Switch Dates For Corn Silage

The Wisconsin USDA-NASS Crop Progress report for May 20 indicated that only 43% of the corn crop had been planted.  For Week 20, only the growing seasons of 1996 (38%) and 1979 (40%) have had slower corn planting progress. With the unsettled weather of this past week over much of the state, planting this year will be further delayed. Crop reporting districts with the slowest planting progress include the North Central (24%), North West (31%) and East Central (31%).

We have been discussing the importance of switch dates for dry and high moisture grain production by summarizing data for the last 10 years at one farm (Arlington, WI). As planting delays continue, many farmers are thinking about changing their end use of corn and are wondering about switch dates for corn silage. This decision is complicated because of the changes that occur in yield and the energy pools found in stover (ivNDFD) and grain (Starch content).

Between 2003 and 2008, we conducted trials that compare corn silage yield and quality of full- and shorter-season hybrids. Forage yield was greatest with full-season hybrids for early planting dates (Figure 1). The regression lines converged on about May 20, but forage yield was not significantly different after that date unlike what has been previously described for grain yield. Little difference was seen between full- and shorter-season hybrids for digestibility of the stover energy pool as measured by ivNDFD. However, shorter-season hybrids had higher starch content on every planting date even though grain yield was lower until after May 24.

Figure 1. Corn forage yield, ivNDFD and starch content response of full-season hybrids (104-108 d RM) and shorter-season (94-98 d RM) hybrids to planting date during 2003 to 2008 at Arlington, WI (N= 324 plots). 

Forage yield, ivNDFD and starch content values were used in the Milk2006 model to calculate Milk per Ton and Milk per Acre (Figure 2). Both Milk per Ton and Milk per Acre of full-season hybrids were greater than shorter-season hybrids when planted early. For Milk per Ton, a switch date occurs around May 15, when the shorter-season hybrids have greater Milk per Ton than full-season hybrids. However, around this switch date Milk per Acre differences between full- and shorter-season hybrids are not that much different. A slight Milk per Acre advantage is seen for shorter-season hybrids until about June 1 and then the gap begins to widen.

Figure 2. Corn forage milk per ton and milk per acre response of full-season hybrids (104-108 d RM) and shorter-season (94-98 d RM) hybrids to planting date during 2003 to 2008 at Arlington, WI (N= 324 plots). 

Thus, if the end-use of corn will be for silage, then farmers can stick with full-season hybrids longer than if corn is used for grain. By June 12, the difference between full- and shorter-season hybrids is about 2000 pounds of milk per Acre (10%).

Another question I have received is, "What about growing brown midrib corn as a way to maintain the energy pools of stover rather than grain?" Between 2009 and 2012, we compared switch dates for full-season conventional and brown midrib corn hybrids. Watch for a future blog, when we will describe these yield and quality differences due to planting date.

Hitting the Bull’s Eye When Switching Corn Hybrid Maturity

The 2013 corn growing season is off to its slowest start in a long time. On May 12 USDA-NASS reported  14% of the corn planted. The slowest start ever recorded was in 1984 when by week 19, only 14% of the corn was planted. Other slow starting years (by Week 19) were 1979 (15%), 1981 (20%) and 1993 (21%). Due to the slow start, especially for farmers in northern Wisconsin, many are considering whether they need to switch corn hybrid maturities. In the north, we really only have one opportunity to switch maturity and still have the potential for grain yield. In southern Wisconsin, we may have two opportunities to switch hybrid maturity.

In Wisconsin each Relative Maturity (RM) unit increases grain yield 1.9 bu/A. So farmers often try to select hybrids that are full-season because they offer the best yield potential. The trade-off is that full-season hybrids are often wetter during fall harvest increasing production costs due to higher grain moisture and greater drying/energy cost (Figure 1). On optimal planting dates grain yield of full-season hybrids is usually greater than shorter-season hybrids. However, the rate of yield decline is faster for full-season hybrids, so that by about May 24 the grain yield of shorter season hybrids is then greater than full-season hybrids for planting in late May and early June. What further complicates this management decision is that grain moisture of shorter-season hybrids is nearly always drier than full-season hybrids. Drier grain produced by shorter-season hybrids has implications for production costs of two different maturities.

Figure 1. Corn grain yield response of full-season hybrids (104-108 RM) and shorter-season (94-98 d RM) hybrids to planting date during 2003 to 2012 at Arlington, WI (N= 388 plots).

