110 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
Irrigation and tillage effects on soil nitrous oxide emissions in maize monoculture
Irrigation and soil management can impact soil nitrous oxide (N2O) emissions. Flood and sprinkler irrigation systems together with conventional tillage are the main practices used in the high yielding maize systems in Mediterranean Spain. The objective of this field work was to quantify the effect of the irrigation system (i.e., flood, F; and sprinkler, S) and the soil tillage system (i.e., conventional tillage, CT; no‐tillage maintaining the maize stover, NTr; and no‐tillage removing the maize stover, NT) on the N2O emissions from the soil during 3 yr (2015, 2016, and 2017). S irrigation, with mean values of 1.35 kg N2O‐N ha−1 yr−1 throughout the 3 yr, obtained 42% lower N2O emissions than F irrigation. On average of the three growing seasons, yield‐scaled N2O emissions by grain yield and by grain N uptake in F irrigation were two‐fold higher than in S irrigation. Moreover, in one out of three growing seasons (2017), no‐tillage systems (i.e., NTr and NT) showed greater yield‐scaled N2O emissions compared with CT. The higher maize grain yield with the S irrigation compared to F irrigation, as well as the lower N2O emissions reported under S irrigation resulted in the reduction of the yield‐scaled N2O emissions. Our findings highlight the role of sprinkler irrigation decreasing N2O emissions in comparison to flood irrigation in Mediterranean agroecosystemsComisión Interministerial de Ciencia y Tecnología. Grant Number: AGL2013‐49062‐C4‐4‐R; Secretaría de Estado de Investigación, Desarrollo e Innovación. Grant Numbers: AGL2015‐68881‐REDT, FJCI‐2014‐19570, IJCI‐2016‐27784, PhD fellowship BES‐2014‐06917
Pre-anthesis ovary development determines genotypic differences in potential kernel weight in sorghum
Kernel weight is an important factor determining grain yield and nutritional quality in sorghum, yet the developmental processes underlying the genotypic differences in potential kernel weight remain unclear. The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum. Kernel development was studied in two field experiments with five genotypes known to differ in kernel weight at maturity. Pre-fertilization floret and ovary development was examined and post-fertilization kernel-filling characteristics were analysed. Large kernels had a higher rate of kernel filling and contained more endosperm cells and starch granules than normal-sized kernels. Genotypic differences in kernel development appeared before stamen primordia initiation in the developing florets, with sessile spikelets of large-seeded genotypes having larger floret apical meristems than normal-seeded genotypes. At anthesis, the ovaries for large-sized kernels were larger in volume, with more cells per layer and more vascular bundles in the ovary wall. Across experiments and genotypes, there was a significant positive correlation between kernel dry weight at maturity and ovary volume at anthesis. Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related. The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion
Pre-anthesis ovary development determines genotypic differences in potential kernel weight in sorghum
Kernel weight is an important factor determining grain yield and nutritional quality in sorghum, yet the developmental processes underlying the genotypic differences in potential kernel weight remain unclear. The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum. Kernel development was studied in two field experiments with five genotypes known to differ in kernel weight at maturity. Pre-fertilization floret and ovary development was examined and post-fertilization kernel-filling characteristics were analysed. Large kernels had a higher rate of kernel filling and contained more endosperm cells and starch granules than normal-sized kernels. Genotypic differences in kernel development appeared before stamen primordia initiation in the developing florets, with sessile spikelets of large-seeded genotypes having larger floret apical meristems than normal-seeded genotypes. At anthesis, the ovaries for large-sized kernels were larger in volume, with more cells per layer and more vascular bundles in the ovary wall. Across experiments and genotypes, there was a significant positive correlation between kernel dry weight at maturity and ovary volume at anthesis. Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related. The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion
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Simulating maize yield in sub-tropical conditions of southern Brazil using Glam model
The objective of this work was to evaluate the feasibility of simulating maize yield in a sub‑tropical
region of southern Brazil using the general large area model (Glam). A 16‑year time series of daily weather data
were used. The model was adjusted and tested as an alternative for simulating maize yield at small and large
spatial scales. Simulated and observed grain yields were highly correlated (r above 0.8; p<0.01) at large scales
(greater than 100,000 km2), with variable and mostly lower correlations (r from 0.65 to 0.87; p<0.1) at small
spatial scales (lower than 10,000 km2). Large area models can contribute to monitoring or forecasting regional
patterns of variability in maize production in the region, providing a basis for agricultural decision making, and
Glam‑Maize is one of the alternatives
Model parameterization to simulate and compare the PAR absorption potential of two competing plant species
Mountain pastures dominated by the pasture grass Setaria sphacelata in the Andes of southern Ecuador are heavily infested by southern bracken (Pteridium arachnoideum), a major problem for pasture management. Field observations suggest that bracken might outcompete the grass due to its competitive strength with regard to the absorption of photosynthetically active radiation (PAR). To understand the PAR absorption potential of both species, the aims of the current paper are to (1) parameterize a radiation scheme of a two-big-leaf model by deriving structural (LAI, leaf angle parameter) and optical (leaf albedo, transmittance) plant traits for average individuals from field surveys, (2) to initialize the properly parameterized radiation scheme with realistic global irradiation conditions of the Rio San Francisco Valley in the Andes of southern Ecuador, and (3) to compare the PAR absorption capabilities of both species under typical local weather conditions. Field data show that bracken reveals a slightly higher average leaf area index (LAI) and more horizontally oriented leaves in comparison to Setaria. Spectrometer measurements reveal that bracken and Setaria are characterized by a similar average leaf absorptance. Simulations with the average diurnal course of incoming solar radiation (1998–2005) and the mean leaf–sun geometry reveal that PAR absorption is fairly equal for both species. However, the comparison of typical clear and overcast days show that two parameters, (1) the relation of incoming diffuse and direct irradiance, and (2) the leaf–sun geometry play a major role for PAR absorption in the two-big-leaf approach: Under cloudy sky conditions (mainly diffuse irradiance), PAR absorption is slightly higher for Setaria while under clear sky conditions (mainly direct irradiance), the average bracken individual is characterized by a higher PAR absorption potential. (∼74 MJ m−2 year−1). The latter situation which occurs if the maximum daily irradiance exceeds 615 W m−2 is mainly due to the nearly orthogonal incidence of the direct solar beam onto the horizontally oriented frond area which implies a high amount of direct PAR absorption during the noon maximum of direct irradiance. Such situations of solar irradiance favoring a higher PAR absorptance of bracken occur in ∼36% of the observation period (1998–2005). By considering the annual course of PAR irradiance in the San Francisco Valley, the clear advantage of bracken on clear days (36% of all days) is completely compensated by the slight but more frequent advantage of Setaria under overcast conditions (64% of all days). This means that neither bracken nor Setaria show a distinct advantage in PAR absorption capability under the current climatic conditions of the study area
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