Wednesday, November 28, 2012

“Buy the Traits You Need” - The honor roll of top-performing corn hybrids tested in 2012

The principles for selecting corn hybrids in the transgenic era include: 1) using independent yield trial data and multi-location averages, 2) evaluating consistency of performance, 3) assuming that every hybrid must stand on its own for performance, 4) paying attention to seed costs, and 5) buying the traits you need. This publication addresses the principle of “Buying the traits you need.”

There are numerous sources of independent yield trial data, but few of these sources summarize data over numerous locations for the same set of hybrids. In the UW Corn Hybrid Performance Trials publication (A3653), multi-location averages are presented in Tables 7-22.

As farmers make hybrid selection decisions they must consider buying hybrids with the traits they need for their farming operation. Often farmers do not need all the traits sold in hybrids. For example, the corn rootworm trait is not usually required for production fields in northern Wisconsin. “Buying the traits you need” can be confusing due to the number of hybrids and transgenic technologies available to farmers. Tables 1 (silage) and 2 (grain) list hybrids that were starred for both yield AND performance index(ices). They are sorted by trait cohorts. For details about the specific transgenic technology and performance see A3653.

Evaluating consistency of performance is done by considering yield for individual locations in A3653 Tables 7-22. Also, consistency can be evaluated using Table 2 (Hybrid Index) and Table 23 (Hybrid History).

Transgenic technologies interact with the underlying genetic germplasm of hybrids within a “family.” These interactions can often result in poor performance. Always assume that every hybrid must stand on its own for performance when selecting hybrids. Do not select hybrids from genetic “families.”

A downloadable spreadsheet that can help calculate seed costs between two hybrids is at

Tuesday, November 27, 2012

Highlights for Wisconsin Corn Production during 2012

Most people would like to forget the 2012 growing season, especially many farmers in southern Wisconsin. The season was dominated by extreme drought conditions that started early (Figure 1). These conditions would not be relieved as the season progressed.

Due to warmer than normal conditions during March, planting started quickly and then was delayed by wet conditions around May 1. Over the entire growing season, growing degree-day accumulation was above the 30-year normal. During May, June, and July, precipitation was significantly below average in southern Wisconsin, while northern Wisconsin had above-average precipitation. Drought conditions continued through August and September in the southern half of Wisconsin and were also observed in the northern half of the state. Due to a dry and relatively warm September and October, good grain drying occurred, with harvest grain moisture lower than normal in all trials. Test weight was above average for most locations. Little insect or disease pressure was observed in most trials. Fall weather conditions, although dry, were ideal for harvest and fall farm work.

Figure 1. U.S. drought monitor on July 17, 2012. Southern Wisconsin was hit with extreme drought that would not be relieved during the remainder of the growing season.

Grain and silage yields were below the 10-year average at most sites (Tables 1 and 3). Locations that were significantly below the 10-year average included the southern zone (Arlington, Janesville, and Lancaster) and sites with sandy soils (Chippewa Falls and Spooner).

Table 1. Corn grain yield (bushels/Acre) of hybrids grown at various locations in Wisconsin during 2012. The percent change is the relative change for corn yield during 2012 compared to the 10-year average from 2002-2011. N= the number of hybrids tested at each location.

Even though production was below normal, grain yield was not as bad as 1988 (Table 2). Nearly every location was affected by drought, except for the irrigated site located at Hancock.

Table 2. Corn grain yield (bushels/Acre) of hybrids grown at various locations in Wisconsin during 1988. The percent change is the relative change for corn yield during 1988 compared to the 10-year average from1978-1987. N= the number of hybrids tested at each location.

Table 3. Corn forage yield (Tons Dry Matter/Acre) of hybrids grown at various locations in Wisconsin during 2012. The percent change is the relative change for corn yield during 2012 compared to the 10-year average from 2002-2011. N= the number of hybrids tested at each location.

Record yields in spite of the drought

For grain performances over a zone (South central), the top yielding hybrid was G2 Genetics 5H-806 at 259 bu/A. For a location (Hancock), the top yielding hybrid, G2 Genetics 5H-0504, set the highest location record yield at 299 bu/A. In the South central zone, 8 of the top 10 hybrids set record yields for the zone. Fifteen hybrids broke into the All-time Top 50 list for a location. All were grown in the South Central production zone.

For silage performances over a zone (South central), the top yielding hybrid was Dairyland EXP-11302 at 11.3 T/A. For a location (Galesville), the top yielding hybrid was Dairyland EXP-11302 at 12.3 T/A. In the Northern zone, 8 of the top 10 hybrids set record yields for the zone.

For a complete report on commercial hybrids for corn production in Wisconsin see 2012 WISCONSIN CORN HYBRID PERFORMANCE TRIALS Grain - Silage - Specialty - Organic December 2012  A3653.

Monday, November 26, 2012

University of Wisconsin Crop Variety Trial Results Are Available to Farmers

One of the most important decisions a farmer makes is the selection of high performing adapted hybrids and varieties. Selecting the correct hybrid/variety can often mean the difference between profit and loss. Plant breeders and agronomists test thousands of commercial and new experimental lines for several years at many locations over a range of plant populations and other management practices. Performance trials determine which hybrids/varieties have yielding ability superior to current cultivars and estimate disease resistance and other important characteristics.

Results from the 2012 crop variety trials conducted by the University of Wisconsin can be found at the websites below. These trials are a "consumer report" of commercial varieties and hybrids offered for sale to farmers in Wisconsin. These results are derived from replicated plots grown around Wisconsin at university research stations and farmer fields, and offer the best predictor for next year's potential performance.

Friday, October 12, 2012

Demonstration/Strip Trials - What should you learn from them?

The drought experienced this year has been unique. Drought occurs somewhere in Wisconsin nearly every production season. What has been unique this year is how widespread the drought is and the variability seen even between fields within a farm. In one field, corn might be barren and across the road good yields are measured. In many ways I was surprised to see corn hang-on as long as it did given the length of time no rain was received. In some of the fields yield-checked, we are finding ears with 16-18 kernel rows and 30-40 kernels per row.

Evaluating last year’s 'experiments' and using the lessons learned will help with next year's crop. Some new practices work and fit into your management style, others don't.

Every fall many farmers visit and evaluate hybrid demonstration plots planted by seed companies and county Extension personnel, among others. When checking out these plots, it's important to keep in mind their relative value and limitations. Demonstration plots may be useful in providing information on certain hybrid traits, especially those that are usually not reported in state corn performance summaries.

Use field days to make careful observations and ask questions, but reserve any decisions until you have seen the "numbers." Appearances can be deceiving.

