Farm Progress

Take Soil Fertility Further | Mind Your Ps and NsTake Soil Fertility Further | Mind Your Ps and Ns

Larry Stalcup

December 28, 2011

7 Min Read


Taking advantage of new and powerful corn hybrids requires getting the most out of yield-building nitrogen (N). And efficient phosphorus (P), potassium (K) and other soil-nutrient use keeps input costs in line.

That’s on Gill Mumm’s mind as he incorporates proven fertility practices with new and advanced fertilizer materials designed to enhance production. Mumm farms with his brothers Brent and Curt and father Ronnie in Chester, NE, near the northeast Kansas border. They are among growers interested in new and improved products and application methods providing more ways to get the most out of the soil.

Nutrient management was among the hottest topics at the recent North Central Extension-Industry Soil Fertility Conference (NCEISF) hosted by Iowa State University (ISU) in Ames. Everything from products designed to enhance liquid manure management to using more micronutrients were on the agenda.

It’s the type of information the Mumms relish. They aren’t afraid to try new fertilizer alternatives. They run about a mostly irrigated 50-50 corn and soybean rotation with some wheat worked into the program. “We often lack enough P, so we try to keep it built up with an 11-52-0 dry fertilizer program,” Mumm says.

To make the application more uniform, they used a capsulated product that contains four nutrients in one pellet. They product, MicroEssentials SZ (12-40-0-10-1), is applied at a rate of about 125 lbs./acre, Mumm says.

The product claims to distribute the N, P, K, sulfur and zinc in proper amounts for every square foot.

The main N source is either a 28% or 32% liquid and some anhydrous ammonia. The pelleted blend is normally applied in the fall or early spring before a 32% liquid N application. “We usually push for total N of 190-220 lbs./acre,” Mumm says. “With the liquid applications, we can cover ground in half the time, it’s more uniform and it’s safer.”

The pelleted dry blend is also applied on corn stalks on acres to be planted in beans the following year. “The uniform release of P will help us get a good start on the bean ground,” Mumm says.

Nutrient input costs are among the highest budget-busters for growers. Purdue University Extension Agronomist Robert Nielsen reminds growers to use common sense when using new products. “No miracle products are out there,” says Nielsen, also a corn specialist. “But new products, like pellets, may help growers simplify the application.”

New and old fertilization ideas

Here are old and new fertilization ideas growers can consider in their corn and bean programs. Some are from private companies and some are from university reports at the NCEISF conference.

•Banding is not necessarily better for strip-till, according to a new University of Illinois research.

The  study revealed that strip-till was superior to no-till and increased yield in soybeans. However, the results showed no difference in yield between fertilizer-application methods.
Researchers compared different combinations of P and K rates applied in no-till by either broadcasting or deep-banding 6 in. below the surface, and in strip-till by deep banding 6 in. below the surface.
“Strip-till allows growers to apply fertilizer in a band in the subsurface – it has almost become the norm these days,” says Fabian Fernandez, U of I assistant professor of crop sciences. “Fertilizer placement offers no difference for yield. “Most growers are deep banding fertilizer if they strip-till, when in reality there is no need to do this, at least for soybean. Our research shows when fertility levels are adequate, there is no advantage and you can broadcast P and K to achieve the same results.”
 Fernandez says deep-band placement normally requires more equipment, expense and time.
“P doesn’t move far in the soil. With broadcast application, it tends to accumulate at the soil surface,” Fernandez said. “With subsurface application, we saw P levels decrease on the soil surface. Although subsurface band applications may not increase yield, they could decrease P levels on the surface which could be an environmental benefit to reduce the potential of P runoff.”
Subsurface banding of fertilizers is sometimes promoted as a more efficient placement method, and some believe the same yield level can be attained with lower fertilizer rates, Fernandez says.
“We observed no evidence to suggest a fertilizer-rate reduction can be accomplished with subsurface banding without similar yield declines as observed for broadcast applications,” he says.
This research, “No-Till and Strip-Till Soybean Production with Surface and Subsurface Phosphorus and Potassium Fertilization” was published in the Agronomy Journal.

