Nitrogen fertilization and crop diversity effects on soil carbon and nitrogen cycling in Iowa cropland

Nitrogen is critical to sustaining the profitability and productivity of agricultural systems. However, plant-available forms of N are highly mobile and cropland N losses have negative environmental consequences. Nitrogen management strategies differ depending on the farming system, with diverse crop rotations (i.e., those including perennial legume crops) and integrated crop-livestock systems relying primarily on biologically-fixed and recycled N, and simple maize (Zea mays L.)-based systems relying primarily on synthetic N fertilizer inputs. The goal of this research was to investigate C and N cycling in farming systems that span a range of N management strategies and to use this knowledge to advance sustainable N management. Within continuous maize and maize-soybean [Glycine max (L.) Merr.] systems at four Iowa locations, I assessed changes in surface soil organic C (SOC) content over time across a range of N fertilizer rates. I found that N fertilization increased SOC content, with the greatest SOC storage in the optimally-fertilized continuous maize treatment. Using the continuous maize plots at two of these long-term N rate experiments, I investigated legacy impacts of N inputs on fertilizer N use efficiency by tracing isotopically-labeled N fertilizer into crop and soil pools. Fertilizer N recovery was less than 50% at both locations and exhibited a curvilinear response to historical N rate. In my third study, I used three long-term field experiments to determine the impact of crop rotation diversity on SOC content, biochemical composition, and distribution among physical fractions at different depths. Despite greater belowground C inputs in the diverse rotations, crop rotation diversity had inconsistent effects on SOC stocks, and minimal impact on the mechanisms of SOC storage. Finally, I compared the profitability of simple cash grain and integrated crop-livestock systems. The analysis revealed no effect of farming system on profitability, but indicated that more labor is required in the integrated crop-livestock system. The results indicate that simple maize-based systems receiving agronomically optimum synthetic N inputs can sustain SOC and provide adequate financial returns, but result in high N losses from cropland. The adoption of biologically-based N management would reduce cropland N losses with minimal profit loss

Changing religious structures and civil society in Latin America: The case of Nicaragua

Two phenomena have been ongoing in Central America over the past 30 years. The first has been a change in the dominant religious structures in the region with the growth of Evangelical Protestantism and Pentecostalism, as well as ongoing changes within the Roman Catholic Church, such as the rise and fall of Progressive Catholicism. The other major phenomenon has been the establishment of democratic regimes across the isthmus. Putnam, Inglehart, Almond & Verba, among others, assert that for a democracy to flourish a vibrant civil society must be present. These scholars, along with Huntington, Weber, and Wald et al. believe that religious institutions are among the most efficient providers of civil society because of their size and type of associational activity. Furthermore, some religious institutions are more conducive to democracy than others.;This paper examines support for democracy to determine which religious institutions produce the strongest civil society. It also examines whether this religious trend supports or undermines democratization efforts. Using survey data collected in the spring and summer of 2003 in the Granada, Managua, Masaya, and Pueblos Blancos areas of Nicaragua, the paper tests the differences in the forms of civil society produced based on the associational activities undertaken by people from specific denominations

Bovine mammary gland development during gestation

Ten pairs of identical twin heifers were slaughtered at succes-sive two month gestation intervals to study mammary gland development during gestation. Gland composition showed trends of decreasing fat and DNA concentration and of increasing water, percent DFFT, RNA concentration and RNA/DNA ratio as gestation progressed into peak lactation. Udder, gland and DFFT weights, DNA g/gland and alveolar surface area all generally increased throughout gestation until parturi-tion but at peak lactation they had decreased. These results were supported by histological and gross appearance of the glands. Data from six pairs of identical twins were used to plot semilogarithmic regression lines of the parameter vs. time. Parameters investigated were; full trimmed udder weight, glands only weight, DFFT weight, DNA (mg/kg body weight), DNA (g/gland) and alveolar surface area. Their rates of change per month were: 10.8 percent, 22.0 percent, 30.5 percent, 25.3 percent, 24.0 percent and 30.0 percent, respectively. All param-eters measured indicated that bovine mammary gland growth during gesta-tion was continuous from conception to parturition and that no further development occurred up to peak lactation

Comparative Analysis of Photovoltaic Systems across multiple environments

The Cal Poly National Electrical Contractors Association (NECA) Student Chapter proposes to participate in study through the NECA ELECTRI‐International Student Passport Initiative that will fabricate and install four (4) photovoltaic systems in impoverished areas of Ecuador. Following the installation, the NECA student chapter will monitor the operation of the systems and perform a comparative study of the systems across the various ranges of geography, humidity, elevation and ecological conditions

The Role of Art Education in the K-12 Curriculum in West Virginia A Comparative Case Study Using Ethnographic Methods

The visual arts are considered a core subject in the United States public school curriculum. However, the way in which visual arts curriculum is implemented in schools is largely left up to the individual states. This study focused on how art educators\u27 design, direct, find support, and operate visual arts programs in the K-12 public school system in West Virginia. Ethnographic research methods were implemented for this study