In general, there are two major categories of on-farm research trials. The first is replicated trials that try to account for field variability with repeated randomized comparisons. Examples include trials conducted by universities and by public and private plant breeders. The other type is non-replicated demonstrations such as yield contests, on-farm yield claims, demonstration/strip trials and farmer observation and experience.

Field variability alone can easily account for differences of 10 to 50 bushels per acre. Don't put much stock in results from ONE LOCATION AND ONE YEAR, even if the trial is well run and reliable. This is especially important in years with tremendous variability in growing conditions. Years differ and the results from other locations may more closely match your conditions next year. Use data and observations from university trials, local demonstration plots, and then your own on-farm trials to look for consistent trends.

A few suggestions on how to evaluate research test plots:
  1. Walk into plots and check plant populations. Hybrids with large ears or two ears per plant may have thin stands.
  2. Scout for pest problems. Hybrid differences for pest resistance and tolerance should be monitored and noted all season, but will be most apparent in the fall. Counting dropped ears is a good way to measure hybrid ear retention and tolerance to European corn borers.
  3. Check for goose-necked stalks. This is often root pruning caused by corn rootworms. Hybrids differ in their ability to regrow pruned roots.
  4. Find out if the seed treatments (seed applied fungicides and insecticides) applied varied among hybrids planted, e.g. were the hybrids treated with the same seed applied insecticide at the same rate? Differences in treatments may affect final stand and injury caused by insects and diseases.
  5. Differences in standability will not show up until later in the season and/or until after a wind storm. Pinch or split the lower stalk to see whether the stalk pith is beginning to rot.
  6. Break ears in two to check relative kernel development of different hybrids. Hybrids that look most healthy and green may be more immature than others. Don't confuse good late season plant health ("stay green") with late maturity.
  7. Visual observation of ear-tip fill, ear length, number of kernel rows, and kernel depth, etc. don't tell you much about actual yield potential. Hybrid differences are common for tip kernel abortion (“tip dieback” or “tip-back”) and “zipper ears” (missing kernel rows). Even if corn ear tips are not filled completely, due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the numbers of kernels per row may still be above normal.
  8. Be careful with test plots consisting predominately of one company's hybrids. Odds are stacked in their favor!
  9. Other observations that should be made:
    • Dry down rate
    • Test weight
    • Disease damage
    • Grain quality
    • Ease of combine-shelling or picking
Further Reading

Saturday, October 6, 2012

To Rotate, or Not to Rotate - What Are You Going to Do in 2013?

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Crop rotation is a universal management practice that has been recognized and exploited for centuries and is a proven process that increases crop yields. In the Midwestern U.S., a biennial rotation of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] produces significant increases in the yields of both crops.

There are clear indications that the current corn-soybean rotation is unstable, easily disrupted by weather, disease, and insects, and rely heavily on foreign trade and biofuel production. Midwest cropping systems although productive, are highly specialized, standardized and simplified to meet increasing demands (Brummer, 1998; Kirschenmann, 2002).

Many of these cropping systems are approaching monoculture systems that need to incorporate technological advances, high fossil fuel based inputs, and genetic engineering to remain sustainable. Cropping systems specializing in one or two crops with little attention to crop diversity could lead to biological and physical soil degradation and ultimately soil chemical degradation (Kirschenmann, 2002). Nature’s plant and animal diversity is currently replaced with a small number of cultivated plants and domestic animals (Altieri, 1999).

The mechanism for the rotation effect is unknown. One hypothesis is that one factor causes the effect. Another hypothesis is that multiple factors cause the effect and risk of expression depends upon the environment. Research evidence began mounting in the 1970’s, which indicated that in spite of all the management inputs a farmer might impose, there was still a yield advantage to be obtained from rotations. These studies showed that corn yields are usually higher when the crop is rotated with some other crop rather than grown continuously. Yield advantages to corn from rotating with some other crop are at least 10%. In addition, soybean yields also improved by 10% when the crop is rotated out of a continuous pattern.

More research that is recent has shown this increase to be even greater than expected with responses up to 19% (Figure 1). The rotation effect lasts two years increasing corn grain yield 10 to 19% for 1C and 0 to 7% for 2C.

Figure 1. Corn yield response to rotation following five years of soybean during 1987 to 2006 at Arlington, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn.

Adding a third crop like wheat (Triticum aestivum L.) does not increase corn grain yield, but does improve soybean grain yield (Figure 2).

Figure 2. Corn and soybean yield response in a corn-soybean-wheat rotation during 2004 to 2006 at Arlington, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn or soybean.

If there is only a one-year break in the rotation then the second corn phase is equivalent to continuous corn (Figure 3).

Figure 3. Corn yield response in various corn-soybean rotations during 1998 to 2000 at Arlington, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn.

At least two break years are needed to measure a response in the second corn phase compared to continuous corn (Figure 4).

Figure 4. Corn yield response in various rotations during 1990 to 2004 at Lancaster, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn.

Although scientists cannot yet satisfactorily explain the rotation effect, farmers can exploit it every year. In 2013, more acres will likely be planted to a third year of corn. These acres will be at continuous corn yield levels regardless of the number of break years. It will be important for growers to consider getting back to rotating crops. The age-old practice of rotating crops, which for a while was considered unnecessary, has returned to today's agriculture with proven benefits.

Literature Cited

Altieri, M.A. 1999. The ecological role of biodiversity in agroecosystems. Agric. Ecosyst. Envron. 74:19-31.

Brummer, E.C. 1998. Diversity, Stability, and Sustainable American Agriculture. Agron. J. 90:1-2.

Kirschenmann, F. 2002. Why American agriculture is not sustainable. Renewable Resour. 20:6-11.

Further Reading

Cropping systems and rotations. See

Friday, August 3, 2012

Some Observations During the 2012 Drought

Although we have received significant rains in the last 10 days, much damage has occurred and many fields will not recover. County agents have estimated that about 20 to 30 percent of the fields in the southern tier of Wisconsin counties are barren. For stressed fields that have only partially pollinated, it becomes increasingly difficult to predict how plants react to increasing stress and the best management recommendations.

One observation that many farmers have noticed is lack of brace roots. Roots will not grow into dry soils. Since most of southern Wisconsin did not received any rainfall from June 1 until July 20, right during brace root formation, many plants have not developed brace roots. Some fields have lodged and most of those fields have recovered and are vertical. Brace root formation can still occur, but will slow as grain-filling proceeds.

Pollination at Arlington has progressed well (Table 1). Kernels per ear have ranged from 437 to 599 kernels per ear. During most years we produce about 400 to 600 kernels per ear, which at 30,000 ears/A and 280 mg per kernel will yield 140 to 200 bu/A.

