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Soybean [Glycine max (L.) Merr.] seed cost has increased dramatically with the introduction and adoption of herbicide-resistant cultivars, generating interest from growers to reduce seeding rates to the lowest possible level that does not affect yield. Research indicates that greater seeding rates are needed to maximize yield under low-yielding environments and less seed is needed in high-yielding environments, but this has not been confirmed with recent research in Virginia. The objectives of this research was to 1) determine the yield response of soybean cultivars with differing growth habits and maturities grown in full-season and double-crop systems to seeding rate under different yield environments; and 2) compare two seeding rates in large on-farm strip-plots to determine if the growth environment within the field affects the yield response to seeding rate. For objective 1, small-plot research was conducted on Piedmont and Coastal Plain sites across Virginia from 2017 thru 2020. Maturity group (MG) 4 or 5 cultivars were planted in 46-cm rows at the following seeding rates: full-season soybean – 74,130, 148,260, 222,390, 296,520, 370,650, and 444,780 seed ha-1; and double-crop soybean – 197,680, 296,520, 395,360, 494,200, 543,620, and 593,040 seed ha-1. One cultivar per MG was used in 2017 and 2018, but the experiments were expanded to include two cultivars, differing in canopy structure, within each MG in 2019 and 2020. On-farm research compared a high and low seeding rate with a 100,000 seed ha-1 difference based upon grower current practices. To determine growth influence on the yield response, normal difference vegetative index (NDVI) was measured at 2-week intervals from late-vegetative to late-reproductive stages in small-plot and on-farm experiments. Double-crop soybean required an average of 205,000 more seed ha-1 than full-season soybean. Although yield response varied with site and year, MG 4 cultivars usually yielded more than MG 5 at higher seeding rates, but less at lower seeding rate. No differences between cultivar canopy structure were present in full-season systems; differences were revealed in double-crop systems but were not consistent over sites. To obtain 95% of maximum yield, 170,000 to 390,000 seed ha-1 were required in full-season soybean and 470,000 to 550,000 seed ha-1 were required in double-crop soybean. While the NDVI response to seeding rate generally reflected the yield response at most site-years, relationship between yield and NDVI was weak. In on-farm experiments, higher seeding rates yielded more at 3 of 6 sites, but differences varied within the field. The yield-NDVI relationship was stronger due to greater variability within the field, but these differences due to seeding rate could not be discerned. Growing environment, primarily amount and distribution of rainfall, greatly influenced these results; therefore, more exact site-specific seed rate recommendations will be difficult in Virginia's environment. / Master of Science / Soybean is one of the world's most important seed legumes and contributes a major portion of global protein concentrate for livestock feeding and oil for human consumption therefore, it is essential to continually and sustainably increase yield while maintaining profitability for growers. Through adoption of precision agriculture technology by Southeastern farmers, site-specific management using variable rate application and/or automatic section control of inputs are able to be utilized when field variability is assessed. Additionally, on-farm experiments validate small plot research with larger field-scale evaluations with proper technology and design. In this study various seeding rates on soybean yield in both small-plot and on-farm experiments, as influenced by variable growth and yield differences within the field, was determined. On-farm research allowed better observation of yield response to seeding rate for each field, allowing the evaluation of production practices under realistic growing conditions. Ultimately, it is expected that more early-season growth in areas of the field with greater productivity will result in greater yields using less seed per hectare. The utilization of vegetative indices as well as remote sensing technology contributed largely to the analysis of yield and varying seeding rates. Accordingly, measurements were correlated with one another to determine if remote sensing techniques can be substituted for ground measurements in predicting yields.

