C.O.R.N. Newsletter 2007-38

Short Soybean Plants and Big Yields

Authors: Jim Beuerlein

The 2007 soybean growing season was, to say the least, both different and the same as other years. There was drought in some areas and flooding in others; yield disasters and new record highs; serious insect problems and no insects; severe disease and little disease all depending on which times in the growing season you were taking notes and on your location in the state. There was lots of soybean greenstem which made harvest troublesome and generated lots of questions, and there was less late season disease than normal. The 2007 season may set a new yield record or at least come very close to the 2004 and 2006 record of 47 bushels per acre.

The crop was planted in a timely manner and into moist soil, which resulted in an early start with good stands. The dry weather in late May through much of July caused plants to produce large root systems, but it reduced top growth; which is the usual reaction to early season drought. Dry topsoil eliminated the development of root rot diseases that normally reduce the size and function of root systems. Large, healthy root systems along with reduced vegetation resulted in a major increase in water use efficiency. Two other yield promoters were the less than normal insect damage in most areas, and less foliar disease which kept carbohydrate production high late into the grain filling period. The root systems were able to take up water and nutrients later into the grain fill period than normal, which supported high rates of photosynthesis during the warm, sunny days in September.

Normally, the soybean crop dies as the result of poorly functioning root systems that are unable to deliver the needed water and nutrients late into the grain filling period. The result of poorly functioning root systems is digestion of leaves and stems to complete pod fill, causing the leaves to turn yellow and fall to the ground. The same action causes the stems to dry and become rigid. When plants are able to produce seeds of adequate size for the next growing season without the digestion of the plant leaves and stems, those structures stay green until water movement from the root stops completely or until they are killed by frost. Leaves are more easily digested than stems and are consumed first. Occasionally a situation known as greenstem occurs, in which only the leaves get digested, turn yellow and fall to the ground while the stems remain intact and green. This is what happened in many Ohio fields this fall, and was both a curse and a blessing. While harvesting research plots I noted that plots with greenstem usually had high yields, with grain at the same moisture content as plots without green stems, so the two characteristics, high yield and green stems, went hand-in-hand.

2007 reminded us of the importance of large, healthy root systems. The selection of varieties with good resistance to root rot diseases and the use of seed treatment fungicides are two actions producers can take to improve root system size and health. Longer crop rotations will reduce the negative impact of some diseases and insects. The elimination of soil compaction and the improvement of soil structure will also increase the size of the root system. As tillage is reduced, soil structure improves, but that improvement can be negated by machinery traffic when the soil has high levels of moisture.

We were also reminded that large plants don’t always result in big yields and that small plants can also produce big yields. The more leaf area a crop has the more water it uses. Thus, smaller plants, reduced populations, and crops with low water needs are usually recommended for droughty soils. If our growing seasons continue to be droughty we will need to make adjustments to cultural practices to improve water use efficiency and maintain productivity. As always, the best game plan for high profitability is to continue doing the correct things in the correct way and at the correct time.

Watch Out for Mold in Stored Grain

Authors: Dirk Maier

Farmers and elevator managers should check corn in storage because temperatures were optimal for mold growth early this storage season, a Purdue University Extension expert says in a university report.

Moisture conditions through out the growing season varied by location, but the state saw temperatures in the high 80s and even 90s, causing some concern.

"One of the concerns that I have is the fact that the corn has been sitting relatively dry at high temperatures, but some at 16% to 17% moisture hasn't gone through the dryer and that can cause mold growth, particularly blue-eye mold," says Dirk Maier*, Purdue Extension postharvest grain quality expert.

"Blue-eye" mold is the discoloration of a corn kernel caused by the production of blue-green fungal spores. Two groups of fungi usually cause blue eye, Aspergillus glaucus or a species of Penicillium.

The presence of blue-eye mold indicates that something went wrong in the grain storage process, Maier says.

Blue-eye mold can grow at lower moisture contents and may stay in the grain even after it's been cooled. It would be arrested during that period of time, but when temperatures become warm in the spring, the mold can continue to grow and create problems that can result in quality discounts at the time of sale, he says.

"With the weather change that we are experiencing, now is the time to take advantage of this cooler weather and really use aeration to cool
down the grain," Maier says. "Hopefully by the end of October, temperatures will be in the mid- to lower-50s and at that point farmers and elevator managers can turn off their fans until the next cold front moves in. Moving a cooling front through a typical grain storage bin takes at least 150 to 200 hours.

"A normal temperature management approach for storing grain is that by mid- to late-November, grain temperatures should be cooled down with
aeration into the 40s and then by the end of the year into the low 30s and upper 20s."

During this initial cooldown, Maier advises farmers and elevator managers to look for any type of steam coming from the grain or any odor coming off the grain.

Both are indicators that the grain is not in as good of condition as it should be. It's possible that there is a problem in one bin and not another; it just depends on when it was harvested and what the moisture content is, he says.

