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Agronomists describe options for dealing with effects of drought

July 19, 2012 | 0 comments

Barring any unexpected and substantive changes in the weather patterns that have taken hold in the past several months, growers of crops, especially corn, should prepare themselves to undertake some unusual practices in the upcoming weeks to salvage at least some value from this year's crop.

That was the gist of the descriptive and prescriptive packages of advice from agronomists in Wisconsin, Illinois, and Kentucky, a climatologist, and a federal crop insurance specialist during a July 11 Webinar titled "Managing Through the Drought" and sponsored by the American Society of Agronomy.

The Webinar attracted hundreds of attendees and generated more than 50 questions - most of which could not be dealt with individually during the time allotted for the presentation.

If farmers in the dozens of states affected by the various stages of the year's drought were looking for immediate relief, they didn't get it in the opening presentation by Brian Fuchs, a climatologist at the University of Nebraska's National Drought Mitigation Center.

With color-coded maps, he traced the development of the drought as it began in several parts of the country during the fall of 2011, describing it as "extreme" and "exceptional" in some areas today.

For the nation as a whole, 56 percent was in drought status and 76 percent "abnormally dry" by the first week of July - the highest such numbers since 1999, Fuchs indicated.

He noted that this was an increase from a drought status of 37 percent in April and has become comparable to a few years in the 1930s, 1950s, and 1980s.

On the immediate horizon, Fuchs expects the drought to "spread and intensify" until at least Sept. 30, creating conditions in states such as Indiana, Illinois, Wisconsin, Missouri, and Arkansas that tend to occur once in every 50 to 100 years.

There is a 50 to 60 percent chance of the development of an El Nino weather phenomenon which would bring some relief in the latter part of this year, probably starting in the southwest part of the country, he stated.

The much higher than normal temperature component of the current weather pattern dates to the fall of 2011 and continued through much of the past winter, Fuchs observed.

He said this prompted many farmers to begin field tillage during March, thereby inadvertently prompting a loss of soil moisture reserves which is now a contributing factor to failing corn crops.

In the lifetime of many current farmers, 1988 stands out as a year of drought and high temperatures.

As to whether this year is better or worse than 1988, University of Illinois crop scientist Emerson Nafziger said the situation is better at the moment but would become worse if no significant rain falls over a wide area in the coming weeks.

The 2012 corn crop had a great start in Illinois and adjoining states with early planting, high degree day accumulations, which accelerated growth, and the deep growing of roots in areas which were already dry at planting time, Nafziger pointed out.

He said this carried over to the very good plant health and leaf color that has persisted at least so far during the drought.

Perilous Pollination Period

As a consequence of the rapid growth of the corn, about 80 percent of the corn in Illinois had reached the silking and pollination stage by July 8, Nafziger reported.

Around the country, 50 percent of the corn was approaching pollination compared to an average of 19 percent by then, he added.

In many corn fields, the timing of the pollination window was as bad as it could be because it coincided with the record high temperatures during the first week of July and the overall lack of moisture to sustain corn plants, Nafziger and University of Kentucky agronomist Chad Lee agreed.

Nafziger cited a water depletion table provided by the John Deere Company, which shows how the curling of corn leaves results in a double whammy for the corn crop.

Most of the sunlight strikes the soil, thereby further depleting the moisture, and the corn leaves are not receiving the sunlight that is essential for the photosynthesis, which sustains plant growth, he explained.

Corn plant leaves curl because the atmospheric demand for moisture overwhelms the amount of water that is available to the plant, Nafziger noted.

Other signs of severe plant stress are rat-tailed tassels and emergence of silks after the production of pollen has already been completed, he stated.

Those factors, combined with the cutting of silks by corn rootworm beetles, definitely reduce kernel set, Nafziger observed.

Even with the kernels that managed to set this year, it is certain that a significant number will eventually abort, he remarked.

The kernels that survive will need sugar to develop - a nutrient that must be supplied via the sunlight that lands on the leaves, Nafziger pointed out.

In addition, much of this year's corn will need 9 to 10 inches of rain in the coming weeks in order to complete a reasonable amount of grain fill, he indicated.

Once the leaves degrade and turn pale or white, the condition is irreversible, Nafziger said.

In his observations this summer, he has found that "no-till corn got hammered" as any extra residue on the soil surface has not helped to alleviate the stresses posed by the combination of drought and heat.

In Kentucky, the condition of the corn crop is dire with only five percent rated as good and none as excellent and a salvage mode has set in for growers, Lee said.

Daytime temperatures of above 100 degrees prevailed at the peak time for pollination, resulting in fertilization of only about 50 percent of the ears in many corn fields and with as few as five kernels on some of those ears, he reported.

Lee cited research work that documents corn yield losses of one percent for every four-hour period during which leaves curl, losses of four percent when temperatures top 93 days for six consecutive days, and accumulated yield losses of up to 48 percent from those stresses even if pollination occurred and there is sufficient moisture.

At Henderson, KY, just across the Ohio River from Illinois, temperatures topped 93 degrees for eight consecutive days this summer, Lee reported. "The combination of heat and water stress came at the worst possible time."

Picking up on Nafziger's point about the requirement for plant sugar to fill corn kernels, Lee indicated that corn plants need to produce 78 pounds of glucose sugar in order to generate one bushel of grain corn.

For soybeans, that number jumps to 120 pounds of glucose sugar. Those are equivalents of 15,580 pounds of glucose sugar for a corn yield of 200 bushels per acre and 5,965 pounds for a soybean yield of 50 bushels.

