In this week's Crop Watch:

Welcome back to Crop Watch!

This is the first issue of the 2000 publication season for Crop Watch, the NU Cooperative Extension newsletter for crop production and pest management. Readers who subscribed in 1999, but not for 2000, will receive this issue free. An order form is available on page 10 so you can resubscribe now and avoid missing future issues.

The faculty and staff at the Institute of Agriculture and Natural Resources who contribute stories and information have targeted several special issues as well as planning for the core of the newsletter — timely information on crop production and crop protection issues in Nebraska.

For more information about the newsletter, contact me by phone at (402) 472-7981 or by Email at ljasa1@unl.edu.

Lisa Jasa
Editor
Crop Watch News Service

Managing fertilizer use in dry soils

With below-normal soil moisture prevalent in much of Nebraska, producers may consider changing how they use fertilizer this spring. Dry soil influences how fertilizer can be applied and what happens to it after application.

Application rates

Of greater concern is the ability to seal the injection slot. If the soil is very dry and cloddy, the farmer may observe white "smoke" behind the applicator. This "smoke" is actually water vapor condensed from the air by escaping ammonia. Although it takes a lot of "smoke" to add up to any significant fertilizer loss, it's still best to try to minimize fertilizer loss. If vapor loss cannot be minimized by 1) going to a deeper injection depth, 2) slowing down, or 3) reducing the application rate, it may be advisable to wait for better soil conditions or switch to a different form of nitrogen fertilizer.

The amount of ammonia applied last fall for spring row crops was significantly reduced from normal levels — producers were concerned about the effects of dry soil on fertilizer retention as well as excessive wear on application equipment. Fall ammonia application is an acceptable practice on heavier-textured soils, if applied late enough that soil temperatures are cool and the likelihood of significant nitrification is low. Due to the warmer than normal winter, ammonia applied last fall may have partially nitrified and could be leached; however, dry soil conditions have generally minimized any nitrate leaching from fall-applied ammonia. Continued dry conditions will insure that fall-applied nitrogen will be in the root zone when the crop needs it this spring.

Broadcast fertilizers

Both dry and liquid fertilizers broadcast on the soil surface will be influenced by large amounts of residue, which may not have decomposed significantly due to the dry winter. Urea and nitrogen solutions can lose nitrogen to the atmosphere through ammonia volatilization when surface-applied to high residue soils. If incorporated with residue, the nitrogen in broadcast fertilizers can be immobilized in decomposing residue, resulting in delayed availability to the crop.

Starter fertilizers

Producers should be cautious about applying starter fertilizer with the seed this spring. Starter fertilizers which contain nitrogen and potassium are particularly hygroscopic — they will draw moisture away from the seed, resulting in germination damage and loss of stand. This effect will be accentuated with dry soils. Placing starter fertilizer in a band a couple of inches away from the seed will minimize the potential for germination damage.

Recent storm activity has brought temporary relief to many within the state who have been suffering through an extremely dry five-month pattern. The last two weeks have been very active, with a major snow storm and isolated thunderstorm activity. Conditions indicate this may continue for another two weeks.

Precipitation from these events has added an additional 1-1.5 inches of available water into soil profiles. Enough precipitation has fallen across southwest Nebraska to move it from a severe to a moderate drought classification. The eastern two-thirds of the state still remains under severe drought conditions, but will likely be moved into the moderate category if current short-term forecasts prove true.

The long-term outlook has not changed dramatically. The Climate Prediction Center continues to call for drier and hotter than normal conditions for Nebraska during March. In addition, the long lead outlooks call for below normal precipitation from March to September.

Southwest Nebraska has the highest probability of receiving below normal precipitation from March to May. The southern half of the state has the highest probability of receiving below normal precipitation during the April-June and May-July reporting periods. The eastern third of the state has the highest probability of receiving below normal precipitation from July to September.

Statistical analysis performed by the late Ralph Neild, NU professor of horticulture, during the 1980s indicates that the odds are remote that eastern Nebraska will make up the total precipitation deficit accumulated since September 1 before the average corn emergence date of May 15. There is only a 7-15% probability that eastern Nebraska will make up these precipitation deficits. (Local conditions may vary.)

Dr. Neild also found that fall and spring recharge were important components affecting non-irrigated corn yields. His analysis suggests that 12 inches of fall and spring moisture and normal growing season moisture are required to produce average yields. When accumulated moisture falls below 12 inches, below normal dryland yields are more likely.

