Kristen S. Veum

Parallel factor analysis of fluorescence EEM spectra to identify THM precursors in lake waters

Dissolved organic matter (DOM) can react with chlorine and yield undesirable disinfection byproducts (DBPs), e.g., trihalomethanes (THMs). Numerous studies have demonstrated that various DOM constituents have DBP formation potentials. We explored in this study the use of fluorescence excitation–emission (EEM) spectroscopy to identify THM precursors in 55 lakes in Missouri, USA. EEMs of the lake waters were decomposed into five factors of different origins through parallel factor analysis. The correlations between the component scores of the factors and THM formation potentials reveal that factors 1 and 2 are likely THM precursors and provided better surrogates than SUVA (dissolved organic carbon-normalized UV254) for predicting DBP formation potential. Thus, monitoring the component scores of the DOM-origin factors would provide a practical tool to identify THM precursors and facilitate utilities to choose appropriate techniques for DBP mitigation and optimize the degree of water treatment.

Conservation effects on soil quality indicators in the Missouri Salt River Basin

The Conservation Effects Assessment Project (CEAP) was initiated in 2002 to quantify the potential benefits of conservation management practices throughout the nation. Within the Central Claypan Region of Missouri, the Salt River Basin was selected as a benchmark watershed for soil and water quality assessments. This study focuses on two objectives: (1) assessing soil quality for 15 different annual cropping and perennial vegetation systems typically employed in this region, and (2) evaluating relationships among multiple measured soil quality indicators (SQIs). Management practices included annual versus perennial vegetation, and varying grass species composition (cool-season versus warm-season), tillage intensity (no-till versus mulch-till), biomass removal, rotation phase, crop rotation (corn [Zea mays L.]–soybean [Glycine max L. Merr] versus corn–soybean–wheat [Triticum aestivum L.]) and incorporation of cover crops into the rotation. Soil samples were obtained in 2008 from 0 to 5 cm (0 to 2 in) and 5 to 15 cm (2 to 6 in) depth layers. Ten biological, physical, chemical, and nutrient SQIs were measured and scored using the Soil Management Assessment Framework (SMAF). Across SQIs, biological and physical indicators were the most sensitive to management effects, reflecting significant differences in organic carbon (C), mineralizable nitrogen (N), β-glucosidase, and bulk density. In the 0 to 5 cm layer, perennial systems demonstrated the greatest SMAF scores, ranging from 93% to 97% of the soils inherent potential. Scores for annual cropping systems ranged from 78% to 92%: diversified no-till, corn–soybean–wheat rotation with cover crops (92%) > no-till, corn–soybean rotation without cover crops (88%) > mulch-till corn–soybean rotation without cover crops (84%). Conversely, in the 5 to 15 cm layer, no-till cropping systems scored lower for overall soil function (58% to 61%) than mulch-till systems (65% to 66%). In the 0 to 5 cm layer, biological soil quality under the diversified no-till system with cover crops was 11% greater than under no-till without cover crops, and 20% greater than under mulch-till without cover crops. The effect of rotation phase was primarily reflected in 64% lower mineralizable N following corn relative to soybean. Additionally, soil nutrient function was significantly affected by biomass removal. The results of this study demonstrate that the benefits of conservation management practices extend beyond soil erosion reduction and improved water quality by highlighting the potential for enhanced soil quality, especially biological soil function. In particular, implementing conservation management practices on marginal and degraded soils in the claypan region can enhance long-term sustainability in annual cropping systems and working grasslands through improved soil quality.

Veterinary Antibiotic Effects on Atrazine Degradation and Soil Microorganisms.

