Second, an early preplant treatment reduces most if not all weed competition as the crop emerges from the soil. Although this early competition may not be the most critical with respect to yield, it can quickly reduce yield as corn enters the two-leaf stage. Another advantage is that in years with limited moisture, the herbicide has a greater chance of being activated before the crop emerges. A disadvantage of the early preplant treatment is decreased residual activity after emergence. Common sense tells you the earlier a herbicide is applied to the soil, the earlier it will stop working. Postemergence programs need to be carefully evaluated and the weed history of the field needs to be considered before selecting a weed control strategy.

Preplant is similar to early preplant and many of the same herbicides can be used. Treatments are typically made 0-10 days before planting. Preplant doesn’t give you the advantage of catching early weeds, but it may give you the needed residual for setting the stage for a good POST treatment. A preemergence treatment applied after the crop is planted but before emergence offers many of the same advantages. An additional advantage is that it allows the producer to increase the length of control. This works well with conventional till fields. This also provides increased management flexibility later in the season as summer annuals begin to emerge.

Table 2 lists labeled preemergence herbicides and their application timings. As always, read, understand, and follow the label supplied with each product. For further evaluation of herbicide efficacy on weeds and weed/crop competition, see the 2001 Guide For Weed Management in Nebraska. It is available at your local Cooperative Extension Office.

Brady Kappler
Weed Science Educator
Alex Martin
Extension Weed Specialist

Jumpstarting your corn crop --

When and where to use starter fertilizers

The response of corn growth and yield to starter fertilizer depends on the date of planting (the weather before and during emergence), starter fertilizer formulation, placement method, soil tillage (residue coverage), and soil test nutrient levels (including possible nutrient stratification). Rates of root growth and nutrient uptake are particularly low on cool, wet soils, soils with generally low nutrient status, or soils with compaction. The wide variation in these factors and their possible combinations explains why many research studies seem to provide inconsistent results. In addition, starter fertilizers also appear to lower grain moisture content at harvest. When assessing the profitability of using starter fertilizers, this also must be considered.

Current UNL recommendations are based on the assumption that starter fertilizer is a good method to get phosphorus into the ground but it often does not add much economic benefit when soil tests are above the critical level. However, most research on starter fertilizers for row crop production in Nebraska has been conducted in tilled conditions. Research in Kansas, Iowa, South Dakota and Minnesota, suggests that a more differentiated view on starter fertilizers is required. In general, starter fertilizer for corn is more important in high-residue, reduced tillage systems than with conventional tillage.

Consider the following guidelines:

1. On no-till or ridge-till soils with soil test levels of less than 15 ppm Bray-1 phosphorus, always apply a liquid or dry nitrogen-phosphorus starter fertilizer. Application rates depend on the placement method (see below). For placement of at least 2 inches to the side of the seed, starter fertilizer should be applied at a rate of 20-30 lb N/acre and 10-20 lb P₂O₅/acre. On eroded soil with less than 2% organic matter, add 5-10 lb sulfur to the starter mix. On sandy soils with relatively low soil test potassium level (less than 150 ppm K), consider adding about 10 lb K₂O to the starter mix.
   Note: Rates cited above refer to 2 inches to the side of the seed or 2 x 2 inch starter placement (2 inches to the side of the seed and 2 inches deep). If that is not possible and starter is applied in-furrow with the seed, reduce the nitrogen rate in the starter and drop KCl from it to lower the salt index to below 10 lb/acre. Those nutrients must then be applied by other means.

2. On no-till or ridge-till soils with high soil organic matter, phosphorus (>15-20 ppm) and potassium levels (>150-200 ppm), yield response to starter fertilizer is less certain and mainly occurs in years with cool weather after planting. Starter fertilizer can be applied to supply all the fertilizer phosphorus needed, but nitrogen rates should be reduced. Sulfur or potassium should only be included if local field tests indicate a response to starter application of those nutrients.
   Note: Response to starter fertilizer has been found even on soils with medium to high soil test phosphorus or potassium and probably depends on the degree of nutrient stratification that has occurred in the past, i.e., the length of no-till or ridge-till cultivation. The frequency of a profitable response to starter fertilizer generally increases with decreasing soil test P and K levels, so knowing those is important for deciding on starter rates. Research in Illinois and Wisconsin also suggests that response to starter is larger with late planting of corn and use of longer-duration hybrids.

