Key Physiological Parameters Related to Differences in Biomass Production of Maize and Four Sorghum Cultivars Under Drought and Free Air CO2 Enrichment

AbstractGiven the future increase in temperature and the decrease in summer precipitation, in temperate regions sorghum could be an alternative energy crop besides maize due its better drought tolerance. However, it remains open how future elevated atmospheric CO2 concentrations ([CO2]) may affect these interactions. To address this question four sorghum cultivars and one maize cultivar were grown at moderate climate condition in Germany under different levels of water (WET and DRY) and CO2 supply (385ppm and 600ppm) using free air CO2 enrichment (FACE) technique combined with rain shelters. The objectives of the study were to investigate whether there is genetic variation among sorghum cultivars and whether sorghum cultivars perform better than maize under drought and elevated [CO2]. Following results were achieved: DRY plots received half as much water as compared to WET. Sorghum had higher stomatal density and transpiration rate at very high light as compared to maize. Maize had a higher biomass yield than sorghum under all growth conditions. Sorghum cultivars differed in their growth response to the treatments. Leaf growth of sorghum was delayed in early summer as compared to maize and thus caused differences in seasonal light absorption. Radiation (RUE) and water use efficiency (WUE) of biomass production under WET were highest for maize and varied among sorghum cultivars. CO2 enrichment enhanced RUE and WUE under drought in all plants. Variation of RUE among sorghum cultivars seemed to be related to differences in cold tolerance. Consequently, maize is better adapted to the prevailing German weather conditions and thus has a higher biomass yield under drought and present or future [CO2] than current cultivars of sorghum

Do maize crop models catch the impact of future [CO2] on maize yield and water use?

Do maize crop models catch the impact of future [CO2] on maize yield and water use?. iCROPM2016 International Crop Modelling Symposiu

Drought stress effects on wheat are mitigated by atmospheric CO2_{2} enrichment

The atmospheric CO$_{2}$ concentration is predicted to increase and to generate a rise in the global surface temperature, and change the seasonal precipitation pattern. This could aggravate the severity of summer drought conditions and affect crop yield. We studied the effect of the interaction of CO$_{2}$ and water supply on seasonal absorption of photosynthetically active radiation and radiation-use efficiency of aboveground biomass production to understand the processes contributing to final yield. Wheat was grown over two years in open-top chambers at present or future (+280 ppmv) atmospheric CO$_{2}$ concentration and under sufficient water supply or drought stress in lysimeters with a soil depth of 0.4 m (first year) or in the field with unrestricted root growth (second year). Drought stress was started after the first node stage by halving the water supply. Our results show that under sufficient watering, CO$_{2}$ enrichment did not affect the green area index or seasonal radiation absorption. Drought stress always decreased the green area index and accelerated canopy senescence, which in the second year resulted in a decrease of 23% in the seasonal radiation absorption under the present atmospheric CO$_{2}$ concentration. CO$_{2}$ enrichment stimulated the green area index under drought stress in the second year and seasonal radiation absorption was only decreased by 16%. Radiation-use efficiency was reduced by drought and increased by CO$_{2}$ elevation and the CO$_{2}$ effect was higher under restricted (+60%) than under sufficient watering (+32%). This implies that CO$_{2}$ enrichment enhanced final biomass and grain yield by less than 10% under well-watered conditions and by more than 44% under drought stress conditions, respectively. This study indicates that the increase in atmospheric CO$_{2}$ concentration will attenuate the effects of summer drought on wheat grain yield

Integrating Wheat Canopy Temperatures in Crop System Models

Crop system models are generally parametrized with daily air temperatures recorded at 1.5 or 2 m height. These data are not able to represent temperatures at the canopy level, which control crop growth, and the impact of heat stress on crop yield, which are modified by canopy characteristics and plant physiological processes Since such data are often not available and current simulation approaches are complex and/or based on unrealistic assumptions, new methods for integrating canopy temperatures in the framework of crop system models are needed. Based on a forward stepwise-based model selection procedure and quantile regression analyses, we developed empirical regression models to predict winter wheat canopy temperatures obtained from thermal infrared observations performed during four growing seasons for three irrigation levels. We used daily meteorological variables and the daily output data of a crop system model as covariates. The standard cross validation revealed a root mean square error (RMSE) of ~0.8 °C, 1.5–2 °C and 0.8–1.2 °C for estimating mean, maximum and minimum canopy temperature, respectively. Canopy temperature of both water-deficit and fully irrigated wheat plots significantly differed from air temperature. We suggest using locally calibrated empirical regression models of canopy temperature as a simple approach for including potentially amplifying or mitigating microclimatic effects on plant response to temperature stress in crop system models

