A simulation model of competition between winter wheat and Avena fatua for light (original) (raw)
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Journal of Agronomy and Crop Science, 2013
In every agroforestry system, the tree canopy reduces the incident radiation for the crop. However, cereal varieties were selected, and most crop growth models were designed for unshaded conditions, so both may be unsuited to agroforestry conditions and performance. In southern France, durum wheat productivity was monitored over 2 years in an agroforestry system including walnut trees and under artificial shade conditions. Yield components were measured in both full and reduced light conditions. The cereal yield was always decreased by shade; by almost 50% for the heaviest shade conditions (31% of light reduction). The main effect of the shade was the reduction in the number of grains per spike (35% at the most) and in the weight of grains (16% at the most). The mean grain weight was moderately affected, while the protein content was increased in shaded conditions (by up to 38% for artificial shade). Consequently, the protein yield per hectare was less reduced by the shade than the dry matter grain yield. A crop model (STICS) was also used to simulate the crop productivity in full light and shaded conditions, but the crop LAI and the yield components were not correctly simulated in the shade. The simulations emphasized the sensitivity of the wheat grain filling to shade during the critical period, 30 days before flowering, for yield elaboration. Further experimental and modelling studies should take into account the heterogeneity of shade intensity due to the shape of the tree crown, the width of the crop alley and the orientation of the tree rows and the modification of carbon allocation inside the plant.
Plant competition for light analyzed with a multispecies canopy model
Oecologia, 1990
Competition for light among species in a mixed canopy can be assessed quantitatively by a simulation model which evaluates the importance of different morphological and photosynthetic characteristics of each species. A model was developed that simulates how the foliage of all species attenuate radiation in the canopy and how much radiation is received by foliage of each species. The model can account for different kinds of foliage (leaf blades, stems, etc.) for each species. The photosynthesis and transpiration for sunlit and shaded foliage of each species is also computed for different layers in the canopy. The model is an extension of previously described single-species canopy photosynthesis simulation models. Model predictions of the fraction of foliage sunlit and interception of light by sunlit and shaded foliage for monoculture and mixed canopies of wheat (Triticum aestivum) and wild oat (Avena fatua) in the field compared very well with measured values. The model was used to calculate light interception and canopy photosynthesis for both species of wheat/wild oat mixtures grown under normal solar and enhanced ultraviolet-B (290–320 nm) radiation (UV-B) in a glasshouse experiment with no root competition. In these experiments, measurements showed that the mixtures receiving enhanced UV-B radiation had a greater proportion of the total foliage area composed of wheat compared to mixtures in the control treatments. The difference in species foliage area and its position in the canopy resulted in a calculated increase in the portion of total canopy radiation interception and photosynthesis by wheat. This, in turn, is consistent with greater canopy biomass of wheat reported in canopies irradiated with supplemental UV-B.
European Journal of Agronomy
A stumbling block to the adoption of silvoarable agroforestry systems is the lack of quantitative knowledge on the performance of different crops when competing for resources with trees. In NorthWestern Europe, light is likely to be the principal limiting resource for understorey crops, and most agronomic studies show a systematic reduction of final yield as shade increases. However the intensity of the crop response depends on both the environmental conditions and the shade characteristics. This study addressed the issue by monitoring winter wheat (Triticum aestivum L.) growth, productivity and quality under artificial shade provided by military camouflage shade-netting, and using the Hi-sAFe model to relate the artificial shade conditions to those applying in agroforestry systems. The field experiment was carried out over two consecutive years (2013-14 and 2014-15) on the experimental farm of Gembloux Agro-Bio Tech, Belgium. The shade structures recreated two shade conditions: periodic shade (PS) and continuous shade (CS), with the former using overlapping military camouflage netting to provide discontinuous light through the day, and the latter using conventional shade cloth. The experiment simulated shading from a canopy of late-flushing hybrid walnut leaves above winter wheat. Shading was imposed 16 (2013-14) and 10 (2014-15) days before flowering and retained until harvest. The crop experienced full light conditions until the maximum leaf area index stage (LAI max) had been reached. In both years, LAI followed the same dynamics between the different treatments, but in 2013-2014 an attack of the take-all disease (Gaeumannomyces graminis var. tritici) reduced yields overall and prevented significant treatment effects. In season 2014-15 the decrease in global radiation reaching the crop during a period of 66 days (CS:-61% and PS:-43%) significantly affected final yield (CS:-45% and PS:-25%), mainly through a reduction of the average grain weight and the number of grain per m 2. Grain protein content increased by up to 45% under the CS treatment in 2015. Nevertheless, at the plot scale, protein yield (t/ha) did not compensate for the final grain yield decrease. The Hi-sAFe model was used to simulate an agroforestry plot with two lines of walnut trees running either north-south or east-west. The levels of artificial shade levels applied in this experiment were compared to those predicted beneath trees growing with similar climatic conditions in Belgium. The levels used in the CS treatment are only likely to occur real agroforestry conditions on 10% of the cropped area until the trees are 30 years old and only with east-west tree row orientation.
