Skip Navigation

5/11/2009 - 5/17/2009

Drift Management Considerations

By Mark Hanna, Department of Agriculture and Biosystems Engineering and Kristine Schaefer, Pest Management and the Environment

Warmer weather means emerging crops and more outdoor activities. Locally produced foods are expanding and home gardening is showing increased interest as a way to save costs. These and other factors make it particularly important to review spray drift reduction procedures.

Increasing droplet size so that small droplets don’t become entrained in ambient air currents is a key to drift reduction. Seasoned readers of ICM News should already be familiar with common procedures to reduce drift. Techniques include:

• Operating nozzles at a lower pressure
• Using a larger tip size (which also lowers pressure for a given application rate)
• Maintaining boom height at the lowest level consistent with nozzle overlap
• Using a low-drift nozzle style such as venturi or air-induction tip
• Driving more slowly near field borders when using a spray controller (lowers pressure)

In addition, weather factors are important. Avoid off-site drift by spraying when wind speeds are below 10 miles/hour (mi/h), with prevailing winds away from sensitive areas, and avoiding application during dead calm conditions (e.g., atmospheric inversion). If high wind speeds have persisted for several days and weeds or pest populations are continuing to grow, applicators may feel compelled to go ahead with applications. Before filling the sprayer and heading to the field, it’s good to review just how far a spray droplet can travel.

All nozzle tips produce a range of droplets, although low-drift style nozzles minimize the number of small sized droplets (fines). As shown in the chart below, droplets 200 microns and less in diameter can travel across fence lines 25 feet or more with wind gusts of 15 mi/h.  In some cases, a non-herbicide resistant crop or sensitive plant species may be only a few feet across a property line. Adjusting nozzle type and sprayer pressure and leaving an unsprayed buffer area may be necessary in certain situations. 

drift distances



Mark Hanna is an extension agricultural engineer in agricultural and biosystems engineering with responsibilities in field machinery. Hanna can be reached at or (515) 294-0468.  Kristine Schaefer is a program specialist in the Department of Entomology serving on the Pesticide Management and the Environment team. Schaefer can be reached by email at or by phone at (515) 294-4286.

Assessing Corn Stands for Replanting

By Roger Elmore and Lori Abendroth, Department of the Agronomy

As of May 10, eighty-one percent of Iowa’s corn was planted and 24 percent was emerged, according to USDA-NASS. Some planting undoubtedly occurred since May 10. Good to excellent crop emergence reports come from across the state by ISU Extension Agronomists.  There are a few reports though of less-than-desirable corn emergence due to crusting, poor seed bed, herbicide damage, etc. As the crop emerges, this is a great time for producers to assess their corn stands. What went well? What didn’t? What action should be taken?

Two situations may cause producers to consider replanting
• Corn emerged non-uniformly resulting in different plant developmental stages within a row. Replanting a field like this will not be a benefit as long as plant populations are reasonable. Although the smaller plants compete with their larger neighbors for resources, only extreme conditions warrant replanting. If half the plants are two leaves behind the rest of the plants within a row, yields can be reduced by 5-10 percent. Estimate yield loss in fields exhibiting non-uniform development using a tool on uneven emergence posted at the agronomy extension website

 • Corn populations are significantly lower than desired. Replanting may benefit the producer in this case. Consider several things and make comparisons when determining if a specific field fits this category:

a) Estimate stands. Measure the existing plant population in several random areas in the field.  Use the Replant Checklist† for steps to evaluate an existing stand in a problem field. 

b) Estimate yields. The most important factor in deciding whether or not to replant is to calculate expected yield with the current stand versus what you could potentially have if you replanted. Table 1 provides some guidelines for this decision. Data contained here show relative yield potential for numerous planting dates and plant populations based on recent yield data, planting date trends, and modern ranges in plant populations.

assessing corn stands


A producer has a field that may need to be replanted and could be done next Monday, May 18. The field was originally planted April 26 but has a final stand of 24,000 plants per acre. Is there a yield advantage to replanting?

