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Efficient fertilizer use crucial for wheat farmersqrcode

Sep. 12, 2012

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Sep. 12, 2012
Wheat farmers can count on high fertilizer prices becoming a consistent factor in annual production budgets, says a Texas AgriLife Extension fertility specialist. So farmers need to fine-tune operations to make certain their fertility programs are as efficient as possible.
Options should include annual soil tests, deep sampling, proper placement, proper timing and proper rate to mesh with intended crop use.
Farmers also may want to look at organic fertilizer sources, such as chicken litter, but should be careful about non-traditional products that may not come with unbiased testing.
“We’ve seen significant changes in the price of fertilizer in the past 10 years,” said Mark McFarland, Extension soil fertility specialist, during a Big Country Wheat Conference in Abilene, Texas. “We’ve seen costs go to levels we have not seen before, and, even though they have moderated a bit in the past two or two-and-a-half months, prices are still 200 percent to 300 percent higher than historical levels.
“I don’t see prices going down,” McFarland said. “The global market demand will keep them high. So, high nutrient costs will remain a substantial part of wheat production economics.”
Wheat producers will need to factor those high prices into production budgets and find ways to make that investment as profitable as possible. “The keys to fertility efficiency are type of nutrient, rate of application, method of application and timing of application,” he said.
Type and rate should be determined by soil tests. “With current fertilizer prices, we are promoting annual soil sampling. Wheat producers must verify what nutrients are needed and also credit the amount already available in the soil, including residual from previous crops.”
Deficiencies hurt yield
Deficiencies can be costly. McFarland said nitrogen may be the most challenging to manage since it changes and transforms after application and may be lost to soil leaching or into the atmosphere.
“We recommend a split application for wheat,” he said. “That way we make certain we have nitrogen available at peak demand and also minimize the potential for losses from heavy rainfall or other climate factors. Split applications also give us an opportunity to judge crop conditions and potential before we topdress so we can apply the most effective and most economical rate.”
Rate and timing also depend on crop use. Demand may be different for wheat intended for grain, grazing or as a dual purpose crop. Yield potential and available moisture also affect fertility rate.
McFarland said farmers should look deeper for residual nitrogen, especially if they planted and fertilized a crop last year and drought prevented typical production. “Nitrogen is very soluble and moves in the soil profile, so we recommend farmers sample deeper than the 0 to 6-inch depth they usually pull from.”
Nitrogen that has moved deeper into the soil profile is still available to the crop. Tests have shown substantial amounts of nitrogen as deep as 48 inches — from 78 to 210 pounds per acre, McFarland said. “At just 24-inch depths, we still find significant amounts of nitrogen available. With the current price of fertilizer, that may represent a significant savings.”
He said farmers who use residual nitrogen can decrease typical application rates by the amount identified and produce equal yields. “But farmers have to measure it to know how to adjust rates.”
Savings could range from $10 to more than $100 per acre, depending on the crop need and the amount of residual nitrogen available. “And that’s just for nitrogen; other nutrients are also found at depth. We recommend farmers consider deep sampling, especially if they put out fertilizer last year and had no crop to utilize it.”
Pull two samples
Farmers will have to pull two samples, one from the usual 0- to 6-inch depth to determine nitrogen, phosphorus, potassium calcium, magnesium, sulfur, micronutrients, and pH. They’ll need to take a second sample from 0 to 18 or 24 inches to determine residual nutrient levels with depth. He also suggested farmers use N-rich strips in season to judge the proper amount of topdress nitrogen. N-rich strips consist of narrow strips laid out in the wheat field with each strip receiving a different rate of preplant fertilizer. Strips are fertilized with increasing rates of nitrogen (for example 0, 40, 80, and 120 pounds per acre) up to the maximum rate for the expected yield.
Producers evaluate each strip to determine between which increments there is no difference in plant growth. They use the last discernible improvement to establish topdress rate. If the last strip to show a yield advantage is 80 pounds per acre, and the grower applied 40 pounds per acre at planting, he needs to topdress his field with 40 pounds to bring the total to 80 pounds.
Phosphorus also makes a difference. “Phosphorus stimulates early root formation, increases tillering and increases seed size.”
But, unlike nitrogen, phosphorus is stable. “It stays put. If farmers apply phosphorus to the surface it doesn’t migrate into the root zone,” he said.
“We need to incorporate phosphorus to 5 or 6 inches. That will improve uptake substantially and increases production potential. Phosphorus prices are close to nitrogen costs, so we need to put it where the plant can take advantage of it.”
McFarland said he’s seen more potassium deficiencies than usual the past few years. “And I’m not sure why. It could be that fields have been cropped for many years, and natural soil levels are decreasing. And, under dry conditions, root uptake of soil potassium already is limited. But potassium is important. It plays a role in cold hardiness and water use efficiency.”
He also cautioned growers about “non-traditional” fertilizer products. “With current high nutrient prices, silver bullets are being marketed to producers to enhance fertilizer efficiency. The problem is that often no research is available to back up many of these claims. Be sure to have independent, nonbiased research before using a new product.”
Humic acid is a product that’s been touted in recent years as a means of enhancing fertility. “We’ve looked at it in cotton, corn and grain sorghum and saw no response compared to traditional products.”
He said humic acids occur naturally in the soil anyway, “probably from one-half to one ton per acre. So if we only add 1 to 3 gallons per acre it’s not likely to have much impact.
“Look for sound scientific data before deciding to use any new product.”
Organic nutrient sources, such as chicken litter, can offer “real bargains.” The biggest factors will be transportation cost and moisture content. If a farmer can have chicken litter delivered and spread for $65 to $75 a ton, he should do the math and see how it compares to standard inorganic products. “Also, do an analysis on compost or manure to determine what’s in it and then compare that dollar to dollar with inorganic fertilizers.”
But, whether it’s chicken litter, compost or typical fertilizer products, McFarland says the keys remain the same. Select the type of fertilizer, the rate, the method and the time of applications based on crop conditions, moisture and intended crop use. And measure — soil sample — to make certain that what you apply is exactly what you need.

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