• Biologicalsand other production additives claim to provide more nutrients to root zones. “With P and K inputs, sometimes only 10-20% are available to the plant because they are tied up in the soil,” says Shannon Smith, product manager for Agri-Gro, Doniphan, MO.

One of his company’s products, FoliarBlend, is among biologicals designed to promote beneficial bacteria growth. “It helps make nutrients more available to help reduce input costs,” Smith says. “It can help reduce P and K application rates by up to 33% and N by up to 15%.”

The liquid product is applied at 1-3 pts./acre mixed with herbicides or other chemical applications. University of Missouri tests show a 15-18-bu./acre increase in corn yield through the use of the biological, says Smith.

Slow-release fertilizer systems are helping growers get more timely distribution of N and other nutrients. Kugler Co., McCook, NE, is among several producers of slow-release fertilizer products. Kugler’s Leigh Hoyt says the product is not designed to replace a full fertilizer program, but to help spread overall nutrient release more effectively.

“For example, our KQ-XRN liquid product is a 28-0-0 product that is 72% slow release,” he says, adding that the application rate is 1-3 gal./acre at a cost of about $8-9/gal. It can be applied through aerial, ground-rig or a center pivot. “You can run it four times during corn plant’s life, usually, V4, V8, flag leaf and brown silk.”

• Biochar can help promote grain yield as an additive to liquid swine manure, according to research by Agriculture and Agri-Food Canada and the Ontario Ministry of Agriculture, Food and Rural Affairs reported at the NCEISFfertility conference. Along with better yield possibilities, there were indications that “off-site movement of N from fall-applied manure is reduced” with biochar added.

The researchers found lower tile-nitrate and subsoil nitrate concentrations that could move to groundwater. The ag ministry indicated that the effective rate was “about 5 tons/hectare (2 tons/acre),” and use of this material will be economical if it is obtained as a waste rather than a high-value product.” Biochar research has also shown positive results through ISU studies.

• Micronutrients as starter, foliar fertilization: Early research by agronomists at Kansas State University indicate that corn and soybean production in high-yield environments may benefit from the combined use of starter and foliar fertilization, including macro- and micronutrients. In their 2010 research, agronomists Nathan Mueller and Dorivar Ruiz Diaz applied starter and foliar fertilizer treatments with combinations of N, P, K and micronutrients iron, zinc, manganese, boron and copper.

Soil and tissue samples showed that chloride (included in the starter), zinc and copper showed significant increases in corn-tissue concentration with starter application. Early corn biomass also increased significantly at both test locations with the use of starters. Corn and soybean grain yield response varied by location, with significant yield increase for soybean with starter application of NPK+micros at one location. However, the agronomists say other locations for corn and soybeans showed no statistically significant effect of treatments in 2010. They stress that additional studies of the final 2011 numbers and future crops are needed to confirm their findings.

• Incorporating fertilizer reduces P loss: Ohio State University plant scientists are developing better methods of preventing P runoff. Their work indicates that incorporating commercial fertilizer reduces dissolved runoff P compared to leaving it on the soil surface.  

They studied incorporating fertilizer at two locations. One had been no-tilled for at least 20 years and the other had not. At both sites, the surface application of commercial fertilizer in the no-till plots resulted in similar runoff P concentrations with or without a cover crop at both locations. 

Respect your residue: The removal of corn residue from fields for livestock feed, bedding or a bioenergy resource reduces the amount of plant material residue remaining for soil-surface protection. Thisreduces carbon return to soil and potential soil organic matter, and alters the cycling of plant nutrients, says John Sawyer, ISU Extension soil fertility specialist and agronomy professor.

He says the agronomic and environmental impacts of tillage and corn-residue removal practices are still debated. However, both tilled and no-till cropping systems could see additional runoff and nutrient loss.

Nielson says good, solid runoff management can be the best practice growers can take to improve their fertilizer’s efficiency.

“There are different challenges for growers in different growing areas,” he explains. “We have so many areas of poorly drained soils in Indiana (and the eastern Corn Belt), with too much rainfall at the wrong time of the season. Growers need to look at ways to maintain N, via underground tile or surface drainage.”

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