Wise fertility management cuts costs
By ALAN NEWPORT
Fertilizer purchases don’t hurt as much today as they did a year ago, but they’re still high enough to warrant wise econo-misering.
The place to start is with good soil samples in each pasture, says Dennis Hancock, University of Georgia forage specialist. Hancock has been talking to pasture managers about how to pinch those fertilizer pennies without emptying the forage bank. He offers valuable advice to all managers of introduced and therefore fertilized pastures, no matter where they live.
1 Test first.
Hancock’s point about pasture is you can’t know what to apply or cut without knowing what shortages you have or how well those additions may work. That’s age-old, and pretty obvious, advice.
One of the most important things you can do is figure your yield goals and your fertility response on any given piece of land, adds Jerry Volesky, range and forage specialist at North Platte, Neb.
2 Match soil needs.
Don’t use standard blends such as 13-13-13, Hancock says. In most cases you’re paying for and adding some nutrients you don’t need. He offers this example:
If a beef producer applied 1,471 pounds of 17-17-17 to meet a fertilization level of 250-65-225, it would cost, at current prices, about $405 per acre.
Yet that same amount of fertility could be created with 488 pounds of urea (46-0-0), 141 pounds of diammonium phosphate (18-47-0), and 375 pounds of potash (0-0-60) for just under $300 per acre.
Hancock adds that depending on the price of litter, 4 tons of chicken litter and 110 pounds of potash could produce the same level of fertility for about $160 per acre. The caveat to this last example is not everyone has manure products available, and they vary to some degree in price and shipping cost.
3 Split applications.
Splitting application of fertility can increase effectiveness because it decreases volatilization, runoff and leaching. It can also reduce risk from drought and early or late freezes. Really dry conditions or dry soil at normal fertilization time might be cause to cut back or not fertilize, depending on expectations.
Hancock quotes data indicating forage yield increases of 5% to 10% and nitrogen use efficiency increases of 25% to 30%.
In the Northern Plains that might mean up to three nitrogen applications for irrigated cool-season forages, Volesky says. Typically that would be as spring growth begins in earnest, again in early fall to boost production, and then early in summer to get a little more growth before summer dormancy.
Timing is a real issue, however, Volesky warns. Plants are very good at taking up nitrogen, and if weeds or non-target grasses are more prevalent at application time, they will get the benefit.
“Uptake is really quick after nitrogen is applied — as little as five to seven days,” Volesky adds.
4 Target the best land.
If you want to cut your fertility bill — just flat out cut back — consider fertilizing your best land and ignoring or reducing inputs on your worst, Hancock says. Or, consider grazing meadows where you’ve traditionally cut hay and cutting hay on grassland you’ve typically grazed.
In either case the idea is to get the most response from your fertility dollars. To do this well, however, you need soil tests and decent records on production to know where you’ll get the most bang for dollars spent and pounds applied, Volesky says.
In addition, grazing returns 70% to 85% of the forage nutrients to the ground in urine and feces. Well-distributed grazing makes this even more effective.
5 Redistribute nutrients.
Time-controlled, managed grazing not only does a better job redistributing nutrients, but also allows the forage to build stronger roots and produce more yield.
Hancock offers these comparisons of harvest efficiencies under different grazing scenarios:
• continuous stocked pastures in the Southeast: 30% to 40% grazing harvest efficiency
• slow rotations of three to four pastures: 50% to 60% efficiency
• faster rotations of six to eight paddocks: 60% to 70% efficiency
• strip grazing with high stock density: 70% to 80% efficiency
He also notes final, overall hay efficiencies can vary from 30% to 70%, mainly depending on how much is lost in storage and feeding.
In practice, most graziers who do a good job managing their grazing with higher stock densities, shorter graze periods and longer recovery periods eventually double or triple their overall stocking rate.
6 Cut your losses.
Dry fertilizer losses can be much greater with urea than ammonium nitrate if the weather is hot and/or dry. If you have a choice between the two, consider cost and potential effectiveness, Volesky says.
Volatilization, which is the release of ammonia into the atmosphere, can cause up to 40% losses with urea if rain doesn’t fall within 48 hours of application, according to University of Missouri agronomists.
Auburn University scientists say the greatest losses most likely will occur when urea or urea-containing fertilizer is surface-applied to a soil where high amounts of plant residue are present. Losses likely will be accelerated if the soil is moist at the time of application, followed by five to seven hot, windy and dry days.
Hay really robs soil of nutrients
Ohio agronomists say every ton of hay removed, regardless of quality, takes with it 13 pounds of phosphorus and 50 pounds of potassium.
The average hay yield in Ohio for decades has been about 3 tons per acre per year. That’s 13 and 50 pounds of P and K, respectively, multiplied times the 3 tons. That equals a removal of 39 pounds of phosphorus and 150 pounds of potassium per acre from the average Ohio hay field.
Since corn grain only removes about 0.27 pounds of potassium per bushel harvested, it would take a yield of more than 555 bushels of corn to remove the same amount of potash that an average Ohio hay harvest removes.
Get more forage fertility info online
For facts about how soil fertility affects forage quality from Clemson University, visit hubcap.clemson.edu/~blpprt. Click on “Pasture fertility” and then “Forage quality as affected by fertility.”
To read a discussion about fertility savings from the University of Arkansas, see www.uaex.edu/howard. Click on “October 2008” under What’s Your Beef.
The University of Georgia’s forage Web page is www.georgiaforages.com.
Texas A&M University’s forage Web page is forages.tamu.edu.
Soil pH influences fertilizer uptake
When soils become noticeably acidic or alkaline, nitrogen and phosphorus uptake decrease significantly, says Dennis Hancock, University of Georgia forage specialist. Potassium is less affected, but still less available in either extreme.
But Hancock makes it black and white with a dual example of soil pH varied by only 5.6 to 6.2. He supposes well-fertilized bermudagrass pastures in his region as the base for this illustration.
The more acidic soil would experience a 35% loss in nitrogen uptake. With 200 pounds per acre of N applied at 45 cents per pound, that would be essentially a $35-per-acre loss in nitrogen efficiency.
The more acidic soil would cause a 50% loss in phosphorus uptake. With 50 pounds per acre applied at 25 cents per pound, that would be a $6-per-acre loss in P efficiency.
The more acidic soil would decrease potassium uptake by 10%. With normal application rates for high productivity in the Southeast running 150 pounds per acre at 75 cents per pound, that would cause an $11 loss in K efficiency.
What nitrogen options exist?
Ammonium nitrate has long been a favorite nitrogen source for pasture fertility because it is more stable than urea, and yet its dry form once gave it some real price advantages.
These days, however, due to worries about the potential use of ammonium nitrate as an explosive and the fact that few plants produce it anymore in this country, it’s getting harder to find and more expensive.
A University of Missouri paper on alternatives to ammonium nitrate fertilizer can be found online at aes.missouri.edu/pfcs/research/prop105a.pdf.
This article published in the January, 2010 edition of BEEF PRODUCERS.
All rights reserved. Copyright Farm Progress Cos. 2010.