In This Issue:
- Twin-Row Corn Production: 2009 Research Update
- Nitrogen Contribution from Red Clover for Corn following Wheat in Western Ohio
- WCR Management in non-Bt Corn
- Scouting for Alfalfa Weevil
- Soil Insecticides on Corn and New Field Crops Insect Control Bulletin
- Proven Production Practices for Increasing Corn Yields and Profits
- Reminders About Marestail Management
- April: Short and Long Term Weather Outlook
We’ve received several inquiries recently concerning the yield potential of “twin-row” corn plantings. Higher seeding rates and new planters that accommodate twin rows are generating interest in twin row corn production. In the popular press there have been reports suggesting that twin rows offer some of the yield increases associated with narrow row corn. Narrow row corn production is usually associated with row spacings of 22-inches or less, and in Ohio the yield benefits from narrowing rows have been inconsistent and usually small. In the typical twin row systems currently used for corn, two rows are placed 7 or 8-inches apart on 30-inch centers (other twin row configurations have been used - in the South twin rows have been planted on a wider center such as 38 or 40-inches). Twin rows make it possible to create narrow rows without changing the row configuration of other equipment, and to avoid costs associated with equipment conversion to a narrow row system. Staying on 30-inch centers allows growers to use the same corn header and tractor tire spacing used in 30-inch corn production.
In 2009, we conducted an evaluation of twin row corn at the OSU-OARDC Northwest Research Agricultural Station near Hoytville, OH. A Great Plains 4 row planter was used to establish corn plots in twin row and 30-inch row spacings. In the twin row spacing configuration, corn was planted in paired rows, 8 inches apart on 30-inch centers. The paired twin rows were planted in a staggered spacing to achieve more uniform spacing between plants. Since hybrids and plant populations may influence corn response to twin rows, we considered hybrids with varying maturities (107-, 111-, and 112-day) and four plant populations (28,000, 33,000, 38,000, and 43,000 plants/A). Grain yields of twin row and 30-in corn (180 vs. 182 bu/A), averaged across the three hybrids and four plant populations, were not significantly different. Although a small but significantly higher yield (approx. 5 bu/A) occurred when plant populations were increased above 28,000 plants/A, twin and 30-inch rows exhibited similar responses to plant population. Hybrids also showed similar response to twin and 30-inch rows. There were no differences in yield between hybrids. Effect of row spacing configuration on stalk lodging was negligible (lodging averaged less than 4% across plots). The grain moisture of twin row corn, averaged across the three hybrids and four plant populations, was slightly higher than 30-in row corn (24.2 vs. 23.6% moisture content).
The 2009 Ohio twin row study was part of a multi-state evaluation of twin row corn supported by Monsanto and Great Plains Manufacturing. The twin row study was also performed at Purdue University and the University of Nebraska. The average yields for the Purdue and Nebraska test sites were higher (232 and 240 bu/A), than that of the Ohio test site (about 181 bu/A); the Hoytville site was drier than much of state. However, the Ohio findings were generally similar to the preliminary results reported by the university researchers in the other states. The yield advantage for twin rows when it occurred was usually less than 3 bu/A. Hybrid and population response to twin rows and 30 inch rows were generally similar. Growing season conditions were somewhat unusual across the Corn Belt in 2009 and we are planning to continue the research in 2010 and obtain more insight on twin performance under different environmental conditions.
In addition to University and Extension evaluations of twin rows, several seed and equipment companies have conducted extensive evaluations of twin rows (see references below for more details). One major seed company reported that in 2009 twin rows out yielded 30-in rows at 16 of 20 locations with an average yield advantage of 3 bu/A. However another company found no performance advantage of twin rows over 30-inch rows based on 2005-2006 studies. Both of these companies compared twin rows using different hybrids and a wide range of plant populations.
