Cover Crop and Nitrogen Fertilizer Management for Potato Production in the Northeast

Potato (Solanum tuberosum L.) rates fourth among the world’s agricultural products in terms of production volume and human consumption and worldwide demand for potatoes will exceed that of rice, wheat, or corn by 2020. Potato consumption has been a major part of the North American diet since early in the 17th century and as a dominant arable crop in the Northeastern United States. There are over 2700 potato fields in the Northeast United States and potato growers often over apply nitrogen (N) fertilizer to ensure against loss of yield. High mobility of nitrate form N fertilization in the soil profile makes it susceptible to leach to the lower soil levels leading to ground water nitrate contamination, other environmental concerns, and increased costs of production. Rye (Secale cereale L.) is the most widely grown cover crop in the Northeast U.S, and its N-scavenging capacity and adaptability to the soils and climates in the region have been well documented. However, it might not be an adequate source of N for the early planted cash crops in the spring because it is not given the opportunity to grow in the spring and accumulate substantial amount of biomass. Therefore, we implemented field experiments to evaluate whether forage radish (Raphanus sativus L.) or winter peas (Pisum sativum L.) could be a more appropriate cover crop than rye in rotation with Dark Red Norland and Superior potatoes in Massachusetts. We also applied four levels of N fertilizer (0, 75, 150, and 225 kg ha-1) in combination with cover crops to tailoring N rates as an external source of N in addition to the released N from cover crop residues. Our study centered on three major topics: (i) Cover crop decomposition rate and trend of nutrient release in a conventional or no till system to evaluate whether there is a synchrony with potato nutrient demands (ii) Tuber yield and nutrient density of potatoes as influenced by cover crops and N fertilization and (iii) Nitrogen use efficiency (NUE) indices, tuber quality, and pest control in potatoes. Our results indicated that a conventional tilling system accelerated the decomposition process and also increased the rate of nutrient loss in the soil compared with a no till system. Among the cover crops used in this study, forage radish or peas accumulated more N than rye. Also, forage radish or peas with narrower C:N ratio released their N content in a faster trend. Potato tuber yield in both varieties was improved, and peas or forage radish outperformed than rye or no cover crop plots in this regard. Also, forage radish was advantageous over winter peas or rye in terms of providing nutrients other than N as suggested by more nutrient dense potatoes. Cover crops, especially peas or forage radish were efficient in reducing N fertilization requirements in both potato varieties as indicated by higher NUE parameters. Potatoes planted after cover crops were less efficient in utilization of the supplied N than potatoes following fallow. Application of high rates of N fertilizer decreased NUE parameters through enhanced vegetative growth or probably environmental losses. Forage radish or peas exhibited more synchrony with potato N demands at its critical growth stages in terms of N release from residues. Cover crops did not produce potato tubers of higher quality than no cover crop plots. Colorado potato beetle infestation was lower in potato plants after rye early in the spring than with the other cover crops; however, later in the season all of the treatments showed the same infestation. Weed infestation tended to be lower in cover crop plots than in no cover crop plots, yet, rye and forage radish were advantageous over winter peas for suppressing weeds. Overall, it is proposed that planting forage radish as early as possible in late August or early September could produce more potato yield and improve nutrient density than winter peas or winter rye. Also, to get the most out of the released nutrients, especially nitrogen, it is important to prepare the land and plant potatoes as early as possible in the spring

Two-Stage Stabiliser Addition Protocol as a Means to Reduce the Size and Improve the Uniformity of Polymer Beads in Suspension Polymerisation

A 2-stage stabiliser addition protocol is suggested for reducing the size and improving the uniformity of polymer beads resulting from conventional suspension polymerisation. The stabiliser load was divided into an initial charge and a secondary addition. The use of a low concentration of stabilizer in the initial charge served to assist drop rupture while avoiding significant reduction in drop size and production of too many satellite droplets. The secondary addition time of stabiliser occurred just before the onset of the growth stage when drops were vulnerable to coalescence but were robust against break up due to their high viscosity. The secondary addition of stabiliser served to provide stability to monomer drops during the growth stage and as a result the drops underwent limited coalescence. This resulted in the formation of smaller and more uniform polymer beads in comparison to beads obtained by conventional suspension polymerisation at the same overall concentration of stabiliser

