farmgate: Making Crop Management Decisions After A Severe Storm
Your corn is up and doing well, good to excellent, you think. But suddenly one of those increasingly frequent storms sweeps through the county and combination of heavy rain, high winds, and hail leave your crop shredded, down, temporarily submerged, and in fair to poor condition at best. Here it is June 18, and what do you do now?
Those types of severe storms washed through Nebraska and Iowa, and the University of Nebraska offers a series of factors in the June 12th issue of Crop Watch to consider the next step.
• Severe flooding may have created gullies in fields which will have to be smoothed before replanting, if that is the choice. Sweep tillage may keep residue in place, but requirements for moving soil will destroy the residue and leave the soil susceptible to more erosion.
• While hail damage to corn may look bad, its seriousness depends on the maturity of the plant. The degree of potential injury increases as the plant approaches silking, then after that stage the potential for injury gradually declines.
1. Up to the 5 leaf stage the growing point of the corn is below the soil, and the early loss of 5 leaves will mean little to the 19 to 21 leaves that will share the burden of producing an ear.
2. Hail damage from the V8 to V11 stage will affect row numbers, but kernels per row will not be determined until V17.
3. From the tassel stage to maturity, no more leaves will develop and the tassel will not be replaced. The 6 to 8 leaves above the ear are the most important for its development.
• When considering replanting due to poor stands, corn planted in early June will have a 50% yield loss compared to typical timing. It may be better to keep an existing stand with a 50% stand loss than consider replanting.
• If the corn is herbicide tolerant, that will help manage weed competition in a reduced stand. With delayed plant growth, insect problems can increase in non-Bt hybrids. And hail damaged corn is also more susceptible to diseases.
• If the damaged crop was glyphosate tolerant, beware of potential problems with volunteer corn in a new crop. Conventional corn can be easily controlled if the field is replanted to glyphosate tolerant soybeans.
• Both soybeans and sorghum can be planted later than corn without the yield loss, but check your previously applied herbicide labels to ensure against unanticipated problems.
• If corn is replanted, destroy the damaged stand so it does not steal water and nutrients from the new corn. Tillage is preferable over mowing, which will not kill the old crop. Chemical control may be the best option, but glyphosate tolerant corn will be a problem.
1. Select Max is effective but very slow acting, and will require a 6 day interval before replanting.
2. Glufosinate or paraquat will not delay planting, but effectiveness is questionable.
• Replant options may be restricted if a pre-emergent herbicide has been used.
1. Corn can be replanted, and a shorter season hybrid may be the best choice.
2. Soybeans can be planted, unless atrazine is in the field.
3. Sorghum provides more flexibility, and is adaptable to common corn herbicides.
4. Consult the table for replanting intervals if common herbicides are used.
• If soybeans were damaged and replanting is planned, the expected yield loss from the replanted soybeans must be compared to the anticipated yield loss from the original beans. Replanting requires additional cash for inputs and there will be a yield penalty.
• Leaving a poor stand of soybeans may require added costs for weed control.
• A general guideline is to leave a field alone if plant populations are greater than 50,000 plants per acre, the stand is uniform, and the field can be kept weed free.
• Emerged soybeans will recover unless the plant is destroyed below the first node, where buds can produce new leafing branches.
• If soybeans must be replanted:
1. Narrow row spacing and higher seeding rates will more quickly close the canopy and suppress weeds.
2. Early maturing beans will flower early but not grow very tall. Taller plants should be planted to maximize yield potential.
3. Do not plant early varieties that have not been adapted to your zone.
Summary:
Mid-season storms can create nightmarish management decisions regarding replanting, since the decision has to involve alternative crops, field preparations, weed control challenges, and how to destroy the damaged crop. If decisions are made to replant, many fields may have to be treated differently than the original crop due to the lateness in the season.
Posted by Stu Ellis on June 18, 2009 12:31 AM to farmgate