Optimum Soybean Planting Date

Past research by Iowa State University has shown that the optimum planting date for soybeans, assuming favorable soil conditions, is the first week in May for the northern third of Iowa. The optimum date for the southern two thirds of Iowa is the last week of April. Given that rapidly changing soybean genetics have shown improvements in both yield and disease resistance, this trial was designed to demonstrate the planting recommendation under local conditions.

Responses to Adding Fat to Corn-Based Diets Supplemented with Urea and Soybean Meal for Finishing Steers

Yearling steers were fed corn-based diets supplemented with urea or soybean meal plus urea, and none, 2%, or 4% fat. All steers were implanted with Revalorâ-S and fed for 118 days. Adding fat did not improve performance of the steers in the feedlot or improve carcass characteristics. Feeding soybean meal increased rate of gain, improved feed efficiency, increased carcass weight, and tended to improve carcass quality grades compared with feeding urea. Adding 4% fat decreased feed intake, suggesting that corn-based diets may contain enough oil to approach the quantity of fat that can be utilized effectively in a ruminant diet.

Effect of Fungicides and Plant Populations on Soybean Disease and Yield

Applications of foliar fungicides on soybeans have been shown to reduce disease pressure and protect yield under the right conditions, especially in environments that have very wet or humid conditions. In the past decade, fungicide use in Iowa has increased. Initially, growers were concerned with the potential threat of soybean rust, which is controlled effectively by foliar fungicides. In Iowa, however, there has not been any case of yield reduction due to soybean rust. New potential purposes for foliar fungicides include “plant health” benefits and the reduction of foliar diseases endemic in Iowa such as Septoria brown spot, Cercospora leaf blight, and frogeye leaf spot. Currently what is not known is how the efficacy of fungicides is affected when agricultural practices change. Our question: How does plant population affect the efficacy of fungicides?

Elite Soybean Test—North

The purpose of this test was to evaluate the experimental elite soybean lines adapted to northern Iowa. The 2011 Elite Test included commodity–yellow hilum soybeans and large seed and high protein beans, along with commercially grown varieties released by Iowa State University tested for comparison of agronomic traits. These varieties are used in the production of soy foods.

Evaluation of Soybean Varieties Resistant to Soybean Cyst Nematode

Use of resistant soybean varieties is a very effective strategy for managing soybean cyst nematode (SCN), and numerous SCN-resistant soybean varieties are available for Iowa soybean growers. Each year, public and private SCN-resistant soybean varieties are evaluated in SCN-infested fields in Iowa by Iowa State University personnel. The research described in this report was performed to assess the agronomic performance of SCNresistant soybean varieties and to determine the effects of the varieties on SCN numbers or population densities.

Northwest Iowa On-farm Research Soybean Yield Response to Headline Fungicide

Six years ago the Northwest Iowa On-Farm Research Project was started to cooperate with local farmers to compare crop production methods on a field scale size. Through this project, over 300 replicated comparisons have been done. Beginning in 2012, the Northwest Iowa On-Farm Research project will be recognized as a part of Iowa State University Farmer Assisted Research and Management (FARM) program. This program will also expand to southwest Iowa, north central Iowa, and central Iowa.

Soybean Response to Sulfur Fertilization

The objective of this trial was to investigate response of soybean to sulfur fertilization when grown on irrigated coarse sand soil with low organic matter.

Broadcast and Band Phosphorus and Potassium Placement for Corn and Soybean Managed with Till or No Till

No-till minimizes the incorporation of crop residue and fertilizer with soil; resulting in wetter, colder soils and the accumulation of organic matter, phosphorus (P), and potassium (K) near the soil surface. Banding of P and Kcould be more effective than broadcast fertilization by counteracting stratification, applying nutrients in the root zone (starter effect), and minimizing reactions with the soil that may reduce their availability to plants. Therefore, a long-term study was established in 1994 to evaluate P and K fertilizer rates and placement methods for grain yield of corn and soybean managed with no-till and chiselplow/disk tillage.

Soybean Aphid Threshold

Soybean aphid has been a major pest for producers in Northwest Iowa since their first major outbreak in 2003. Control measures for managing this pest are warranted almost every growing season and much research is being done on managing this pest. Insecticide applications have been the sole management technique for soybean aphid and will continue to be important in the future. An economic threshold of 250 aphids/plant is the current threshold level recommended by Iowa State University. This study was conducted to determine if the current recommendations are useful in managing soybean aphid and maintaining profitability for producers.

Glyphosate, Manganese, and Zinc Soybean Trial

Often there is yellowing of soybeans following glyphosate applications that has been attributed by some as manganese or zinc deficiency. There have been varied reports of impacts of this ‘yellow flash’ on soybean yields. The trial was conducted to investigate such claims.

Evaluation of Fungicides and Herbicides for Management of White Mold of Soybean

Several new fungicide products are either available or will be available for management of white mold of soybean. This study was conducted at the Muscatine Island Research and Demonstration Farm, and one farmer’s field in northeast Iowa.

Soybean Replant Study

Every spring, farmers are faced with the decision of whether to replant soybeans because of stand losses due to hail storms, soil crusting, and damping off. A common practice when faced with this decision is to “thickenup” the stand by planting additional seed into the existing stand. Although this practice is usually discouraged by agronomists, there has been little research done to compare this practice with keeping the existing stand or destroying the stand and replanting.

Phosphorus and Potassium Rates and Placement Methods for Corn and Soybean Managed with No-till or Tillage

No-till management for corn and soybean results in little or no incorporation of crop residues and fertilizer with soil. Subsurface banding phosphorus (P) and potassium (K) fertilizers with planter attachments could be more effective than broadcast fertilization, because in no-till with broadcast fertilizer, both nutrients accumulate at or near the soil surface. A long-term study was initiated in 1994 at the ISU Northwest Research Farm to evaluate P and K fertilizer placement for corn and soybean managed with no-till and chiselplow tillage.

Soybean Planting Dates in Northeast Iowa

Soybean planting date studies of various types have been conducted at this site since 1976. Earlier tests included later planting dates (May through mid-June), differing variety maturities, and comparisons with starter fertilizer and Ridomil fungicide soil treatments. Research reports on these studies can be found in previous annual progress reports with the last summary in the 2001 and 2009 reports.

Effect of Certified Organic Products on Soybean Aphid

The soybean aphid (Aphis glycines), native to China, has become the most economically damaging insect in soybeans in northeast Iowa. Soybean aphid may have up to 18 generations per year, beginning with overwintering eggs on the alternate host buckthorn. In spring, winged aphids migrate from buckthorn to nearby emerged soybeans. Generations advance in these fields, and then another winged migration occurs in summer spreading from these fields to others. A third migration occurs in fall with aphids moving back to buckthorn. Depending on the season, soybean proximity to buckthorn, and soybean aphid migration patterns, populations of aphids tend to peak in soybeans anywhere from late July to early September. With higher aphid populations, the production of honeydew (the excrement of the aphid) and the resulting black fungus that grows on it (sooty mold) may become apparent. Aphid feeding may cause stunted plants, reduced pods and seeds, and may also transmit viruses that could cause mottling and distortion of leaves, reduced seed set, and discolored seeds.