As of February 28, the eastern third of Nebraska had accumulated 4-7 inches of precipitation since September 1. This indicates that 5-8 inches of moisture is needed in the next eight weeks to provide a 50-50 chance of receiving normal yields. This represents 125%-175% of normal precipitation for the period, and does not affect the need for normal growing season precipitation.

The long-lead outlooks don't look promising, but they may not be totally accurate. These outlooks are incorporating the current La Nina event into the forecasts; however if La Nina dies suddenly, these forecasts will certainly be prone to error. Perhaps the recent stormy pattern is an indication that La Nina is beginning to wane.

No-till protects the soil surface with crop residue, reducing erosion and crusting. The residue acts as a mulch to reduce evaporation and keeps the soil surface cooler. In drought conditions, unprotected soils may be too hot and dry for proper root development.

Using no-till or ridge-till can save you far more than fuel, labor, and equipment costs. The savings in soil moisture can be just as important, especially in a year when soil moisture and precipitation is limited.

Too often the soil will dry to the depth of tillage. An average silt loam soil can hold about 2 inches of available soil moisture per foot of soil. Tilling 6 inches deep and allowing the soil to dry to the depth of tillage could result in a loss of up to 1 inch of soil moisture. Shallower tillage, even row crop cultivation, can still result in moisture losses of about ½ inch. By not tilling or cultivating, you can minimize these moisture losses.

Some say the soil needs to be tilled to "open it up to let water in". Unfortunately it dries to the depth of tillage so the initial water let into the soil just replaces what was lost rather than adding to the soil moisture reserve. Tillage breaks up and pulverizes the soil surface, making the soil prone to crusting from raindrop impact. Tillage actually creates a condition that seals the soil, resulting in more runoff.

Disking dries the soil and destroys soil structure.

Tillage destroys the residue cover that protects the soil from raindrop impact, reducing erosion and crusting of the soil and allowing more rainfall to soak in. The residue also slows water runoff allowing time for infiltration and acts as a mulch to reduce moisture evaporation from the soil.

Some people recommend tillage for herbicide incorporation for better weed control. While very shallow tillage with good soil mixing may help weed control, it also dries the soil and "plants" weed seeds. Deeper tillage dilutes the herbicide with more soil and dries the soil even more. Rainfall will incorporate herbicides more uniformly than a tillage operation, provided the herbicide label allows it and the herbicide is applied early enough to receive rainfall. Usually there is enough rain in early April to activate a preemergence herbicide; however the chances diminish by waiting until late April or until after planting when weeds may have already gotten a start.

Higher fuel costs — about 40% more this year — also are a factor when considering tillage. The diesel fuel requirements for the typical disk-disk-field cultivate tillage system is about 3.77 gallons per acre including knifing in fertilizer, planting, and one row crop cultivation. By switching to a no-till system, the fuel use decreases to about 1.43 gallons per acre including knifing in fertilizer, planting, and two sprayings. There is a corresponding decrease in labor requirements and an improvement in planting timeliness without preplant tillage.

Unwanted or excess pesticides can be safely disposed of at 20 sites statewide between March 14 and April 7.

Agricultural, home, structural, lawn and garden pesticides will be accepted for disposal; however, those in pressurized containers will not be accepted.

In the past three years, this cooperative venture between the Nebraska Department of Agricultureand NU's Cooperative Extension Division has disposed of more than 1.1 million pounds of pesticides through incineration. Local businesses and government agency staff also provide assistance at individual sites.

Preregistration isn't necessary to deliver pesticides to any of the sites and there are no fees for up to 1,000 pounds of pesticides. If products total more than 1,000 pounds, the Nebraska Department of Agriculture will charge $1 per pound for each pound over 1,000. To make arrangements to dispose of more than a half ton of pesticides, contact Rich Reiman at the Nebraska Department of Agriculture at (402) 471-2394. This provides advance notice to the disposal subcontractor if special handling is needed.

The subcontractor receiving, handling and disposing of the collected materials is NSE Environmental of Lincolnshire, Ill. They will take the pesticides to El Dorado, Ark., for incineration.

The program accepts waste pesticides only. Oil and oil filters, antifreeze, paint, varnishes, thinners, cleaners and solvents will not be accepted.