3. On fine-textured soils with conventional tillage (disk, chisel, plow), yield response to starter fertilizer is erratic and often not economical. Yield response is likely at low soil test phosphorus and or potassium levels combined with cool weather during early growth. Focus on maintaining soil test phosphorus and potassium in optimal ranges through a dry fertilizer program (broadcast). As long as soil test levels are low to medium only, apply starter fertilizer at a reduced rate in addition to broadcasting phosphorus or potassium or band-apply phosphorus at a 50% rate. Once soil test levels are in the optimal range, focus on maintaining them and concentrate on accurate soil testing.
   Note: In on-farm trials conducted in Nebraska, the average corn response to starter fertilizer when available soil phosphorus was less than or equal to 10 ppm was 4 bu/acre with yield increases in 60% of the trials; otherwise, the mean gain was just 2 bu/acre with significant increases in only 17% of the trials. Corn yield was increased by an average of 10 bu/acre when starter fertilizer was applied to sandy and sandy loam soils, while the mean response was only 0.2 bu/acre on fine texture soils. Most of this work was done on tilled soils.

4. Placement: Agronomically, placing dry or liquid starter 2 inches to the side on the soil surface or 2 inches to the side of the seed and 2 inches deep provides the best response and allows applying higher rates without crop damage. If this kind of placement is not feasible, reduce rates, particularly those of nitrogen and potassium, and place the starter over the row. In-furrow placement increases the risk of salt effects on emergence and should only be used at lower rates of starter fertilizer, not exceeding a salt index of 5-10 lb/acre. (See Starter Fertilizers for Corn, Grain Sorghum, and Soybeans,NU NebGuide G77-361) for estimating the salt index of starter fertilizer). Also note that starter fertilizers are hygroscopic — they will draw moisture away from the seed, resulting in germination damage and loss of stand if corn is planted into very dry soil and the starter is placed too close to the seed.

Achim Dobermann
Soil Fertility Specialist

With mixed crops and pastures, ensure all pesticide restrictions are followed

Herbicides and insecticides are commonly used in hay fields and pastures to control weeds and insect pests. They can be very effective, but they must be used according to label instructions or serious problems can occur.

This can cause difficulty for forage producers who have increased their use of mixtures of grasses and legumes, especially with alfalfa. A pesticide must be labeled for use on each component of a mixture to be legal to use. Thus, a pesticide that is registered for use on alfalfa but not for grass should not be applied to a pasture or hay field that contains a mixture of alfalfa and grass, even if over 50 percent of the stand is alfalfa.

What could happen if you use one of these pesticides improperly? When misuse occurs, the appropriate state agency has the authority and is expected to take whatever action is needed to keep any potentially affected food or feed commodity out of the channels of trade until it is determined that no harmful or illegal residues will occur. That could include all the hay produced from the treated area. It also might involve livestock that grazed the treated pasture or even milk produced by cows fed hay from the improperly treated area. As you can tell, the penalty could get quite severe.

So -- as you discover insects or weeds you wish to spray in pastures and hay fields this year, carefully read the pesticide label to make sure it is approved for all the plants in your field. If you don’t, the consequences could be serious.

Bruce Anderson
Extension Forage Specialist

Setting planters and drills for the season

In the shop

• Read the owner’s manual for suggested maintenance and lubricate as directed.
• Check the operation of the seed metering devices and replace worn parts.
• Adjust the seed metering devices using this year’s seed to match seed size and shape.
• Check, adjust, and lubricate chains, sprockets, bearings, and fittings. Replace worn ones.
• Adjust or replace the seed-furrow opener disks and other ground engaging components.
• Properly inflate the all tires, including those on the tractor.

In the field before planting season

• Set the toolbar and the hitch point at the proper height to match soil conditions and any ridges.
• Level the planter from front-to-rear, slightly tail down to help with seed-to-soil contact.
• Blind plant a short distance to check operation: check residue cutting and handling, check penetration to desired seeding depth, evaluate seed-to-soil contact, and evaluate closing the seed-vee.
• Adjust downpressure springs to improve residue cutting and seedbed penetration.
• Add weight as needed for the downpressure springs to work against and to keep the drive wheels in firm contact with the ground to avoid slippage.