Table 1. Pollination progress of Pioneer 35F48AM1 in a planting date study during 2012 at Arlington, WI.
Planting date Silking date Sampling date Kernel rows Kernels per row Kernels per ear Percent pollinated
March 26 July 9 July 18 16.0 30.8 492 79
July 24 16.3 31.3 599 83
July 31 15.8 27.8 437 76
May 8 July 15 July 18 16.5 27.3 450 73
July 24 16.8 35.8 599 88
July 31 16.3 31.4 510 82
May 21 July 21 July 24 16.3 29.1 473 68
July 31 15.8 35.4 557 88

Rock River Labs (Watertown, WI) reports that corn silage samples from IA IL, IN, MI, SD, and WI have been averaging 74.6% moisture (Table 2). Forage moisture is too wet for all ensiling structures. Nitrate-N levels have been low and averaged 706 ppm with only one sample above 4000 ppm. Remember to freeze your corn silage sample before sending to a forage lab for Nitrate-N testing.

 Table 2. Corn silage moisture and Nitrate-N levels from
Rock River Labs during July 2-27 (Watertown, WI).
Parameter Mean Standard
Min Max
Moisture (%) 74.6 9.0 13.9 87.6
Nitrate-N (ppm) 706 720 0 4330

Thursday, July 19, 2012

Was Yesterday's Rain Enough to Save the Corn Crop?

Yesterday, we finally received significant rainfall (approximately 1 to 3 inches) in southern Wisconsin. Although a little late for some fields, it will relieve the stress long enough for some fields to complete pollination. Today I have been asked quite often, "Is this rain enough to save the corn crop?"

On July 21, 2005, I published an article called the "The Million Dollar Rain." During the 2005 growing season, we encountered a very similar weather pattern to what we have seen so far in 2012. In 2005, we were dry until July 20. In 2012, we were dry until July 19, although it is a leap year. During 2005 and after that "Million Dollar" rain, we received about one inch of rain per week and ended with a record yielding year.

Water is supplied to the plant by three sources: 1) stored soil water, 2) rainfall, and 3) irrigation, where available. Corn fields require 20 to 24 inches (543,086 to 651,703 gallons of water per acre) of water to yield 150 to 200 bushels per acre. About two inches of water is held in every foot of soil. Corn roots can grow five to seven feet deep. During pollination, corn requires 1/3 of an inch of water per day for evaoptranspiration, which will decrease to around 1/4 inch per day as grain filling proceeds.

Up to this point during 2012, we have relied on soil water in the profile due to the lack of rainfall. During a normal growing season our three wettest months are June, July and August when we receive about 4 inches of precipitation each month. During 2012, we started the growing season warmer than normal, so plant development is ahead of normal. We have not had much rainfall in southern Wisconsin since the first week in June. Corn plants have used up all of the stored soil water. An indication of this is plants with early morning leaf-rolling.

So, this rainfall  will supply corn plant needs for about 3 to 9 days if there was no runoff. We still need to get at least one inch of rainfall per week through the middle of September to finish the 2012 growing season.

Further reading


What Worked, What Didn't Work During the Drought of 1988?

As we begin to evaluate the success of corn pollination during the 2012 drought, it might be useful to also evaluate which management decisions were most beneficial during this growing season. Although a season like 2012 is rare and extreme, it will likely happen again. Taking some time now to evaluate your management decisions might help during a future growing season.

Our last major drought year was 1988. There were numerous experiments established around the state by Dr. Paul Carter. Below I summarize his results for a number of management decisions that were important at the time including hybrid selection, plant density, date of planting, tillage and rotation decisions. The question is, "How do these decisions affect grain yield during a drought growing season?"

Hybrid performance

Hybrid performance was lower than the previous 10-yr average at 8 of 11 locations (Table 1). No grain yield was harvested at Chippewa Falls. Three locations, Galesville, Hancock (irrigated) and New London, had greater yields than the average of the previous 10-years. All other locations had 18 to 51% lower yields with Lancaster significantly lower than normal. Harvest grain moisture averaged 18.7% to 24.7% among the trials. Plant lodging was less than 6% at all locations. At 9 of 11 locations, the maximum yielding hybrid was better than the 10-year average.

Table 1. 1988 Wisconsin Corn Performance Trials Summary.   
1978-1987 1988 Percent Max Min
Location N Yield N Yield change Yield Yield
Arlington 756 185 166 131 -29 175 84
Janesville 706 184 166 151 -18 186 104
Lancaster 706 146 166 71 -51 111 35
Fond du Lac 718 138 151 114 -17 151 71
Galesville 718 157 151 162 3 217 104
Hancock 719 170 151 198 16 236 166
Chippewa Falls 510 141 --- --- --- --- ---
Marshfield 510 125 126 99 -21 127 58
New London/Waupaca 514 152 126 172 13 195 113
White Lake 54 135 58 94 -30 111 64
Spooner 534 115 116 87 -24 145 34
Yield= bushels per acre
N= number of hybrids tested
Percent change=  the yield during 1988 compared to the average yield of the previous 10 years

Plant density

The plant density which produces maximum yield has been increasing over time, but what happens during a growing season with drought? During 1988, a plant density experiment was established at nine locations with target densities of 18,000; 24,000; 30,000 and 36,000 plants per acre. At 7 of 9 locations, grain yield either increased or was not affected as plant density increased (Table 2). At Lancaster, grain yield decreased 16 bu/A from low to high plant density, while at Spooner grain yield decreased 27 bu/A. So even during drought years when a response to plant density is not expected, higher plant densities were only detrimental at two locations. The best recommendation would be to manage for potential yield with higher plant density because the only risk for return on investment is minor seed costs.

Table 2. Grain yield (bu/A) of corn planted at target plant densities of 18000, 24000, 30000 and 36000 plants/A at various locations in Wisconsin during 1988.
Actual Harvest Plant Density (plants/A)
Location 18100-20500 22500-24100 28600-29900 33300-36800 LSD(0.10)
Grain yield (bushels/A)
Janesville 125 133 137 139 7
Lancaster 64 62 50 48 9
Fond du Lac 109 112 118 108 NS
Hancock 160 175 193 188 9
Galesville 133 163 172 174 9
Chippewa Falls 39 34 32 20 NS
Marshfield 88 87 89 85 NS
New London 109 112 118 108 NS
Spooner * 78 71 66 51 11
* At Spooner target plant density was lower and resulted in harvest densities of 15900, 18600, 22000, and 24500.

Date of planting

Earlier planting dates are typically recommended for avoiding drought growing conditions. However, during 1988 the planting dates of May 13 and May 18 were higher yielding than earlier planting dates (Table 3). Some of the better performance of later planting dates has to do with timing of when drought (heat and water stress) occurs during the life cycle of the corn plant. Another interaction is the distribution of rainfall during the growing season.

