October 4, 2002

As days became shorter, corn and sorghum harvest was underway across much of the state. Photo by Brett Hampton

In this week's Crop Watch:

Purple or pink streaks on the seed coat are the primary symptom of purple seed stain and discoloration can range from streaks to large blotches. The fungus grows into the pod and spreads though the hilum, resulting in seed discoloration being centered on the hilum. In some cases the entire seed may be discolored. The fungus overwinters on soybean residue. Spores are splashed onto plants during the growing season and the fungus grows into the pod.

Conditions that favor purple seed stain develop when wet weather delays harvest or warm, wet weather hits when plants have begun to reach maturity (growth stages R7 and R8) or when pods are completely brown. This has been the case in Nebraska in many fields. In some fields, stress conditions forced plants to mature prematurely. These plants did have pods with seed, many of which have purple seed stain. Rapid dry-down prevents seed infection and recent cool weather slows the rate of fungus growth, but if moisture continues into harvest I expect there to be an abundance of this discolored seed.

Eastern Nebraska recommendations

Some nitrogen-fixing legumes, such as hairy vetch, can be good cover crops for Nebraska; however, it is too late to sow these. The best option is winter rye if sown soon. Winter rye needs to be established this fall with the expectation that it will make good growth early next spring. In late April or early May, it can be killed with a herbicide or with tillage.

Several factors need to be considered when determining whether a cover crop would benefit your operation.

Soil residual nitrogen. Soil nitrate levels are expected to be high where dryland crops did poorly. Nitrate is susceptible to leaching, causing loss of nitrogen and potential ground water contamination. On fine-textured soils with little stored soil water, the risk of extensive leaching is low compared to sandy soils or soils that contain much water. A dry matter yield of 1500 lb per acre is a realistic expectation for a winter rye cover crop sown in early October and allowed to grow until early May. The dry matter should be about 3.5% to 4.0% nitrogen with 45 to 60 lb nitrogen per acre per 1500 lbs of dry weight. This nitrogen should be fully credited when estimating nitrogen fertilizer needs if the cover crop is killed by incorporation. If killed with a herbicide and left on the surface, some nitrogen will be lost to the air during drying, but most of it should become available during the season.

Potential for wind and water erosion. Soil erodibility needs to be considered, as well as the expected ground cover by crop residues. If ground cover next spring is likely to be less than 50% on highly erodible land, a cover crop should be seriously considered.

Toxic effects of winter rye. Research has indicated that there may be some toxic or alleopathic effect from rye, especially if the rye plant tissue is less developed in the spring. Corn yield following a rye cover crop was reduced by 9% in one year but there was no effect in the other two years of a study conducted at the NU Agriculture Research and Development Center near Mead.

Residual effects of herbicides. The residual effect of the herbicide clomazone (e.g. Command) which was applied to a 2002 soybean crop may inhibit rye growth. Also, atrazine applied at more than 1.25 lb active ingredient per acre could reduce cover crop performance.

Water use by the cover crop. A cover crop will deplete water from the soil, meaning less water would likely be available for the 2003 crop. While difficult to estimate, soil water loss may be increased over evaporation by 2 inches for each 1500 lb dry weight produced. If winter and spring precipitation fully recharges the soil water profile, this will not be a concern. However, with predictions of a relatively dry winter, producers should keep this in mind when considering a cover crop for non-irrigated fields.

Cost of establishment. The costs of seed (about 50 lb/A) and sowing the winter rye need to be weighed against the potential benefits.

Grazing of the cover crop. The spring growth of the rye cover crop is highly digestible, with high protein content. However, avoid grazing when the soil is wet so compaction doesn't develop, affecting subsequent crop performance.