Collection dates and sites, all of which are open from 8 a.m. to noon, are:

• March 14: ABK Fencing, Tecumseh
• March 15: Papio Missouri River NRD, Omaha
• March 16: Wal-Mart parking lot, Fremont
• March 17: Farmers Co-op elevator, Plymouth
• March 20: Farmers Co-op, York
• March 21: Aurora Co-op, Aurora
• March 22: Fairfield Non-Stock Co-op, Fairfield
• March 23: Ord Airport, Ord
• March 24: Custer County Weed Control, Broken Bow
• March 25: Kearney Recycling Center, Kearney
• March 27: Agri Co-op, Holdrege
• March 28: Red Willow County Fairgrounds, McCook
• March 29: Grant Co-op, Grant
• March 30: WESTCO, Alliance
• March 31: Swann Transfer Station, Chadron
• April 3: Helena Chemical Co., Bassett
• April 4: Central Farmers Co-op, O'Neill
• April 5: Cedar Valley Ag Services, Albion
• April 6: Madison County Weed Control, Norfolk
• April 7: NU Haskell Ag Laboratory, Concord

The pesticide disposal project is funded by a Nebraska Environmental Trust Fund grant to the Nebraska Fertilizer and Ag Chemical Institute and a U.S. Environmental Protection Agency grant to the Nebraska Department of Environmental Quality.

Designing a Bt refuge for your field

One of the issues concerning the use of Bt transgenic corn hybrids is resistance management. European corn borer (ECB) larvae that feed on Bt corn are exposed to much higher levels of the Bt toxin over a much longer time than with the use of foliar Bt insecticides, such as Dipel or M-Peril. Under this high level of selection pressure, the potential for resistance developing is high. Resistance management strategies have been designed to prevent or at least delay this.

An important principle of resistance management for European corn borers and Bt corn is the use of refuge plantings. A refuge is any ECB host plant (e.g. non-Bt corn, potatoes, and some weeds) not producing Bt proteins or not being treated with conventional Bt formulations. The purpose of the refuge is to supply a source of Bt-susceptible ECB that could mate with resistant ECB potentially emerging from nearby Bt corn. In current resistance management strategies the refuge must be non-Bt corn because other ECB host plants do not produce enough moths. Specific resistance management information will be a part of each corn seed bag label. Be sure and discuss resistance management with your seed dealer.

The EPA has established the following resistance management requirements for 2000.

1. On each farm, growers may plant up to 80% of their corn acres with Bt corn. At least 20% of their corn acres must be planted with non-Bt corn and treated only as needed with insecticides. Decisions to treat the refuge should be based on economic thresholds. Conventional Bt products (liquids or granules) must not be used on the non-Bt refuge.

2. Plant non-Bt corn refuge within, adjacent to, or near to the Bt cornfields. If the grower intends to treat the refuge it should be placed within 1/4 mile of the Bt field, if at all possible. In any case, the refuge must be placed within 1/2 mile of the Bt field.

3. If refuge is established as strips within a field (Figure 1E), the strips should be no narrower than six rows.

4. If possible, locate refuge plantings to protect potentially vulnerable non-host insects (e.g. Monarch butterfly). Refuge plantings can serve as buffer zones between the Bt cornfield and the habitat of non-target insects.

   Figure 1 presents some general refuge configurations for use within fields.

Refuge Considerations

Linear blocks, brackets, or border refuge plantings (Figs. 1A, B, and C) are relatively easy to plant, treat, monitor, and harvest. They have the added advantage of acting as buffer areas between the Bt corn and non-target habitat or non-GMO cornfields.

Strips (Fig. 1E) have the advantage of providing susceptible ECB to all parts of the Bt field, but they also have several drawbacks. Strips cannot be treated separately from the Bt corn.

Harvest may be difficult if non-Bt strips dry down differently than the Bt corn. Also, it is difficult to keep track of where the strip rows begin and end, so monitoring is more difficult.

Do not plant strips narrower than six rows or mix seed. This increases the risk of resistance occurring because ECB larvae often move from plant to plant. Corn borer larvae that can survive eating small amounts of Bt (low level resistance or tolerance) can end up on a non-Bt plant and survive.