The yield potential associated with the existing stand is 95 percent since the planting date is between April 20 and May 5 and the population is close to 25,000 plants per acre. If the field is replanted at 35,000 plants per acre, yield potential is approximately 87 percent. In this example, the producer increases yield potential by leaving the original stand and not replanting. Realize also, extra costs not only will occur from replanting upfront but also potentially post-harvest due to higher grain moisture content.

Replanting is not an easy decision.  Numerous factors determine a field’s yield potential. Consider data like that presented in Table 1 as a tool in approximating what may result based on our best available research data. Realize that actual yield losses may be greater or less than what is shown.


†  When using the ‘Replant Checklist’ make sure to use Table 1 in this newsletter for determining yield potential rather than Table 2 shown in the ‘Replant Checklist’ webpage article. The latter was based on older research data.


Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. Lori Abendroth is an agronomy specialist with research and extension responsibilities in corn production. Elmore can be contacted by email at or (515) 294-6655;Abendroth can be contacted by email at or (515) 294-5692.

May Crop Outlook

By Chad Hart, Department of Economics

With the May reports, USDA updated its estimates for 2008/09 and put out its first official estimates for 2009/10. On the corn side, ethanol and export demand are increased by 50 million bushels each for 2008. Both of these uses have experienced a rebound over the past few weeks.

With feed usage holding steady at 5.35 billion bushels, ending stocks are projected at 1.6 billion bushels, roughly in line with the ending stocks level coming out of the 2007 crop. The estimated season-average corn price for 2008/09 held steady at $4.20 per bushel and futures at the close of business before the reports were roughly in line with USDA. 

For 2009, USDA set acreage at 85 million acres, from the March Prospective Plantings report, but set yields at 155.4 bushels per acre, 1.5 bushels below trend due to the lack of planting progress in the eastern Corn Belt.  While Iowa has planted over 80 percent of its corn, slightly ahead of average, Illinois and Indiana are way behind schedule.  Typically, Illinois would have nearly 85 percent of its corn planted by this time and Indiana would have 70 percent.  This year, both states are around 10 percent. 

Given the yield adjustment, projected production for 2009 is set at 12.09 billion bushels, slightly below last year’s level. Ethanol and export demand are projected to increase again, with feed usage declining (offset by higher availability of distillers grains). Ethanol demand is expected to reach 4.1 billion bushels, following the Renewable Fuels Standard levels. Export demand is expected to increase as international feed demand is projected to recover and feed wheat supplies are somewhat limited. Ending stocks are estimated at 1.145 billion bushels, with usage continuing to grow and production holding steady. The season-average price for 2009/10 is projected at $4.10 per bushel, down 10 cents from 2008, but up 50 cents from USDA’s unofficial outlook in February.


planting date chart


For soybeans, 2008/09 crushing demand is increased by 5 million bushels to 1.64 billion bushels, while exports added 30 million bushels to reach 1.24 billion bushels. These changes send projected ending stocks to 130 million bushels, so projected stocks are very tight once again. China continues to lead the export market and the reduction in the South American soybean crop has allowed U.S. soybean exports to continue deeper into the marketing year. The 2008/09 projected season-average price is $9.85, up 20 cents from last month based on the strength of export demand and the tight stock situation.

For 2009, acreage is set at 76 million acres and yields are held at trend, 42.6 bushels per acre. Planting progress is slightly behind in Iowa and significantly behind in Illinois and Indiana. In fact, soybean plantings in Illinois are less than one percent of expected so far. The delays in planting are not projected to impact production, estimated at 3.195 billion bushels, just under the record from 2006. Domestic crushing is projected to increase slightly, but exports are expected to continue at a record pace for the 2009 crop. Ending stocks for 2009 are estimated at 230 million bushels, as the production gains exceed the usage increases. Season-average prices are projected at $9.45 for the 2009 crop year.

Weather and planting progress will remain the major driver for crop prices over the short term. Exports have been supportive as well. Longer term, the markets will continue to watch the development of biofuel regulations. The recent releases by the California Air Resources Board and the federal Environmental Protection Agency, incorporating indirect land use change and greenhouse gas emissions, were seen as negatives to the biofuel industry. But these policies are being phased in over a few years and are subject to additional review, so biofuel policy uncertainty remains.