Data from the Braunschweig FACE (free-air CO2 enrichment) experiments on sugar beet at adequate and low levels of nitrogen supply

An experiment was carried out during 2 years in order to investigate the effect of rising atmospheric CO2 concentrations at different nitrogen supply on growth, yield and sugar content of sugar beet. Sugar beet was grown twice (2001, 2004) within a crop rotation at ambient and elevated atmospheric CO2 concentration (375 and 550 ppm) fertilized with a high (126, 156 kg N ha-1) or low level (63, 78 kg N ha-1) of nitrogen supply. In the second year another cultivar was used to prevent infestation by rhizomania, which occurred on one half of the field plots at the end of the season of 2001. In 2004, shading was included as an additional treatment. Data set includes data on management, soil condition, weather, below and above ground growth (individual leaves, leaf area index, total biomass, beet yield and composition, water soluble carbohydrates, root biomass). Data can be used to validate the effect of elevated CO2 concentration in sugar beet growth models

Data from the Braunschweig FACE (free-air CO2 enrichment) experiments on sugar beet at adequate and low levels of nitrogen supply

Sugar beet was grown within a crop rotation over two rotation cycles (2001, 2004) at ambient and elevated atmospheric CO2 concentration (375 and 550 ppm) with practical (126, 156 kg N ha-1) and low levels (63, 78 kg N ha-1) of nitrogen supply. In the second year another cultivar was used to prevent infestation by rhizomania, which occured on one half of the field plots at the end of the season of 2001. In 2004, shading was included as an additional treatment. The objectives were to investigate the growth response of sugar beet to elevated CO2 concentration at high and low nitrogen availability. Data set includes data on management, soil condition, weather, below and above ground growth (individual leaves, leaf area index, total biomass, beet yield and composition, water soluble carbohydrates, root biomass)

Free-air CO2 enrichment modifies maize quality only under drought stress

International audienceClimate scenarios show that atmospheric CO2 concentrations will continue to increase. As a consequence, more frequent and severe drought periods are expected. Drought will thus modify plant growth. Although maize is a major crop globally, little information is available on how atmospheric and climatic changes will change maize quality. Here, in a field experiment, maize was grown in 2007 and 2008 under ambient (380 ppm) and elevated CO2 (550 ppm) using free-air CO2 enrichment. In 2007, maize was grown under well-watered conditions only. In 2008, we applied a drought stress treatment in which the plants received only half the amount of water of the well-watered treatment. We measured the concentrations of minerals and quality-related traits in aboveground biomass and kernels at the end of each growing season. Results show first the absence of effect of elevated CO2 under well-watered conditions. By contrast, drought stress modified several traits and interactions under elevated CO2. These results support the hypothesis that the C4 plant maize does not react to an increase in atmospheric CO2 as long as no drought stress is prominent. This finding contrasts with the impact of elevated CO2 on C3 plants. Several drought stress effects found in our study will have important implications for food and feed use. However, the effects of drought stress on the traits were less pronounced under elevated CO2 than under ambient CO2 level. Hence, an elevated CO2 concentration mitigates the drought stress impacts on elemental composition and quality traits of maize

Pedestrian Walking Behavior Revealed through a Random Walk Model

This paper applies method of continuous-time random walks for pedestrian flow simulation. In the model, pedestrians can walk forward or backward and turn left or right if there is no block. Velocities of pedestrian flow moving forward or diffusing are dominated by coefficients. The waiting time preceding each jump is assumed to follow an exponential distribution. To solve the model, a second-order two-dimensional partial differential equation, a high-order compact scheme with the alternating direction implicit method, is employed. In the numerical experiments, the walking domain of the first one is two-dimensional with two entrances and one exit, and that of the second one is two-dimensional with one entrance and one exit. The flows in both scenarios are one way. Numerical results show that the model can be used for pedestrian flow simulation