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managing fertilizer inputs

AUBURN UNIVERSITY, Ala.—Even as markets continue to fluctuate, farmers continue to farm.

Alabama Cooperative Extension System agents and specialists are continuing their work in the field to help producers make educated decisions throughout the growing season. In addition to field work and variety trials, these professionals are crunching numbers and running scenarios to help producers maximize efforts and inputs this spring.

Fertilizer Input Management

Audrey Gamble, an Alabama Extension soil scientist, said there are several things farmers can consider for managing their fertilizer input costs. Gamble recommends six practices to help producers maximize production and profitability.

  • Use research-based soil test recommendations.
  • Use a soil sampling strategy which accounts for field variability.
  • Be realistic about yield goals.
  • Compare nutrient rates in fertilizer products.
  • Make pH a priority.
  • Implement a plant tissue sampling program.

Soil Test Recommendations

applying fertilizer“Decades of research have been used to correlate soil-extractable nutrients with increases in yield to develop fertilizer recommendations for Alabama crops,” Gamble said. “In Alabama, this research is based on yield increases according to Mehlich1-extractable soil nutrients. However, in the Blackbelt region the Mississippi extract is used.”

Gamble said Auburn University recommendations continue to be evaluated for newer, higher yielding row crop varieties. The soil test reports from the Auburn University Soil Testing Laboratory use formulas to calculate the recommended phosphorous (P) and potassium (K) to the nearest 10 to 30 pounds.

It is important to note that fertilizer recommendations from private, commercial laboratories may not be based on local research. More information about converting results from private soil test labs to Auburn recommendations is available at www.aces.edu and in the Alabama Soil Test Recommendation Tool.

Soil Sampling Strategies

Gamble also recommends a soil sampling strategy, which accounts for field variability.

“Soil acidity and nutrient content can vary widely throughout a field,” Gamble said. “Precision technologies increase the producer’s ability to apply fertilizer and lime where it is most needed. It also enables producers to avoid applications where soil test levels are sufficient.”

Precision application is different from traditional methods, which offer a one and done recommendations for fertilizer application. These may be less effective than prescription applications.

Zone sampling allows producers to divide the field into management zones based on knowledge of a specific field. One method for creating zones is to divide a field according to soil type. Another method is to divide a field according to yield potential. This decision is based on information from yield maps or farmer knowledge of the field.

Grid sampling techniques are widely used to assess field variability in Alabama soils. This method divides fields into rectangles with uniform spacing. Producers collect samples accordingly. Most grids in Alabama are 2.5-acre grids.

Yield Goals

Gamble recommends setting a realistic yield goal based on location and crop.

“For some nutrients, fertilizer recommendations vary by yield goal,” Gamble said. “For example, nitrogen recommendations for corn will vary according to anticipated yield.”

She said it is important to ask “What fertilizer rate can help me maximize profitability?” instead of focusing on “What fertilizer rate can maximize yield?”

The content piece Managing Fertilizer Costs in Times of Economic Uncertainty details different nitrogen applications in different soil types. The most effective application rates may be different than what a producer would expect. Gamble recommends seeking professional advice before making an application.

Prioritize pH

“Maintaining soil pH is the first step to improving soil fertility for crop production,” Gamble said. “Most Alabama soils are naturally low in pH and require lime to create soil conditions to boost production.”

As the pH of a soil varies, the availability of macronutrients—like nitrogen and phosphorous—and micronutrients—like zinc or iron—also varies. Maintaining a soil pH according to soil test recommendations will ensure the maximization of availability of all plant nutrients.

Gamble said soil pH maintenance improves crop quality and yield. She said this is “money well spent.”

Plant Tissue Sampling

Tissue testing can serve a dual purpose for producers.

Diagnostic testing can help producers identify a nutrient deficiency issue. In this case, producers should collect plant tissue from the deficient area, as well as an adequate crop growth area.

Nutrient monitoring is also a tool for producers to use throughout the season to monitor crop nutrient status. Farmers can use the information from tissue testing to adjust fertilizer applications. To ensure consistency, collect samples at the same time of day.

The content piece Managing Fertilizer Costs in Times of Economic Uncertainty details best practices for collecting tissue samples.

More Information

Find more information about nutrient management and limiting fertilizer input costs in the content piece Managing Fertilizer Costs in Times of Economic Uncertainty. More information is also available online at www.aces.edu or by contacting your county Extension office.

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