Beware of High Nitrates

For barren corn and that which does not justify a harvest as grain, Lee recommends a descending order of taking it as silage, baled dry hay, or green chopping. When making silage, he prefers storing it in plastic bags rather than bunkers.

Regardless of how drought stricken corn is harvested, users of the crop need to be aware of the likelihood of a high nitrate content, Lee warned. He suggests cutting it at heights of 12 to 15 inches to reduce the nitrates somewhat.

Laboratory tests of the stricken corn in Kentucky have shown nitrate concentrations of above 10,000 parts per million compared to the 5,000 ppm that is considered to be excessive for livestock feed, Lee stated.

He emphasizes checking feed values and getting a nitrate test before feeding such corn.

For ensiling the drought-stricken corn, harvest at 60 to 65 percent moisture and allow it to cure for least four to five weeks in order to address the nitrate concern, Lee advised.

To make baleage at 45 to 50 percent moisture, be sure to crimp or condition the stalks and avoid using older style balers because of easily they could be damaged, he cautioned.

With the baleage, use extra twine and give it at least seven rounds of plastic wrap in order to preserve it, Lee continued. For dry hay, let the moisture drop to 10 to 15 percent so mold will not develop, he added.

Fungicides, Fertilizers Fruitless

The three agronomists on the Webinar discouraged any thoughts of applying fungicides or extra fertilizer as a way to salvage drought and heat stressed corn and soybeans.

Nafziger stated a definite "no" to supplementing with nitrogen on corn and Wisconsin soybean specialist Shawn Conley noted that a cost-prohibitive 160 pounds of foliar nitrogen per acre would be required to make a difference.

"Only water will help," Nafziger emphasized. As it turned out, many corn growers "planted more corn than needed this year" and fields in which there were frequent planter skips are faring somewhat better, he observed.

To a question about the drought-tolerant corn hybrids that are still in the development stage, Nafziger replied that this year's conditions are "so severe" that representatives of the companies engaged in that research are being very reserved in making any claims.

"They're not miracle plants. They need water," Lee remarked.

Herbicide Carryover

a Concern

Don't forget about the possibility of herbicide carryover, especially with atrazine, Lee pointed out.

Pay special attention to this after a corn crop and check the application records for any followup crop or timing restrictions, Conley added.

Lee also mentioned a possible carryover of nitrogen that was not used by corn as a variable with a followup planting of winter wheat.

In those cases, back off on the planting date of the wheat in order to avoid excess foliage growth and aphid infestation before the winter, he advised.

Another concern expressed by a Webinar questioner was the production of corn seed for 2013. Nafziger said no specific information was available on that but noted that pollination was certainly a problem for seed corn acres.

A Lifeline for Soybeans

According to Conley, the situation isn't critical yet for soybeans because of their "tremendous plasticity" or wide recovery window, which could lead to yields of 40 bushels per acre even if substantial rain doesn't arrive until early August.

He noted that many of the roots are deep but pointed out that the pattern of root growth has left some soybeans lagging for potassium.

With a shortage of moisture, soybean plants will have shortened internodes but this doesn't necessarily have an effect on yield because new flowers continue to appear for several weeks and only about 20 percent of them have emerged so far as plants have reached the R2 and R3 growth stage.

Lee said many of the soybeans in Kentucky are at the same stage.

Rain becomes critical at the R4 and R5 growth stage, Conley observed. With minimal rain, the protein content of soybeans increases while the oil percentage goes up with sufficient rain, he indicated.

Drought prompts closure of stomata, reduces nitrogen fixation, and causes leaf drop, Conley said.

Hastened growth limits yield and extra flowers abort but "the real concern" is the possible abortion of seeds and even whole pods, he remarked.

Contrary to Nafziger's observation about no-till corn this year, Conley said there is a history in Wisconsin of four to five bushel per acre yield advantages for no-till soybeans.

Replying to a question, he indicated that having narrow rows is an advantage this year because of faster row closure.

While there's a definite possibility that the drought will have a significant impact on soybean yields in Wisconsin and elsewhere, Conley cited two other related concerns.

They are that charcoal rot is more likely during a drought and that spider mites thrive during dry weather.

Crop Insurance Coverage

What's certain about the effect of the drought and heat this year is that claims for crop insurance payments are going to mount.

Addressing that point during the Webinar was Tim Hoffmann, a crop insurance specialist who has been with the U.S. Department of Agriculture's Risk Management Agency for 31 years.

After record payments so far of $10.8 billion in indemnities on crop insurance claims for 2011, or a loss ratio of 91 percent of premiums compared to 56 percent for 2010, Hoffmann assured everyone concerned that sufficient funds are available for the claims that will be made for this year for losses attributed to drought.

To all insured crop growers, Hoffmann strongly advised staying in touch with one's insurance agent so documentation can be made about non-traditional timing of crop harvest and use.

Make sure that an appraisal is made before a crop is removed or that a representative strip be left, he stressed.

Minimal requirements for maintaining crop insurance eligibility are to carry out normal crop care, which could include weed and pest control. Hoffmann said irrigation is not required in an attempt to salvage a crop from drought.

An information source on crop insurance is the www.rma.usda.gov Web site.

In Wisconsin, updates of advisories by agronomists are being consolidated on the http://fyi.uwex.edu/drought2012 Web site.

A national update is available at https://www.agronomy.org/education/drought-resources.

A recording of the July 11 Webinar is being posted at https://www.certifiedcropadviser.org/certifications/self-study.

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