Nitrogen dynamics in cover crop-based no-till corn

Legume/grass cover crop mixtures and sidedress subsurface band manure application are two approaches to improving nitrogen (N) use efficiency in a cover crop-based no-till corn (Zea mays L.) system. The objectives of this study were to: 1) quantify cover crop biomass and N content in response to different hairy vetch (Vicia villosa Roth)/cereal rye (Secale cereale L.) sown proportions, 2) evaluate the effects of cover crop species proportions and pelletized poultry litter (PPL) application method on residue decomposition, and 3) model the spatio-temporal dynamics of soil inorganic N as influenced by different cover crop residues and subsurface band-applied PPL. Results suggest that cover crop mixtures can accumulate as much biomass as a cereal rye monoculture and as much N as a hairy vetch monoculture, and have decomposition patterns intermediate between those of monocultures. Subsurface band PPL application provided a localized N source that did not influence decomposition of surface mulches

New Approach for Thermal Protection System of a Probe During Entry

One of the biggest challenges for any thermal protection system (TPS) of a probe is to provide a sufficient barrier for heat generated during descent in order to keep the temperature inside of the probe low enough to support operational temperature of equipment. Typically, such a goal is achieved by having the ceramic tiles and blankets like on the Space Shuttle, silicon based ablators, or metallic systems to cover the probe external surface. This paper discusses the development of an innovative technique for TPS of the probe. It is proposed to use a novel TPS which comprises thermal management of the entry vehicle. It includes: a) absorption of the heat during heat pick load by a Phase Change Material (PCM), b) separation of the compartment which contains PCM from the rest of the space vehicle by a gap with a high thermal resistance, c) maintaining temperature of the internal wall of s/c cabin temperature by transfer heat from the internal wall to the "cold" side of the vehicle and to reject heat into the space during the flight and on a ground, d) utilization of an advanced heat pipe, so called Loop Heat Pipe to transfer heat from the cabin internal wall to the cold side of the s/c and to reject the heat into environment outside of the vehicle. A Loop Heat Pipe is capable of transferring heat against gravit

Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize

Nitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N fertilizer management, and associated changes in SOC quantity and quality, on the fate of N fertilizer inputs is uncertain. Using two 15-year N fertilizer rate experiments on continuous maize (Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on the fate of added N. Across the historical N fertilizer rates, which ranged from 0 to 269 kg N ha−1 yr−1, we applied isotopically-labeled N fertilizer at the empirically-determined site-specific agronomic optimum rate (202 kg N ha−1 at the central location and 269 kg N ha−1 at the southern location) and measured fertilizer recovery in crop and soil pools, and, by difference, environmental losses. Crop fertilizer N recovery efficiency (NREcrop) at physiological maturity averaged 44% and 14% of applied N in central Iowa and southern Iowa, respectively (88 kg N ha−1 and 37 kg N ha−1, respectively). Despite these large differences in NREcrop, the response to historical N rate was remarkably similar across both locations: NREcrop was greatest at low and high historical N rates, and least at the intermediate rates. Decreasing NREcrop from low to intermediate historical N rates corresponded to a decline in early-season fertilizer N recovery in the relatively slow turnover topsoil mineral-associated organic matter pool (0–15 cm), while increasing NREcrop from intermediate to high historical N rates corresponded to an increase in early-season fertilizer N recovery in the relatively fast turnover topsoil particulate organic matter pool and an increase in crop yield potential. Despite the variation in NREcropalong the historical N rate gradient, we did not detect an effect of historical N rate on environmental losses during the growing season, which averaged 34% and 69% of fertilizer N inputs at the central and southern locations, respectively (69 kg N ha−1 and 185 kg N ha−1, respectively). Our results suggest that, while beneficial for SOC storage over the long term, fertilizing at the agronomic optimum N rate can lead to significant environmental N losses

Late-Season Nitrogen Applications Increase Soybean Yield and Seed Protein Concentration

Low seed and meal protein concentration in modern high-yielding soybean [Glycine max L. (Merr.)] cultivars is a major concern but there is limited information on effective cultural practices to address this issue. In the objective of dealing with this problem, this study conducted field experiments in 2019 and 2020 to evaluate the response of seed and meal protein concentrations to the interactive effects of late-season inputs [control, a liquid Bradyrhizobium japonicum inoculation at R3, and 202 kg ha−1 nitrogen (N) fertilizer applied after R5], previous cover crop (fallow or cereal cover crop with residue removed), and short- and full-season maturity group cultivars at three U.S. locations (Fayetteville, Arkansas; Lexington, Kentucky; and St. Paul, Minnesota). The results showed that cover crops had a negative effect on yield in two out of six site-years and decreased seed protein concentration by 8.2 mg g−1 on average in Minnesota. Inoculant applications at R3 did not affect seed protein concentration or yield. The applications of N fertilizer after R5 increased seed protein concentration by 6 to 15 mg g−1, and increased yield in Arkansas by 13% and in Minnesota by 11% relative to the unfertilized control. This study showed that late-season N applications can be an effective cultural practice to increase soybean meal protein concentration in modern high-yielding cultivars above the minimum threshold required by the industry. New research is necessary to investigate sustainable management practices that increase N availability to soybeans late in the season