• Soil testing where corn will follow corn should include a deep nitrate test. Sample at least two feet deep, preferably three or four feet. If you don't sample to four feet, include a default value of 3 ppm to four feet (for fine and medium soils) in your calculation. Your NRD may offer a cost-share program for soil testing.
• Manure applied to soil at agronomic rates for nitrogen or phosphorus will rarely cause a salt toxicity to crop roots after planting. Excessive application rates or non-uniform application may cause salt problems. When beginning to apply manure to your soil have EC measured on a soil sample in order to get a background value. Repeat the test every three or four years to see if salts are accumulating. Protect your next crop and the environment: apply manure at agronomic rates for nitrogen.

Without precipitation to supplement irrigation, many systems were unable to keep up with crop demand. Irrigation systems are designed to supplement normal rainfall patterns in a given area. In years of extreme drought, such as this year, systems are taxed to or beyond capacity. If systems were designed to meet crop water demand during periods of severe drought, pump size, energy needs and costs would all be much greater than what would normally be needed. While designing irrigation systems to meet a typical range of crop water needs may be cost efficient in the long run, in a year of severe drought, it may leave even irrigated crops under stress.

In these situations crop stress can be reduced by ensuring that the irrigation system is uniformly applying water on the field and that none is misdirected. Uniform water application can help reduce total water pumped and deep percolation and limit movement of chemicals below the root zone. During drought the uniformity of water application becomes very visible and can be easily evaluated since there is little or no supplemental water available to mediate the effect on the crop.

During harvest, survey your field from the combine to identify any patterns or problem areas where irrigation may have been uneven. Many center pivot systems are operated with drops extended down into the corn canopy. Lack of uniform water application will appear as circular patterns in the field. This will be more evident with systems that have drops spaced more than 5 feet apart and is especially visible during a drought. UNL research indicates that yields may decrease up to 40 bushels per acre between drops when drops are spaced too far apart in the corn canopy. In years with normal precipitation, the areas between drops may not become stressed and be visible because rain supplements the irrigation. However, the area close to the drops will likely be over-irrigated, resulting in additional pumping costs. Either way, the lack of uniform water application has reduced your bottom line.

Although drops are mostly influenced when operated in a corn canopy, nonuniform water application can occur anytime drops are located too far apart. Regardless of the crop, surveying the field before harvest is an excellent way to evaluate just how your system operated.

For furrow irrigators an inability to move water across the field fast enough was one of the biggest problems this year. Top portions of the fields may have received more than enough water while the bottom end of the field may have been shorted. Surge irrigation is a system that can improve uniformity of furrow irrigation systems by shortening the time to advance water to the end of the field as compared to conventional practices. UNL research has shown that surge performs even better under hot dry conditions.

Yield loss that averages as little as one to two bushel per acre is all that it would take to pay for adding additional drops if the spacing of in-canopy nozzles is too wide. Likewise, only a two to three bushel per acre yield increase is needed to pay for a surge valve. While it's too late to correct irrigation problems this year, surveying your field at harvest can provide important insight into changes that may need to be made to your irrigation system for next season.

The example Initial assumptions 1,000 acres of cropland. 600 acres of PFC (old) corn base. 500 acres of corn, 1998-2001. 500 acres of soybeans, 1998-2001. Crop base options with given assumptions Option 1: 600 a. corn base (60% of cropland). Option 2: 600 a. corn base; 400 a. soybean base (60%; 40%). Option 3: 500 a. corn base; 500 a. soybean base (50%; 50%). Option 4: 500 a. corn base; 500 a. soybean base (50%; 50%). Option 5: 501-599 a. corn base; 499-401 a. soybean base (50.1%-59.9%; 49.9%-40.1%). Other initial assumptions Corn Soybeans PFC (old) or direct yields 85 bu/a 31 bu/a Ave. actual yields, 1998-2001 130 bu/a 40 bu/a Partially updated yields, 1998-2001; CC (3) 122 bu/a 37 bu/a National loan rate $1.98/bu $5.00/bu Expected 12-month price $1.95/bu $4.95/bu Target price $2.60/bu $5.80/bu Direct payment (DP) rate $0.28/bu $0.44/bu Counter-cyclical payment (CCP) rate $0.34/bu $0.36/bu Direct and counter-cyclical payments made on 85% of base. Oilseed base selected in Option 5 is halfway between minimum and maximum.

