Soil and Plant Fertility Management for Soybeans

Producers utilizing a two year rotation of corn and soybean often apply fertilizer on a biannual basis, spreading recommended amounts of phosphorus and potassium for both crops prior to corn establishment. This approach minimizes application costs and is in accordance with university fertility recommendations that have found a low probability of fertilizer yield response when soils tested at the medium/optimum level or above. However, the field trials on which these state recommendations were developed are often several decades old. Increases in average corn and soybean yields and associated increases in crop nutrient removal rates have called into question the validity of these recommendations for current production environments. This study investigated the response of soil test levels and grain yield to annual and biannual fertilizer applications made at 1x and 2x rates of current university fertilizer recommendations.

Species Diversity is a Good Predictor of Prairie Plant Persistence in Restorations

Prairie restoration projects sometimes fail because of heavy invasion by invasive weeds, especially if they are not intensively managed. Few restoration projects are sampled after the first few years post-establishment, and little is known about what predictors are significant in maintaining restored communities over the very long term. Here, we stopped weeding experimental restoration plots to determine if persistence (that is, remaining unchanged after weeds are allowed to invade) of native prairie in western Iowa was related to planted species diversity

Second Year Performance of Honeycrisp on 31 Dwarfing Rootstocks in the Iowa Planting of the NC-140 2010 Regional Apple Rootstock Trial

To evaluate the adaptability and performance of new and promising apple rootstocks in the dwarfing size-control category, a NC-140 regional rootstock trial was established in 2010 at 12 sites in the United States (CO, IA, IL, IN, MA, MI, MN, NJ, NY, OH, UT, WI), two sites in Canada (BC, NS), and one site in Mexico (CHIH) with Honeycrisp serving as the test cultivar. The Iowa planting, located at the ISU Horticulture Research Station, includes 31 rootstocks with new selections from the Cornell-Geneva breeding program (G, CG.), Russia (Bud), Germany (PiAu), and Japan (Supp), with M.26, M.9 Pajam 2, and M.9 T337 serving as industry standards. Tissue cultured propagated (TC) rootstocks of G.41, G.202, and G.935 were included for comparison with normal (N) stool bed propagated rootstocks. This report summarizes the tree-growth characteristics of the Iowa planting during the 2011 growing season.

Testing a Warning System for Anthracnose Fruit Rot on Day-neutral Strawberry

Anthracnose fruit rot (AFR) of strawberry is caused by three Colletotrichum spp. In the Midwest, however, only Colletotrichum acutatum is found. This fungus can attach itself to apparently healthy plants and spread throughout without causing symptoms on the foliage. When fruit begin to ripen and weather conditions are rainy and warm, AFR can suddenly cause great damage to the fruit. To protect against AFR where it has appeared in the past, growers need to spray every 7 to 10 days beginning at the start of bloom until harvest.

Western Research Farm Summary

Includes Farm Summary and Research Farm Projects.

Yields of Corn, Soybeans, and Alfalfa in Western Iowa: 1990 to 2011

The ISU Western Research Farm, Castana, Iowa is one of the oldest in Iowa dating to 1946. It also has a unique location in the loess hills of western Iowa. The research farm was set up to study the deep loess soils, particularly crop production and soil conservation methods. Although the work at the research farm has transitioned away from traditional plot work, yields of major crops grown at the farm, and climate data are collected each year. Crop yields are a reflection of current technologies and weather. In western Iowa, rainfall is especially critical and is often the limiting factor.

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.

Horticulture Research Station Summary

Includes Farm Staff, Farm and Weather Summary and Research Station Projects.

Evaluation of a Blended Refuge for Corn Rootworm

The purpose of this study was to evaluate the effectiveness of the blended refuge concept against corn rootworms. The treatments evaluated include a pure stand of Herculex XTRA (HXX), a pure stand of Roundup Ready 2 (RR2), a pure stand of RR2 with Force 3G applied overtop, and two treatments with the refuge in a bag concept–one with 95 percent HXX and a 5 percent RR2 blended refuge and the other with 90 percent HXX and a 10 percent RR2 blended refuge.

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.

Muscatine Island Research Farm Summary

Includes Farm and Weather Summary and Research Farm Projects.