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Iowa State University

Plant Sciences

Proceedings of the Integrated Crop Management Conference

1991

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Soybean Cyst Nematode- Biology And Management, Gregory L. Tylka Dec 1991

Soybean Cyst Nematode- Biology And Management, Gregory L. Tylka

Proceedings of the Integrated Crop Management Conference

The soybean cyst nematode, Heterodera glycines, is a small, unsegmented plant-parasitic roundworm that attacks the roots of soybeans. Although many plant-parasitic nematodes are believed to be endemic or native to the United States, the soybean cyst nematode was apparently introduced from Japan. Soybean cyst nematode was first discovered in the United States in 1954 in North Carolina. It has since spread to 28 additional states in the Southeast and Midwest. It was first discovered in Iowa in Winnebago County in 1978. The presence of soybean cyst nematode has been confirmed in 52 counties within Iowa (Figure 1) and it is ...


A Perspective On The 1991 Iowa Crop, Garren O. Benson Dec 1991

A Perspective On The 1991 Iowa Crop, Garren O. Benson

Proceedings of the Integrated Crop Management Conference

One of the definitions of perspective is "to see clearly". I don't claim such ability, especially in late October when neither the final crop yields nor research results are known. Most would call 1991 an unusual crop year, but I'm reminded of a former colleague who was fond of saying that in the last 30 years he had yet to see a "normal" year. Perhaps the best word to describe the 1991 crop year would be crazy. This is especially true when you consider that the state's corn and soybean yields will end up close to "average".


Balancing Corn Yield Goals And N Fertilization Rates, D. L. Karlen, L. A. Kramer Dec 1991

Balancing Corn Yield Goals And N Fertilization Rates, D. L. Karlen, L. A. Kramer

Proceedings of the Integrated Crop Management Conference

Establishing realistic yield goals is essential for environmentally and economically sustainable crop production. It is also important because many of the variable inputs, including fertilizer N rates, are often based upon those goals. If yield goals are beyond what uncontrollable factors such as rainfall can support, many controllable inputs such as N fertilizer will probably be used at rates in excess of crop needs. This scenario will result in reduced nutrient recovery, decreased profitability or return on fertilizer investment, and an increased potential for N loss to groundwater resources. If yield goals are set too low, crop nutrient needs may ...


Aglime For Corn And Soybean Production, Regis Voss Dec 1991

Aglime For Corn And Soybean Production, Regis Voss

Proceedings of the Integrated Crop Management Conference

Liming acid agricultural soils has been a long-time proven practice to maintain/improve crop yields, particularly forage legumes, and to favorably affect soil chemical, biological and physical properties.


Factors Affecting Agricultural Chemical Losses To Surface And Ground Water Resources, J. L. Baker, J. L. Hatfield Dec 1991

Factors Affecting Agricultural Chemical Losses To Surface And Ground Water Resources, J. L. Baker, J. L. Hatfield

Proceedings of the Integrated Crop Management Conference

The major chemical factors determining concentrations and losses of agricultural chemicals from cropland are their persistence and adsorption to soil. The major hydrologic factors are rate and route of infiltration. The major management factors are the rate, method, timing, and choice of applied chemicals; cropping; and tillage system. To determine the "Best Management Practices" (BMPs) to reduce chemical losses, their mechanisms of interactions with the soil and management practices must be understood. Depending on soil adsorption, pesticides and nutrients can be mostly lost with surface runoff water, sediment, or water percolating out of the root zone (water which may return ...


Seed Quality Evaluation Methods, Tim J. Gutormson Dec 1991

Seed Quality Evaluation Methods, Tim J. Gutormson

Proceedings of the Integrated Crop Management Conference

Seed quality evaluation methods will be discussed during a tour of the I.S.U. Seed Testing Laboratory. The following discussion of seed quality is provided as background or reference information. The importance of quality seed stocks is often taken for granted in U.S. agriculture. High quality seed supplies of the major crops have evolved through the competive nature of the U.S. seed industry. However, occasionally an emergence, contamination, or seed quality question arises. To help answer these seed quality questions it is useful to understand seed evaluation methods and labeling requirements.


Impact Of Tillage, Crop Rotation, And Chemical Management Practices On Groundwater Quality, Rameshwar S. Kanwar Dec 1991

Impact Of Tillage, Crop Rotation, And Chemical Management Practices On Groundwater Quality, Rameshwar S. Kanwar

Proceedings of the Integrated Crop Management Conference

Contamination of groundwater by nitrate and pesticides has been documented by various state and federal agencies in the United States. Groundwater pollution is of increasing concern in the United States because about 50 percent of the drinking water comes from groundwater. A recent study suggested that water pollution is the most damaging and widespread environmental effect of agricultural production. Recent research conducted in Iowa and surrounding states has indicated the incidence of groundwater contamination by pesticides and nitrogen fertilizers (Baker and Johnson, 1981; Everts and Kanwar, 1990; Gast et al., 1978; Hallet al., 1989; Hallberg, 1989; Kanwar et al., 1985a ...