Table 3. Grain yield (bu/A) response to planting date during 1988 at Arlington, WI.
Experiment 1 Experiment 2
Planting date Grain yield (bu/A) Planting date Grain yield (bu/A)
April 18 59 April 27 67
May 13 63 May 26 84
LSD(0.10) NS LSD(0.10) 8


During the 1980s, no tillage was becoming popular as a management practice. Usually due to cool, wet soils corn often experience "slow growth syndrome" and yielded lower than conventionally tilled fields. During 1988, there were no differences between no-till and conventional-till in six experiments conducted at Janesville and Arlington (Table 4).

Table 4. Corn grain yield (bu/A) response to tillage during 1988 at Arlington and Janesville, WI.
Location Conventional tillage No tillage LSD(0.10)
Arlington-Experiment 1 62 64 NS
Arlington-Experiment 2 83 69 NS
Arlington-CS rotation 75 77 NS
Arlington-CSW rotation 70 72 NS
Janesville-Experiment 1 117 112 NS
Janesville-Experiment 2 117 109 NS


Rotation is probably the easiest management decision we have available to get "free" yield. During drought (stress) years it is even more important. Rotated corn increased grain yield 16 to 36 bu/A (29 to 59%) over continuous corn grain yield.

Table 5. Corn grain yield (bu/A) response to crop rotation  during 1988 at Arlington, WI.
Rotation Grain yield (bu/A)
Continuous corn 61 56
Corn-Soybean 97 82
Corn-Soybean-Wheat -- 72
LSD(0.10) 16 15

Tuesday, July 17, 2012

Will We Have Enough Corn?

I have been getting questions about the impact of the drought on corn production from this year's crop. It is still too early to predict the success of pollination and the drought's impact on yield and production, although it is not looking good. Once we are through pollination we can better estimate and at least get a feel for what to expect during this fall's harvest.

Another indicator may be to look back at other years that were considered to be drought years in Wisconsin and the U.S. (Figure 1). In Figure 1 the rolling average mean is + two years on either side of a central year. For example, the rolling average for 1988 is the mean yield or production of 1986 through 1990. There were numerous 'dry spells' during the 1950s, however, six growing seasons, 1936, 1976, 1980, 1983, 1988 and 2002 have been identified as significant 'drought' years in the Corn Belt (filled symbols in the graphs).

Figure 1. Corn grain yield (Bu/A) and production (Bushels x 1000) in Wisconsin and the United States. Filled symbols indicate drought years. Data source: USDA-NASS.
Most of these 'drought' years had yields lower than the 5-yr average. Wisconsin yields were better than U.S. yields during 4 of 6 drought years. In 1976, Wisconsin grain yields were 80% of the 5-yr average, in 1988 yields were 63% of the 5-yr average.

Corn production in Wisconsin is relatively small compared to overall U.S. production. Nationally the most significant years impacting production were the droughts of 1983 and 1988 where production was 56% and 69% of the 5-yr average.

Corn production influences price, so the more important statistic for the consumer of corn is production. Consumers include livestock feeders such as beef, dairy, pork and poultry; ethanol; export markets; other food, seed and industrial uses; and additionally a surplus is carried over to the next year. In 2011, corn growers produced 12.4 billion bushels of field corn (USDA, 2012). The total corn supply, including the corn carried over from 2010, was13.5 billion bushels. About 34% was used for livestock, 37% for ethanol production, 12% for export, 11% for other uses and 6% for carryover to the next year. In addition about 33% of the corn used to produce ethanol is fed by the livestock industry as dried distiller grains and gluten feed.

The additional acres planted to corn during 2012, a 5% increase compared to 2011, will become important for the overall production of corn. These will be needed along with the the carry over to supply consumers during 2013.

Literature cited

USDA-NASS. 2012. Quick Stats.

Further reading

Anonymous. 2012. A tale of two corns. National Corn Growers Association Fast Facts. Website

Friday, July 13, 2012

Corn Pollination: How to determine success under stress (video)

Dr. Joe Lauer, University of Wisconsin Corn Agronomist, takes you into the field to show you how to determine when pollination has occurred using the ear-shake test. He also talks about how important this is when making management decisions during periods of drought stress on corn. By knowing if pollination has been successful or not, a grower can better choose when to harvest for maximum forage yield.
Or check out the video here.

Wednesday, July 11, 2012

Corn Transgenic and Trait Technologies in UW Trials during 2012

The weather during 2012 is proving to be similar to other drought years like 1976, 1988, 1989 and 2005. Yields decreased during these years, except for the 2005 season when record grain yields were recorded. A big difference between 2005 and previous drought years was the presence of transgenic traits in corn hybrids, especially Bt-ECB traits, and eventual rainfall that started in the first few weeks of July.

European corn borer and increased stalk tunneling damage is often associated with drought stressed environments. Water transpiration cools important plant parts when it is able to get to those structures. If ECB tunnels are present, water flow to leaves and the ear is interrupted and surface temperature can increase along with stress. Modern hybrids have a greater capacity to maintain the integrity of the stalk for efficient water use. I often hear comments from farmers that "these hybrids can withstand greater stress." However, when the water in the soil profile runs out, it runs out regardless of whether or not it is transgenic.

The objective of the University of Wisconsin Corn Hybrid Performance Trials is to provide unbiased performance comparisons of hybrid seed corn available in Wisconsin. In 2012, a total of 510 corn hybrids are being evaluated in 53 experiments at 14 locations (Figure 1). 

Below is a list of technologies included in the program with the corresponding number of hybrids being evaluated in various zones and trials (Table 1). These include both transgenic and trait technologies. In the table below, an “_S” indicates a silage trial for the region, while an “_ORG” indicates and organic trial. Leafy and bmr traits are not listed.

New transgenic technologies include Optimum® AcreMax® Xtra. New native trait technologies include Agrisure Artesian™.

For a complete list of technologies being tested in 2012, click here.

Tuesday, July 10, 2012

Options for Double-Cropping Barren Corn

The optimum crop to plant in an emergency forage situation should be determined by 1) when and how it will be utilized, 2) the forage quality needed, and 3) seed availability and cost (Undersander, 2008). Since the decision to harvest barren corn should not be made until after pollination (July 10 to August 1), limited cropping options are available for double-cropping if pollination is unsuccessful and results in barren corn.  However, farmers may be in an emergency forage situation where they need to produce forage for a dairy or other livestock operation. Little consideration is given to quality, rather biomass production is the goal during the remaining time left of the growing season. We are truly trying to make the best of a bad situation.