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Master of Science / Department of Agronomy / Ignacio Ciampitti / Genotype by seeding rate interaction can play a critical role in wheat (Triticum aestivum L.) yield potential. The objectives of this study were to i) quantify wheat yield response and ii) early-season plant establishment related to the planting technology under diverse seeding rates and with contrasting varieties relative to their tillering ability. Four studies were established at two locations during two growing seasons (2015-16 and 2016-17) at Ashland Bottoms (dryland and conventional till in the first year and no-till in the second year) and at Topeka (irrigated and no-tillage for both years) field research stations (KS, US). Two winter wheat varieties were planted with two different planting systems (singulated and conventional drill) at four different seeding rates (45, 90, 135, and 180 kg ha⁻¹). Early-season measurements consisted of stand counts, canopy coverage (estimated via imagery collection via small-unmanned aerial vehicle systems - sUAVS), determination of early-season gaps within the stand of plants, and spacing between plants. Early season measurements (emergence progression, stand count, and canopy coverage) and biomass did not present differences among treatments. At Ashland, across 2-yrs, single factors seeding rate and genotype significantly impacted yields. Seeding rate factor positively affected yields, ranging from 4.7 to 5.4 Mg ha⁻¹ with seeding rates going from 45 to 135 kg ha⁻¹, respectively. For the genotype factor, the variety WB Cedar (high-tillering) presented an overall yield of 605 kg ha⁻¹ greater than WB 4458 (low-tillering). Across locations, the seeding system did not influence yields for both years of the study. At Topeka, the seeding system significantly influenced yields in 2017, with singulation outyielding the drill system, in 161 kg ha⁻¹. Further research is needed at a farmer-scale testing more winter wheat varieties and focusing on lower seeding rates to better understand the potential benefits of the implementation of this new technology.

3 pp. / Production practices for grain sorghum are discussed including hybrid selection, planting date, seeding rate, row configuration, irrigation, fertilization, pest control, and harvesting.

Made available in DSpace on 2014-06-11T19:22:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-18Bitstream added on 2014-06-13T20:09:13Z : No. of bitstreams: 1 veronese_m_me_botfca.pdf: 856581 bytes, checksum: 56b31a95bc712cf6ffca191fada0521b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Em sistemas de semeadura direta, o calcário tem sido aplicado superficialmente. Devido a sua baixa solubilidade e mobilidade, tem ocorrido excesso de calcário nos primeiros centímetros do perfil do solo. Pesquisas têm demonstrado resultados contraditórios quanto à movimentação do calcário e a correção da acidez em profundidade, na presença de espécies de cobertura. O objetivo deste trabalho é estudar a contribuição diferencial de espécies de cobertura em Sistema de Semeadura Direta sobre a mobilização no perfil do solo, dos produtos da dissolução do calcário e bases trocáveis. O experimento foi instalado e conduzido, por dois anos agrícolas (2008/2009 e 2009/2010), na Estação Experimental do Programa de Monitoramente de Adução (PMA) da Fundação MT, localizada no município de Itiquira-MT. O delineamento experimental foi em blocos completos ao acaso, em parcelas sub subdivididas com: sistema de cultivo: soja/pousio/soja, soja/milheto/soja e soja/braquiária/soja; aplicação do calcário: em superfície, incorporado a 20 e 40 cm de profundidade, e doses de calcário: 0, 0,5, 1,0 e 2,0 vezes a quantidade necessária para elevar a V % = 50 na profundidade de 20 cm. Foram realizadas amostragens de solo para determinação da fertilidade após 490 e 620 dias da aplicação do corretivo. No pleno florescimento do segundo cultivo da cultura da soja, foi feita a amostragem de folhas para análise química nutricional e a avaliação do desenvolvimento do sistema radicular. Após a maturação do segundo cultivo da soja foi estimada a produtividade de grãos. Os resultados foram submetidos às análises estatísticas, utilizando-se o pacote estatístico Sisvar / In no-tillage seeding systems, limestone has been applied on the soil surface. Due to its low solubility and mobility, a limestone excess has been occurring in the first centimeters of the soil profile. Studies have shown contradictory results regarding limestone mobility and acidity correction in depth, in the presence of covering species. This study aimed to evaluate the differential contribution of covering species in no-tillage systems on the mobility in the soil profile, products of limestone dissolution and exchangeable bases. The experiment was installed and carried out in the Experimental Station of the Fertilizer Monitoring Program (Programa de Monitoramento de Adubação - PMA) at FUNDAÇÃO MT, in the city of Itiquira, MT, Brazil. The experiment had completely randomized block design in parcels that were subdivided as follow: crop system: soybean/fallow/soybean; soybean/millet/soybean; soybean/brachiaria/soybean; limestone application on the surface and incorporated at 20 and 40 cm depth, and limestone doses: 0, 0.5, 1.0 and 2.0 times the necessary amount to increase V % = 50 at 20 cm depth. Some soil samplings were done to determine fertility after 490 and 620 days of corrective application. During the second soybean cultivation flowering, leaf sampling was done for chemical and nutritional analysis and root system development evaluation. After maturing of the second soybean cultivation, grain productivity was estimated. The results were submitted to statistical analysis using the Sisvar statistical package

