Seasonal and Rotational Influences on Corn Nitrogen Requirements

This project was designed to study the N fertilization needs in continuous corn (CC) and corn rotated with soybean (SC) as influenced by location and climate. Multiple rates of fertilizer N were spring applied, with the intent to measure yield response to N within each rotation on a yearly basis for multiple years at multiple sites across Iowa. This will allow determination of N requirements for each rotation, differences that exist between the two rotations, responses to applied N across different soils and climatic conditions, and evaluation of tools used to adjust N application.

Evaluation of Narrow Row Soybeans

Producers continue to look at different management practices to increase corn and soybean yields. One area of interest is planting corn and soybeans in narrow rows. Traditionally, these crops have been planted in row widths of 30 to 38 in. Planters on the market today have the capability to plant corn and soybeans in 15- and 20-in. rows, as well as in twin rows that are spaced eight inches apart. This study was set up to evaluate the yield impact of planting soybeans in 15-in. rows versus the traditional 30-in. row spacing.

Placement Methods of Phosphorus and Potassium for Corn and Soybean Managed with No-till and Chisel-plow/Disk Tillage

No-till management limits 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 K could 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, this long-term study was established in 1994 to evaluate P and K fertilizer placement methods and grain yield of corn-soybean rotations managed with notill and chisel-plow/disk tillage.

Impact of Liquid Swine Manure Application and Cover Crops on Ground Water Quality

The primary objective of this project was to determine the impact of appropriate rates of swine manure applications to corn and soybeans based on nitrogen and phosphorus requirements of crops, soil phosphorus accumulation, and the potential of nitrate and phosphorus leaching to groundwater. Another purpose of this long-term experimental study was to develop and recommend appropriate manure and nutrient management practices to producers to minimize the water contamination potential and enhance the use of swine manure as inorganic fertilizer. A third component of this study was to determine the potential effects of rye as a cover crop to reduce nitrate loss to shallow ground water.

Effect of Date of Planting on Soybean Sudden Death Syndrome

The objectives of this project was to study the effect of planting date on the onset of soybean sudden death syndrome (SDS). It is believed, that avoiding planting soybeans into wet cold soil may delay or lower the severity of SDS. Planting date for soybeans is important and can have a large effect on yield potential.

Corn Response to Sulfur Application Rate

Historically, sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. Soils supply, or a combination from sources such as soil organic matter, profile sulfate, manure, and precipitation have met crop S needs. However, over the past few years, S deficiencies in alfalfa and corn have been documented. Large crop yield responses have been measured in some fields containing soils with low organic matter, side-slope landscape position, or coarse soil texture, especially in northeastern Iowa. The objective of this study was to determine S response in corn and soybean in north-central Iowa.

Improving Prairie Restorations

Deciding when and how to plant prairie to simultaneously establish native prairie seedlings and prevent weed (non-prairie species) invasion can be challenging. Planting cover crops is an increasingly common management practice for prairie plantings. The idea is based on the assumption that the cover plant will act as a nurse plant to prairie seedlings and will have a positive effect on seedling recruitment by increasing weed suppression. This is predicted to lead to reduced weed biomass and increased prairie establishment in restoration plantings.

Northeast Research Farm Summary

Includes Farm and Weather Summary, Research Farm Projects and Experiments in Previous Animal Reports.

High Yield of Soybeans Study

The research project was designed to study soybean plant and yield responses to certain products. Soybean producers generally look to maximize profit, and with increased soybean prices, financial returns have been obtained from even smaller yield responses. The project began in 2011 as a two-year study designed to look at the effects of both seed and foliar treatments applied to soybeans.

Evaluation of Bt and Non-Bt Corn with and without Soil Insecticides for Control of Corn Rootworm

The purpose of this study was to evaluate the effectiveness of Bt corn and soil insecticides, either alone or in combination, for the control of corn rootworm. Evaluation of Bt hybrids included SmartStax, SmartStax with a blended refuge (refuge in the bag), and Herculex XTRA. Soil insecticides evaluated were SmartChoice-SB, Counter-SB, Aztec, and Force.

Effects of Headline® on Soybean Aphid Resistant and Susceptible Varieties

With the introduction of soybean aphid-resistant varieties, growers have another option for controlling the pest. This study was designed to see how each variety responded to Headline® fungicide at different application timings.

Effects of Seed Treatments and a Soil-applied Nematicide on Corn Yields and Nematode Population Densities

Plant-parasitic nematodes are microscopic worms that feed on plants. Almost every nematode that feeds on corn is capable of feeding on many other plants. These nematode parasites are thought to be native to most Iowa soils and to have fed on native plants before corn was grown as a cultivated crop. Population densities (numbers) of most species of plant-parasitic nematodes that feed on corn have to increase to damaging levels (called damage thresholds) before yield loss occurs.

A Comparison of Soybean Seed Treatments

Seed treatment options are available to manage various fungi, insects, and nematodes that can damage soybeans before, during, and after emergence. These treatments are potentially beneficial for stand establishment and for protection against soybean cyst nematode (SCN). However, these seed treatments represent an additional cost to the producer.

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.

Soybean Aphid Efficacy Evaluation

Soybean (Glycine max), grown in Iowa and most of the north central region of the United States, has not required regular insecticide use. The soybean aphid, Aphis glycines (Hemiptera: Aphididae), causes yield losses from direct plant feeding, and has been shown to transmit several plant viruses. In Iowa, soybean aphid can colonize soybean fields in June and has developed into outbreaks in July and August capable of reducing yields by nearly 40 percent.