Chad Hart is a grain markets specialist and an assistant professor of economics with research and outreach responsibilities in grain and bioenergy crop marketing. Hart can be reached at or by calling (515) 294-9911.

Degree Days - Slow but Steady Progress in Planting

by Rich Pope, Corn and Soybean Initiative

Iowa recorded temperatures close to season normals the week of May 4. Seasonal accumulated degree days are hovering near average in all crop reporting districts.

accumulated degree days as of May 10, 2009

Scattered rainfall limited field work in some areas, but statewide another one-fifth of corn acres were planted, raising the planted acreage in Iowa to around 80 percent. Between one-fourth and one-third of the corn can now be rowed. Soybean planting has picked up, and about 20 percent is now planted.

There are some concerns about stand establishment in corn fields. Areas with rotting mesocotyls were reported, especially in the southern third of Iowa. Also, a few reports of crusts interfering with emergence were maded; light rains have alleviated the problem in some cases.

Early in the season, crop planting and emergence in Iowa are leading the Corn Belt. Reports of planting delays are particularly common in Illinois, Indiana and Ohio.


Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted by email at or by calling 515-294-5899.

May 11 Crop and Weather Report

Iowa State University Extension climatologist Elwynn Taylor, integrated pest management specialist Rich Pope, plant pathologist Daren Mueller and corn agronomist Roger Elmore join Doug Cooper for the weekly crop and weather report on May 11.

Taylor says weather patterns are starting to show a wet period moving into the Corn Belt and that could be very bad news for Illinois, Indiana and Ohio. La Niña continues to lose strength and should not be factor in the 2009 growing season.

Weed control early in the growing season is very important and producers should begin scouting fields soon, according to Pope.

Mueller reports soybean rust survived the winter in Louisiana and will be watched for any movement north this summer.

Elmore tells Cooper planting progress is encouraging and barring any weather delays corn farmers should complete corn seeding very soon. He says crusting remains a problem in areas of the state that received very heavy rainfall.

New Funding Opportunities for Organic Production in Iowa

By Kathleen Delate, Departments of Agronomy and Horticulture

Farmers interested in transitioning into organic agriculture or expanding their organic acres in production have a three-week period to sign up for government support beginning May 11. This new initiative from Congress, announced May 5, addresses the special "organic conversion assistance" component of USDA-NRCS-EQIP (Environmental Quality Incentives Program).

Funding under the organic conversion section of the farm bill is capped at $20,000 per farm per year; and $80,000 per farm in any 6-year period. The sign-up period runs Monday, May 11 through Friday, May 29 at local NRCS offices.

Six core conservation practices (conservation crop rotation, cover cropping, integrated pest management, nutrient management, rotational grazing, and forage harvest management) are being made available to transitioning organic farmers on a nationwide basis. Each state may then also add a variety of "facilitating" conservation practices specific to the type of agriculture in their region.

Organic farming has the potential to provide strong environmental benefits for soil and water quality, climate change mitigation, and biodiversity. In recognition of this fact, Congress retooled the EQIP program in the 2008 Farm Bill, providing an overall EQIP priority for organic farming, as well as a specific EQIP subcomponent for farms converting in whole or in part to organic farming. The new initiative addresses the special organic conversion assistance component of EQIP in particular.

Organic farmers may opt to compete in this special pool with the tighter payment caps, or may opt instead to compete in the regular EQIP pool for which the 6-year cap is $300,000. However, under the new initiative, farmers will receive higher payments, relative to conventional EQIP rates, for five of the six national core practices for organic conversion option. The higher payment rates reflect the higher management costs associated with the mandatory three-year organic transition period and the higher ongoing management costs associated with organic farming.

For more information, contact Larry Beeler, Assistant State Conservationist for Programs, Iowa NRCS at (515)284-4355.


Kathleen Delate is an extension organic agriculture specialist. She can be reached by email at or phone (515) 294-7069.

This article was published originally on 5/18/2009 The information contained within the article may or may not be up to date depending on when you are accessing the information.

Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.