“On-The-Fly” Fabrication of Highly-Ordered Interconnected Cylindrical and Spherical Porous Microparticles via Dual Polymerization Zone Microfluidics

A microfluidic platform with dual photopolymerization zones has been developed for production of novel uniform interconnected porous particles with shapes imposed either by the geometry of the external capillary or by the thermodynamic minimisation of interfacial area. Double w/o/w drops with well-defined internal droplet size and number were produced and then exposed to online photopolymerization to create the porous particles. Cylindrical interconnected porous particles were produced in a segmented flow where the drops took the shape of the capillary. The microfluidic set up included an extension capillary where the drops relaxed and conformed to their thermodynamically favoured morphology. Window opening of the particles occurred “on-the-fly” during UV polymerization without using any offline auxiliary methods. A distinction was made between critically and highly packed arrangements in double drops. The window opening occurred consistently for highly packed spherical drops, but only for critically packed drops containing more than 6 internal cores at internal phase ratio as low as 0.35. The size and number of cores, shape and structure of double drops could be precisely tuned by the flowrate and by packing structure of the inner droplets

Influence of the Deeper Scaffolding Framework on Problem-solving Performance and Transfer of Knowledge

One of major goals of education is to prepare effective and efficient problem solvers. The purpose of this study was to determine the impact of the DEEPER framework of scaffolding problem solving on three important variables: problem-solving performance, domain knowledge acquisition, and transfer of knowledge in a problem-based learning environment in higher education. In this quasi-experimental study, the pretest-posttest control group design was used to collect data. One hundred and nine students participated in this study. They were randomly assigned to two groups: the treatment group and the control group. The two groups were asked to solve an ill-structured problem on the role of aqua insects in the biological assessment of river water. The control and treatment groups differed in the nature of instructional scaffolding that they received during problem solving. The treatment group used the DEEPER process scaffolds, and the control group was asked to solve the problem using a more traditional, rationale-based scaffold. The data was gathered to determine if there were any differences between the groups on three dependent variables: domain knowledge, transfer of knowledge, and problem-solving performance.The findings of this study demonstrate that while the implementation of the DEEPER scaffolding of problem-solving resulted in improved problem-solving performance in the treatment group, differences were not observed on the measure of domain knowledge acquisition. Transfer of knowledge was not significantly impacted according to a test of the differences in group means, however correlational analyses revealed a positive relationship between two of the DEEPER tasks and performance on the measure of knowledge transfer. Most of the tasks embedded within each of the DEEPER scaffolding steps were positively correlated with students' problem-solving performance and the magnitude of these relationships was moderate to strong. Thus, it appears that the DEEPER framework for scaffolding problem solving provides a useful method for designing and structuring problem-solving activities for novice science learners at the higher education level.School of Teaching and Curriculum Leadershi

Evolution of particle size distribution in suspension polymerisation reactions

Suspension polymerisation processes are commercially important for the production of polymer beads having wide applications. Polymers produced by suspension polymerisation can be directly used for particular applications such as chromatographic separations and ion-exchange resins. Particle Size Distribution (PSD) may appreciably influence the performance of the final product. Therefore, the evolution of PSD is a major concern in the design of a suspension polymerisation process. In this research, methyl methacrylate (MMA) has been used as a model monomer. A comparative study of MMA suspension polymerisation and MMNwater dispersion was carried out, for the first time, to elaborate the evolution of mean particle size and distribution. Polyvinyl alcohol (PVA) and Lauroyl Peroxide (LPO) have been used as stabiliser and initiator, respectively. Polymerisation experiments were carried out using a 1-litre jacketed glass reactor equipped with a turbine impeller and a condenser. The stabiliser, initiator and chain transfer concentrations, inhibitor concentration and type, reaction temperature, impeller speed, and monomer hold up were used as variables. A mathematical model was developed to predict the kinetics of polymerisation as well as the evolution of PSD by population balance modelling. The experimental results were compared with the model predictions. From the comprehensive experimental results, the characteristic intervals of a typical suspension polymerisation were realised as: 1) Transition stage during which PSD narrows dramatically and drop size decreases exponentially due to higher rate of drop break up in comparison with drop coalescence . _ until a steady state is reached. The importance, and even the existence, of the transition stage have been totally ignored in the literature. The results indicate that increasing the impeller speed, and PV A concentration will lead to a shorter transition period. Also increasing the rate of reaction, via increasing initiator concentration, and reaction temperature will shorten this period. ABSTRACT 2) Quasi steady-state stage during which the rate of drop break up and drop coalescence are almost balanced leading to a steady-state drop size and distribution. The occurrence of this stage is conditional. Low impeller speed and PV A concentration may remove the quasi steady-state stage completely and drops may start growing considerably after a sharp decrease in size during the transition stage. 3) Growth stage during which the rate of drop break up considerably falls below the rate of drop coalescence due to the viscosity build up in drops leading to drop enlargement and PSD broadening. Results show that the onset of the growth stage may not be fixed and it depends on the balance of the forces acting on drops. The onset of the growth stage in terms of time was advanced with decreasing stirring speed and PV A concentration and increasing monomer hold up. Under a static steady state, which is formed when a high concentration of PV A is used, there is almost no growth. 4) Identification stage during which a solid-liquid suspension is attained and the PSD and mean particle size remain unchanged afterwards. The onset of this stage appears to be fairly constant for different formulations. The developed model could fairly predict the rate of polymerisation. It was also capable of predicting the evolution of particle size average and distribution qualitatively in the course of polymerisation. The results can be used as a guideline for the control of particle size and distribution in suspension polymerisation reactors. A more quantitative exploitation of the model has been left for a future research.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Preparation and characterization of tunable oil-encapsulated alginate microfibers