Quite a bit of year-to-year variability can exist on a farm. Table 1 describes maximum yield dates and rate of yield loss for full-season hybrids described previously and includes data for shorter-season hybrids. On average maximum grain yield was about 16 bu/A greater for full-season hybrids. In some years the date when maximum yield occurs is earlier for shorter-season hybrids, but on average is similar between full- (April 28) and shorter-season (April 30) hybrids. Full-season hybrids lose on average about 1.6 bu/A per day in late May compared to only 1.0 bu/A per day for shorter-season hybrids. So when considering grain yield only, the time to switch corn hybrid maturity between full- and shorter-season hybrids ranges between May 1 and June 2 with the average at May 24. In 2009, a very cool year, the shorter season hybrid always had greater yield than the full-season hybrid.

Table 1. Corn grain yield response of full-season hybrids (104-108 d RM) and shorter-season (94-98 d RM) hybrids to planting date during 2003 to 2012 at Arlington, WI (N= 388 plots). In 2012, no shorter-season hybrids were grown.

But grain yield isn't the only factor in this management decision (Table 2). Both grain price and drying costs must also be factored into the economics as described previously. Currently energy costs are about $1.60 to $2.00 per gallon for liquid propane. So if we figure a corn price of $5.00 to $6.00 per bushel, then our hybrid maturity switch date using the above data would be May 17 to May 19. As corn price increase maturity switch dates become later. Conversely, as drying cost increase maturity switch dates become earlier.

Table 2. Switch dates between full- and shorter-season corn hybrids for various Energy:Corn price ratios. Data includes full-season hybrids (104-108 d RM) and shorter-season (94-98 d RM) hybrids planted on different dates during 2003 to 2012 at Arlington, WI (N= 388 plots). 

UWEX recommends the following general guidelines when considering switching corn hybrid maturity. For the next few days, if the weather is good and your fields are fit, proceed with planting the hybrids you have in hand. When using these guidelines, please remember that growing season, site and management influence a particular hybrid's actual days to maturity.

Table 3. Relative maturity of adapted corn hybrids for different planting dates and relative maturity zones. Derived from UWEX A3353 - Corn Replant/Late-Plant Decisions in Wisconsin.

Although the penalty for late planting is important, growers also need to be careful to avoid tillage when soil is too wet. Yields may be reduced somewhat this year, but effects of soil compaction can reduce yields for several years to come. Your decision to switch hybrid maturity depends upon:

1. Desire to accept risk: Longer season hybrids offer the highest yield potentials, but may also increase drying costs and/or delay harvest.
2. Potential use: For dry grain, relative maturities should be shorter-season within the maturity range for the latest acceptable planting date. For ear corn, high moisture corn, and silage, relative maturities should be longer-season within the maturity range for the latest acceptable planting date.
3. Field conditions: Shorter-season hybrids within the maturity range for the latest acceptable planting date should be selected when field conditions include heavy crop residue, reduced tillage, and heavy soil textures.
4. Hybrid dry down and grain quality characteristics: Longer-season hybrids within the latest acceptable planting dates should have fast grain dry-down and high test weight characteristics.
5. Ease of trading original hybrids for superior shorter-season alternatives.

Literature Cited

Lauer, J. 1997. Corn Replant/Late-Plant Decisions in Wisconsin. UWEX 3353.

Further Reading

http://corn.agronomy.wisc.edu/Management/L010.aspx

Hoeft, R.G., E.D. Nafziger, R.R. Johnson, and S.R. Aldrich. 2000. Modern corn and soybean production. First edition, MCSP Publications, Champaign, IL.

Hellevang and Morey, Energy Conservation and Alternative Sources for Corn Drying. National Corn Handbook - 14.

Evaluation of Ascend®: Hormones that stimulate corn growth

During years with strong grain prices numerous products appear that seem too good to be true. If there was any growing season when a corn root growth enhancer should work it was during the  drought of 2012. Ascend® is touted as a "... tool to increase plant efficiency" and "... can stimulate higher yields through a larger root mass ..."

Ascend® contains the plant growth regulators cytokinin (0.09%), gibberellic acid (0.03%) and indole butyric acid (0.045%). It can be applied on the seed, in-furrow at planting, 2x2 or 3 inches below the seed at planting, at the 3-4 leaf stage and/or at the 8-11 leaf stage.

We tested the plant growth regulator Ascend® by applying it to an adapted hybrid and comparing it to the same hybrid left untreated at eleven locations in Wisconsin. Applications were made at the labelled rate and timing of 3.2 oz/A at V3-V4. Locations that exhibited significant drought stress included Chippewa Falls, Lancaster, Janesville, Arlington and Fond du Lac. Hancock was an irrigated site.