The 2002 farm bill offers three distinct types of support for producers of covered commodities (wheat, feed grains, oilseeds, cotton and rice).

First, traditional marketing loans essentially assure a minimum price on all bushels produced, either through marketing loan gains or loan deficiency payments. Loan levels have been increased for wheat and feed grains but decreased for soybeans in the new legislation. This may slow, if not reverse, the expansion in soybean acres that has been underway since the mid-1990s. The other two support provisions-direct and counter-cyclical payments-are based on historical crop bases and yields, not the current year's output. A key change is that soybeans and other oilseeds become full program crops for the first time. Producers may choose among five different crop-base options. Four of the five options are carried over from the old farm bill and its production flexibility contracts (PFCs):

• Option 1: 2002 PFC (old) wheat and feed grains bases.
• Option 2: 2002 PFC (old) wheat and feed grains bases; add minimum oilseed acres.
• Option 3: 2002 PFC (old) wheat and feed grains bases; substitute maximum oilseed acres.
• Option 4: New bases to reflect acres planted (or prevented from planting), 1998-2001.
• Option 5: 2002 PFC (old) wheat and feed grains bases; partially substitute oilseed acres.

CC (1): Retain PFC (old) yields.

CC (2): Add 70% of the difference between the PFC (old) yield and the actual yield, 1998-2001, to the PFC yield.

CC (3): Multiply the actual yield, 1998-2001, by 93.5%.

Although recent rains in parts of Nebraska helped ease this summer's drought, most of the state remains dry. Agricultural Climatologist Steve Hu expects that dry pattern to continue statewide. "I wish I could say we are going to see more precipitation this winter, but that's not what my analysis shows," the Institute of Agriculture and Natural Resources scientist said.

Hu uses sophisticated statistical analysis to predict precipitation anomaly patterns. Anomalies are important because they indicate departures, or variations, in long-term averages. His predictions are based on his research, which analyzed 112 years of precipitation data and identified precipitation variation patterns throughout most of the last century.

According to his analysis, this winter's temperatures in northern Nebraska should be slightly above normal with near normal temperatures in the southern half of the state.

"Precipitation should be on the dry side for northern and western portions of Nebraska. However, there could be above average precipitation in the southeastern section of the state," Hu said. His analysis also indicates the dry summers Nebraska has experienced in recent years should continue, possibly for the next five to seven years. Fall and winter precipitation patterns in the next few years also should be drier, he said.

"Not all those years and not all seasons in each year of the next five to seven years will be dry. There will be wet years, but a majority of those years will be on the dry side," Hu said.

Hu said he has a high degree of confidence in his predictions. They are based on advanced analysis of historical precipitation data collected at weather stations statewide and from Kansas, Missouri, Illinois, Iowa, Colorado and Wyoming. These states' weather patterns can strongly influence what happens in Nebraska and help support and amplify the historical data that Hu analyzes.

"Sophisticated data analyses and computer modeling greatly improves the accuracy of predicting weather trends and anomaly patterns. I think it's one of the best methods to predict local rainfall and I give it a confidence rating of better than 70%," Hu said.

His statistical analyses indicate that precipitation patterns follow 18- to 23-year cycles. This pattern accurately reflects Nebraska's intensive drought periods during the 1930s, 1950s and late 1970s. This pattern shows a 10-year wet period ending in the late 1990s, followed by the current extended dry pattern.

"Those extended patterns form from an overall trend that can be examined on a year-to-year basis," Hu said, explaining that not all years in the extended dry period will be dry. "We will have some periods of wet weather within the current (dry) pattern ... but overall, in the dry phase of the cycle, precipitation will be below normal."