Field Crops Research, 2004
Cereal crop species and varieties differ in competitive ability against weeds mainly as influenced by differences in canopy architecture. The FASSET crop model was used to separate the effects of a number of crop traits on the suppressive ability of winter wheat varieties and the ability to tolerate weeds. The model simulated the competition between different varieties of winter wheat and a sown grass mixture for light, water and nitrogen. Crop physiological parameters of eight varieties and one variety mixture were estimated from measurements in a 3-year field experiment. The parameters estimated were thermal time from emergence to flag leaf appearance, thermal time from flag leaf appearance to anthesis, thermal time from anthesis to yellow ripeness, height development rate and final plant height, specific leaf area, leaf area per N uptake, vertical displacement of leaf area, and extinction coefficient for light.
A wheat canopy model linking leaf area and phenology
European Journal of Agronomy, 2005
The accurate simulation of leaf area in wheat models is important because leaf area intercepts light and stores nitrogen, and the arrangement of leaves influences the transmission of foliar diseases and inter-species competition. In this paper, we report on the development and testing of a model that links a mechanistic phenological model that depends on the prediction of leaf appearance (Sirius) with a simplification of a detailed canopy model that calculates the numbers and areas of leaves on mainstems and tillers (ARCWHEAT1). The simplification of the detailed canopy model from ARCWHEAT1 assigns a particular area with the each cohort of leaves associated with a mainstem leaf, but does not predict the number of elements. This is used to replace the empirical curve representing green area index (GAI) development in Sirius. Area development in each layer is described by potential functions, representing how growth proceeds in the absence of resource limitations. Actual area achieved is derived from these potentials using simple limitation rules. Potential for future growth is updated according to the history of resource availability. We propose that modelling potential areas in this fashion is a straightforward way to describe the genetic control of the plant phenotype. The new model requires the calibration of fewer cultivar specific parameters than either of the parent models, making cultivar calibration simpler. It also provides steps towards the simulation of the development of foliar disease and its impact, improved simulation of inter-species competition and the risk of lodging, under a wide range of management and environmental scenarios. This creates a framework for the design of the optimal canopy ideotype to suit these scenarios.
Modeling Light and Temperature Effects on Leaf Emergence in Wheat and Barley
Crop Science, 1991
Phenologicai development affects canopy structure, radiation interception, and dry matter prodnction; most crop simulation models therefore incorporate leaf emergence rate as a basic parameter. A recent study examined leaf emergence rate as a function of temperature and daylength among wheat (Triticum aestlvum L) and barley (Hordeum vulgate L.) cultivars. Leaf emergence rate and phyllochron were modeled as functions of temperature alone, daylength alone, and the interaction between temperature and daylength. The resulting equations contained an unwieldy number of constants. Here we simplify by reducing the constants by >70%, and show leaf emergence rate as a single response surface with temperature and daylength. In addition, we incorporate the effect of photosynthetic photon tlox into the model. Generic fits for wheat and barley show cultivar differences less than ± 5% for wheat and less than _+ 10% for barley. Barley is more sensitive to daylength changes than wheat for common environmental values of daylength, which may be related to the difference in sensitivity to daylength between spring and winter cultivars. Differences in leaf emergence rate between cnltivars can be incorporated into the model by means of a single, nondimensional factor for each cultivar.