Predicting developmental growth stages in soft red winter wheat (Triticum aestivum L.) (SRWW) could improve agronomic management in Kentucky. However, predicting SRWW development is complex due to vernalization requirement and photoperiod sensitivity differences of cultivars. The objectives of this study are to (1) determine ability of Kompetitive Allele Specific PCR (KASP) genotyping to predict phenotype; (2) determine the relative vernalization requirement (RVR) of 50 SRWW cultivars in a greenhouse (GH) assay; and (3) measure growing degree-days (GDD) required by cultivars to reach eight growth stages in a field assay. Fifty SRWW cultivars were characterized with 14 KASP markers for Vrn and Ppd loci. Additionally, cultivars were grown in a GH, vernalized outdoors for three, six, or nine weeks, and moved back into the GH where days to full flower were measured. Cultivars were also seeded into hill plots monthly from October to March at Princeton (2016; 2017) and Lexington, KY (2017) in three field trials. Cumulative GDD to emergence, green-up, pseudo-stem erection, jointing, flag leaf, beginning flower, full flower, and harvest maturity were measured. Field trials and supporting historical wheat development data suggest that prediction of SRWW growth and development is possible using a cumulative GDD scale in Kentucky.

Seeding is an important variable in controlling or directing the assembly of peptides. The presence of impurities, responsible for creating a 'dip' in the surface tension versus peptide concentration profile, is used to determine the critical aggregation concentration (CAC). This phenomenon is investigated to differentiate crude and high purity EAK16-II peptide. The purified peptide did not show this 'dip' and clearly indicated a critical aggregation concentration for EAK16-II at 0. 09 mg/mL by surface tension measurements. Conversely, a surface tension 'dip' is clearly observed for the crude EAK16-II peptide. Atomic Force Microscopy imaged the nanostructures of aggregates. The presence of impurities induces fibre formation below the CAC. This study provides information about the seeding effect of peptide assembly at low concentrations as well as the modification of surface activity of assembled peptide particles. Alanine, glutamic acid and lysine were used as model seeding agents to simulate the seeding phenomenon and better understand the nucleation mechanism of peptide assembly. All amino acid monomers were able to induce fibre formations at low peptide concentrations. However, only glutamic acid and lysine were able to produce the surface tension dip profile observed in the crude peptide. This information may be of importance in understanding fibrillogenesis occurring in conformational diseases and other biomedical applications including drug delivery.

Seeding is an important variable in controlling or directing the assembly of peptides. The presence of impurities, responsible for creating a 'dip' in the surface tension versus peptide concentration profile, is used to determine the critical aggregation concentration (CAC). This phenomenon is investigated to differentiate crude and high purity EAK16-II peptide. The purified peptide did not show this 'dip' and clearly indicated a critical aggregation concentration for EAK16-II at 0. 09 mg/mL by surface tension measurements. Conversely, a surface tension 'dip' is clearly observed for the crude EAK16-II peptide. Atomic Force Microscopy imaged the nanostructures of aggregates. The presence of impurities induces fibre formation below the CAC. This study provides information about the seeding effect of peptide assembly at low concentrations as well as the modification of surface activity of assembled peptide particles. Alanine, glutamic acid and lysine were used as model seeding agents to simulate the seeding phenomenon and better understand the nucleation mechanism of peptide assembly. All amino acid monomers were able to induce fibre formations at low peptide concentrations. However, only glutamic acid and lysine were able to produce the surface tension dip profile observed in the crude peptide. This information may be of importance in understanding fibrillogenesis occurring in conformational diseases and other biomedical applications including drug delivery.

No description available.