With conditions in most of the state ranging from abnormally dry to exceptional drought and no way of predicting next year's soil moisture levels, farmers should consider when and how much water their crops will need, said Bob Klein, a cropping specialist at NU's West Central Research and Extension Center at North Platte.

"The catch to selecting 2003 crops will be water availability," he said. "If water levels are limited, it may not be a good idea to plant all acres to corn or soybeans. But even with water concerns, it's still important to select the highest producing and better performing hybrids and varieties because there isn't much difference between water use."

Most reservoirs are at extremely low levels and soil moisture is nearly depleted in many areas. If producers get water from an irrigation district, they also need to think about when their crops will need water.

"Yields will be limited if crops need water before or after it's available," he said. "This is why it's also a good idea to talk to crop insurance agents to check on coverage. Crop insurance agents can determine the coverage you will have on your irrigated acres. Producers may have to switch their plans if water delivery time and amount are not based on their needs."

With limited water supplies and limited irrigation systems, some farmers may want to consider planting a portion of their acres to winter wheat, Klein said. For example, if a pivot can only apply enough water on two-thirds of the field to keep up with corn's water use, producers could plant one-third of the field to wheat.

"If the wheat is taken to harvest and weeds are controlled in the fall, this helps build up soil moisture for the next crop, usually corn or grain sorghum, " he said.

Crop growers in southern Nebraska could consider planting sorghum.

"Sorghum can be beneficial because it uses less water and also waits for water better than corn," Klein said. "The key is to check with crop insurance agents and a Farm Service Agency before making changes."

No-till or reduced-till farming also is important this year, Klein said.

"Every producer should consider no-till farming because the crop residue helps reduce evaporation, traps snow and increases water infiltration rates," he said. "With every tillage operation, one-third to one-half inch of soil moisture is lost. Crop residue also helps control weeds."

Producers also should plan ahead for weed problems so they can be controlled quickly to conserve moisture and reduce crop stress, he said.

Andrea Fischer
IANR News and Publishing

A variety of woody florals are being tested for production and marketing in Nebraska.

Nestled down by the river where you're planting a riparian buffer or in the shelter of a windbreak, you just may be able to slip in plantings of curly willows or pussy willows which can be sold to wholesale and retail florists across Nebraska.

Fall is also an excellent time to treat musk and plumeless thistles with herbicides. Both plants act as biennials or winter annuals and rarely as summer annuals. Almost all of the plants that flower and produce seed next year will be present as rosettes this fall. That means controlling weeds this fall will usually substitute for a spring treatment. This can help move the workload away from the spring "crunch". There is one qualification with fall treatments. Examine the area to make certain there are enough plants to justify treatment; a dry summer and fall reduce seed germination and treatment may not be warranted.

With fall herbicide applications, some weather related factors will need to be heeded. Soil moisture must be adequate to support active growth. In drought stressed plants herbicide absorption and translocation can be greatly reduced. With a drought stress situation it is more cost effective to forego treatment until more favorable conditions exist next season.

Questions often arise regarding the impact of frost on weed response to herbicides. Frost does not automatically signal the end of the season for applying foliar active herbicides. Many of our most serious biennial and perennial weeds are quite frost tolerant. The key is to examine the foliage. Healthy green foliage indicates active growth and favorable conditions for treatment. If the foliage has become discolored due to low temperatures, the herbicide effect will be reduced.

With leafy spurge the key is to break the stem and check for the presence of the white latex like substance. Bob Masters, formerly at UNL with the Agricultural Research Service, determined that the presence of latex indicated a plant actively growing and responsive to herbicide.

Some plants may actually become more susceptible to herbicides after a frost. Bob Wilson, Extension weeds specialist at the Panhandle Research and Extension Center in Scottsbluff, recorded an increase in Canada thistle control with treatments applied after a frost. Again the key is to examine the foliage to make certain there has been no low temperature damage.

To do that, University of Nebraska agronomists in 1999 launched the Ecological Intensification Project. The comprehensive, long-term study explores the most cost-effective, environmentally friendly ways to achieve yields usually seen only in yield contests.

