Planting date (PD), seeding rate (SR), genotype, and row spacing (RS) influence hard red spring wheat (HRSW, Triticum aestivum L. emend. Thell.) and soybean [Glycine max (L.) Merr.] yield. Evaluating HRSW economic optimum seeding rates (EOSR) is needed as modern hybrids may improve performance and have different SR requirements than cultivars. Two cultivars and five hybrids were evaluated in five North Dakota environments at two PDs and five SRs ranging from 2.22-5.19 million live seeds ha-1 in 2019-2020. Planting date, SR, and genotypes have unique yield responses across environments. Hybrid yield was the most associated with kernels spike-1 (r=0.17 to 0.43). The best hybrid yielded greater than cultivars in three environments. The EOSR ranged from 4.08-4.15 and 3.67-3.85 million seeds ha-1 for cultivars and hybrids, respectively. Hybrids are economical if seed prices are within $0.18 kg-1 of cultivars. In soybean, individual and synergistic effects of PD, SR, genotype relative maturity (RM), and RS on seed yield and agronomic characteristics, and how well canopy measurements can predict seed yield in North Dakota were investigated. Early and late PD, early and late RM, and two SRs (457 000 and 408 000 seed ha-1) were evaluated in 14 environments and two RS (30.5 and 61 cm) were included in four environments in 2019-2020. Individual factors resulted in 245 and 189 kg ha-1 more yield for early PD and late RM, respectively. The improved treatment of early PD, late RM, and high SR factors had 16% yield and $140 ha-1 more partial profit greater than the control. When including RS, 30.5 cm RS had 7% more yield than 61 cm RS. Adding 30.5 cm RS to the improved treatment in four environments resulted in 26% yield and $291 ha-1 more partial net profit compared to the control. A normalized difference vegetative index (NDVI) at R5 was the single best yield predictor, and stepwise regression using canopy measurements explained 69% of yield variation. North Dakota farmers are recommended to combine early PDs, late RM cultivars, 457 000 seed ha-1 SR, and 30.5 cm RS to improve soybean yield and profit compared to current management trends.

Previous research has uncovered a large, positive and causal link between education and health. This paper is devoted to examining the topic in the former Czechoslovakia. My analysis is conducted on a data set pooled from the Survey of Health, Ageing and Retirement in Europe (SHARE). I utilize a continuum of ages at school entry, caused by the use of a single school cut-off, to identify the effect of education on health, which is uniquely created from the PCA method and using 30 questions of the SHARE. Therefore, I apply instrumental variable approach with a month of birth as an instrument for education. The results from the first-stage suggest that the instrument is not valid, since a correlation between the instrumental (Month of birth) and the instrumented variable (education) is very low and insignificant. The results remain insignificant even after adjusting for different measures of education, health, institutional changes or heterogeneous effects. As the most probable cause, I state the inability to control for non-compliers in my instrumental variable regressions. As a consequence, all the results regarding the link between education and health are inconclusive. Powered by TCPDF (www.tcpdf.org)

Relatively little change in national soybean (Glycine max) yield over the previous years have led many farmers to creating management regimes focused on plant stress. Field experiments consisting of two different relative maturity (2.8RM and 4.5 RM) soybean cultivars were established at three locations across Kentucky in 2013 and 2014. Each maturity group received a single application, sequential applications, or a combination of the following treatments: N’N-diformyl urea, lactofen, lambda-cyhalothrin with thiamethoxam, and azoxystrobin with propiconazole. Relative maturity and yield environment*treatment interactions were observed to be significant (p 0≤.05). 4.5 RM soybean cultivars yielded significantly greater (800 kg ha-1) than 2.8 RM cultivars. Compared to the untreated check, no treatment in the yield environment*treatment interaction significantly increased yield. Significant yield decrease varied across yield environment, but was observed for treatments containing a combination of lactofen and N’N-diformyl urea. Application of stress management practices was not a consistent approach to improving soybean yield.

