PLYMOUTH, Minn. — With U.S. corn production reaching record levels over the past few years, averaging 160 bushels per acre in 2004 and 143 bushels per acre in 2005, fertilization has become the key component to achieving those high yields.

Phosphorus and potassium frequently are limiting nutrients for crop production in North America and should be tested for and replaced each year as needed, said Dan Froehlich, U.S. agronomy manager for the Mosaic Co.

“The best and most accurate way for growers to know what nutrients will be needed by the crops they grow is to conduct a soil test,” he said. “This management tool allows growers to take much of the guesswork out of a soil fertility program and to predict which nutrients are needed in certain fields.”

Estimates made by the Potash and Phosphate Institute show many growers in key production areas are not replacing the soil nutrients that have been removed by their crops, Froehlich said.

These nutrient deficits may cause yield shortfalls in the future if soil tests reveal a drop below critical levels, he noted.

Whenever crops are removed from the field during harvest, the nutrients in the harvested portion of the plants also are removed, thus leaving the soil a bit more depleted than before. Replacing these harvested nutrients is a bare minimum for maintaining soil fertility levels, Froehlich said.

Failure to replenish the soil supply of nutrients will result in a gradual depletion of soil fertility and can ultimately lead to diminished crop yield and quality.

With input costs for agricultural crops an ongoing challenge, growers and industry professionals are trying to find ways to cut expenses.

While it’s tempting for farmers to cut back to save money, it may be a costly move, Froehlich said. A significant negative impact on crop yield is possible when crops are not fertilized properly, he noted.

While there’s no doubt all corn production input prices have increased over the last 15 years, fertilizer has increased at one of the lowest rates, Froehlich said.

When compared with fuel, machinery, seed, wages and ag chemicals, fertilizer lands fourth on the U.S. Department of Agriculture’s index of input prices paid by farmers, he noted.

Clearly, all of these factors are essential to any farming operation, Froehlich said. The key is to manage them efficiently, he explained.

Successful growers are using smart fertilizer practices, Froehlich said. These growers are utilizing on-farm nutrient supplies and prioritizing fields and areas within fields as to which have the greater need for fertilization, he said.

They also are allocating money to the correct nutrients to create a balanced approach, which will maximize the effectiveness of all nutrients, he added.

And, finally, these successful growers are continuously reexamining their current practices to ensure they are reaching their most profitable yields, Froehlich said.
One common approach for making fertilization recommendations, especially for P and K, is called the “sufficiency” concept and is based only on the predicted crop response to each added nutrient, he explained.

Fertilizer is applied only when there is a good chance that there will be a profitable response that year.

The other common approach to P and K fertilizer recommendations, Froehlich said, is the “build and maintenance” concept.

With this system, nutrients are added in excess of the minimum crop requirement to build the nutrient concentrations in the soil to the point where they will not be limiting.

Whatever the approach, growers need to consider the value of the crop and compare the costs of potential yield loss with the expenses associated with fertilization, Froehlich stressed.

“It is important for growers to minimize decisions that result in short-term cost savings, but long-term cost increases,” he said.

Successful farmers base input decisions on site-specific facts that help assure them that they will get optimum returns from dollars invested in inputs such as fertilizer, he said.

No matter what the economic or agronomic environment, farmers need to make the basics of a profitable crop production program a top priority, Froehlich said. Proper soil fertility is the foundation on which high yields are built, he added.

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