A total of 2400 to 2900 Growing Degree Units (GDUs) accumulate during a growing season in southern Wisconsin. About 1500 GDUs accumulate by August 1 leaving 1200 GDUs for the rest of the season (Mitchell and Larsen, 1981). Much depends upon the date of the first killing frost in the fall.

A comprehensive study on emergency forages was conducted between 2002 and 2004 by Petersen et al. (2003; 2004a; 2004b) and Undersander (2008). Factors included planting date (early May, Early June and Early July), crop species (n= 18 treatments), and location (Pelican Rapids, MN, St. Paul, MN, Arlington, WI, Marshfield, WI and Spooner, WI). Table 1 describes the results of various crop species planted July 1 during 2003 and 2004 at Arlington, WI. 

Dry matter (DM) production ranged from 1.0 to 13.0 Tons DM/A depending upon the growing season and species (Table 1). Corn for silage was usually among the highest yielding options for all planting dates and environments. One-cut bmr forage sorghum at times produced the highest DM yields (especially in southern Wisconsin), but performance was inconsistent and often failed to reach the target harvest maturity and moisture. 

Small grains with or without pea produced low yields when planted July 1. Other studies also confirm this observation. Maloney et al. (1999) planted various small grain species August 18, 1992 and August 12, 1993 and measured yields of 0.3 to 1.8 T DM/A. However, Contreras-Govea and  Albrecht (2006) measure average oat yields of 3.0 T DM/A when planted August 7and 9, 2001 at Arlington and Lancaster, WI.

Table 1. Dry matter yield (T DM/A) of various crops planted on July 1 at Arlington during 2003 and 2004. Data derived from Peterson et al. (2004b) and Undersander (2008).

Corn 7.6-9.0      ---
BMR Sorghum 9.4 13.0
Barley 1.2 2.0
Barley/Pea 2.0 2.0
Oat/Pea 2.3 2.8
Sudangrass 3.1 3.5
Sorghum x Sudangrass 4.6 ---
Japanese Millet 3.6 4.1
Hybrid Pearl Millet 4.4 3.0
Siberian Foxtail Millet 2.9 1.8
Golden German Millet 2.6 2.1
Alfalfa 1.0 1.0
LSD (0.05-0.10) 0.8 0.8

In another study, Lauer et al., (2005, 2006) produced yields of 5.3-8.6 T DM/A on July 1 planting dates (Table 2). Yield decreased as planting dates were delayed to August 1, however, yields were still greater than many species planted July 1 in the Peterson et al. (2004b) and Undersander (2008)  studies (Table 1). In 2005, the August 1 planting date produced 2.1-3.4 T DM/A. Full-season hybrids produced the greatest dry matter yield and Milk per acre when planted during July (data not shown). No significant interaction among corn hybrid types was measured for Milk per Ton, although brown midrib hybrids tended to produce the best quality.

Table 2.  Dry matter yield (Tons DM/A) of corn planted near July 1, July 15 and August 1 at Arlington during 2005 and 2006. Data derived from Lauer (2005; 2006).

Planting date 2005 2006
July 1 6.5 - 8.6 5.3 - 6.4
July 15 4.3 - 6.8 3.4 - 3.7
August 1 2.1- 3.4 0.6 - 0.8
LSD (0.10) 1.1 0.4

Corn can produce significant dry matter yield when planted during July, but the amount produced depends upon when a fall killing frost occurs. Forage quality will be similar to other grass species. Maturities should be long enough so that flowering occurs when a killing frost occurs to take advantage of the first forage quality peak (see Figure 1 in another blog article).

A negative for double-cropping corn is seed expense. There may be options for obtaining inexpensive seed from seed companies. There is no guarantee that drought will be relieved enough to germinate and allow for production. 

Growers need to check on options available from their insurance companies before taking action and planting corn in late June and July for emergency forage. Herbicide labels must be adhered to before switching to other crops. A small amount of fertilizer may be justified in late-planted areas.

Literature Cited

Contreras-Govea, F.E., and K.A. Albrecht. 2006. Forage Production And Nutritive Value Of Oat In Autumn And Early Summer. Crop Sci. 46:2382-2386.

Lauer, J., K. Kohn, and P. Flannery. 2005. Date of Planting and Hybrid Influence on Corn Forage. In Studies on cultural practices and management systems for corn. Wisconsin Research Report, Department of Agronomy, p. 110-111.

Lauer, J., K. Kohn, and P. Flannery. 2006. Date of Planting and Hybrid Influence on Corn Forage. In Studies on cultural practices and management systems for corn. Wisconsin Research Report, Department of Agronomy, p. 90-91.

Maloney, T.S., E.S. Oplinger, and K.A. Albrecht. 1999. Small grains for fall and spring forage. J. Prod. Agric. 12:488-494.

Mitchell, V.L., and R.W. Larsen. 1981. Growing degree days for corn in Wisconsin. UWEX Geological and Natural History Survey. 22 pp.

Peterson, P., M. Endres, D. Holen, C. Sheaffer, V. Crary, D. Swanson, J. Larson, and J. Halgerson. 2003. Emergency forage plantings. Research progress report. 

Peterson, P., D. Undersander, M. Endres, D. Holen, K. Silveira, M. Bertram, P. Holman, D. Swanson, J. Halgerson, J. Larson, V. Crary, and C. Sheaffer. 2004a. How emergency forage crops grew in 2003. Research progress report.

Peterson, P., D. Undersander, M. Bertram, P. Holman, D. Holen, V. Crary, M. Endres, and C. Sheaffer. 2004b. Emergency forage options for July planting. Research progress report.

Undersander, D. 2008. Emergency forages. UWEX Research Summary. 3 pp.

Further Reading

Coblentz, W.K., M.G. Bertram, and N.P. Martin. 2011. Planting Date Effects On Fall Forage Production Of Oat Cultivars In Wisconsin. Agron. J. 103:145-155.

Coblentz, W.K., M.G. Bertram, N.P. Martin, and P. Berzaghi. 2012. Planting Date Effects On The Nutritive Value Of Fall-grown Oat Cultivars. Agron. J. 104:312-323.

Coblentz, W., and M. Bertram. 2012. Fall-Grown Oat Forages: Cultivars, Planting Dates, and Expected Yields. Focus on Forage 14(3): 3 pp.

Lauer, J. 2008. Planting corn in June and July! - What can you expect? Agronomy Advice. June 2008 Field Crops 28.421-57.

Vander Velde, K. , Craig Saxe, and Ken Barnett. 2005. Emergency Forage Plantings in Central Wisconsin.