The design for planting strips will depend on your planter. For example, dedicating three end row units of a 12-row planter will effectively give you a 25% refuge and maintain the six-row strip size. If you have a six-row planter you can achieve the 25%, six-row refuge by splitting the planter into three units of Bt and three units of non-Bt. Only strip half of the cornfield. Four-row or single-hopper planters are not suitable for this refuge option.

The European corn borer that is susceptible to Bt from the refuge must be present at the same time as possible Bt-resistant ECB from the Bt corn. To achieve this the corn hybrid in the refuge should be agronomically similar (e.g. similar days to maturity) to the Bt hybrid, planted at the same time as the Bt field, and managed in the same manner as the Bt field. In this way the ECB moths will be equally attracted to the refuge and Bt cornfield. Larvae also will develop at the same rates and emerge as adults at the same time.

Using a neighbor's cornfield as a refuge is not allowed because the hybrid selection, planting time, pest control, and other production activities are not under the control of the grower planting the Bt corn.

Planting only non-irrigated pivot corners as refuge is not recommended because the corn plants in these areas are significantly different and less attractive to ECB moths than the corn under irrigation. Remember, the idea is to produce some Bt-susceptible ECB moths.

The closer the refuge is to the Bt field the better. This brings Bt-susceptible ECB in close proximity to any Bt-resistant ECB that may survive in the Bt cornfield. Female ECB generally mate close to where they emerge as adults, so having nearby refuge increases the chances that susceptible ECB will mate with a resistant ECB.

You can use a combination of refuge configurations to meet the required 20% refuge.

Figure 2 presents two examples of how you might establish a refuge for a Bt cornfield.

Fewer herbicides than usual are being introduced to the ag market this year as many companies seem to be reacting cautiously to volatility in the ag market and uncertainty about marketing GMOs.

We expect to see combinations of several currently labeled herbicides as well as an influx of glyphosate products into the market.

With commodity prices and soil moisture conditions at less than favorable positions, producers may want to carefully examine their crop insurance options this year. The deadline for applying for multiple-peril insurance for corn, grain sorghum, and soybeans is March 15.

While the forecasts for drought are a concern this year, a variety of factors can affect the crop, both positively and negatively, and reacting to weather predictions alone would not be good risk management. Base the amount of crop insurance you buy on your needs if a disaster does occur, rather than just on the possibility of adverse weather alone.

Determine your insurance needs based on your financial situation, your own risk tolerance, and your marketing plan, then decide what coverage you want. Also consider what low yields, low commodity prices or a devastating storm would do to your operation.

This year's federal crop insurance program offers several new options and the opportunity for producers to guarantee revenue despite low commodity prices. In addition, the government is providing an additional 25 percent discount for insurance premiums purchased above the minimum, allowing producers to obtain more insurance coverage without increasing costs. This is a decrease from the 30% available in 1999.

Insurance agents will be able to provide information on the costs of various coverages, but you need to assess what's cost efficient for your operation. There are two aspects to consider:

1. your cash flow needs to cover operating expenses, debt payments and family living costs and how much crop insurance you need to meet those needs; also consider the cost efficiency and whether the expense of high end coverage is worth the added expense for your operation.

2. your marketing plan and how you can use crop insurance as a base to do some forward pricing before harvest, and how it may affect how much insurance you need.

Insurance options

There is a minimum catastrophic coverage, for which the price election has been reduced from 60% to 55%. Several "additional" insurance options are also available under the Multiple-Peril Crop Insurance (MPCI) program.

1. Catastrophic Coverage (CAT) — Provides coverage at 50% of the Actual Production History (APH), yield with insurance payments based on 55% of the established price.

2. Additional APH Insurance — Up to 75% yield coverage and 100% price elections. The guarantee is based on producer records of actual yields for up to 10 consecutive years. If less than four years of records are provided, an FCIC transitional yield is used for the missing years.

3. Group Risk Plan (GRP) coverage is based on county yields and is available in some counties. The maximum dollar protection under GRP is the expected county yield times the GRP price x 1.5. Indemnity payments are based on the percentage short fall of the NASS (Nebraska Agricultural Statistical Service) county yield compared to the trigger yield. The trigger yield is the coverage level chosen by the producer times the expected county yield.

4. Crop Revenue Coverage (CRC) provides a revenue guarantee and is available for corn, grain sorghum, soybeans and winter wheat in Nebraska. In 2000 in Nebraska, 80-85% coverage is available for corn, soybeans and sugar beets.