Tough decisions confront corn growers with freeze-damaged crops

With over a million acres of cotton and rice going out of production and into corn in 2007, it is little surprise that growers from Virginia to Texas took advantage of warm March weather to plant corn.

But on Easter weekend Mother Nature delivered a surprise with heavy snowfall in Virginia and below freezing temperatures as far south as the Panhandle of Florida.

Then, only a week later, a second blast of cold weather brought flooding rains and near freezing temperatures to the upper Southeast. Though not near the record-breaking cold temperatures recorded in the Easter cold front, the cold temperatures, heavy rain, and in some cases devastating wind will likely delay and prevent recovery of some crops damaged by the earlier storm. In other cases, it will further delay planting.

Final results of the impact of the Easter storm probably won't be known until crops are harvested.

Of utmost interest will be the negative impact of the cold weather on the extra corn acreage in the Southeast. Most growers who switched to corn or increased corn acreage still plant other crops, so getting corn in early in many cases fit better into the overall planting scheme for multiple crops.

Likewise, getting corn out early creates less of a management hassle with cotton, soybeans, peanuts, and other crops grown in the Southeast.

The record cold temperatures couldn't have come at a worst time for corn growers.

In many cases growers had never grown corn before or had not grown the crop in over a decade. If growers followed modern practice they upped seeding rates to take maximum advantage of the yield potential of today's hybrid corn varieties. And, if they went one step farther and planted on narrow-rows to increase yield, the total affect may be a disaster thanks to the record cold.

Seeding rates for productive soils should range from 28,000 to 33,000 seeds per acre. Such seeding rates should result in actual plant populations ranging from 26,000 to 30,000 plants per acre. This broad range of plant populations is considered optimum for soils with historical yields of 125 bushels per acre or greater.

Variable seeding rate technology is likely not profitable for soils within this category, no matter how great the range of yields.

Adding to the woes of new corn growers is the high cost of fertilizer, in particular nitrogen. Corn is a nitrogen hungry crop and putting out a high nitrogen starter fertilizer is an expensive practice, but replanting corn and paying that expense, or part of it, a second time will put a damper on the near record prices being offered for corn.

The early April cold weather will likely have a season-long effect on the 2007 corn crop in the Southeast. Much of the corn planted in the Southeast in March had not germinated fully when the cold weather hit on Easter weekend. When corn seed and young seedlings absorb moisture and freeze, the seed membrane or coleoptile toughens and does not allow the seedling corn plant to emerge properly.

The result of a coleoptile that fails to “release” the developing leaves is a plant that “cork screws” underground, or leaves that rupture out of the coleoptile on the side rather than emerging through the tip. The problems with the coleoptile are primarily the result of the cold and wet conditions.

Seminal, or seed roots in corn anchor the plant and absorb minor amounts of water and nutrients during the first two weeks of growth. If freezing temperatures hit during this critical time, the corn plant can be damaged and its yield potential significantly reduced.

Prolonged warm weather from Virginia to South Carolina prompted many growers to get their crop in early, but set them up for the untimely cold Easter weather.

Corn seed that germinate when soil temperatures are conducive for growth will produce a second root system, called nodal roots, which provide nutrients for the plant throughout the growing year. If the seed roots are damaged, the nodal roots do not form properly, resulting in long-term damage to the corn plant.

Glenn Rountree, Extension farm agent in Isle of Wight County in southeastern Virginia says, “corn growers have a limited window of opportunity for planting and many of the larger acreage growers felt they had to take advantage of the warm March temperatures to get part of their corn crop planted. Those who could wait to plant, did so,” Rountree says.

In eastern North Carolina, Billy McLawhorn, president of MCSI Agricultural Consulting in Cove City, N.C., says, “we have a mixed bag of timing in corn planting. We have some growers who had planted all their corn and had most of it up and growing, some who were in the midst of planting and some who hadn't started planting when the cold weather hit. In general, everything above ground seems to have done okay.”

Wade Thomason, an associate professor of agronomy and small grain specialist at Virginia Tech says the warm temperatures that preceded the record cold may mitigate some of the damage to grain crops. Most growers know by now the extent of damage to their corn crop in terms of plant populations, and they will need to carefully assess the level of damage and determine whether to replant corn or something else, he explains.

Determining the level of damage may provide some difficult management decisions. Different soil textures and topography create different climatic zones for plants which creates an uneven susceptibility to low, high, wet, dry conditions. As a result, a grower may lose part of a row of corn and a few feet away there may be no damage. Determining what to replace and what to leave alone will be a major decision for many corn growers in the Southeast.

Paul Carter, research coordinator for Pioneer Seed, says recovery from early season death of above ground tissue depends on several factors:

  • Stage of growth: Potential for recovery is higher at VE-V2 than for V3-V4 stages because energy reserves still exist in the seed to support growth.

  • Amount of green tissue remaining: The more green tissue for the plant to live on until there is enough re-growth for photosynthesis, the higher the potential for recovery, especially at V3-V4 stages when seed reserves are nearly depleted.

  • Weather conditions during re-growth: Dry, warm conditions are more favorable than cold and wet weather.

  • Number of frost events: Plants at this stage will often recover from one episode, but reserves can be depleted with multiple frosts while damaged seedlings are recovering. The probability that plants will not re-cover or that the stand will contain non-competitive — runts — is increased with repeated frost damage/recovery cycles.

Experience has shown that seedlings with tissue damage within 0.5 inches or less of the growing point will most likely not recover. Even if plants survive, potential to produce competitive plants with acceptable yield potential is compromised.

Seedlings less severely damaged, with more than 0.5 inches of healthy tissue above the growing point often will survive and develop into plants with high yield potential, Carter says.

After determining the viable stand that remains, growers need to compare yield expectations of the damaged stand versus a late replanted stand, and consider replant costs and pest management issues.

Yield expectations of frost-damaged stands can be assessed by measuring stand loss when corn plants are at the six-leaf collar stage or less.

North Carolina State University Professor and Corn Specialist Ron Heiniger says there is still time to re-plant corn for those who determine that to be necessary and an economic option. Research in Virginia and western North Carolina suggests that corn can be planted from mid- to late-June with a reasonable opportunity for profit.

Data from a two-year study at the Piedmont Research Station in Salisbury, N.C., indicates corn planted as late as June 15 can produce a profitable yield. With high corn prices still in effect, later planted corn would be more profitable than at the time the tests were conducted.

Heiniger stresses growers should realize that the risk of crop failure increases when corn is planted late. In particular, two problems associated with late-planted corn must be addressed by careful management and in-season scouting if late-planted corn is to be a success.

First, there is a much greater chance that corn will be severely damaged by late generations of European corn borer and corn ear worm. The use of Bt carrying corn hybrids or field application of insecticide when corn reaches the V8 stage (waist high) is necessary to prevent economic loss or, in some cases, complete crop failure.

Second, there is an increased likelihood that corn will experience heat and drought stress in the two week period prior to silking. To minimize the chance of drought and/or heat effecting pollination and kernel number, planting date and hybrid maturity should be selected so that corn reaches silking stage in late-July or early-August when the chances of rain from tropical storms increase, Heiniger explains.

April 2006 was one of the warmest on record and April 2007 was one of the coldest on record. Just when grain growers appeared to have a two or three year window of profitability for their crop, Mother Nature steps in to dampen the enthusiasm.

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