January 26, 2022
Dr. Fernando Miguez
Associate Professor, Department of Agronomy, Iowa State University.
The 2022 Wernsman Crop Science Lecture
Wednesday, March 9, 2022 at 3:30 PM
Dr. Maria Salas Fernandez
Department of Agronomy, Iowa State University
Students in SSC 601/801 are required to present a seminar during the Crop and Soil Science Seminar time. This week, we have three presentations by Courtney Alexander, Lily Kile, and Anna Weigel. Below are the details of each seminar, including abstracts. Each student is to present for 15-18 minutes, including questions.
Master of Soil Science (MR) Student
Advisor: Dr. Deanna Osmond
Perfluorooctane Sulfonic Acid (PFOS) and Polyfluoro Alkylated Substances (PFAS): Literature Review
Polyfluoro alkylated substances (PFAS) and perfluorooctane sulfonate (PFOS) are a class of chemicals that have become the topic of scientific discussion and will be the subject of this literature review. There are approximately 4,700 variations in existence and due to its composition, it is a nonbiodegradable toxin. Many PFAS products are considered to be essential use, and cannot be replaced without adequate substitutes. An example is PFAS firefighting foams. These compounds are released into the environment through water. The carbon-fluorine tail hydrophobic head group promotes its dissolution in water; it can accumulate on the surface of soils and then move into water. Exposure of PFAS occurs through industrial manufacturing; PFAS is released into the groundwater through seepage. The US Environmental Protection Agency is developing a federal enforceable PFAS standard for drinking water limit to protect the public. Currently, states set their own health advisory goals for acceptable limits. Exposure to PFAS chemicals can cause health issues, which is why standards are critical. Low birth weight in fetuses whose mother was exposed is the most noted. Adults with high lifelong exposure experience obesity and impaired glucose tolerance. Avoiding point sources (i.e. firehouses, military bases, and contaminated drinking water) lessens the likelihood of elevated PFAS in blood levels. The population is exposed through drinking water due to non-filtration at the treatment plant. To reduce PFAS contamination, reverse osmosis home water filters have been effective in removing a percentage. Active carbon soil washing remediation can remove 73% of PFAS in soils but the cost is inefficient. As we learn more about the effects of PFAS, it is important to monitor air and water for these chemicals and set standards, as we look for alternative and safety products.
Master of Science Student
Advisor: Dr. Alex Woodley
The Use of Winter Cover Crops for Nitrogen Management in Organic Sweet Potato Production
This study evaluates three different cover crops for their effectiveness at managing nutrients for organic sweet potato production. The cover crops included were cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), and Austrian winter pea (Pisum sativum). Fallow plots were also grown to compare cover crop treatments with sodium nitrate applied at 0%, 25%, 50%, 75%, 100%, and 150% recommended rates of nitrogen, allowing a fertilizer equivalency estimate. Cover crops were terminated and incorporated two weeks prior to sweet potato planting. The nitrogen availability in the soil, yield data, and nutrient tissue data were measured throughout the growing season. Data obtained from cover crop tissue samples indicate that the C:N ratio generated by crimson clover is above the 25:1 threshold, and even as high as 50:1, making quick release of nitrogen through mineralization unlikely. However, the Austrian winter pea C:N ratios consistently were lower than other cover crop treatments at 20:1. Tissue and root nitrogen concentrations from crimson clover and Austrian winter pea cover crops uptake and store leaf nitrogen at rates equivalent to the 25% recommended nitrogen fertilizer rate (20kgN ha-1). Cereal rye stored nitrogen at a lesser rate, equivalent to the no added nitrogen control. In-season immobilization of soil nitrogen was not apparent with cereal rye. Marketable yield showed no statistically significant differences in yields among any of the cover crop treatments or nitrogen treatments applied less than 100%, despite accumulation of nitrogen in the plant tissue and roots. Nitrogen treatment rates of 100% and 150% showed significantly lower yields. Overall legume cover crops showed a contribution of N to the sweet potato, but this did not improve yields. Lastly, the late termination timing of cover crops for a sweet potato planting, makes crimson clover impractical as a source of available nitrogen due to a high C:N ratio.
Master of Science Student
Advisor: Dr. Luke Gatiboni
Phosphorus Critical Levels for Corn Grown in Greenhouse Conditions in North Carolina Soils
A critical level is the soil test value of a specific nutrient after which no increase in yield will be observed. In North Carolina, one critical value for phosphorus has been established state-wide and is used to calculate fertilizer recommendations. However, this value does not consider variations in soil characteristics throughout the state, specifically texture, which can affect critical levels. Over-application of P is leading to environmental concerns, so critical values should be adjusted to consider these discrepancies. This study was conducted to evaluate ten NC soils to compare P critical levels throughout the state and among soils of different textures and adsorption capacities. Effects of P fertilizer rates in corn grown in greenhouse conditions for 49 days were evaluated on height, plant weight, and P uptake. Increasing soil test P significantly impacted plant height, weight, and P uptake in plant tissue. Critical levels determined for dry matter varied from 38 to 80 mg/dm3, with clayey soils typically having lower critical levels than sandy soils. Texture has a significant effect on critical levels of NC soils. Incorporating these variations in critical levels would be a useful tool for improving P fertilizer recommendations and reducing excess P applications.
April 13, 2022
Dr. Carl Crozier
Professor Emeritus, Crop and Soil Sciences
Monica Aguilar, National Cooperative Business Association – CLUSA International Ecuador Field Coordinator