Twin-Row.com Online Resource Center [sponsored by Great Plains Manufacturing] http://www.twin-row.com/
Evaluation of Twin Rows in Corn. 2009 Monsanto National Summary http://www.twin-row.com/sites/default/files/monsanto_twinrowreport.pdf
Genetic Interactions in Twin Rows. AgriGold Research – 2009. http://www.twin-row.com/sites/default/files/agrigold_twinrow.pdf
Inclusion of a winter legume cover crop into a crop rotation has been suggested as a method to provide a substantial portion of the N (nitrogen) requirement of the following crop. While the benefits of winter cover crops such as reduced soil erosion, increased soil organic matter, and increased mulch cover have been well documented, the N contribution to the subsequent crop has shown to be variable. The objective of this study was to determine the N contribution from a red clover cover crop following wheat to a subsequent corn crop. The experiment was conducted at two western Ohio locations over 3 yr. At both locations, red clover was either interseeded into wheat or seeded after harvest, the red clover cover crop was eliminated with tillage or herbicide application, and corn was planted with three N rates (0, 90, and 180 kg N ha–1). The data revealed that for three of the four site years (when the cover crop was successfully established) there was no N contribution attributable to the presence of red clover. The one site that did show a N contribution revealed that the amount of N contributed was less than 90 kg N ha–1. However, even when no N benefit was found, yields were improved by non-N-related rotational effects. Improved water infiltration and moisture conservation are often identified as the primary non-N benefits of cover crops, and this may be the case for this particular site-year. Significant reductions in N fertilization rates following a red clover cover crop are likely to result in lost corn yield opportunities in western Ohio.
Rotational effects are non-N-related factors that produce increased yields. These effects can be misinterpreted as N contribution if inappropriate comparisons are made in the absence of N rates. Reducing N applications based on that misinterpretation may lead to limited N supply to a following non legume crop that can represent loss of yield opportunity. Soil tests for N do not show what N may become plant available as cover crop residues decompose. Subsequent crop performance is likely the best way to determine cover crop benefits. To determine whether increased yields following a cover crop are due to rotational effects or N contribution, a range of N rates, including a check (0 N), need to be applied to a crop both following a cover crop and no cover crop. The relationship between the N response curves will determine whether or not there is a N contribution.
In temperate climates such as Western Ohio, soils may remain frozen for several months, in which no growth or decomposition occurs, decreasing N accumulation and delaying N release. Decreases in N accumulation due to lack of growth decreases the potential N contribution from a legume cover crop, and delays in N release due to cool spring temperatures decrease the N supplying ability of legume cover crops. Cover crops grown in warmer, southern latitudes are more likely to show N contributions due to greater cover crop growth during winter months and more rapid turnover of residues returned to the soil in the subsequent crop year. This rticle was adapted from Agronomy Journal (102:210-215, January, 2010).
We have heard of more growers moving to corn that does not contain the Bt-insecticidal trait which offers control against some insect pests, especially against western corn rootworm (WCR) and it’s behavioral variant. The variant (aka first-year corn rootworm), are WCR that will oviposit in soybean fields during fall. When these fields are rotated to corn the following year, the first-year corn could be at risk to WCR damage. Part of the reasoning may be due to the apparent decrease in WCR populations during the past few years, as suggested by OSU Entomology and Extension surveillance and supported by data from other states. So, do you need to protect non-Bt corn against WCR and WCR-variant damage? The answer lies in practicing good IPM. If you are planting non-Bt corn after corn, in most cases WCR protection is warranted. If you are planting first-year, non-Bt corn, it may depend on where in Ohio your fields are located and the history of variant WCR-variant. First, our multi-year surveillance for variant WCR has suggested that the distribution covers most of western Ohio and has extended into parts of central Ohio (for the most recent distribution map, see http://entomology.osu.edu/ag/fycr/08fycr.pdf. Second, the history of variant-WCR plays a role. Have your fields been previously damaged from variant WCR? Was there any suspected damage last year? If you lie in the variant WCR distribution zone, or have had prior history, then you might want to consider protection. Fortunately, Ohio WCR pressures are low to moderate in most years. Our data shows that either soil insecticides or the high rates of seed treatments work well in protecting against damage. The decline in WCR numbers has been consistent for 2 straight years, but this is far from proving a trend. Thus, there may still be a need to protect non-Bt corn against WCR.
With the current warm temperatures, we have reached the time when alfalfa growers, especially in southern Ohio, should begin monitoring for alfalfa weevil. Scouting should begin when heat unit accumulations, beginning from January 1, reach between 250- 300 heat units (HU). This time period is when we begin to have weevil egg hatch and start to see feeding. These levels are now being reached in southern Ohio, with Piketon coming in at 243 HU and Jackson at 234 HU. The Western Branch, near South Charleston, is only at 174. We would expect that central and northern Ohio will reach the 250-300 levels in the coming week(s). Remember that fields that have a south facing slope tend to warm up sooner and need to be checked for weevil earlier. We will update heat unit accumulations in the coming weeks in this C.O.R.N. newsletter.