In the field during planting season, especially when changing fields

• Check residue cutting and handling. Leave more residue over the row as the weather warms up to reduce seedbed drying.
• Check planting depth and seed-to-soil contact. Back off on pressure in wet soils that are easily compacted.
• Slow down to improve seed placement uniformity.
• Check seed spacing for proper population.
• Adjust harrows on drills to redistribute residue and help close the seed-vee.

Paul Jasa
Extension Engineer

Row cleaning can enhance no-till corn production

The effects of crop residues and their removal from the row area in no-till systems have been inconsistent in the Corn Belt. In most of the studies, the crop residue was removed at planting. In Iowa, removal of residue from a 6-inch band resulted in increased corn plant emergence, but only occasionally increased yield. In southern Minnesota, emergence of corn following corn reached 50% four days earlier with row cleaning and yields of corn after corn and of corn after soybeans were an average of 5 bu/A more with row cleaning. The benefit of row cleaning was greatest when anhydrous ammonia rather than ammonium nitrate was the main nitrogen source, and when no starter fertilizer was applied.

As part of the Nebraska Soybean and Feed Grains Profitability Project, Jerry Mulliken has conducted replicated trials on his farm in Dodge County for four years to evaluate the effect of row cleaning on corn yield following soybean. He cleans a 6-inch band 14 days before planting when he applies the pre-plant herbicide. Mulliken uses a notched or tined furrow opener running just below the residue layer, while moving less than 1 inch of soil. By combining the row cleaning operation with the herbicide application, the added cost is estimated to be $3/A. The average gain in corn yield with row cleaning has been 5.5 bu/A (see table). The reason for the increase yield is not apparent, especially since the harvest population was not increased.

While the response to row cleaning in the southern Minnesota study was greatest if no starter fertilizer was applied, Jerry’s trials have been done with 4-6 gallons of 10-34-0 applied in the seed furrow to strips where crop residue was removed and to the strips where residue remained.

Row cleaning 14 days before planting appears to be sufficiently promising that no-till producers may want to test it by conducting replicated comparisons on one or more of their fields. Row cleaning in the fall might be considered although wind or weather may move the residue. Combining row cleaning with another operation is important to reducing costs. Row cleaning on highly erodible land can result in increased soil erosion, especially when planting up and down slopes.

Charles Wortmann
Extension Nutrient Management Specialist

Table 1. Plant population and yield variances in cleaned and uncleaned corn rows. (Mulliken) Year Plant population Yield, bu/A Residue removed Residue remained Residue removed Residue remained 1998 17,800 18,100 122 119 1999 20,800 20,400 130 127 2000 17,600 16,800 138 130 2001 18,800 21,500 120 112 Mean 18,700 19,200 127.5 122.0

New options for controlling seedling insects and corn rootworms

Recently, a couple of changes have occurred in the fight against seedling attacking insects. Several liquid insecticides have become labeled for use, and advances in seed coating technology have allowed insecticide to be applied to the seed, enabling farmers to buy pre-treated seed that is ready to plant. While these products are primarily for seedling insect control, some of the new treatments are labeled for protection against corn rootworms and other crop pests.

Seed applied insecticides

While seed coating advancements have led to increased protection from more pests, the costs of these pre-treated products are higher than the traditional hopper-box treatments. These seed-applied insecticides do offer several advantages:

1. Uniformity of treatment on each seed.
2. Ease of use; no mixing, measuring or special equipment is required.
3. Less exposure to insecticide residues and dusts.
4. Rates of active ingredients are low compared to soil insecticides.
5. Some are systemic and will provide some control of foliage feeding insects such as flea beetles.

1. Increase plants stands. They only help protect what you plant.
2. Protect against poor germination due to mechanical damage to seed, poor storage, genetic differences, or poor farming practices.
3. Most products do not give season long protection. Many only last as long as it takes for the plants to emerge or germinate.
4. Protect against all insects.