Pricing Drought Stressed Corn Silage

Arriving at a fair and equitable price for corn silage is difficult due to the number of factors involved that are dynamic and biologically variable. Some factors include production costs, grain price, harvesting costs, costs of handling, hauling and storage of forage, grain drying costs, fertility and organic matter value of stover, and forage quality (especially starch content and neutral detergent fiber digestibility-NDFD). The amount of moisture has a major influence on its feed value and needs to be considered to accurately determine fair silage prices. Some growers will want to calculate the price based on corn grain yield (as the alternative harvestable crop) and some dairymen will want to calculate the price based on alternative forages (primarily alfalfa as the alternative forage source). In either case the final price is affected by supply and demand within a region. Before any decision, consult an insurance agent for additional impact on indemnity payments for sale of silage versus grain.

For a worksheet and guidelines to assist determining pricing solutions for drought affected corn silage, click here

Also, a Corn Silage Pricing Decision Aid (written as an Excel spreadsheet decision support system) can help arrive at an equitable price between buyers and sellers.

Further Reading

Hesterman, O.B., and  P. R. Carter. 1990.  Utilizing Drought-Damaged Corn. National Corn Handbook, NCH-58.

Monday, July 9, 2012

Nitrate Toxicity Issues in Barren Corn

The risk of nitrate poisoning increases as pollination becomes poorer. Nitrate problems are often related to concentration (i.e. the greater the yield the less chance of high nitrate concentration in the forage). If pollination is poor only about half of the dry matter will be produced compared to normal corn forage.

Let the plant tell you whether nitrates are a problem. Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in growing green leaves.  In grasses, nitrates accumulate at the base of the main shoot. If nitrates are accumulating then new growth (tillers) will likely be visible near the base of the plant. 

Under stressful growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems, and other conductive tissue. If moisture conditions improve, the conversion process accelerates and within a few days nitrate levels in the plant returns to normal. A return to non-stressed conditions following substantial rainfall should decrease nitrate accumulation, but chopping should be delayed for 3 to 5 days.

Check fields affected by drought that have plants stunted with significant firing. Nitrate toxicity will likely be a problem if growth is reduced to less than 50% of normal and/or high levels of nitrogen were applied.

Raising the bar

If you suspect an issue, then raise the cutter bar. The highest concentration of nitrates is in the lower part of the stalk or stem (Table 1), so raising the cutter bar on a corn silage chopper will leave most nitrates in the field. Depending upon farm forage needs, raising the cutter-bar on the silage chopper reduces yield but increases quality. For example, raising cutting height reduced yield by 15%, but improved quality so that Milk per acre of corn silage was only reduced 3-4% (Lauer, 1998). In addition the plant parts with highest nitrate concentrations remain in the field.

Table 1. Nitrate nitrogen of corn plant parts harvested for silage.
Plant partNO3N
Upper 1/3 of stalk153
Middle 1/3 of stalk803
Lower 1/3 of stalk5524
Whole plant978
derived from Hicks, Minnesota

Nitrates are reduced through ensiling

Nitrate concentration usually decreases during silage fermentation by one-third to one-half, therefore sampling one or two weeks after filling will be more accurate than sampling during filling. If the plants contain nitrates, a brown cloud may develop around your silo. This cloud contains highly toxic gases and people and livestock should stay out of the area. The only way to know the actual composition of frosted corn silage is to have it tested by a good analysis lab.

It is prudent to follow precautions regarding dangers of nitrate toxicity to livestock (especially with grazing and green-chopping) and silo-gasses to humans when dealing with drought-stressed corn.

Nitrate testing

If drought-stressed corn is ensiled at the proper moisture content and other steps are followed to provide good quality silage, nitrate testing should not be necessary. It is always prudent to test or feed to a few cull cows.

Samples taken for nitrate test must be frozen or analyzed immediately as nitrate will decline in tissue over 3 to 4 hours. If above toxic, levels feed hay or some other forage in the morning and graze corn a couple hours in the afternoon.

Marshfield Plant and Soil Analysis Laboratory
8396 Yellowstone Dr.
Marshfield, WI 54449-8401
Phone: (715) 387-2523

Literature Cited

Lauer, J. 1998. Corn Silage Yield and Quality Trade-Offs When Changing Cutting Height. Agronomy Advice. December, 1998. Field Crops 28.47-20.

Harvesting Barren and Poorly Pollinated Corn

Poor corn pollination can be caused by numerous factors including drought, hail, frost, corn rootworm silk feeding, and foliar diseases. Often poorly pollinated corn can be utilized by livestock systems involving cattle. Corn forage quality is influenced by pollination success. In general if some kernels are developing, it is better to wait with harvest. But, if the plant is barren, then harvest can occur at any time.

Forage quality of normally pollinated corn

Corn has two peaks in forage quality: one at pollination and one at harvest maturity. Forage quality as measured by Milk per Ton is high during vegetative phases prior to flowering (Figure 1). Like all forages, quality decreases after flowering. Unlike other forages, quality improves beginning around R3. The early peak in forage quality at pollination is high in quality but too wet for ensiling. The later peak is more familiar, and is the one we typically manage for when producing corn silage because it maximizes biomass yield and quality.

Figure 1. Corn silage yield and quality changes during development. 

Forage quality of barren and poorly pollinated corn

The first peak in Figure 1 occurs around flowering and will continue if pollination is unsuccessful. Drought stressed corn has increased sugar content, higher crude protein, higher crude fiber and more digestible fiber than normal corn silage. Drought generally reduces yield and grain content resulting in increased fiber content, but this is often accompanied by lower lignin production that increases fiber digestibility.

If pollination is poor yet some kernels are developing, the plant can gain dry matter and farmers should wait with harvest. Coors et al. (1997) evaluated the forage quality of corn with 0, 50 and 100% pollination of the kernels on an ear during 1992 and 1993. These years were not considered “drought” stress years, but they can give us an idea as to quality changes occurring due to poor pollination. These plots were harvested in September.

A typical response of corn to stress is to reduce grain yield. Bareness reduced whole-plant yield by 19% (Table 1). Kernels on ears of 50% ear fill treatments were larger and tended to more than make up for reduced numbers (Albrecht, personal communication). With the exception of protein, as ear fill increased, whole-plant forage quality increased.

Table 1. Forage yield and quality of corn with differing amounts of pollination grown at Madison in 1992 and 1993 (n= 24).
%% of control%%%%%
100 (control)1007.549267754
LSD (0.05)60.31111
derived from Coors et al., 1997

Harvesting and Handling Barren Corn

Farmers often can increase biomass yield in a field of barren corn by double-cropping. If corn is barren and it has been determined that pollination and fertilization of kernels will not or did not occur, then the barren corn can be harvested at anytime and another crop planted. 

