5/08/01
Corn and Soybean Planting Considerations for 2001
D. R. Hicks, S. L. Naeve, D. Hexum
University of Minnesota
Early May is moving quickly past. The field conditions across most of Minnesota and the weather forecast for the next few days are such that corn and soybean planting will not progress much in the next few days. So it will be a few days before a significant acreage of corn and soybeans are planted. There are other factors, which should be considered with late planting which may affect the decisions growers make about maturities.
In late April, we suggested staying with the maturities of corn until May 25, assuming that most growers are planting relative maturities of 5 to 7 earlier than we think is full season. For example 110 is full season in the southern one-third of the state, but many growers have been planting 103 to 105 RM hybrids. The 103 to 105's should reach maturity if planted by May 25. Remember that we planted 110 and 115 RM hybrids in southern MN in the 60's and 70's and the average planting date was late May. Figure 1 gives the growing zones of Minnesota and the recommended full season hybrid maturities for each zone. The average planting date has moved one-half day earlier each year for the past 25 years; the average planting date is now May 7. So with using earlier than full season hybrids and with earlier planting corn has reached maturity earlier in September and there has been more time and more ideal conditions for field drying in the past few years (since 1993).
Yield and Relative Corn Maturity
Full season hybrids yield more than do hybrids that are earlier than full season. The yield relationship with maturity is this: there is one bushel per acre yield difference for each one RM unit difference between hybrids. That is, we would expect a 105 RM hybrid to yield 5 bushels per acre more than a 100 RM hybrid if planted prior to May 15. The yield difference becomes smaller when planting occurs between May 15 and May 25. It is true that one can find some 100 hybrids that yield higher than some 105's, but on average, the 105's should yield five bushels higher.
Late Planting and Kernel Moisture
Later planting of any hybrid maturity will result in a later maturity date and higher grain moisture content throughout the harvest time period which means that more percentage points of moisture will have to be removed from grain to prepare it for proper storage.
Kernel Moisture and Relative Corn Maturity
With the same planting date, earlier hybrids will mature earlier in the fall than hybrids with higher RM ratings. And the difference in kernel moisture content with each one RM unit is 0.5 percentage points. That is, 100's will be 2.5% points lower in moisture content at any date during the fall than are 105 RM hybrids. So if we plant 105's rather than 100's we will have the potential to dry 2.5 more points of moisture. That will cost $7 per acre for a 150-bushel yield and assuming 90 cents per gallon of LP gas. If 105's yield five bushels more, the value of that five bushels is $10 at $2/bushel (plus the LDP payment for five bushels). With these assumptions, the economics are still in favor of planting 105's, if planting occurs in the next few days. If not, the economics shift to the earlier hybrids.
If growers want to change some hybrids, they should call their dealer now! There will be an opportunity for some exchange of hybrids. But not everyone can do this and the chances of getting seed of the best yielding earlier hybrids are limited.
Planting Date and Test Weight
Later planting increases the possibility of corn not reaching maturity before the first killing frost. The result would be lower than normal test weight and poorer kernel quality. However, if the heat unit accumulation is normal for the season, planting hybrids of 100 and 105 RM as late as May 25 should result in normal test weight grain. Planting earlier hybrids would reduce the possibility of low-test weight grain.
Drying Cost
LP gas prices are higher; it will cost more to dry grain this fall. Yield level and points of moisture necessary to remove affect the drying cost. Assuming LP gas price of 90 cents per gallon, the costs to remove 1 to 10 points from each bushel for various yield levels are given in Table 1. For example, removing five points of moisture from a 150 bushel yield cost $14.18 for the energy cost of on-farm drying (off-farm custom drying costs will be higher).
Table 1. The cost of removing 1 to 10 points of moisture
from corn grain for various yield levels
(LP Gas price of $0.90/gallon and electricity of 9
cents/KWH)
|
|
Points of moisture removed per bushel |
|||||
|
Yield(Bu/A) |
1 |
2.5 |
5 |
7.5 |
10 |
|
|
|
|
|
($/acre) |
|
|
|
|
100 |
1.89 |
4.73 |
9.45 |
14.18 |
18.90 |
|
|
125 |
2.36 |
5.91 |
11.81 |
17.72 |
23.63 |
|
|
150 |
2.84 |
7.09 |
14.18 |
21.26 |
28.35 |
|
|
175 |
3.31 |
8.27 |
16.54 |
24.81 |
33.08 |
|
|
200 |
3.78 |
9.45 |
18.90 |
28.35 |
37.80 |
|
Switching From Corn to Soybeans
Some are considering shifting from corn to soybeans because of the planting date, costs of production, and anticipated LDP payments. The most compelling reason not to do that is the potential increase in the population of Soybean Cyst Nematodes. This can be partially minimized by planting SCN resistant varieties, which may not yield as high as normal soybean varieties. SCN populations can explode under continuous soybeans; using resistant varieties is a long-range strategy for minimizing the buildup of the cyst population and is essential to maintain high yield potentials for future soybean crops.
The rate at which a soybean crop develops and matures in the late summer and early fall is strongly influenced by daylength (calendar date) and cool temperatures. Therefore, late-planted soybeans (planted in late May and early June) mature only slightly later (around 1 week) than those planted earlier (early May). For this reason most farmers can maintain their original planting decisions and plant the soybean varieties that they purchased last winter. Only those producers that purchased very long season varieties should be concerned about early frost damage.
Early “group II” maturity varieties are considered full season varieties for southern Minnesota. Likewise, “group I” varieties for the central portion of the state, and “group 0 and 00” varieties north of Interstate 94 are considered to be full season varieties locally. Some are planting soybean varieties with maturity ratings higher than these and have been producing high yields with good bean quality for the past few years. But the past few years have been early planting dates with good drying temperatures in mid to late September. With a normal heat unit season, we believe maturities given above can be planted as late as June 5 to 10 if that's necessary. Therefore, the situation with soybean maturities is not as critical as it is with corn.
Figure 1. Maturity Zones and Recommended Full Season Hybrid Maturities for Each Zone
The University of Minnesota is an equal opportunity educator
and employer.
Copyright © Regents of the University of Minnesota. All rights reserved.
URL: http://www.soybeans.umn.edu/resources/news/news_5-08-01.htm
Last Modified 8/9/05 by:
Sarah Jameson-Jones
Web Designer/Developer
james039@umn.edu