2009
ABSTRACT Grain legume-cereal intercrops allow a gain of productivity grown along the growth cycle on the same piece of land under low input (of which nitrogen (N) fertilizers) levels. This is partly due to a better use of soil nitrogen (larger available soil N per plant for cereal N uptake and an increased contribution of N fixation for pea nutrition) under combinations (species and crop management systems) fully optimized within a given soil and climate environment. Modeling is a powerful tool to explore a wide range of combinations. It can be further used as a decision making oriented-tool provided below-ground resources and light sharing is satisfactorily simulated. Our work aimed at designing a new dynamic intercrop growth model (Azodyn Inter-Crop (IC)) based upon Azodyn for wheat and Afisol for pea. Nitrogen and water partitioning between species is firstly driven by nitrogen and water demand of each species. When intercrop demand is larger than soil supply then water and N acquisition is limited by root exploration, soil nutrient supply and N taken up by the companion species as it concurrently depletes available below-ground resources. The “functional” root layer concept allows to account for advantage towards species with a faster root penetration rate. Leaf area expansion is driven by daily satisfaction of N demand, itself computed through an adapted version of N dilution curve to intercrop growth. Light sharing depends on leaf area index (LAI) growth and leaf properties (reflectance, leaf angle) of each species. Model outputs show Azodyn-IC can satisfactorily simulate N taken up, LAI, light interception efficiency and crop growth of each sole- and intercropped species along the growth cycle leading to realistic yields for the applied N fertilizer rates. It also emphasizes competition for light and below-ground resources within intercrops is tightly and dynamically linked within intercrop.
Shade Avoidance and Wheat (Triticum aestivum L.) Productivity
TJPRC, 2014
Two filed experiments were conducted at the experimental farm; faculty of Agriculture Benha University during 2012 and 2013 seasons to study the effect of shading through controlling plant density with using varied seed rates i.e., 40 kg./fed. as recommended for control, 10 kg/ fed. (as 1/4 of recommended; 20 kg/fed. (as 1/2 of recommended) and 30 kg /fed. (as 3/4 of recommended on wheat (Triticum aestivum L.) growth and productivity. The obtained results showed that, different applied treatments significantly increased all of the studied growth characteristics i.e. plant height, leaves number, tillers number, total leaf area, dry weight / plant and total chlorophyll SPDS at 70 and 110 days after sowing in both seasons. The highest values of these traits - except that of plant height, were existed with 10 kg/ fed. i.e. the quarter of the recommended amount of seeds. But in case of plant height, the highest value was existed with 40 kg/ fed. (i.e. control recommended amount in the two seasons. Also, the growth correlation: crop growth Rate (CGR), Net assimilation Rate (NAR) and photosynthetic efficiency (PE) significantly increased with all applications at 110 days after sowing in both seasons. As for yield and yield components, i.e., Number of spike/ plant, spike length, main spike weight (g), number of grains/spike, number of spikelets/spike and grain yield g / plant; significantly were increased with different applied treatments in the two seasons. The highest values were existed with the rate of seeds at 10 kg/ fed. (i.e, the quarter of recommended amount). In addition, the same rate of seeds gave the highest values of each of N, P, K, Mg, Ca, Fe, Zn, Cu, Total carbohydrates and crude protein content in Flag leaf at 110 days and in grains, as well, at harvest time during 2012 and 2013 seasons.
Journal of experimental botany, 2010
Intimate relationships exist between form and function of plants, determining many processes governing their growth and development. However, in most crop simulation models that have been created to simulate plant growth and, for example, predict biomass production, plant structure has been neglected. In this study, a detailed simulation model of growth and development of spring wheat (Triticum aestivum) is presented, which integrates degree of tillering and canopy architecture with organ-level light interception, photosynthesis, and dry-matter partitioning. An existing spatially explicit 3D architectural model of wheat development was extended with routines for organ-level microclimate, photosynthesis, assimilate distribution within the plant structure according to organ demands, and organ growth and development. Outgrowth of tiller buds was made dependent on the ratio between assimilate supply and demand of the plants. Organ-level photosynthesis, biomass production, and bud outgro...