Before harvesting check with your crop insurance agent and follow their instructions for collecting adjustments. Also, make sure that there are no herbicide restrictions on the forage for livestock feeding. Aflatoxin and other grain quality problems are insurable causes of loss, so growers can receive indemnities for problems.  Continue to protect insured crops from further damage – you cannot graze an insured crop or chop it for forage or silage without first receiving permission from your crop insurance agent, or you will forfeit indemnities.  You do not have to use the forage yourself, but can sell it.  The same applies if you decide to terminate the insured crop and plant a new crop – you must first receive permission or you will forfeit any indemnity. Farmers who insured their corn for silage can receive an indemnity not only if their silage yield is low, but also if their silage is grain deficient.

The harvesting challenge is that green, barren stalks will contain 75-90% water. If weather remains hot and dry, moisture content drops, but if rain occurs before plants lose green color, plants can remain green until frost.

Barren corn is difficult to harvest because it is rank and too wet for silage storage structures. Arlington UW-ARS staff have had some success using a discbine to cut barren corn into a windrow. The windrow would need to dry for a few hours to desiccate the forage. A forage chopper with a hay pickup attachment is then used to gather and chop the windrow into a wagon for transport to a storage structure for ensiling.

Grazing is an option, but be careful about nitrate toxicity problems. If grazing, consider potential for nitrate toxicity. This is especially likely to be a problem if growth was reduced to less than 50% of normal and/or high levels of nitrogen were applied.

Forage moisture

If the decision is made to harvest the crop for ensiling, the main consideration will be proper moisture for storage and fermentation. The crop will look drier than it really is, so moisture testing will be critical. Be sure to test whole-plant moisture of chopped corn to assure yourself that acceptable fermentation will occur. Use a forced air dryer (i.e. Koster), oven, microwave, electronic forage tester, NIR, or the rapid "Grab-Test" method for your determination. With the "Grab-Test" method (as described by Hicks, Minnesota), a handful of finely cut plant material is squeezed as tightly as possible for 90 seconds. Release the grip and note the condition of the ball of plant material in the hand.
  • If juice runs freely or shows between the fingers, the crop contains 75 to 85% moisture. 
  • If the ball holds its shape and the hand is moist, the material contains 70 to 75% moisture. 
  • If the ball expands slowly and no dampness appears on the hand, the material contains 60 to 70% moisture. 
  • If the ball springs out in the opening hand, the crop contains less than 60% moisture. 
The proper harvest moisture content depends upon the storage structure, but is the same for drought stressed and normal corn. Harvesting should be done at the moisture content that ensures good preservation and storage (Table 2).

Table 2. Recommended moisture content (%) for corn stored in various types of storage structures.
Horizontal bunker silos70-65
Bag silos70-60
Upright concrete stave silos65-60
Upright oxygen limiting silos60-50
derived from Roth et al., 1995

Literature Cited

Coors, J. G., Albrecht, K. A., and Bures, E. J. 1997. Ear-fill effects on yield and quality of silage corn. Crop Science 37:243-247.

Roth, G., D. Undersander, M. Allen, S. Ford, J. Harrison, C. Hunt, J. Lauer, R. Muck, and S. Soderlund. 1995. Corn silage production, management, and feeding. NCR 574, American Society of Agronomy, Madison, WI. 21 pp.

Saturday, July 7, 2012

Corn Management Decisions During Drought Depend Upon Pollination Success

I have been dreading writing this article. I was hoping rain might fall, but the forecast is not positive for the next 10 days. It is becoming clear that corn farmers in the southern four tiers of counties in Wisconsin might have to make the best of a bad situation.

After pollination (July 10 to August 1), the key plant indicator to observe and base future management decisions upon is the success of pollination. Each ovule (potential kernel) has a silk attached to it. When a pollen grain falls on a silk, it germinates, produces a pollen tube that grows the length of the silk which fertilizes the ovule in 12 to 28 hours. If fertilization of the ovule is successful, within 1 to 3 days the silk will detach from the developing kernel. Silks will remain attached to unfertilized ovules and be receptive to pollen up to 7 days after emergence. Silks eventually turn brown and dry up after pollination is over.

Two techniques are commonly used to assess pollination success or failure. The most rapid technique to determine pollination success is the “shake test.” Carefully unwrap the ear husk leaves and then gently shake the ear. The silks from fertilized ovules will drop off. The proportion (%) of silks dropping off the ear indicates the proportion of future kernels on an ear. Randomly sample several ears in a field to estimate the success of pollination.

The second technique is to wait until 10 days after fertilization of the ovules. The developing ovules (kernels) will appear as watery blisters (the "blister" R2 stage of kernel development).

Management Guidelines for Handling Cornfields with Poor Pollination

Typical management options and uses are available for corn that has successfully pollinated. If pollination is unsuccessful, we are usually trying to make the best of a bad situation.

If pollination is good, harvest in a normal fashion for either grain or forage use. If pollination is poor yet some kernels are developing, the plant can gain dry matter and farmers should wait with harvest. In Wisconsin, many farmers have the option of harvesting poorly pollinated fields for silage use. If there is no pollination, then the best quality forage will be found as close to flowering as possible. Quality decreases after flowering. The challenge is to make sure that no potential pollination occurs and that the forage moisture is correct for the storage structure.

Drought-stressed corn can be grazed or used for forage, either as green chop or silage. Because of the potential for nitrate toxicity, grazing or green chopping should be done only when emergency feed is needed. The decision to chop corn for silage should be made when:

1. You are sure pollination and fertilization of kernels will not or did not occur and that whole-plant moisture is in the proper range for the storage structure so that fermentation can occur without seepage or spoilage losses. If there is no grain now, florets on the ear were either not pollinated or have not started to grow due to moisture stress, and the plant will continue to be barren. If the plant is dead, harvest should occur when whole plant moisture is appropriate for preservation and storage.

2. If pollination and fertilization of kernels did occur but it was poor, do not chop until you are sure that there is no further potential to increase grain dry matter and whole plant moisture is in the proper range for the storage structure. These kernels may grow some, if the plant is not dead. If kernels are growing, dry matter is accumulating and yield and quality of the forage is improving.

Further Reading

Lauer, J.G. 2006. Concerns about drought as corn pollination begins. Agronomy Advice Field Crops 28.493-42. July 2006.

Friday, July 6, 2012

What Happens Within the Corn Plant When Drought Occurs?

To begin talking about water influences on corn growth and development and yield we must begin with the concept of evapotranspiration. Evapotranspiration is both the water lost from the soil surface through evaporation and the water used by a plant during transpiration. Soil evaporation is the major loss of water from the soil during early stages of growth. As corn leaf area increases, transpiration gradually becomes the major pathway through which water moves from the soil through the plant to the atmosphere.