Soybean Cyst Nematode- Identification And Extraction Techniques, Gregory L. Tylka Dec 1991

Soybean Cyst Nematode- Identification And Extraction Techniques, Gregory L. Tylka

Proceedings of the Integrated Crop Management Conference

A major factor limiting soybean production in Iowa is parasitism by the soybean cyst nematode, Heterodera ~lycines. Soybean cyst nematode is now known to be present in 52 counties within Iowa. It is very likely that the nematode is present in many other counties as well, but the nonspecific nature of the above-ground symptoms of soybean cyst nematode damage makes early identification or diagnosis of infestations difficult. The primary above-ground symptoms of soybean cyst nematode damage are chlorosis or yellowing and stunting of the soybean plants. These symptoms are not unique and often can be attributed to damage due to ...


Soybean Residual Effects On A Following Corn Crop, Richard M. Shibles, Irvin C. Anderson, Edgar S. Escuro Dec 1991

Soybean Residual Effects On A Following Corn Crop, Richard M. Shibles, Irvin C. Anderson, Edgar S. Escuro

Proceedings of the Integrated Crop Management Conference

The reason for the yield advantage of rotations is still speculative. Differences in soil nutrients, soil moisture, diseases, insects, weeds, and soil physical properties have all been considered to be responsible for this effect. It was not until the late '70s that a non-nitrogen soybean effect on the following corn crop was substantially documented. Corn after soybeans consistently performed better than second-year corn irrespective of nitrogen fertilization. In previous work done with the soybean-corn rotation, there has never been an evaluation of the potentially different effects of soybean varieties on following corn yields. This study aimed to evaluate whether such ...


The Role Of Sensing Devices In Herbicide Application: Present And Future, David A. Mortensen Dec 1991

The Role Of Sensing Devices In Herbicide Application: Present And Future, David A. Mortensen

Proceedings of the Integrated Crop Management Conference

For as long as farming has been practiced, farmers have realized that yield, soil characteristics, and pest infestations vary across fields. Until recently, farmers have dealt with this variation by manually adjusting fertilizer applications according to fertility test results, and have spot sprayed pesticides to control localized pest populations. The technology to increase the ease and precision of such applications has increased tremendously in the past five years. Much of this progress can be attributed to increased computing capacity and speed. Several developments have occurred that will significantly impact the way in which weeds are controlled in the near future ...


Reduced Herbicide Rates- The Wisconsin Experience, Jerry Doll, Thomas Mulder Dec 1991

Reduced Herbicide Rates- The Wisconsin Experience, Jerry Doll, Thomas Mulder

Proceedings of the Integrated Crop Management Conference

Many fanners are reevaluating their weed management practices to see if their use of herbicides can be modified. Since 1989, we have done work on reduced herbicide rates in com. A total of 11 trials with preemergence herbicides and one with preplant incorporated products have been done. A trial in soybeans with preemergence and postemergence products was done in 1991. We achieved a reduced use of chemicals by either lowering the rate of a broadcast, preemergence or postemergence spray or by applying a preemergence herbicide in bands over the crop row.


Nebraskaherb: A Bio-Economic Model For Weed Management, David A. Mortensen, Alex R. Martin, Fred W. Roeth Dec 1991

Nebraskaherb: A Bio-Economic Model For Weed Management, David A. Mortensen, Alex R. Martin, Fred W. Roeth

Proceedings of the Integrated Crop Management Conference

The number of computer applications for purposes of weed control decisions has increased dramatically in the past eight years. During this time, many efficacy-, and population based weed control decision aids have been developed. One such program, NebraskaHERB, an economic threshold based herbicide selection model, has been developed at the University of Nebraska. This weed management program has been completed for postemergence weed control in soybeans and similar programs will be developed for corn and additional crops. NebraskaHERB, available on floppy disks, runs on IBM compatible personal computers. This user friendly program quickly determines: whether or not it is cost ...


Herbicide Resistance, Micheal D. K. Owen Dec 1991

Herbicide Resistance, Micheal D. K. Owen

Proceedings of the Integrated Crop Management Conference

Herbicide resistance is defined as "the inherited ability of a plant to survive a dosage of a herbicide to which the wild population is sensitive". Weeds that are resistant to specific herbicides have become dominant members of field populations in many locations throughout the world. These resistant populations have caused growers considerable economic loss and long term management considerations. Plant geneticists have recently introduced crops that have been developed specifically for enhanced tolerance or resistance to herbicides that typically cause serious injury to the hybrids or varieties. These events, the development of herbicide resistant weed populations and the release of ...


Old And New Weed Management Practices In Alfalfa, Jerry Doll Dec 1991

Old And New Weed Management Practices In Alfalfa, Jerry Doll

Proceedings of the Integrated Crop Management Conference

Once forages are established, they are seldom treated with herbicides. This is in sharp contrast to row crops like com and soybeans where 90% of the acreage receives au herbicide. How should we view the fact that herbicides are not widely used in forages? What will be the trends for weed management in the seeding year? Today's forage producers are placing significant emphasis on forage quality. What implication do these have for how we manage weeds in forages in the future? Will the limited use of herbicides in established forages increase significantly? Let's first review the weed management ...