Alfalfa weevil scouting is accomplished by collecting a series of three 10-stem samples randomly selected from various locations in a field. Place the stem tip down in a bucket. After 10 stems have been collected, the stems should be vigorously shaken in the bucket and the number of larvae in the bucket counted. The shaking will dislodge the late 3rd and 4th instar larvae which cause most of the foliar injury. Close inspection of the stem tips may be needed to detect the early 1st and 2nd instar larvae. The height of the alfalfa should also be recorded at this time. Economic threshold is based on the number of larvae per stem, the size of the larvae and the height of the alfalfa. The detection of one or more large larvae per stem on alfalfa that is 12 inches or less in height indicates a need for rescue treatment. Where alfalfa is between 12 and 16 inches in height, the action threshold should be increased to 2 to 4 larvae per stem depending on the vigor of alfalfa growth. When alfalfa is 16 inches in height and there are more than 4 larvae per stem, early harvest is recommended. See the OSU Alfalfa Weevil FactSheet http://ohioline.osu.edu/ent-fact/pdf/0032.pdf for more on alfalfa weevil scouting and thresholds.
For insecticides that are labeled for alfalfa weevil, see http://entomology.osu.edu/ag/images/Alfalfa_Weevil%281%29.pdf.
Remember it is still too early to worry about potato leafhoppers because they do not move into Ohio until May.
There are two corn soil insecticide matters that should be brought to growers’ attention. The first item is that there is a newly labeled soil insecticide called SmartChoice, which contains chlorethoxyfos (an organophosphate that is the same active ingredient as in Fortress) and bifenthrin (a pyrethroid). SmartChoice is labeled for corn rootworm larvae and various secondary pests. There are two rates on the SmartChoice label, one for when used as the only control tactic against rootworm larvae (4.0 to 4.5 oz./1000 row ft) and a second rate when used in combination with a Bt-containing transgenic hybrid (3.0 to 3.5 oz./a000 row ft) which would provide a grower two tactics against rootworm larvae. However, in Ohio we do not feel the rootworm pressure throughout the state would usually justify the added expense of using two separate control tactics. Plus, for secondary soil insect pest control, the transgenic corn hybrids will also have a low rate of an insecticide seed treatment. Based on our past experiences, either a Bt transgenic hybrid or a soil insecticide, SmartChoice now being one of them, will give you good control. SmartChoice is available in the SmartBox system, and should be applied in-furrow.
The second item relates to Regent, a soil insecticide which contains the active ingredient fipronil that has been labeled on corn in Ohio for rootworm larval and other secondary pest control. EPA has recently cancelled the use of this material on corn, although current stocks can continue to be sold and used. The manufacturer can sell product already manufactured until May 11, 2011, while dealers can sell and growers can use available product until existing stocks are exhausted.
Bulletin 545, Control of insect Pest of Field Crops, has been revised for 2010 and is now available on our Agronomic Crops Insects web page at http://entomology.osu.edu/ag . The bulletin lists all the insecticides, miticides, and molluscicides that are labeled for major insect, mite, and slug pests of alfalfa, corn, soybean, and small grains (including wheat).
The record high corn yields achieved by many Ohio farmers in 2009 have generated considerable interest in what can be done to sustain and push yields even higher. According to some agronomists and crop specialists, we have entered a new era in corn production characterized by higher annual rates of yield improvement. These higher rates are attributed to several factors, including genetic technologies that allow for greater expression of corn genetic yield potential by withstanding various crop stresses.
In the quest for high yields, considerable attention has been given to increasing various inputs, including seeding rates and fertilizers, narrowing row spacing, and making preventative applications of foliar fungicides, growth regulators and biological stimulants. However, the additional costs of some of these practices and inputs may prohibit their use except perhaps for those growers interested in participating in corn yield contests on high yielding sites. A more practical and economic approach to achieving high yields is to follow proven cultural practices that enhance corn performance. Not only are these practices the foundation for successful corn production but they will also help exploit the yield potential offered by new technologies.
Ten Proven Practices for Increasing Corn Yields and Profits
1. Know the yield potential of your fields, their yield history, and the soil type and its productivity.
2. Choose high yielding, adapted hybrids. Pick hybrids that have produced consistently high yields across a number of locations or years. Select hybrids with high ratings for foliar and stalk rot diseases when planting no-till or with reduced tillage, especially after corn. Select high yielding Bt rootworm resistant hybrids where is potential for the western corn rootworm damage.