Crop simulation models (CSMs) are used to evaluate management and environmental scenarios on crop growth and yields. Two corn (Zea Mays L.) crop growth simulation models, Hybrid-Maize, and CERES-Maize were calibrated and validated under Virginia conditions with the goal of better understanding corn response to variable environmental conditions and decreasing temporal yield variation. Calibration data were generated from small plot studies conducted at five site-years. Main plots were plant density (4.9, 6.2, 7.4, and 8.6 plants m-2); subplots were hybrids of differing relative maturity (RM) [early = Pioneer® Brand "34B97" (108 day RM); medium = Pioneer® Brand "33M54" (114 day RM); and late = Pioneer® Brand "31G66" (118 day RM)]. Model validation was generated from large scale, replicated strip plot trials conducted at various locations across Virginia in 2005 and 2006. Prior to model adjustments based on calibration data, both CSMs under predicted corn grain yield in calibration and validation studies. CERES-Maize grain yield prediction error was consistent across the range of tested plant density while accuracy of Hybrid-Maize varied with plant density. Hybrid-Maize-estimated biomass production was highly accurate. Greater leaf area index (LAI) and biomass production were measured than was predicted by the CERES-Maize CSM. Both CSMs were modified based on calibration data sets and validated. Validation results of the calibrated CSMs showed improved accuracy in simulating planting date and environmental effects on a range of corn hybrids grown throughout Virginia over two years. We expect that both modified models can be used for strategic research and management decisions in mid-Atlantic corn production. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objectives of this thesis were: To estimate the relative maturity group of old and modern soybean cultivars used in Southern Brazil; To quantify the branches contribution in the leaf area index; To characterize the development and the overlap period of vegetative and reproductive phases, growth in height and the emission of nodes after the beginning of flowering in determinate and indeterminate plant type cultivars in different sowing dates and soybean regions in Rio Grande do Sul and; To identify key biophysical and management factors governing variation in soybean yield potential in Southern Brazil. Were conducted 47 experiments using 23 soybean cultivars in five growing seasons (2010/2011, 2011/2012, 2012/2013, 2013/2014 and 2014/2015) at 12 sites in Rio Grande do Sul. The relative maturity group these cultivars that had not yet been classified ranged from 4.8 to 7.3. Most cultivars showed a reduction on total leaf area index, maximum, of main stem and of branches, in the duration of the reproductive phase, of the total development cycle with delay on sowing date regardless of the maturity group and type of growth. The indeterminate type cultivars had a higher overlap period of vegetative and reproductive phases, growing in height and emission nodes after the beginning of flowering bigger than determinate type cultivars. The potential yield ranged from 2.8 up to 6.0 Mg ha-1, depending on the amount and distribution of water during the growing season and the photothermal coefficient during reproductive stages of the soybean. / Os objetivos desta tese foram: Estimar o grupo de maturidade relativa de cultivares antigas e modernas de soja; Quantificar a contribuição das ramificações no índice de área foliar; Caracterizar o desenvolvimento e a duração do período de sobreposição das fases vegetativa e reprodutiva, o crescimento em estatura e a emissão de nós após o início do florescimento em cultivares modernas de soja com diferentes grupos de maturidade relativa, tipos de crescimento, semeadas em épocas e regiões produtoras de soja no Rio Grande do Sul e; Identificar as variáveis meteorológicas e de manejo que governam o potencial de rendimento em soja no sul do Brasil. Foram conduzidos 47 experimentos utilizando 23 cultivares de soja, durante cinco estações de crescimento (2010/2011, 2011/2012, 2012/2013, 2013/2014 e 2014/2015) em 12 locais no Rio Grande do Sul. O grupo de maturidade relativa das cultivares que ainda não tinham sido classificadas variou de 4.8 a 7.3. Há redução dos valores de índice de área foliar máximo, da haste principal e das ramificações, da duração da fase reprodutiva e do ciclo total de desenvolvimento, com o atraso da época de semeadura, independentemente do grupo de maturidade relativa e tipo de crescimento. As cultivares com tipo de crescimento indeterminado apresentam maior período de sobreposição das fases vegetativa e reprodutiva, crescimento em estatura e emissão de nós após o início do florescimento do que as cultivares determinadas. O potencial rendimento de soja variou de 2,8 até 6,0 Mg ha-1, dependendo da quantidade e distribuição da água durante a estação de crescimento e do coeficiente fototérmico durante os estágios reprodutivos da soja.

A review of available corn relative maturity groups in Mississippi shows a limited range of maturity groups in use. Research focusing on expanding the range of maturity groups was conducted in MS in 2015 and 2016. Along with expanded maturity groups, treatments of fertilizer (10-34-0), foliar zinc, and a plant hormone blend were studied to shorten the growing season. Four site years in MS were studied to determine optimal plant maturity group and treatment for length of season. The results showed decreased yield of 0.09-0.15 Mg ha-1 (1.5-2.3 bu ac-1) for each day of decreasing relative maturity in three of four site years. The addition of starter fertilizer increased vegetative growth stage, plant height V5 and V7, SPAD values at V5, and significantly decreases days to tassel and silking reproductive growth stages but did not affect yield.