Soil Compaction Research Summary, Stewart W. Melvin, Donald C. Erbach Dec 1991

Soil Compaction Research Summary, Stewart W. Melvin, Donald C. Erbach

Proceedings of the Integrated Crop Management Conference

Soil compaction has become a major topic of discussion among scientists and crop producers in recent years. Even though some producers consider soil compaction to be a problem on their own farms, they feel resigned to the fact that there is little they can do to control it. Some recent solutions have been offered based on research efforts with soil compaction. There is significant interest in developing crop production systems with controlled traffic to help control the problem of soil compaction. There have also been new machine developments to address the problem of soil compaction, particularly with rubber tracked equipment ...


Controlling Corn Diseases, C. A. Martinson Dec 1991

Controlling Corn Diseases, C. A. Martinson

Proceedings of the Integrated Crop Management Conference

Root and Stalk Rots, Leaf Diseases, and Leaf Disease Control


Band Injection Of Herbicides For Reducing Environmental Losses, Steven K. Mickelson Dec 1991

Band Injection Of Herbicides For Reducing Environmental Losses, Steven K. Mickelson

Proceedings of the Integrated Crop Management Conference

Herbicides can be an important component for weed control in profitable crop production when selected and used properly. When herbicides are incorrectly applied, however, losses to the atmosphere, surface water, and ground water can be the result. Banding as opposed to broadcast application can reduce herbicide input, but losses of herbicides to the atmosphere during spray application can still be substantial, particularly on windy days (Tremwel, 1985). In addition, herbicide applied directly to crop residue is subject to greater volatilization losses (Burt, 1974; 1987). Crop residue with conservation tillage reduces water and sediment losses, and thus can be an effective ...


Do One Year's Seeds Really Make Seven Year's Weeds?, Robert G. Hartzler Dec 1991

Do One Year's Seeds Really Make Seven Year's Weeds?, Robert G. Hartzler

Proceedings of the Integrated Crop Management Conference

The primary reason for controlling weeds during crop production is to eliminate crop yield losses due to competition between the crop and weeds. However, the majority of Iowa farmers strive to obtain higher levels of weed control than necessary to protect crop yields from weed competition. In most instances, the rationale for this contradiction is the concern over the impact of weed seed production on future weed populations. Most weed species are prolific seed producers, and seed dormancy enables weed seeds to survive for long periods of time. Thus, it is true that weeds allowed to go to seed in ...


Weed Seed Dormancy And Germination, Micheal D. K. Owen Dec 1991

Weed Seed Dormancy And Germination, Micheal D. K. Owen

Proceedings of the Integrated Crop Management Conference

Weeds are consistent problems in agriculture because of seed dormancy. Without dormancy, weed seeds would not survive in the soil for any period of time. Also critical are the factors that influence dormancy. These factors which describe seed dormancy also serve to "determine" when the seed has the greatest potential to germinate successfully, and thus survive to replace the seed bank. Understanding the concepts of seed dormancy and factors that influence the continuation or termination of dormancy thus allowing germination are critical for the development of an effective weed-management program.


Approaches To Transferring Sustainable Agriculture Research, Richard Pirog Dec 1991

Approaches To Transferring Sustainable Agriculture Research, Richard Pirog

Proceedings of the Integrated Crop Management Conference

Iowa is a national leader in sustainable agriculture research and education. Although many states have made verbal commitments to natural resource and environmental issues, Iowa passed the landmark 1987 Iowa Groundwater Protection Act, which established the Leopold Center for Sustainable Agriculture. Although the Leopold Center is known primarily for funding research to develop profitable farming systems that conserve Iowa's natural resources, it also has a mandate to develop with the Iowa Cooperative Extension Service and other organizations an educational framework to deliver research findings to Iowa citizens.


Wheat, Wayne R. Hansen Dec 1991

Wheat, Wayne R. Hansen

Proceedings of the Integrated Crop Management Conference

These are the results of a three-year project in conjunction with Ogilvie Mills, Inc., Keokuk. The 1990 and 1989 studies were conducted at the Southeast Research Center. The 1988 studies were conducted at Lang Enterprises, Inc., near Donnellson. There are three studies in the project and each study includes hard red spring wheat, hard red winter wheat, and soft red winter wheat. There are three varieties of each crop type selected for protein content and disease and lodging resistance.


Corn Fermentation By-Products: Properties And Uses, Stanley J. Henning Dec 1991

Corn Fermentation By-Products: Properties And Uses, Stanley J. Henning

Proceedings of the Integrated Crop Management Conference

Fermentation is broadly define as an enzymatically controlled transformation of an organic compound. In breweries and wineries, energy-rich compounds such as sugars and other carbohydrates are broken down through enzymatically controlled anaerobic processes to carbon dioxide and alcohol. Often overlooked are other potentially important fermentation products such as organic acids. Corn is an important source of energy-rich carbohydrates and consequently can be considered to be an important feed-stock for the fermentation industry. In the midwest, corn is probably one of the most efficient crops that converts the sun's energy to a carbohydrate product easily transported and processed into its ...