Veterinary antibiotics (VAs) in manure applied to agricultural lands may change agrichemical degradation by altering soil microbial community structure or function. The objectives of this study were to investigate the influence of two VAs, sulfamethazine (SMZ) and oxytetracycline (OTC), on atrazine (ATZ) degradation, soil microbial enzymatic activity, and phospholipid fatty acid (PLFA) markers. Sandy loam soil with and without 5% swine manure (w/w) was amended with 0 or 500 μg kgC radiolabeled ATZ and with 0, 100, or 1000 μg kg SMZ or OTC and incubated at 25°C in the dark for 96 d. The half-life of ATZ was not significantly affected by VA treatment in the presence or absence of manure; however, the VAs significantly ( < 0.05) inhibited ATZ mineralization in soil without manure (25-50% reduction). Manure amendment decreased ATZ degradation by 22%, reduced ATZ mineralization by 50%, and increased the half-life of ATZ by >10 d. The VAs had limited adverse effects on the microbial enzymes β-glucosidase and dehydrogenase in soils with and without manure. In contrast, manure application stimulated dehydrogenase activity and altered chlorinated ATZ metabolite profiles. Concentrations of PLFA markers were reduced by additions of ATZ, manure, OTC, and SMZ; adverse additive effects of combined treatments were noted for arbuscular mycorrhizal fungi and actinobacteria. In this work, the VAs did not influence persistence of the ATZ parent compound or chlorinated ATZ metabolite formation and degradation. However, reduced CO evolved from VA-treated soil suggests an inhibition to the degradation of other ATZ metabolites due to an altered soil microbial community structure.

On-farm soil health evaluations: Challenges and opportunities

Interest in soil health (or soil quality) by producers, conservationists, environmentalists, agricultural scientists, policy makers, and many other groups has increased exponentially during the past five years. Yet questions remain: can soil health be measured at the field or farm scale, and can that data be used to improve land management decisions and thus help protect, conserve, and restore our fragile soil resources? Our opinion, based on three years of experience through the Soil Health Partnership (SHP), is that the answer to both of these questions is a resounding yes! Recognizing that several other public and private groups are now expressing interest in assessing soil health, our goals are to (1) summarize several of the SHP lessons learned during the past three years, (2) provide guidelines for future on-farm soil health studies, and (3) share some of our preliminary soil health assessment findings. EVOLUTION OF THE SOIL HEALTH PARTNERSHIP The SHP is a farmer-led initiative of the National Corn Growers Association developed in 2014 with financial and technical support from Monsanto, the USDA Natural Resources Conservation Service (NRCS), United Soybean Board, Walton Family Foundation, Midwest Row Crop Collaborative, Environmental Defense Fund, and Nature Conservancy. The SHP defines soil health as…

Evaluation of the Haney Soil Health Tool for corn nitrogen recommendations across eight Midwest states

Use and development of soil biological tests for estimating soil nitrogen (N) availability and subsequently corn (Zea mays L.) fertilizer N recommendations is garnering considerable interest. The objective of this research was to evaluate relationships between the Haney Soil Health Test (HSHT), also known as the Soil Health Tool or Haney test, and the economically optimum N rate (EONR) for corn grain yield at 17 sites in eight Midwest US states in 2016. Trials were conducted with a standard set of protocols that included a nonfertilized control plus six N rates applied at planting or as a split between planting and sidedress, soil samples for the HSHT prior to planting, and grain harvest at physiological maturity, and determination of EONR for each N application timing. Results indicated that HSHT recommendations with expected yield accounted for ≤28% of the variation in EONR among sites and N timings. Two components of the HSHT not directly used in the HSHT N recommendation for corn, the soil health calculation, or soil health score, and the Solvita carbon dioxide (CO2)-Burst lab test, accounted for the most variation in EONR. These two components were moderately related (R2 = 0.29 to 0.39) to soil organic matter (OM), highly related (R2 = 0.98) with each other, and subsequently both accounted for over one-half (R2 = 0.55) of the variation in EONR for N applied at planting or as a split. With additional research, these two components may help improve N recommendations for corn in the Midwest, especially Solvita CO2-Burst because it costs less to determine than the soil health calculation.

Effects of Cover Crops on Soil Quality: Selected Chemical and Biological Parameters

ABSTRACT Cover crops improve soil quality properties and thus land productivity. We compared soil chemical and biological changes influenced by hairy vetch (Vicia villosa Roth.) and cereal rye (Secale cereal) cover crops grown in Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs), Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualfs), or sand in the greenhouse. Cover crop biomass, soil β-glucosidase, β-glucosaminidase, and fluorescein diacetate (FDA) hydrolase activities, and soil chemical properties were measured at six, nine, and twelve weeks after planting. Cover crop biomass increased with highest (p < 0.0001) yields for hairy vetch and cereal rye in Menfro and Mexico soils, respectively. β-glucosaminidase, FDA, organic carbon (C), total nitrogen (N), and total phosphorus (P) contents significantly decreased in all soils for both cover crops. However, β-glucosidase activity significantly increased (p < 0.0001). Long-term field studies are needed to evaluate soil quality improvement under cover crops, especially for soils with marginal organic matter and fertility.