Published 10 June 2008
Tillage System Choices for June Planting or Replanting after Flooding
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: tvyn
armers who decide to replant ponded areas or even entire fields that were flooded (and where the stand loss justifies replanting on an economic basis) will want to do so with as little tillage as possible. In most field situations, intensive tillage does not make sense because of the additional cost and time that it will take as well as the risk of creating cloddy seedbeds that limit seed germination. Most often, the preferred tillage system for June planting would be no-till. However, there are some no-till adjustments that might be helpful, and there are some unique situations were some tillage might be justified. Here are some tips for tillage and planting decisions for such late planting situations:
- No-till normally makes the most sense. With warm air and soil temperatures during most of June, yield differences between tillage system are even less than they could be with April planting. For example, while tillage might improve yields on certain soils when corn is planted in April following corn, no-till corn should equal conventional tillage corn when farmers plant in June.
- Consider compromises to the “ideal” seedbed moisture condition. Although it is preferable to wait until the surface 2 inches of soil are dry enough to avoid sidewall compaction with planter disk openers, the reality is that corn and soybean yield losses grow with each passing day. If farmers are confident that weekly rainfall will occur for the first 3 weeks after their June planting, then some sidewall compaction can be tolerated with little negative effects on yield. However, if hot and dry weather conditions are expected, it would be foolish to “smear” the seed in..
- Use minimum down pressure on the row units and seed closing wheels. Soils that have been saturated for some time tend to have excess moisture below seed depth. Compaction of those layers with high down pressures can cause problems for root expansion later in the season. The objective in setting down pressure is to use the least pressure required to get sufficient penetration of the seed disk opener, constant seed depth, and adequate closure of the seed furrow. Higher pressures don’t improve things, and may be harmful (particularly for soybean).
- Consider tools to aid soil drying before planting. Superficial tillage (with shallow harrows, coulters and/or rolling baskets) may be helpful to speed up the rate of surface soil drying in cases with matted surface residue or crusted soil. Such tools may not improve otherwise no-till corn or soybean yields, but may advance planting by one or two drying days.
- Recognize the consequences of flooding to soil structure. Soils that have been wet for some time are always the soils most vulnerable to forming clods when they are tilled. Soils that have gone through several wetting and drying periods in normal precipitation intensities will have much better tilth or friability than soil that dries for the first time following a week or more of saturation. So the risk of doing tillage following flooding in June is that the soil is so non-friable that large clods will form easily (especially in the tractor wheel tracks) and that seed to soil contact will be compromised. Cloddy seedbeds are most likely on soils with high clay and low organic matter contents following crops which don’t enhance soil aggregate stability (e.g. following soybean). Similarly, the potential of soil crust formation (and restriction to seedling emergence) following June tillage operations is even more likely than in no-till situations.
- Avoid thinking of tillage as the only way deal with herbicide resistant crops. Farmers using glyphosate-resistant soybean following their earlier 2008 planting of glyphosate-resistant corn may first think of tillage as an expedient method to control these surviving herbicide resistant “volunteer” plants. However, tillage may be more costly (in terms of compromising seedbed quality and delayed planting) than other herbicide options. For additional herbicide versus tillage methods to control the glyphosate-resistant corn, see the recent article by Johnson and Nice (2008).
- Try to spray burndown herbicides as early as possible. Controlling weeds is essential to improve the evaporation rate at the soil surface, and achieving early weed control is more essential for reduced tillage planting situations in June than in April. However, the presence of very tall weeds because of excessive rainfall in May, as well as the recent rains in the first week of June, may limit certain herbicide control options and force some tillage in what earlier might have been candidate fields for no-till cropping.
- Keep any tillage operations shallow. Deep tillage will only go into wetter soil conditions, and involve more compaction and clod formation risk. June tillage pre-planting operations should never be deeper than 3 inches.
- Automatic guidance is helpful. In re-planting situations, automatic guidance (and particularly the most accurate RTK system) assists farmers planting their rows precisely. This will be an advantage where the June crops might still pick up starter fertilizer benefits from the first planting operation, and would also be helpful in avoiding planting directly over any recently side-dressed nitrogen bands.
- Remember where the poorly drained areas are. Once late planting is completed, it might be helpful to consider the adequacy of drainage in these areas. No field drainage system can ever be sufficient for 10 inch downpours, but additional drainage may limit the size of areas requiring replanting this year, and would also improve the odds of success with no-till and strip-till cropping systems.
There is never any true satisfaction in planting or replanting full-season crops this late in June. It is rather like trying to make the best of a very challenging situation. But intensive tillage is rarely required, and mostly involves more risks for farmers planting in June. Properly managed no-till is usually the best choice.
Johnson, Bill and Glenn Nice. 2008. Methods to Control Volunteer Roundup Ready or Glyphosate - Tolerant Corn in a Corn Replant Situation. Purdue Extension Weed Science. [On-line]. Available at http://www.btny.purdue.edu/weedscience/2008/VolCorn08.pdf. [URL accessed 6/10/08].