Issue No. 5, Article 6/April 25, 2008
Prioritizing When Planting Is Delayed
With only 1% of the Illinois corn crop planted as of April 20, it is clear that we are off to a slow start in 2008. That does not automatically mean that planting itself will be late--at least as measured by the date when 50% is planted. But progress is picking up only moderately so far this week, and many areas will see little or no activity the rest of the week. It's small comfort, but the whole Corn Belt is off to a slow planting start, with little done anywhere. That's been helping the price some. And corn that has been planted early into cool soils has not benefited much from that up to now.
The fact that temperatures are now much warmer than they have been before this week is very helpful in getting soils dried out. Warm soils lose water much faster than cool soils, and once soils are warmed up they will tend to retain that heat and so dry out faster following rainfall. Cold fronts will still bring rain that can drop soil temperatures quickly, but we should start to see less "saturated" soil and faster drying from now on. According to the Illinois Water Survey, soil temperatures at the 4-inch depth under bare soil are now reaching about 70 degrees as a daily maximum--a favorable development.
As producers have pulled planters out to tinker with them, taken delivery on seed, and lined up fertilizer supplies, questions come up about what to do first when it's finally dry enough to get started. Here are points to consider:
1. No one can make it dry up faster, but get around to different fields and dig in the wetter, drier, and average areas to see how the soil is drying. There have been few "it's drier than I thought" discoveries this spring, but there could be some as soil temperatures rise.
2. Having the planter and other equipment in shape is a given--a priority that should already have been acted on.
3. It should generally not be a priority to make tillage passes on too-wet soil to "open it up" for faster drying. While it may produce a sense of getting something done, tillage like this can produce clods that are very difficult to break down and that might result in a poor seedbed. Tillage, which is almost always shallow when done in wet soils, also mulches the surface and can delay drying below the depth of tillage. Finally, any tractor and equipment traffic on wet soil will produce compaction, which could be a big problem if it keeps roots from developing fully, especially if we get dry weather later in the season.
4. By now, it is of higher priority to plant when the soil is dry enough than to apply preplant fertilizer. Those who apply fertilizer when it's still too wet to plant often do more harm through compaction and poor sealing (of anhydrous ammonia) than if they had waited to side-dress nitrogen after planting. With auto-steer, it is possible to apply N between the rows after planting but before emergence, or even before planting. There is generally no loss in yield if side-dressing N is delayed up to the 4- or 5-leaf stage of the crop. Placement between the rows also protects the small plants from ammonia damage in case it dries out after planting. If rains continue, ammonia damage will be unlikely, but plants on top of ammonia bands are in considerable danger of damage if it dries out after ammonia was applied in wet soils, even if planting was a week or more after ammonia application.
5. It is a priority to plant as fast as possible once soils are dry enough, especially if it stays dry and fields become ready to plant in rapid sequence. Most producers have large planters and are generally equipped to plant faster than ever, so this is a priority that most have acted on. Auto-steer that allows planting in the dark might be a good investment this year. Unlike many other agronomists, I do not believe that most producers are planting at speeds fast enough to damage yield prospects. It is important to plant at a uniform depth and to have seeds in uniform soil conditions down the row, but planting slower just for better seed spacing is unlikely to produce much payback, unless it also means that plant populations are closer to the target. Many planters drop more seed when run faster, and this can turn out to be an advantage if conditions are good later. That some of these seeds are "doubles" is unlikely to have much effect, other than the cost of some seed that might not boost yields much.
6. While it is important to get good uniformity in seed depth placement, statements I have seen recently that plants emerging outside of a 24- to 48-hour window become "weeds" are not correct. Even the most careful planting cannot assure uniformity of emergence. If it rains and soil temperatures come back down after the crop is planted, emergence will be delayed. Delayed emergence almost always means more spread in emergence time within a field, especially when soils have gotten wet again. It takes about 110 to 120 growing degree days from planting to emergence, but factors like crusting and cloddiness affect emergence timing. So we can expect that emergence, from start to end, might take up to a week in some fields, and 3- to 5-day emergence windows are commonplace. In some of our research with delayed planting down the row, plants that emerged even 2 to 3 weeks late sometimes produced small ears or no ears, but they were also less competitive with their earlier-emerging neighbors, which produced more as a result. Late-emerging plants hurt yields, but they were never "weeds" in that they did not lower yields compared to those when such plants were simply missing (not planted).
7. To reemphasize, the highest priority should be to plant corn seed into the best soil conditions possible, even if it means delaying planting into early May. Early May is a good time to plant corn, with expected yield losses of only 5 to 10 bushels compared to planting in mid-April. It is very easy to lose more yield than this by planting before soils are fit to plant. So while it's hard to wait, those who get aggressive with planting might, depending on how the season goes, end up wishing they had waited the extra few days that experience (or a neighbor or relative) told them would be helpful. One issue that comes into play with planting starting this late is that any replanting that becomes necessary will be costly in terms of late-planting penalty. That raises the value of getting a good stand the first time. It's a challenge I think we can meet if we keep our wits about us.--Emerson Nafziger