3. Follow pest management practices that will provide effective, timely pest control – especially weed control.
4. Aim to complete planting by May 10. If soil conditions are dry, begin planting before the optimum date but avoid early planting or poorly drained soils. If planting late (after May 25 in central Ohio) plant corn borer resistant Bt hybrids.
5. Follow practices that will enhance stand establishment. Adjust seeding depth according to soil conditions and monitor planting depth periodically during the planting operation and adjust for varying soil conditions. Make sure the planter is in good working order. Inspect and adjust the planter to improve stand establishment. Operate planters at speeds that will optimize seed placement. Uneven emergence affects crop performance because late emerging plants cannot compete with larger, early emerging plants.
6. Adjust seeding rates on a field by field basis. On productive soils, which average 175 bu/A or more, final stands of 32,000 plants/acre or more may be required to maximize yields.
7. Supply the most economical rate of nitrogen. Use an application method that will minimize the potential loss of N (incorporation/injection, consider stabilizers under high risk applications, etc.).
8. Utilize soil testing to adjust pH and guide P and K fertilization. Avoid unnecessary P and K application. High soil tests do not require additional inputs.
9. Perform tillage operations only when necessary and under proper soil conditions. Deep tillage should only be performed when a compacted zone is detected and soil conditions are dry (usually late summer).
10. Take advantage of crop rotation - corn grown after soybeans will typically yield 10-15% more than corn grown after corn.
These are by no means the only management practices with which growers need to be concerned but they are keys to achieving high corn yields.
A brief review of marestail biology, resistance, and control as it relates to spring burndown/residual herbicide applications follows.
1. The majority of the marestail populations in Ohio are resistant to glyphosate or ALS inhibitors (FirstRate, Classic, Synchrony, Canopy EX, etc) or both types of herbicides. What this means: it’s generally impossible to control marestail with postemergence herbicides (unless you are using Ignite in LibertyLink soybeans) or with burndown treatments consisting of just glyphosate. We suggest managing marestail as if it has both types of resistance, which will cover you in the event that it does, and also help prevent it from developing resistance. Bottom line: Use a comprehensive burndown program consisting of several herbicides with activity on marestail to ensure complete control of existing plants, and include herbicides with residual activity to ensure control of marestail that emerge after soybean planting.
2. Comprehensive burndown programs that are usually effective on marestail include the combinations listed below. The assumption here is that they will be applied when marestail are less than about 6 inches tall. Increasing the glyphosate rate to 1.5 lb ae/A and the 2,4-D rate to 1 lb ai/A will generally improve control, especially as plants become larger. We have preliminary evidence that some marestail populations are becoming less sensitive to 2,4-D ester. Increasing rates may compensate for this loss of activity, but consider use of something other than just a mix of glyphosate and 2,4-D ester in fields where this mix has performed variably within the past several years. Also, keep in mind that the mix of glyphosate and Sharpen, while effective on marestail, has been variable on deadnettle in our research, so consider adding some 2,4-D ester or Canopy to help control this weed and a few others.
Glyphosate (1.1 to 1.5 lbs ae/A) + 2,4-D ester
Glyphosate (0.75 to 1.5 lbs ae/A) + 2,4-D ester + Sharpen (1 oz) or Optill (2 oz)
Glyphosate (1.1 to 1.5 lbs ae/A) + Sharpen (1 oz) or Optill (2 oz)
Paraquat (0.75 to 1 lb ai/A) + metribuzin (0.38 lb ai/A) + 2,4-D ester
Ignite (29 oz) + Sharpen (1 oz) or Optill (2 oz)
Ignite (29 oz) + metribuzin (0.38 lb ai/A)
Where marestail are not ALS-resistant, the addition of a residual herbicide containing chlorimuron (Canopy/Cloak, Valor XLT, Envive) or cloransulam (FirstRate, Gangster, Sonic, Authority First) can improve burndown. Products containing flumioxazin (Valor) or sulfentrazone (Authority/Spartan) should not be applied with Sharpen.
3. What are my options for control of large marestail (10 to 20 inches), especially when it’s no longer possible to use 2,4-D ester? Best option is probably a high rate of Ignite (32 to 36 oz) in combination with metribuzin. We have also had effective control with the combination of Ignite and Sharpen in preliminary studies. However, as many growers learned last year, it might still be better to use 2,4-D ester and wait another week to plant soybeans, even as we move into late May.