“Corn average yields throughout the state are only about half of what we think the biological yield potential is in terms of genetics, climate and soils,” said Achim Dobermann, an Institute of Agriculture and Natural Resources soil scientist and project coordinator.

“If we want to stay competitive in the long run, we must learn how to consistently grow these crops at 70% to 80% of their true yield potential,” he said. “This will increase profitability and perhaps have positive effects on the environment if nutrient-use efficiency can be increased.”

Statewide corn yields average about 150 bushels per acre. Researchers think true yield potential for eastern and central Nebraska is closer to 300 bushels per acre. During the study’s first three years, the highest yields were consistently 250 to 260 bushels per acre in drip-irrigated plots.

“We can get 250 to 260 bushels per acre regardless of climatic variability among years,” Dobermann said. That’s less than originally expected because high nighttime temperatures during grain fill hurt yields the past two years. Plant distribution also wasn’t as precise as it could be.

As part of this project, researchers are examining a multitude of yield-influencing factors, including soil fertility, carbon sequestration, nitrate leaching and soil microbial function. They’re conducting similar research on soybeans.

By year’s end, they’ll create a map of yield potential and optimum planting dates for Nebraska using climate and research data. This map will show producers how planting date and hybrid choice influence yield potential by region.

Within three years, scientists will combine yield results with findings from an IANR soil fertility project to revise corn nutrient management recommendations, emphasizing efficiency for elevated yields.

Researchers hope to create better crop-growth models, including planting dates, crop densities and nutrient requirements, to help farmers maximize yields. Existing models underpredict yields in better growing environments such as Nebraska, said Ken Cassman, agronomy and horticulture department head and project leader.

The government someday might pay farmers for carbon sequestration on their land, he said. “If you underestimate yield, you underestimate the amount of carbon that may remain in the soil, which could cost farmers money.”

Better management also has environmental benefits. Fine-tuning inputs means fewer chemicals to run off or leach into water. Cropland that traps more carbon may help reduce the buildup of carbon dioxide, a major greenhouse gas.

“Through research, we can create the most environmentally friendly production systems in the world,” Cassman said. “This could lead to branding Nebraska products as environmentally friendly, which would add value. Good management could help Nebraska producers be competitive in global markets where environmental issues are increasingly important.”

Producing more corn when prices are low may seem a bad idea, but higher yields could be pivotal to long-term viability for crop producers and global food security, Cassman said.

“Economists who watch global markets say U.S. corn and soybeans will remain a crucial component for food security in coming decades,” he said. Thanks to excellent soils, Nebraska can more easily meet environmental standards than can competitors like Brazil where soils are poorer.

“We can’t take our eyes off the ball. Right now production costs in places like Brazil are lower, but their production costs will rise faster than ours.”

Higher yields through intensive management, guided by improved understanding of yield potential and input requirements, also should help farmers maximize shorter term profits, Cassman said.

A renewed interest in wheat has surfaced this year as we progress into what looks like dry growing conditions this fall. Growers need to start giving thought to how they intend to mange their corn and soybean fields after harvest if soil moisture is not recharged. How important is tillage this fall? What was the financial payback for the fall or spring tillage? Will herbicide carryover affect next year's crops? Should some fields be rotated to a different crop? How much carryover nitrogen should I account for? Is fall fertilization in my best interest this year? Should I cultivate corn and soybean fields during the growing season? All these questions equate to significant dollars for each operator. In many instances they may mean the difference between profit and loss.

Oct. 1 - Grand Island

Oct. 3 - Alliance

Oct. 8 - North Platte

Oct. 15 - Lexington

Oct. 21 - Ainsworth

Oct. 22 - Norfolk

Oct. 30 - Norfolk

Oct. 31 - Beatrice

The contact for the Farm Mediation program at the Nebraska Department of Agriculture is Marian Beethe, (402) 471-6890 or marianjb@agr.state.ne.us

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