Table 2. Wireworm study, Nebraska City, 2001 (Hand-planted plots), 35 plant maximum stand possible (3 repetitions) (Z B Mayo) Treatment Rate of product or amount ai Plant population 6/29/01 Cruiser (Adage) 50 g ai/100 kg 31.5 Cruiser (Adage) 100 g ai/100 kg 31.0 Cruiser (Adage) 200 g ai/100 kg 31.8 ProShield 30.3 Kernel Guard Supreme 26.5 Untreated 22.0 Untreated 23.5 Force 3 G 4 oz/1000 ft of row 30 (LSD = .05 (alpha = 4.6)

As stated earlier, the newer seed- applied insecticides are attempting to go beyond the traditional early season protection role. Not only do they protect against early season insects such as wireworms and seedcorn maggots; some are labeled for use against other pests such as flea beetles and corn rootworms.

Gaucho and Prescribe from Gustafson are new products commonly available for corn. Many seed companies are now making these treatments available as an option. The active ingredient in both is imidacloprid, a systemic insecticide that has been used in other crops such as sorghum. The product used for both Gaucho and Prescribe is Gaucho 600. The imidacloprid rate for corn varies according to the target insects. If only seedling insect control is desired, the rate is lower and will be sold under the name Gaucho. Two rates of Gaucho will be available, one for field corn and another higher rate for more susceptible inbreds (Gaucho Extra). Gaucho, although systemic, does not claim to protect the seedling plant from wireworm attack after the plant has emerged from the seed. Flea beetle control is expected through the first true leaf stage for Gaucho and through the fifth leaf stage for Gaucho Extra. When the rate is increased further to provide suppression of corn rootworms, the product is sold under the brand name Prescribe. “Suppression” is a category we would rather not see on a label, but it does indicate that some mortality of target insects will occur. However, under certain conditions, control may not be considered satisfactory. It is expected to give much longer control of flea beetles.

These products will be sold through your seed dealer as pre-treated seed and the cost will range from approximately $9-$11 a bag for Gaucho to about $40 a bag for Prescribe. Cost per acre will vary with the planting rate. (i.e. at 80,000 kernels a bag, 30,000 planting rate at $10 per bag; 80,000/30,000 = 2.66 acres planted per bag; $10/2.66= $3.75/acre cost).

ProShield from Syngenta is a tefluthrin-based seed treatment also labeled for control of corn rootworms that was used in some fields in 2000 and 2001. The seed is coated with Force ST equivalent at approximately two-thirds of the rate of granular Force insecticide. Cost of ProShield will be similar to that of granular insecticides ($15-$18 an acre based on seeding rate).

Clothianidin is a new systemic material from Gustafson. Clothianidin is still in the testing stage but may soon be available.

Cruiser (formerly tested and known as Adage) is a systemic from Syngenta. We do not know how much, if any Cruiser will be available for 2002.

Many growers are now applying liquid insecticides in-furrow with or without starter fertilize. We included Warrior, Pounce, Regent and Capture in our experiments (see Table 1). We also included granular insecticides at various rates.

2001 corn rootworm research results

Table 3. Wireworm study, Nebraska City, 2001 (Field length plots), partial data (Z B Mayo) Treatment Plant population per 20 ft of row 6/08/01 Gaucho 26.0 Gaucho 26.4 Untreated 19.1 Untreated 18.6

We are in the process of rating roots differently from the 1-6 scale used in the past. The new 0-3 scale provides a clearer representation of root pruning than the old scale. In the new scale, a 1, 2, or 3 represents the nodes pruned to within 1½ inches of the plant. Intermediate numbers are percentages of roots pruned. In this scale a 1.50 indicates that one full node (equivalent to a 4 on the old scale) plus 1/2 of the roots of another node have been pruned. In general a rating of 0.5 or below will give satisfactory protection. Bear with us while we get used to this rating scale. Reduced rates continue to be screened and in some cases perform similarly to full rates.

Summary

It appears that these seed applied insecticides and liquid insecticides will be effective in protecting seeds from seed feeding insects such as wireworms and seedcorn maggots. However, based on the results of the experiments described here and other experiments and on the suppression label for Prescribe, we advise caution in selecting these newer seed-applied products as rootworm control choices. Two years of data at the Haskell Ag Lab and the South Central Research and Extension Center have shown that under moderate to heavy pressure these treatments do not perform as well as traditional soil insecticides for corn rootworm control. As with all products, it is necessary for growers to assess their individual situations before selecting a control method. More data can be found on these products on the following University of Nebraska web sites nerec.unl.edu/ipm/jarvi, screc.unl.edu/entomology/index, and entomology.unl.edu.

