Check soil conditions
Check the field for soil crusting. If a hard crust is present and hard enough to restrict emergence, rotary hoeing may be beneficial. However, when soybeans are cracking and need the most help, they are also at the most vulnerable stage. Naeve suggests that it’s okay to try and break up the crust a little bit but be sure to check what’s happening behind the implements.
Assess stands
Whether producers are taking stand counts in corn or soybeans, the methods can be the same. The key is to assess the stand in several places to get the best estimate of what’s happening in the field. At each location, count the number of plants in 1/1000 of an acre- 17 feet 5 inches of a row in 30-inch rows - then multiply by 1000 to get plants per acre.
An alternative method is to roll a measuring wheel along longer row lengths and count the plants. Longer row lengths give more reliable results and consequently, more confidence in the final stand assessment.
Corn
Plant populations
What if stands are less than expected? For corn, a final stand of 26,000 plants per acre should yield about 96% of the maximum yield potential. Even 23,000 plants per acre should yield about 92% of the total yield potential with good row spacing. Coulter explains that corn can continue to yield well at populations of 24,000 and above. However, if there are large gaps in the rows – 16 to 33 inches long – you can expect an additional yield loss of 2% and if gaps are between 4 and 6 feet in size, an additional 5% drop in yield potential could be expected. If populations are reduced to the low 20,000s, yield potential is reduced to 90% or less. As a result, it may be a scenario where replanting should be considered.
Planting dates
From a planting date perspective, corn yield potential is still good. Between 2009 and 2016, UMN Extension conducted 26 planting date trials across Minnesota. On average, when corn was planted between May 13 and May 19, yields were 97 to 98% of the maximum yield. When planting was delayed to between May 20 to May 25, yields were 95% of the maximum and yields were reduced to 92% of the maximum when planting dates were between May 26 and May 30.
What about switching hybrid maturities? Between May 22 and May 28, consider switching to corn hybrids that are 5 to 7 relative maturity (RM) units earlier than the full-season hybrids for your area. Between May 29 and June 4, look at hybrids that are 8 to 15 RM units shorter and from June 5 to 10, choose hybrids that are 8 to 15 RM units shorter than the full-season hybrids. If growers typically order hybrids that are a couple of RM units shorter than full-season hybrids grown in their area, that provides something of a cushion with later planting.
Finally, as we approach May 22 and the time to switch hybrids, weigh the benefits of keeping your current stand against the reduced yield potential of late-planted corn.
Are N rate adjustments needed in corn?
In fields that have had ponding, some applied nitrogen (N) fertilizer will be lost to denitrification. The amount of N loss depends on the duration of flooding, so keep an eye on those areas. UM Extension’s supplemental N corn calculator will help determine if a sidedress application might be needed.
Soybeans
For soybeans, yield potential is still at maximum levels. Where existing stands have been severely damaged and are less than 75,000 plants per acre, it’s early enough that soybeans can be replanted.
In smaller field areas, planting another pass between rows is an efficient way to increase the stand without destroying the old one. When spiking in soybeans, match the maturities of the old stand with the new as closely as possible.
Planting dates
The planting date yield curve for soybeans is similar to corn’s early in the season. While soybean yield potential is still near maximum, it does start to tick down after May 20. After this date, soybeans lose about a half a percent of yield potential per day through early June. Once into the second or third week of June, yield potential decreases a full percentage point per day. This is a cumulative loss, so plant as soon as conditions allow.
What about maturity groups?
If growers plant varieties in a conservative maturity group, there’s no need to change varieties through mid-June. For growers that push the long season varieties, they may want to consider changing to an earlier group. However, there’s no urgency to make any changes until June 10.
Emerging crops and delayed preemergence herbicide applications
Preemergence (PREs) herbicides are very effective and provide a strong foundation for the growing season. However, there are several products that should not be applied to emerging crops, due to potentially severe crop injury. Dr. Aaron Hager, Extension weed specialist at the University of Illinois, published a helpful summary of active ingredients that should not be applied over the top.
If a PRE was planned but didn’t get applied, reallocating some of those savings for a strong postemergence herbicide program may be a good option.
In thin stands, spiking soybeans may result in a better canopy and weed suppression, even if there’s not an obvious yield or economic benefit.
Source : umn.edu