4. Marestail is capable of emerging throughout much of the year, and substantial emergence can occur between now and mid June. Failure to include residual herbicides in preplant herbicide applications is likely to result in marestail at the time of the POST herbicide application, and this is not a good thing. We generally suggest use of a product or combination that contains a full rate of flumioxazin, sulfentrazone, or metribuzin to account for the probable occurrence of ALS resistance. This includes the following: Valor XLT, Envive, Gangster, Sonic Authority First, Valor, Spartan, Authority Assist, and any generic metribuzin product (rate of at least 0.38 lbs ai/A). When using Canopy/Cloak DF, add enough additional metribuzin to bring the rate to at least 0.38 lb ai/A. Where the population is not resistant to ALS inhibitors, use of Canopy/Cloak DF or EX, Python, or Scepter may provide enough residual activity, but this is somewhat of a gamble.
5. We have had good success with April applications of a combination of burndown and residual herbicides, so we suggest applying anytime from now on that the field is fit for traffic. Marestail is most easily controlled when small, and especially before it exceeds about 4 inches in height. The possible disadvantage of applying residual herbicide this early is a loss of residual control too soon in growing soybeans, especially when weather turns wet and soybean planting is delayed. Increasing residual herbicide rates in early April applications may compensate for this somewhat, especially for the shorter residual products – Valor, Authority/Spartan, and metribuzin. The rate of Authority in the 3 oz/A rate of Sonic and Authority First is less than optimum with regard to residual control of marestail, and we suggest increasing the rates of these herbicides when applied in early to mid-April, or supplementing with additional sulfentrazone.
6. What if I applied herbicides last fall? This does not necessarily change the recommendations presented previously in this article. A fall application usually results in control of marestail that overwinter, so what you’ll be dealing with this spring is primarily spring- and summer-emerging marestail plants. This generally results in a much easier burndown situation, and it might be possible to get by with the lower rates of the burndown combinations listed in point #2, or a combination of 2,4-D ester and a residual herbicide. As we move later in spring and the spring-emerging plants increase is size, the burndown program should become more aggressive. Our research has generally shown that a fall application of residual herbicides (Canopy, Valor, metribuzin, etc) is not likely to control marestail through the time of soybean canopy, which is what’s needed in a marestail management program, especially in ALS-resistant populations. It’s still important for the majority of the residual herbicide to be applied in the spring. So, if you applied Canopy or another residual herbicide in the fall, consider applying additional residual herbicide prior to or at soybean planting, using products that will control ALS-resistant marestail as outlined previously in point #4. Keep in mind the three important strategies for successful management of marestail:
2) use a combination of fall and/or spring applications to ensure a weedfree start at soybean planting; and
3) use enough residual herbicide in the spring to ensure control of marestail through soybean canopy.
We have a rain system for late Wednesday into Thursday of this week which should drop 0.10 to 0.75 inches in the southeast half of the state to 0.75 to 2 inches in the far western and northern part of the state, especially the northwest will have the highest totals.Another system would not affect the area until the middle to end of next week. Temperatures will average above normal for the next 2-3 weeks. http://www.weatheroffice.gc.ca/ensemble/naefs/semaine2_combinee_e.html
Rainfall will average normal in the north and west and below normal in the east and southeast. http://www.weatheroffice.gc.ca/ensemble/naefs/produits_e.html
Longer term, the climate models indicate an end of El Nino with a possible La Nina forming from summer into autumn. If this occurs, we would see a close to normal early spring turn warmer and drier than average for later spring into summer. This is worth monitoring as this is a rapid change that could at least create some summertime issues. The official outlook for summer is equal chances or near normal until some of this shakes out in the coming weeks, but I wanted to let you know there is a trend possibly toward a warmer and drier summer.
Example of one climate model now showing this (SINTEX): http://www.jamstec.go.jp/frcgc/research/d1/iod/index.html <http://www.jamstec.go.jp/frcgc/research/d1/iod/index.html>
The Climate Forecasting System (CFS) model is showing a cooler than normal summer at: http://www.cpc.noaa.gov/products/people/wwang/cfs_fcst/images3/glbT2mSea.gif
The CFS is also showing a wetter than normal summer at: http://www.cpc.noaa.gov/products/people/wwang/cfs_fcst/images3/glbPrecSea.gif