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Soil fertility tips in high-cost environment

With ammonium nitrate over 70 cents per pound of nitrogen and phosphate over 80 cents per pound of P2O5, farmers are looking to increase efficiency or adopt new — and sometimes, old — technology. Here are some tips from Southern soil fertility experts:

Soil test. “If you’re not on a soil testing program, get on one,” said Larry Oldham, Extension soil specialist, Mississippi State University. “If you use a land grant university recommendation system, the result is going to be based on the sufficiency philosophy — to supply enough to grow the crop during a growing period. If you go on replacement — X bushels will replace X pounds of potassium (K) and phosphate (P) — this can lead to a higher application rate.

According to Charles C. Mitchell, Extension agronomist, soils, Auburn University, if phosphate (P) and potassium (K) levels are already high, you do not have to apply these nutrients for maximum production because there is enough in the soil to satisfy the crop's needs.

Also remember that there is a lot more total K in the soil than what is measured in a soil test, and it becomes available over time. You should also maintain soil pH to maximize the availability of both applied and native P and K.

Avoid nitrogen losses. “There are volatilization issues when urea is used in hot weather, on heavy crop residues or forages, on high-pH soils, and in dry weather,” Mitchell said. “However, it could still be incorporated, irrigated in, applied just before a rain, used on bare soil or injected.”

There are also commercial additives called urease inhibitors that help to reduce volatilization losses. Compare prices to see if adding a urease inhibitor is worth the additional cost.

“We still like split applications of nitrogen on corn,” Oldham says. “We think it might be a little more efficient. We like to use the liquid sources in Mississippi. Remember that UAN solution, a mixture of urea and ammonium nitrate, has the potential to volatize if we don’t get it in the ground soon after application.”

Use legumes. Winter annual legumes (crimson clover, common vetch or hairy vetch) can provide 90 to 150 pounds of nitrogen per acre to a summer crop, according to Mitchell. “This has been demonstrated for over 110 years by Alabama's old rotation experiment (circa 1896). In fact, cotton with only winter legume nitrogen has produced as much or more yield as cotton with 120 pounds of nitrogen per acre per year and no winter legume (it averaged over 2 bales per acre of non-irrigated cotton the past 10 years).”

Using a legume has more advantages than just the N it provides — it can build soil organic matter. Either winter annual legumes or perennial legumes in permanent, summer grass pastures will improve forage quality plus provide enough nitrogen for 3 tons of dry matter production. For bermudagrass hayfields, this may not be enough nitrogen for maximum production, but it could save one or two fertilizer nitrogen applications.

Use poultry litter. “If you need the P and can’t afford DAP or triple superphosphate, try poultry litter,” Mitchell said. “I'm told there are places where you may still be able to get it spread for around $30 to $40 a ton but it won't stay at this bargain price for long. The farther it has to be transported, the more it will cost, but I'm told some row crop farmers are paying around $60 per ton for it and glad to get it.”

The word has gotten out about poultry litter and most producers cannot find enough litter now. The price is still a huge bargain compared to commercial fertilizers. Most poultry broiler litter is at least a 3-3-2 grade fertilizer (60-60-40 pounds of N-P2O5-K2O per ton). At today's commercial prices, these nutrients are worth over $100 per ton.

Mitchell says poultry litter “has the most fertilizer value the day it comes out of the chicken house. Whatever you do to it is adding costs. So if you pelletize it, it makes it easier to handle, but you haven’t added any value to it.”

But remember that the analysis (percent N-P-K) in raw poultry litter can be highly variable while processed or pelletized litter is more stable.

One problem with poultry litter availability may be due to “poultry houses just not cleaning out the houses fast enough,” Mitchell said. “One reason is that chicken houses are paying more for shavings which are removed with the chicken litter.”

Mitchell says some Alabama cotton producers have hauled poultry litter 150-200 miles to their farms. “That was unheard of 10 years ago.”

According to Oldham, there is a cost-share assistance program under EQIP for poultry litter transportation assistance. The difficulty has been in getting buyers and sellers together.

You should also check with your local Extension office for best management practices regarding the application of poultry litter.

Mitchell says in the short-run, many crops can weather the storm of higher fertility costs. “My research shows that if you’re growing crops such as soybeans and peanuts, they don’t mine much P and K.”

Oldham says do a good job of calibrating your equipment, so you put fertilizer only where you want fertilizer applied.

Since fertilizer supply has been uncertain at times this year, Oldham recommends that producers maintain a good relationship with their fertilizer suppliers. “Suppliers are not wanting to invest a lot of money in inventory and have someone say he can’t afford to buy it.”

So plan ahead and let your supplier know what your anticipated fertilizer needs will be.


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