© 2017 Elsevier LtdA single-step microfluidic approach was developed which allowed a wide range of oil-loaded calcium-alginate microfibers to be fabricated at the same compositions but with different morphologies. A framework for characterization of wavy fibers was developed which linked the fiber morphology and tensile strength to the encapsulation type and geometry. The geometry of oil encapsulates as well as the fibers surface morphology were conveniently tuned via the gelation reaction dynamics and phase flow rates. A 2D mathematical reconstruction of the fiber's surface revealed that fibers having spherical and ellipsoid encapsulates enjoyed the highest surface roughness. Tubular fibers endured the highest tensile force before failure, compared to fibers with other encapsulate geometries at a fixed alginate phase ratio (ϕalg). Fibers with increased ϕalg withstood a higher tensile force. However, the strength of fibers reduced if the increase in ϕalg altered the encapsulate geometry from tubular to discrete oil segments. Tubular fibers also underwent maximum elastic and plastic deformation prior to failure, among all fibers

Integrated Management Practices for Establishing Upland Switchgrass Varieties

Establishment of switchgrass (Panicum virgatum L.) is challenging, and failure in establishment may expose growers to considerable economic risk. The objectives of this research were to (i) evaluate whether management practices are variety-specific for the establishment of switchgrass and (ii) assess the effectiveness of cover crops as preceding crops on ‘Shawnee’ switchgrass establishment. Therefore, two studies were conducted at the University of Massachusetts Agricultural Experiment Station in Deerfield, MA, USA, in the 2011–2012 and 2012–2013 growing seasons. In Experiment 1, cover crop treatments (fallow, oat (Avena sativa L.) and rye (Secale cereale L.)) were the main plots, the two seeding methods (no-till drill and a cultipacker seeder (Brillion)) were the sub-plots, and the two varieties (‘Cave-in-Rock’ (CIR) and Shawnee)) were the sub-sub-plots. The second study was conducted using Shawnee switchgrass and involved the three cover crop treatments used in Experiment 1 using a cultipacker seeder with seed firming prior to planting but not afterwards (consistent in both experiments). The results indicated that a combination of oat and no-till resulted in higher tiller density (493%), lower weed biomass (77%), increased switchgrass biomass (SGB) (283%) and SGB to weed biomass (WB) ratio. Compared with Shawnee, CIR planted into a winter-killed oat residue had higher tiller density (93%), lower weed biomass (18%), higher switchgrass yield (128%) and thus a greater SGB:WB ratio (507%). Trends of switchgrass response to management practices, however, were similar between the two varieties, indicating that seed quality rather than management practices could influence switchgrass’s response to management practices. In Experiment 2, Shawnee tiller density was suppressed by rye as the preceding crop, possibly due to late termination of rye. Shawnee switchgrass yields were below 1000 kg ha−1 under all management practices; thus, harvesting should happen in the year following establishment. Future research should focus on comparing no-till drilling with cultipacker seeder with rolling not only before but after seeding to increase seed–soil contac