BRUCE STEELMAN, County Director, UT Extension Office
Tuesday, June 26, 2012 1:26 pm

The current abnormally dry period has been devastating on homeowners as well as farmers throughout Cannon County. The lack of moisture, coupled with the extreme temperatures and wind, have greatly affected the growth of forages and row crops.

Corn throughout the County is tasseling, plant stress during this time can result in decreased yields. Although much of the yield potential of the corn plant has already been establish earlier in the season, the full yield potential is affected by the extreme conditions.

Temperatures in excess of 95 degrees, especially when accompanied by low relative humidity, can dry out exposed silks, but affect silk elongation very little. Pollen is likely damaged or killed by mid-90's or greater temperatures, especially when accompanied by low relative humidity.

Luckily, pollen shed typically occurs during early to mid-morning hours before temperatures climb to such dangerous heights. Furthermore, pollen maturation for a given tassel occurs over time and 'fresh' pollen is available every morning until pollen shed is complete.

Corn plants often roll their leaves as a defense to conserve moisture. Rolled leaves in the afternoon may not always mean corn is under drought stress. A key indicator of drought stress is when corn leaves begin to roll early in the morning and continues to stay rolled throughout the day.

Severe drought stress is evident when long term wilting of the plant occurs. This affects the pollination process by slowing down silk elongation. Silks begin elongating from the ovules of the ear shoot about 7 days prior to silking. The silks from the butt of the ear elongate first, followed by those from the central part of the ear, then the tip of the ear.

The lack of plant water availability can slow down silk elongation, resulting in delay or failure of the silks to emerge from the ear shoot. Silks that do emerge may dry out rapidly under severe moisture deficits and become non-receptive to pollen. Ironically, drought stress tends to accelerate pollen shed, often resulting in a poor timing 'nick' between pollen shed and silk emergence.

According to Perdue University, beginning about 2 weeks before silk emergence, corn enters the period of grain yield determination most sensitive to drought stress. Continual wilting of the plant due to drought stress at this stage can decrease yield 3 to 4 percent per day. During the actual silking and pollen shed period, severe stress may reduce yield up to 8 percent per day. During the 2 weeks following silking, severe stress may reduce yield up to 6 percent per day.

Hopefully, with the good Lord’s help we will soon get adequate moisture to produce the effect of the current “dry spell.” Livestock producers are urged to consider measures in the event of a prolonged lack of rainfall. Along with maintaining adequate supplies of forages, consider alternative feeds to stretch hay supplies and remember to routinely monitor water sources to ensure a fresh and abundant supply. Reduce the physical restrains of lactating animals by weaning early to lower their nutritional requirements.

Consider culling to reduce the overall forage needs, below are management considerations for you to consider;

Cull Open Cows First. Open beef cows are a liability. They offer no profit potential, only profit reduction. There are no other options except to cull open cows during feed shortage.

Cull Older Cows. As cows pass 10 years of age, their productivity and market value begin to drop. Cull these cows before they become a profit drain and get them on the market while they can still fetch a respectable market price.

Cows with Physical Problems Should be Culled. Cows with bad udders, bad eyes, crippled or bad feet and legs should be “shipped.” These cows will only go down hill in production, condition and value. They also create a “poor image” for the industry.

These cows are more susceptible to stress and are likely to die before “grass.”

Cows that Calve “Out of Season” Should be Considered for the Cull Pen. During short feed supply is a good time to get rid of these cows. An argument for keeping these cows might be made during times of plentiful feed supply, but not in times of feed shortage.

Take a Hard Look at Late Calving Cows. Calving dates should be evaluated and those cows that calve late may miss getting bred next breeding season. For those producers working to shorten the breeding season, culling late calving cows would help.

Poor Producing Cows Should be Critically Evaluated. This is the place where a good set of records would be needed. If records are available, cull those cows that produced cows with low weaning weights. If records are not available, take a look at the calves with their dams.

Cows that lost their calves for any reason should be considered for culling. Cows that have lost their calves since birth will not produce a return and will continue to eat feed and mount expenses.

Plan ahead and consider steps to reduce your effects of this year’s rainfall shortage. Hopefully, the current weather conditions will change and more seasonal conditions will ease the current conditions.

If the Cannon County Extension Office can be of assistance, please contact Bruce Steelman at 563-2554.