Five Fertility Tips

Yield goals, soil fertility levels and cropping systems dictate fertility requirements.

According to the Mississippi State University Extension Service, “Adequate soil fertility is a must for good corn production. Fertility requirements depend on yield goals, soil fertility levels and cropping systems. Balanced fertility management is necessary to produce corn for more profit.” To foster successful corn production in this region, Corn South has gathered five tips from Southern universities to help producers prepare for the upcoming season.

Tip #1: Mississippi State University

According to Bobby Golden, Agronomist, Delta REC. MSU: Numerous methods of zinc delivery to the corn plant are available such as seed treatments, foliar sprays, or zinc granules for either soil incorporation or application in-furrow. The best method to ensure that soil test zinc levels are adequate on fields with a history of zinc deficiency is to apply 10 lbs Zn/acre as Zinc sulfate (30-33 lbs product/acre) blended in with the preplant P & K fertilizer application.

In-season corrections to zinc deficient corn will probably be most likely conducted with a foliar spray. At the V2-V5 growth stage, foliar sprays are perhaps the easiest method to remedy a zinc deficiency, because zinc is only needed in small amounts by the corn plant. Research has shown that supplying 1 lb actual Zn/acre can correct most deficiencies observed between the V2-V5 stage of corn growth. – See more at: corn-observed-in-ms-delta/#sthash.Toc2bNmI.dpuf.

Tip #2: University of Georgia

According to Georgia FACES, corn and cotton share an essential attribute: They need just the right amount of nitrogen to generate high yields. Low dosages can result in stunted plants or yellow, lower leaves, which is very common in corn.

“There’s a lot of emphasis on corn with nitrogen now, making sure it has enough nitrogen all throughout the growing season,” said Glen Harris, a soils and fertility agronomist with the University of Georgia Tifton campus. “Most growers that shoot for high yields will tell you they never want to see those lower leaves turn yellow. If some of those turn yellow, then it’s probably a loss of yield potential.”

Too much nitrogen, however, could result in the nutrient being leached away later in the planting season. Typically, corn and cotton need two applications of nitrogen, once at planting and the other during side-dressing (between first square and first bloom). Too much nitrogen at planting time could lead to a deficiency of the essential nutrient later in the planting season because of leaching.

Tip #3: LSU AgCenter

Taking the lead in field trials is Rick Mascagni, an agronomist at the Northeast Research Station in St. Joseph. He has conducted corn fertility studies on various soil types primarily in northeast Louisiana.

Much of the focus Mascagni’s research centers on the role of N fertilization. Researchers looked at the source of N, timing of the application and the amount applied. When examining a single application of N sources on Commerce silt loam soil, a nitrogen solution of 30-0-0-2 was equal to a combination of granular urea and Agrotain with both producing higher yields than granular urea alone.

“It appeared that loss of nitrogen through volatilization occurred with the urea fertilizer, which is not unexpected,” Mascagni said.

When comparing N applied late in the season, at the 12-leaf stage and at early silk, yields were slightly higher for the early silk application. This finding showed that if farmers are unable to get in a second application earlier in the season, corn yields will respond to N as late as early silk. Mascagni added yields were similar when equivalent N rates were applied either once early season (2- or 3-leaf stage) or split between early season and the 12-leaf or early-silk growth stages.

Another study conducted on Sharkey clay soils in northeast Louisiana produced similar findings. A late application of 60 pounds of N per acre increased yields at both the 12-leaf and early silk stages. In a Commerce silt loam study, yields were not different between equivalent N rates applied once early season or split between either the 12- leaf or early-silk growth stages.

Tip #4: University of Arkansas

We suggest that the N be applied in 2-3 way split to increase use efficiency. One option is to apply 20 percent of the rate pre-plant; 60 percent around the V4-V6 stage and the remainder 20 percent one week before the tassel emerges – the pre-tassel split applies to yield goals larger than 150 bu/A. It is estimated that between emergence and the V4 stage, a corn plant has used less than 10 percent of its total nitrogen requirement, with the largest need occurring soon after the growing point is above ground. Applying a large amount of nitrogen pre-plant is not very efficient.

Producers should use only proven technologies to reduce loss potential. Under extended wet periods, nitrogen can be lost by leaching or denitrification. However, under dry periods or inability to properly incorporate urea, nitrogen can be lost as ammonia gas. At this moment, the University of Arkansas, Division of Agriculture, recommends only NBPTbased products as an effective means to reduce ammonia volatilization risks when urea is not properly incorporated. While most are familiar with Agrotain, there is a new product in the market called Arborite. Both of these products contain NBPT, and when applied based on the manufacturers’ recommendations, they have been effective at reducing ammonia volatilization losses for 10 days or so.

Tip #5: North Carolina State University

Corn plants that are purple because of phosphorus deficiency are showing up even in fields where recent soil-test reports show phosphorus levels to be adequate. The reason is poor root growth rather than lack of fertilizer, and the plants will probably outgrow the problem, said Dr. David Hardy, chief of the department’s Soil Testing Section. Sulfur problems, usually typified by yellow plants, might pose more of a challenge.

Hardy offers advice for addressing nutrient deficiencies: “Based on experience with early season problems, I believe it is always best to collect and submit plant tissue, soil and nematode samples to rule out possible concerns and specifically identify the causes of growth disorders. On sandy soils, corn may be yellow and nutrient deficient, but the ultimate cause could actually be plant-parasitic nematodes.

“Problems should not be addressed based on visual observation alone,” Hardy said. “Growers receive the best diagnosis and recommendations if they submit matching samples from ‘good’ and ‘bad’ areas and completely fill out the diagnostic sample information form associated with each type of test.”

Hardy urges growers who see problems to submit diagnostic samples even if they have a fairly current soil report. Sulfur can leach quickly from the crop root zone, and soils that tested sufficient for sulfur three months ago could now be low.

“Even fertilization programs that include sulfur may not be providing enough to correct or prevent deficiency,” Hardy said. “A combination of soil and plant tissue samples can provide a clear diagnosis of the problem and how to address it. It is not enough to know which nutrient is deficient. Growers need to know how much to apply.”

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