Avoid pitfalls in soil fertility programs


LAKE FOREST, Ill. – Rodney Heinen, founder of the successful agronomic consulting business, Oakhill Consulting, likens the soil to a jar of cookies.

Soil not fertile. The Kansas-based crop adviser, who serves more than 800 customers nationwide, says in many parts of the country, nutrient reservoirs have been reduced to a crumb-like existence due to improper soil fertility practices.

“When there are no more cookies in the cookie jar, you’re not going to get a good crop yield,” Heinen said.

In fact, of the 2.5 million soil samples in a North American summary update conducted by the Potash and Phosphate Institute (PPI) in 2001, 47 percent tested medium or lower in phosphorus and 43 percent tested medium or lower in potassium.

Opportunity. “In light of these nationwide shortages, the current upswing in market conditions presents a unique window of opportunity for growers to replenish essential soil nutrients yet this year,” adds Paul Fixen, senior vice president, North American program director for PPI.

“All too often, however, misconceptions about fertilizer applications result in missed yield opportunities.”

Understanding common “fertilizer fallacies” may help growers realize higher yields and profits:

Myth No. 1. Fertilizer is an expense.

Fact. A balanced fertility program is an investment. Few crop inputs pay greater dividends than fertilizers. Used efficiently, returns of $3, $4 or $5 or more are possible for each dollar invested in fertilizer.

At least one third, and up to two thirds, of a crop’s yield is attributed to the fertilizer alone.

Myth No. 2. It’s always OK to cut back on fertilizer for short-term savings.

Fact. Only when potassium and phosphorus levels are in the high range does a grower have the flexibility to consider skipping applications (it is never a good idea to skip needed nitrogen applications).

If soil test levels are in the low to medium range, cutbacks may equal small savings up front, but substantial yield losses in the end. Managing fertilizer inputs should be viewed as a long-term investment strategy.

By building potassium and phosphorus levels into the high range, growers buy flexibility during market fluctuations.

Myth No. 3. I only need to worry about nitrogen.

Fact. It is rarely a good idea to have all your eggs in the one basket. Diversification creates a better chance of reaching goals sooner.

In a crop nutrient program, that means assuring crops have a balanced supply of all 17 essential nutrients, including phosphorus, potassium, and the secondary and micronutrients, to ensure deficiencies do not limit a crop’s yield potential.

Myth No. 4. It’s good to stick to the same fertilizer program every year.

Fact. Just because a fertilizer program was successful five years ago, does not mean it is effective now. The soil is a dynamic, changing environment.

Many factors, including management, temperature, crops and varieties grown, and the nature of the soil itself, influence the soil’s ability to supply needed nutrients to a growing crop.

Keep an eye on it. Producers need to keep a watchful eye over their soil management program to ensure each crop gets the nutrition it needs to thrive.

Regular soil testing will help growers define soil fertility levels and identify which nutrients need to be supplied.

Myth No. 5. I can catch up on proper soil fertility levels next year.

Fact. If soil test levels are in the high range, “catch up” certainly is possible. But ongoing soil test summaries compiled by PPI reveal a trend that growers are not catching up; they’re getting further behind.

When soils are mined of plant nutrients and not properly replenished, it’s often more difficult financially to return soil productivity to its original level because of the cost of applying several year’s worth of nutrients in one year (and this may not be environmentally sustainable).

To consistently achieve top yields, it is critical to build and maintain proper soil fertility levels.

No nutrient behind. Rob Mikkelsen, a regional director for PPI, agrees that growers need to stay ahead of the soil fertility curve.

“Top quality crops require an adequate supply of all essential nutrients for optimum growth,” he said. “If shortages exist, growth will be limited by the nutrient that is in shortest supply.”
Proven concept. This ‘leave no nutrient behind’ rule, better known as “Liebig’s Law of the Minimum,” is a proven concept that serves crops well, adds Joe O’Connor, agronomist for IMC Global

“Maintaining proper soil fertility levels helps promote vigorous plants that can better resist disease and pests, thereby improving crop yield and quality,” he said.


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