Yield is reduced when evapotranspiration demand exceeds water supply from the soil at any time during the corn life cycle. Nutrient availability, uptake, and transport are impaired without sufficient water. Plants weakened by stress are also more susceptible to disease and insect damage. Corn responds to water stress by leaf rolling. Highly stressed plants will begin leaf rolling early in the day. Evapotranspiration demand of corn varies during its life cycle (Table 1). Evapotranspiration peaks around canopy closure. Estimates of peak evapotranspiration in corn range between 0.20 and 0.39 inches per day. Corn yield is most sensitive to water stress during flowering and pollination, followed by grain-filling, and finally vegetative growth stages.

Table 1. Estimated corn evapotranspiration and yield loss per stress day during various stages of growth.

Growth stage

Percent yield loss per day of stress
inches per day%
Seedling to 4 leaf0.06---
4 leaf to 8 leaf0.10---
8 leaf to 12 leaf0.18---
12 leaf to 16 leaf0.212.1 - 3.0 - 3.7
16 leaf to tasseling0.332.5 - 3.2 - 4.0
Pollination (R1)0.333.0 - 6.8 - 8.0
Blister (R2)0.333.0 - 4.2 - 6.0
Milk (R3)0.263.0 - 4.2 - 5.8
Dough (R4)0.263.0 - 4.0 - 5.0
Dent (R5)0.262.5 - 3.0 - 4.0
Maturity (R6)0.230.0
derived from Rhoads and Bennett (1990) and Shaw (1988)

Vegetative development

Water stress during vegetative development reduces stem and leaf cell expansion resulting in reduced plant height and less leaf area. Leaf number is generally not affected by water stress. Corn roots can grow between 5 and 8 feet deep, and soil can hold 1.5 to 2.5 inches of available soil water per foot of soil, depending upon soil texture. Ear size may be smaller. Kernel number (rows) is reduced. Early drought stress does not usually affect yield in Wisconsin through the V10-V12 stages. Beyond these stages water stress begins to have an increasing effect on corn yield.


Water stress around flowering and pollination delays silking, reduces silk elongation, and inhibits embryo development after pollination. Moisture stress during this time reduces corn grain yield 3-8% for each day of stress (Table 1). Moisture or heat stress interferes with synchronization between pollen shed and silk emergence. Drought stress may delay silk emergence until pollen shed is nearly or completely finished. During periods of high temperatures, low relative humidity, and inadequate soil moisture level, exposed silks may desiccate and become non-receptive to pollen germination.

Silk elongation begins near the butt of the ear and progresses up toward the tip. The tip silks are typically the last to emerge from the husk leaves. If ears are unusually long (many kernels per row), the final silks from the tip of the ear may emerge after all the pollen has been shed. Another cause of incomplete kernel set is abortion of fertilized ovules. Aborted kernels are distinguished from unfertilized ovules in that aborted kernels had actually begun development. Aborted kernels will be shrunken and mostly white.

Kernel development (grain-filling)

Water stress during grain-filling increases leaf dying, shortens the grain-filling period, increases lodging and lowers kernel weight. Water stress during grain-filling reduces yield 2.5 to 5.8% with each day of stress (Table 1). Kernels are most susceptible to abortion during the first 2 weeks following pollination, particularly kernels near the tip of the ear. Tip kernels are generally last to be fertilized, less vigorous than the rest, and are most susceptible to abortion. Once kernels have reached the dough stage of development, further yield losses will occur mainly from reductions in kernel dry weight accumulation.

Severe drought stress that continues into the early stages of kernel development (blister and milk stages) can easily abort developing kernels. Severe stress during dough and dent stages of grain fill decreases grain yield primarily due to decreased kernel weights and is often caused by premature black layer formation in the kernels. Once grain has reached physiological maturity, stress will have no further physiological effect on final yield (Table 1). Stalk and ear rots, however, can continue to develop after corn has reached physiological maturity and indirectly reduce grain yield through plant lodging. Stalk rots are seen more often when ears have high kernel numbers and have been predisposed to stress, especially drought stress.

Premature Plant Death

Premature death of leaves results in yield losses because the photosynthetic 'factory' output is greatly reduced. The plant may remobilize stored carbohydrates from the leaves or stalk tissue to the developing ears, but yield potential will still be lost. Death of all plant tissue prevents any further remobilization of stored carbohydrates to the developing ear. Whole plant death that occurs before normal black layer formation will cause premature black layer development, resulting in incomplete grain fill and lightweight, chaffy grain. Grain moisture will be greater than 35%, requiring substantial field drydown before harvest.

Yield Components and When They Are Determined During the Corn Life Cycle

With the onset of tasseling the corn crop is in a critical growth and development stage for grain yield. The tasseling, silking, and pollination stages of corn development are extremely critical because the yield components of ear and kernel number can no longer be increased by the plant and the potential size of the kernel is being determined.

For example, the potential number of ears per unit area is largely determined by number of seeds planted, how many germinate, and eventually emerge. Attrition of plants through disease, unfurling underground, insects, mammal, bird damage, chemical damage, mechanical damage, and lodging all will decrease the actual number of ears that are eventually harvested. The plant often can compensate for early losses by producing a second or third ear, but the capacity to compensate ear number is largely lost by R1 and from then on no new ears can be formed.

Likewise, kernel number is at its greatest potential slightly before R1, the actual number of kernels formed is determined by pollination of the kernel ovule. The yield component of kernel number is actually set by pollination and fertilization of the kernel ovule. If the ovule is not pollinated, the kernel cannot continue development and eventually dies. No new kernels form after the pollination phase is past.

The only yield component remaining after pollination that has some flexibility is kernel weight. For the first 7 to 10 days after pollination of an individual kernel, cell division occurs in the endosperm. The potential number of cells that can accumulate starch is determined. At black layer formation (R6) no more material can be transported into the kernel and yield is determined.

Literature Cited

Rhoads, F. M. and Bennett, J. M. 1990. Corn. In Stewart, B. A. and Nielsen, D. R. (editors). Irrigation of agricultural crops.  p. 569-596. ASA-CSSA-SSSA, Madison, WI.

Shaw, Robert H. 1988. Climate requirement. In Sprague, G. F. and Dudley, J. W. (editors). Corn and Corn Improvement.  p. 609-638. American Society of Agronomy, Madison, WI.

Further Reading

Lauer, J.G. 2006. Concerns about drought as corn pollination begins. Agronomy Advice Field Crops 28.493-42. July 2006.