"Removing some of the grain from each bin will typically take the peak and center core out where there is a high accumulation of fine materials," Maier says. "This also provides an opportunity to sample the grain and see if you have blue-eye mold damage or other types of grain damage.

"If some bins have better quality grain than other bins, you will want to adjust the marketing schedule according to that and sell, ship or use the lower-quality grain that may not store as well earlier in the marketing year than you do grain that is in really good shape."

Monitoring stored grain regularly is very important, Maier says.

"Typically we recommend to check grain quality every two to three weeks during the colder months and then more frequently in the spring and summer," he says.

See the following helpful pubs for more information:

http://www.ces.purdue.edu/extmedia/BP/BP-49.html

http://www.ces.purdue.edu/extmedia/GQ/GQ-18.pdf

 

Mitigate the Downside Risks of Corn Following Corn

This article is authored by R.L. (Bob) Nielsen, Agronomy; Bill Johnson, Botany & Plant Pathology; Christian Krupke, Entomology; and Greg Shaner, Botany & Plant Pathology. Purdue University, W. Lafayette. November 1, 2007. The article provides citations to a variety of articles and current research on the numerous topic areas related to managing corn following corn. It is a well documented summary that anyone considering corn following corn should read. We recommend you access the article in it's entirety at:http://www.agry.purdue.edu/ext/corn/news/timeless/CornCorn.html. For those wanting a quick summary, below are the highlights from the article.

Nitrogen Fertility Issues

Most agronomists agree that optimum nitrogen (N) fertilizer rates for corn following corn are higher than for corn following legumes (including soybean), with estimates ranging from 30 to 50 additional lbs of N required per acre. Coupled with the oft-cited 7 to 10% lower yield potential of continuous versus rotation corn, the higher required optimum N rates for continuous corn “adds insult to injury”. Preliminary analysis of Purdue’s 2007 Nitrogen Trials from five locations agree with previously published data in that 2nd-year corn required, on average, 35 lbs/ac more nitrogen than corn following soybean even though 2nd-year corn yields ranged from 7 to 22% less (data not yet published).

P & K Fertility Issues

A one-time move to second-year corn will have negligible effects on P & K soil fertility levels. Over a number of years of corn following corn, however, growers should monitor soil phosphorus and potassium levels and adjust P & K fertilizer application rates accordingly.

Stand Establishment Issues

Mitigate the risk of poor stand establishment by selecting hybrids with superior seedling vigor ratings. If you will be switching only part of your soybean acres to second-year corn, target better-drained fields in your farming operation. Where practical, consider burying the stalk residues with tillage to better facilitate seedbed preparation and planting. Consider adopting strip tillage practices. In no-till corn with heavy surface trash conditions, consider the use of row-cleaning attachments for the corn planter. Avoid planting excessively early in order to minimize the risk of sub-optimal soil temperatures during germination and early seedling establishment. Consider using starter fertilizer, especially nitrogen, in a traditional 2 x 2 placement at rates no less than 20 lbs/ac of actual nitrogen. Consider the use of either soil-applied insecticide or insecticide-treated seed if the risk for secondary insect pests (wireworm, seedcorn maggot, etc.) is high.

Disease Management Issues

Mitigate the disease risk in second-year corn by careful hybrid selection with emphasis on resistance to specific diseases as well as on overall good plant health characteristics. Where practical, consider burying the stalk residues with tillage to reduce the abundance of disease inoculum for next year. The use of fungicides is often not considered economical for disease control in commercial feed grain corn production, although the experience of some farmers suggests otherwise. For more information on fungicide use in corn, see http://www.agry.purdue.edu/ext/corn/news/articles.07/Fungicides2007.html.

Insect Management Issues

Mitigate the insect risk in second-year corn by the judicious use of soil-applied insecticides, insecticide seed treatments (high rate formulations), or transgenic resistance (Bt-rootworm) for rootworm. Scout fields during seedling emergence for cutworm and armyworm damage to leaves and stems to determine the possible need for rescue treatments of foliar insecticides. Consider using hybrids with Bt-corn borer traits where appropriate.

Hybrid Selection Issues

Good hybrids for rotation corn tend to be good hybrids for continuous corn. Therefore, growers should first seek out hybrids that demonstrate consistent high yield performance across multiple environments (years and/or locations). Consistent performance across multiple sites is important because multiple sites represent possible weather patterns your farm may experience in the future. Consult closely with your seed sales representative and check out the latest corn hybrid performance results from non-biased sources such as http://www.agry.purdue.edu/pcpp/ Web site.

Once you have identified otherwise good yielding hybrids, then further filter among that group for hybrid characteristics important for a continuous corn cropping system. Such characteristics include hybrid traits for disease resistance, stalk strength, stalk and root health, seedling vigor, and overall stress tolerance. While always important, these traits take on extra meaning when adopting continuous corn strategies because of the increased risk of diseases and often-greater risk of early season stress during the stand establishment period.

