20 research outputs found
Similarity of maize seed number responses for a diverse set of sites
Accurate modeling of maize (Zea mays L.) yields in diverse environments requires
realistic simulation of seed numbers. Response of maize seed number to growth or light
interception soon after pollination has been described with different types of functions.
The objective of this study was to compare maize seed number responses to intercepted
solar radiation or growth with data from a diverse set of sites. Pioneer hybrid 3394
planted near Temple, TX in 1999 at 2.5 to 20 plantsm showed a linear function for seed
number responses to light intercepted per plant in the 11 d following silking and to ear
growth rate in these 11 d. Similar linear seed number responses were found for three
hybrids in Canada at 4 to 13 plantsm. Likewise, the function for Pioneer 3394 in
Temple was found to be similar to a regression for the same hybrid grown in Pennsylvania,
and was similar to a function developed in Kenya. Thus, under the diverse environmental
conditions of these studies, linear seed number functions appeared reasonable at
these sites. Such seed number functions are critical to the understanding of optimization
of planting density to maximum seed production per unit ground area. In the absence
of drought stress, the optimum density will be the minimum planting density which
could attain near-complete light interception at silking. As the probability of
drought stress increases due to decreased soil water holding capacity or decreased
expected rainfall, the optimum density would decrease accordingly.Similarité des réponses du nombre de grains par épi de maïs pour un jeu de sites variés.
La modélisation précise des rendements du maïs (Zea mays L.) dans divers environnements
nécessite une simulation réaliste du nombre de grains par épi. La réponse du nombre
de grains à la croissance ou à l'interception de la lumière aussitôt après la
pollinisation a été décrite avec différents types de fonctions. L'objectif de cette
étude était de comparer les réponses du nombre de grains par épi au rayonnement
solaire intercepté ou à la croissance de l'épi avec les données provenant d'un
ensemble de sites variés. L'hybride Pioneer 3394 planté près de Temple (Texas, USA)
en 1999 avec 2,5 à 20 plantsm a montré une relation linéaire entre le nombre de
grains et la lumière interceptée durant les 11 jours qui ont suivi la sortie des
soies ainsi qu'avec le taux de croissance de l'épi durant ces mêmes 11 jours.
Des réponses linéaires similaires ont été trouvées pour trois hybrides au Canada
avec 4 à 13 plantsm. De même, la relation pour Pioneer 3394 à Temple a été
trouvée similaire à celle obtenue pour le même hybride cultivé en Pennsylvanie
ainsi qu'au Kenya. Ainsi, sous diverses conditions d'environnement de ces études,
une relation linéaire avec le nombre de grains apparaît comme raisonnable dans
ces sites. De telles relations linéaires avec le nombre de grains sont critiques
pour appréhender l'optimisation de la densité de plantation afin d'atteindre le
maximum de production de grains par unité de surface de sol. En l'absence de stress
dû à la sécheresse, la densité optimale sera la densité de plantation minimale qui
permettrait d'atteindre l'interception pratiquement complète du rayonnement au moment
de la sortie des soies. Comme la probabilité de stress hydrique augmente avec la
décroissance de la capacité de rétention en eau du sol ou décroît avec les précipitations
escomptées, la densité optimale devra décroître en tenant compte de ces facteurs
Evaluating hydrologic responses to soil characteristics using SWAT model in a paired-watersheds in the Upper Blue Nile Basin
Watershed responses are affected by the watershed characteristics and rainfall events. The characteristics of soil layers are among the fundamental characteristics of a watershed and they are input to hydrologic modeling similar to topography and land use/cover. Although the roles of soils have been perceived, there are limited studies that quantify the role of soil characteristics on watershed runoff responses due to the lack of field datasets. Using two adjacent watersheds (Ribb and Gumara) which have a significant different runoff response with a similar characterstics except geological settings (including soil characteristics), we studied the effects of soil characteristics on runoff and water balance. The Soil and Water Assessment Tool (SWAT) was used to simulate the surface runoff response at the outlet of the watershed and the optimal model parameters distribution was tested with a non-parametric test for similarity. Results indicated that SWAT model captured the observed flow very well with a Nash-Sutcliffe Efficiency (NSE) of greater than 0.74 and with a PBIAS of less than 10% for both calibration and validation period. The comparison of the optimal model parameter distributions of the SWAT model showed that the watershed characteristics could be uniquely defined and represented by a hydrologic model due to the differences in the soils. Using field observations and modeling experiments, this study demonstrates how sensitive watershed hydrology is to soils, emphasizing the importance of accurate soil information in hydrological modeling. We conclude that due emphasis should be given to soil information in hydrologic analysis
The Temperature-Sensitive Role of Cryptococcus neoformans ROM2 in Cell Morphogenesis
ROM2 is associated with Cryptococcus neoformans virulence. We examined additional roles of ROM2 in C. neoformans and found that ROM2 plays a role in several cell functions specifically at high temperature conditions. Morphologically rom2 mutant cells demonstrated a “tear”-like shape and clustered together. A sub-population of cells had a hyperelongated phenotype at restrictive growth conditions. Altered morphology was associated with defects in actin that was concentrated at the cell periphery and with abnormalities in microtubule organization. Interestingly, the ROM2 associated defects in cell morphology, location of nuclei, and actin and microtubule organization were not observed in cells grown at temperatures below 37°C. These results indicate that in C. neoformans, ROM2 is important at restrictive temperature conditions and is involved in several cell maintenance functions
THE RELATIONSHIP OF PHOTOSYNTHESIS AND DARK RESPIRATION IN GRAIN SORGHUM (SORGHUM BICOLOR (L.) MOENCH) TO YIELD, YIELD COMPONENTS, AND TEMPERATURE
Abstract not availabl
EPIC Evaluation of the Impact of Poultry Litter Application Timing on Nutrient Losses
Recently, changes in the utilization practices of animal manures for fertilization have been encouraged to reduce the potential of nonpoint pollution of lakes and streams from agricultural land. However, the potential impact of changing some of these practices has not been fully studied. The objective of this study was to examine the potential impact of limiting poultry litter application times on nutrient movement important to water quality. The WinEPIC model was used to simulate poultry litter applications during the winter months and chemical fertilizer application, with both cool season and warm season grass pastures on the major soil regions of Alabama. With the warm season grass, soluble nitrogen (N) losses could be reduced if the application of poultry litter was made after 30 December. With the cool season grasses, there was no significant difference in application dates for poultry litter for soluble N losses for any soil region, and no improvement could be noted for limiting applications in northern Alabama compared to southern Alabama. No significant difference was observed for soluble phosphorus (P) losses for application date for either warm season or cool season grass pastures. This indicates that factors other than plant P uptake during the growing season were the dominant regulators of the amount of soluble P lost in runoff. Also, the results would indicate that best management practices such as are administered with the P index are more important than plant growth factors in determining N and P losses to the environment
Conservation Tillage:
Hosford, R.M. Jr. 1976. Fungal Leaf Spot Diseases of Wheat in North Dakota. N.D. Agric. Exp. Sta. Bull