Transgenic corn

Transgenic corn hybrids are being tested and look as good or better than standard soil insecticides. Future availability is still somewhat unknown.

Economics

Soil insecticides at full rates will cost between $11.00 to $15.00 an acre (based on prices found on the internet as of 11/14/01). Reduced rates for seedling insect control depend on the rate selected by the grower. Pounce 3.2 EC costs approximately $0.75 an ounce. Warrior T costs about $1.71 an ounce. Capture 2 EC costs about $2.50 an ounce.

Growers should carefully assess the risk and reward of using any insecticide treatment. Wireworms are very sporadic and normally do not affect a large number of acres. Does it pay to treat every acre with an insecticide when only a few acres will be affected? Using the previous example for Gaucho, 1,000 acres of treated seed would cost $3,750.00. Do your replant costs over the years justify this annual expense? Or do you believe that the increased stand and potentially higher yield shown in some experiments justify the added cost of seed treatments or liquid insecticides for seedling attacking insects?

In any case, soybeans should not be treated with insecticides at planting time. Treating corn with insecticides will depend on:

1. whether it is continuous corn,
2. planting date, and
3. past history of seedling attacking insects.

Plant alfalfa now toprovide for strong root system

More importantly, planting early gives plants time to develop larger root systems so when temperatures turn hot, the roots will be able to supply enough moisture so the plant can survive. Alfalfa seeded in mid to late May often is unable to handle hot temperatures no matter how much soil moisture is available.

I know you might be afraid that a freeze might kill plants following early seeding, but very young alfalfa seedlings can tolerate temperatures as low as 15 to 20 degrees. The danger of freezing actually is greater after plants reach the third or fourth trifoliate leaf stage, or are about 4 inches tall. At this stage, alfalfa begins to react as if it is heading into summer and loses its cold tolerance. The only time a spring freeze is likely to injure new alfalfa seedlings is when alfalfa is planted very early and an extra warm, moist April permits plants to grow to more than 4 inches tall by early May. This doesn’t happen often.

Managing cutworms
Most alfalfa fields should start greening up soon. If yours does not, check it for army cutworms. You may need to spray to save it.

Count the number of cutworm larvae per square foot in several areas. The economic threshold for spraying is four or more army cutworms per square foot on established alfalfa, but just two larvae are needed in fields seeded last year. Once your alfalfa gets four to six inches tall, spraying is unlikely to be beneficial unless you see a lot of active leaf feeding.

The best insecticides for controlling army cutworms in alfalfa are the synthetic pyrethroids. These include Ambush, Pounce, Baythroid, and Warrior. Lorsban also works well. Before spraying, read and follow label directions to safely apply the correct rate.

Bruce Anderson
Extension Forage Specialist

Market Journal

Ken Hubbard, HPCC director, says ag producers who know how to access and use climatic data can reduce weather-related risk.

“We can’t get rid of the risk, but we can, hopefully, minimize the risk,” said Hubbard. Accurate forecasts help producers decide which hybrids to plant, how much and when to irrigate, and when and where to market their crops. The Center collects and interprets climatological data and offers information about how to use the data to reduce risk.

Also on the April 11 edition of “Market Journal,” a look inside the National Drought Mitigation Center. This NU-based organization helps ag producers and government officials develop and implement plans to lessen the impact of drought.

“Market Journal” will be streamed live over the Web and broadcast live via satellite 8-9 p.m. Thursday, April 11. The program can be viewed at any of 20 NU Cooperative Extension downlink locations across Nebraska, or in the Lincoln area on Time-Warner Cable channel 21. To log on to the live Webcast or for a listing of downlink locations, visit the “Market Journal” Web site, http://marketjournal.unl.edu. All programs are archived for later viewing online.

“Market Journal” is a production of NU Cooperative Extension and the University of Nebraska-Lincoln Department of Agricultural Economics.

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