Weed Management Issues

Mitigate the risk of poor giant ragweed and burcucumber control by adjusting weed management plans to include the use of postemergence herbicides that provide residual activity on these weeds. Shifting atrazine use from preplant to postemergence application will extend the residual window of activity and reduce late season weed emergence. Callisto, Hornet, and Peak (Spirit) containing products also provide foliar and residual activity on these weeds, unless the giant ragweed is ALS resistant and would be well suited to use as postemergence treatments.

For better control of late-emerging grass weeds and some small seeded broadleaf weeds, consider adding a reduced rate of an amide (metolachlor (Dual and other formulations), acetochlor (Degree or Surpass and other formulations), dimethenamid (Outlook), or flufenacet (Define) to the postemergence herbicide treatment. Amide herbicides will not control emerged grass weeds. If grass weeds have emerged, a postemergence grass herbicide will be required to control them. All of the chloroacetamide products listed above are labeled for application to emerged corn.

Mitigate the risk of yield loss due to late postemergence herbicide treatments by using residual herbicides at planting and making postemergence treatments before the V3 stage of corn growth. Use the WeedSOFT® Yield Loss Calculator (http://weedsoft.unl.edu/)to assist in your understanding of the impact of early-season weed competition on corn yield.

Glyphosate-Resistant Weeds. Glyphosate-resistant marestail (aka horseweed, Conyza canadensis) is widespread in southeast Indiana and southwest Ohio and effective postemergence control of marestail with glyphosate alone in this region is unlikely. In addition, glyphosate-resistant marestail has now been documented in 15 states in the U.S. In 2006 and 2007, we observed frequent giant ragweed and lambsquarter control problems with glyphosate in soybean and corn. Lambsquarter biotypes with elevated tolerance to glyphosate have been reported in Indiana and Ohio. Purdue and Ohio State weed scientists have conducted extensive field and greenhouse experiments on giant ragweed biotypes with elevated tolerance to glyphosate and have documented populations that show a low level of resistance to glyphosate.

Mitigate the risk of glyphosate resistant weeds by including a variety of herbicide modes of action, especially on weeds that are most problematic to control with glyphosate alone. If glyphosate-resistant corn was grown in a particular field in the previous year, one should also strongly consider using herbicides that rely on other modes of action on the most problematic weeds to reduce selection pressure for glyphosate-resistant weeds. This is particularly important in fields where the grower has noticed increased difficulty in controlling giant ragweed and common lambsquarter. Marestail, lambsquarter and giant ragweed are effectively controlled by many postemergence herbicides in corn. The most effective control of these weeds are usually provided by dicamba, 2,4-D, Hornet, or Callisto-based products containing atrazine, provided the applications are made before weeds are 6 inches tall.

Lambsquarter is easily controlled with tillage and many soil-applied herbicides, so effective management is not difficult if one doesn’t rely solely on postemergence herbicides. If you will be relying on glyphosate in Roundup Ready® (RR) corn and the field has lambsquarter and giant ragweed, the labels for RR corn limit the glyphosate rate to 0.75 lb ae/A.

We have shown that it is critical to use a rate and tankmix partner which is most likely to be effective with the first postemergence treatment, rather than trying to control escapes with higher rates in a second postemergence treatment. You can use state weed control guides such as the Weed Control Guide for Ohio and Indiana – Bulletin 789 to determine the most appropriate tankmix partner with glyphosate to provide effective control of emerged lambsquarter and giant ragweed.

For more information on glyphosate-resistant weeds and specific recommendations on tough to control weeds in RR cropping systems, weed scientists in the North Central region began producing publications on this topic and launched a website to distribute this information. The “Glyphosate, Weeds, and Crops Group Web Site” can be found at http://www.glyphosateweedscrops.org.

Harvest Season Issues

Mitigate the risk of stalk breakage by selecting hybrids with superior overall plant health and stalk strength characteristics. If you will be switching only part of your soybean acres to second-year corn, target better-drained fields in your farming operation. Scout fields for the occurrence of stalk rots prior to harvest and prioritize their harvest schedule if necessary to harvest “weak-kneed” fields early. Consider beginning harvest earlier than usual to avoid finishing in late fall when rain and snow prospects typically increase.

Bottom Line

The decision to switch significant soybean acres to second-year corn acres should be made cautiously with careful attention to both the economics and agronomics of such a choice. While short-term economics may favor second-year corn over soybean production, long-term economics are very much dependent on the economic assumptions made when calculating comparative crop budgets. Growers should recognize that second-year corn yields will range from 7 to 10% less than corn following soybean. Consideration of the risks outlined in this article will help minimize the downside dollar potential of second-year or continuous corn relative to corn following soybean.

Last Weekly Newsletter

This is the last weekly newsletter until April, 2008. This newsletter will be on it winter schedule with a publication every other week with the next issue on 11/20/2007. If there are issues or topics that you would like to see addressed through out the winter months do not hesitate to give any member of the Agronomic Crops Team a call. Our member directory can be found at: https://agcrops.osu.edu/about/directory.php or send an e-mail to mailto:labarge.1@osu.edu