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6 forage fertility tricks

As you learn to manage pastures and hayfields like your row crops, you’ll find that they respond about the same, too. Corn is a grass; your pastures are mostly grass. Not many farmers treat them the same -- yet.

Dennis Hancock, Extension forage specialist for the University of Georgia, says some grazing cattle farms in his state are changing that through intense forage management. He gives these six tricks for improving fertility response of grasslands.

1. Get the pH right.

This soil acidity measure impacts the ability of soil nutrients to be absorbed into plant roots. If the soil is too acidic (pH of less than 6.0), roots of most forage crops are pruned back, limiting nutrient uptake. Hancock says going from a pH of 6.2 down to 5.6 slices nitrogen (N) efficiency by about 35%, phosphorus (P) by 50%, and potassium (K) by 10%. At some common application rates on high-producing pasture and at today’s prices, this loss could cost over $70 per acre in one year, says Hancock.

The solution is applying lime to fields to raise the pH. “That is really job one for fertility,” he says. “Lime is cheap, maybe about $20 an acre in the Midwest.”

He suggests soil-testing your hayfields every year and your pastures on a three-year rotation. That way, every field is tested at least every third year.

2. Avoid standard fertilizer blends.

Hancock says these are homogenized fertilizers with all nutrients in one capsule, and they can be the most expensive way to apply fertilizer. He gives an example of three approaches to fertilizing a pasture or hayfield at an N-P-K rate of 250-65-225 (pounds per acre).

While a homogenized blend could cost over $400 per acre and apply unneeded nutrients, a mix of individual N, P, and K fertilizers precisely tied to the exact need could accomplish the same overall rates at $100 per acre less. Even better, says Hancock, is poultry litter, widely available in his state for $40 per ton. It would take 4 tons to get target rates of N and P, with a little extra K needed, and the total cost would be under $200 per acre.

3. Split N applications.

Avoid the temptation of applying all N at the beginning of the growing season. Cool-season forages may need a little N in the fall to encourage tillering and more N in the spring to increase yields. Warm-season forages may need N split into two to four applications through the summer. Splitting N in this way will generally increase the efficiency of N use by 25% to 30%, Hancock says, and increase yields by 5% to 10%. The only extra cost is the second spreading trip. The N is used more efficiently due to less leaching and volatilization (urea-based products).

With lower amounts of N applied at one time, there will be less risk of nitrate toxicity in the grazed forage.

4. Account for N loss of urea products.

Urea is a more concentrated form of N than some other fertilizer products, but it is also prone to volatilization loss. If you use urea-based products, know that you will lose 10% to 20% of it and even more in extreme cases. If urea is your primary N source, consider using the volatilization inhibitor Agrotain. Hancock says in a summary of research over several years, Agrotain improved N recovery by 19% and improved forage yield by 11%.

5. Apply P in late summer or fall.

Phosphorus is one nutrient that can be applied to established forage crops at any time.

“The timing for P isn’t as critical as it is for N or K, so apply it a little later in the season,” says Hancock. “The advantage of summer or fall is that’s when demand for it is low, so you may find an advantageous price. There may be less risk of runoff at that time.”

6. Split K applications.

Put on half in the spring and half in the fall. This could tie in to your split N application and also fall P. You could get the same benefits as late-summer P -- price incentives at a slow time for fertilizer dealers. The crop will benefit from having nutrients there when it is growing rapidly in spring, and winter hardiness will improve with the fall application.

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