At seven of eleven locations there was no statistical difference when using Ascend®. At three of eleven locations, the untreated plots yielded more than plots treated with Ascend®. At one of eleven locations, Ascend® treated plots yielded more than untreated plots.

Table 1. Corn grain yield response of an adapted corn hybrid treated with Ascend® plant growth regulator to an untreated check during 2012.

At none of the sites that had significant drought stress during the growing season did Ascend® stimulate higher yields. Across all locations there was no statistical difference between corn treated with Ascend® (196 bu/A) and untreated corn (200 bu/A).

Further Reading

For details of the experiments see http://corn.agronomy.wisc.edu/Research/11Miscellaneous/Ascend2012.pdf

Planting Date Effects on Corn Silage Yield and Quality

We have written quite a bit about planting date effects on corn grain yield (high moisture and dry corn). What about its effects on corn silage? As planting date becomes more delayed, there is an increased likelihood that fields intended for grain will be harvested for silage, especially if the year remains cool.

The grain yield response of full-season hybrids to planting date at Arlington for the last 10 years has been described previously. These treatments were established using 8-row plots; four rows were harvested for silage and four rows were harvested later for grain. Figure 1 describes the planting date effect on corn silage yield. The date when maximum forage yield occurs is April 24 nearly 4 days earlier than the date of maximum grain yield on April 28 for these same plots. The relationship is more 'broad shouldered' than what is measured for grain; in other words the planting date window is longer than it is for grain with forage yields still within 95% of maximum yield on May 15.

Figure 1. Corn forage yield response of full-season hybrids (104-108 d RM) to planting date during 2003 to 2012 at Arlington, WI (N= 235 plots). 

The size of the plant 'factory' is not affected by planting date. The number of leaves, the size of the stalk, shank and husk is largely genetically controlled. However, starch content is affected by planting date. Thus, the digestibility of the stover and grain pools is different (Figure 2). Digestibility of stover (ivNDFD) is close to a flat line across the range of planting dates tested (although linear and quadratic coefficients were significant). Starch content decreases with later planting dates.

Figure 2. Corn forage ivNDFD and Starch content response of full-season hybrids (104-108 d RM) to planting date during 2003 to 2012 at Arlington, WI (N= 235 plots). 

When yield and quality is combined using the Milk2006 performance index, we find that Milk per Ton (quality) is not affected as much as Milk per Acre due to the forage yield impact (Figure 3). The optimum planting date for corn silage when measured using Milk per Acre is the same as it is for grain yield. The difference is that the planting date window is slightly longer for silage than it is for grain.

Figure 3. Corn forage Milk per Ton and Milk per Acre response of full-season hybrids (104-108 d RM) to planting date during 2003 to 2012 at Arlington, WI (N= 235 plots). 

Optimum Corn Planting Dates Are Later 'Up North'

Optimum corn planting dates vary with latitude. The northern Corn Belt is limited by heat units during the growing season, especially during the spring when cool, wet soils delay planting and during the fall when early frosts kill plants prematurely. Within Wisconsin we often find that optimum corn planting dates are later 'up-north' than in southern Wisconsin and that yield loss accelerates more quickly resulting in a shorter planting window.

The general shape of the planting date response at a location has been described previously. The last time a statewide corn planting date experiment was conducted at numerous locations was during 1991-1994 (Lauer et al., 1999). Full- and shorter-season corn hybrids were planted on five to eight planting dates between April 19 to June 22.

For the northern sites of Ashland, Spooner and Marshfield, the date when maximum corn yield occurred averaged May 12, while the southern sites of Hancock, Arlington and Lancaster were one week earlier averaging May 5 (Table 1). Corn yields were still at 95% of the maximum yield on May 17 in the north and May 12 in the south. By June 1, corn yield was decreasing at an average rate of 2.3 bu/A per day in the north and at a slower rate moving south to Lancaster.

Table 1. Corn grain yield response to planting date of full-season hybrids at various locations in Wisconsin during 1991 to 1994 (derived from Lauer et al., 1999).

Optimum corn planting dates likely vary with farm, hybrid, field, tillage system and other management factors. In northern Wisconsin, these factors along with latitude result in lower yield potential and when combined with grain moisture and drying costs described previously often makes corn production marginal as we move north.

Further Reading

Lauer, J.G., P.R. Carter, T.M. Wood, G. Diezel, D.W. Wiersma, R.E. Rand, M.J. Mlynarek. 1999. Corn hybrid response to planting date in the northern Corn Belt. Agronomy Journal 91:834-939.