 1,200 pounds per acre. If you are below the critical level of potassium and you apply university recommended rates at today’s potash prices, you could increase your net profit by an average of $24,000.”

Potash is a major source of potassium and helps plants develop strong root systems giving crops greater resistance to drought, disease, and insects. Phosphate is the major source of phosphorus, the energizer of plant production, which increases yields.

Nutrient Balance Trends Sources:

1.) USDA-NASS: P2O5 and K2O nutrient removal obtained from harvested tonnage of crops from each state. Manure applied nutrients subtracted from harvest removal.

2.) AAPFCO: Fertilizer consumption data subtracted from the removal information to obtain a mass balance of nutrient levels for each year for each state. “Commercial Fertilizers 2014” is available; all earlier versions are still available. National fertilizer use data are available in a hard-copy publication, “Commercial Fertilizers 2014”, which is available from The Fertilizer Institute (TFI). The Association of American Plant Food Control Officials (AAPFCO), in partnership with TFI, has published the 2014 edition of the Commercial Fertilizer Report.

Percentage of Soils Below the Critical Level Sources:

International Plant Nutrition Institute: Data presented is based upon percent of samples testing below established critical levels for P and K for major crops in 2015. This includes results of P and K analysis performed on approximately 4.4 million soil samples. Critical Bray P1 equivalent levels for the soils and crops of the Great Plains and Corn Belt are usually around 20 ppm and increase to 25 to 50 ppm for the eastern U.S. Critical ammonium acetate K equivalent levels are generally in the 120 to 200 ppm range. Some crops may require substantially higher soil test levels than the critical level used in this analysis (consult your local university/agronomist for more information).

Important to Note: Soil testing is statewide and can differ within regions of every state and province. Nutrient management should occur on a site-specific basis where management objectives and the needs of individual fields and, in many cases, areas within fields, are recognized. Therefore, a general soil test summary like this one cannot reflect the specific needs of individual farms. Its value lies in calling attention to broad nutrient needs, trends, and challenges, and in motivating educational and action programs that are in turn relevant to growers and their advisers.

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