PRUNING HEIGHT AND ITS EFFECT ON QUANTITATIVE AND QUALITATIVE SEED PRODUCTION IN OLD SAXUAL (Haloxylon aphyllum) FORESTS OF YAZD, IRAN

The high quality and quantity seed production in old saxual shrubs are essential for regeneration and sustainable development of saxual forests in desert areas. The objective of this study was to determine the effects of different pruning height on saxual seed production. The study was carried out in an obviously wilted saxual forest located in Ashkezar desert in Yazd in 1994. The experiment was carried out in a split-plot design with 3 replications, with saxual density (250 and 125 shrubs/ha) as the main plots, and pruning height (10, 35, 70 cm, and a no-cut check) as the sub-plots. Pruning was done on autumn 1994. The forest was protected completely and the quality and quantity of seed production of marked shrubs were investigated on autumn 1999 and 2000. The 2-year results showed that saxual density did not have any significant effect on quality and quantity of saxual seed production (P<0.05). Pruning height had significant effect on percent seed longevity and net saxual seed production (P<0.05). Although no significant difference was observed in viable net seed production under different pruning height, the amount of viable net seed production at 35cm pruning height was 9.7 kg/ha, which seems adequate for saxual regeneration

Calibration and Evaluation of APSIM Model for Simulation of Growth and Development of KSC 704 and Maxima Maize Hybrids under Different Amounts of Nitrogen

IntroductionMaize (Zea mays L.) is one of the most important cereals after wheat and rice in the tropical and temperate regions of the world. Also, its mean production is 8 ton ha-1. Moreover, the total area of under cultivation is 132572 hectares in Iran. Crop simulation models can play an important role in improving agricultural production systems in many developing countries. Crop models can simulate plant growth processes and grain yield instead of conducting several years of field experiments. On the other hands, crop simulation models should be calibrated and evaluated with independent data sets under different climatic conditions. Therefore, the purpose of this research was evaluation of the APSIM model for simulation of growth, development and yield of maize hybrids in Kerman province under different amounts of nitrogen.Materials and MethodsThe APSIM model was calibrated and validated using measured data from a two-year field experiment conducted in the 2014 and 2015 growing seasons. The experiment was a factorial arrangement based on a randomized complete block design (RCBD) with three replications conducted at Kerman province in Iran. Four nitrogen rates (0 (control), 92, 220 and 368 kg ha-1) and two maize hybrids (KSC 704 and Maxima) were included in the study. Moreover, inputs of APSIM model were climatic, soil, plant and management data. In order to calibrate the APSIM model, the data of field experiment in the first year (2014) (including flowering date, physiological maturity date, leaf area index, biological yield and grain yield) were included. Moreover, Data from the second experiment (2015) were used to validate the model.Results and DiscussionOur results showed that APSIM model accurately predicted phenology (nRMSE=4.5%). But the APSIM model did not capture the effect of nitrogen stress on phenology. At the evaluation step, the model couldn’t accurately predict the maximum leaf area index (nRMSE=26 and 18% for SC 704 and Maxima hybrids, respectively) which led to overestimate of the results. The nRMSE values for the biological yield of SC 704 and Maxima hybrids were 13.9% and 5.7%, respectively. Furthermore, the values of Wilmot agreement index (d) for these SC 704 (0.95) and Maxima (0.99) indicated a close agreement between the field-measured and simulated values. Furthermore, the nRMSE for grain yield simulation of SC 704 and Maxima hybrids were 13.2 and 11.9 percentage, respectively, revealed that the model accurately simulated the grain yield of maize hybrids.ConclusionThe evaluation of the APSIM model with the experimental data revealed that the model predicted grain yield, biological yield, days to flowering and maturity of maize hybrids reasonably well. This indicates that the model could be applied for assessing various management practices in maize agro-ecosystems under all parts of the semi-arid regions which has the similar characteristics to the study location. On the other hands, the APSIM model couldn’t predict the effect of different nitrogen levels on phenology

Σχεδιασμός κοχλιοφόρου αντλίας κονιαμάτων με μεταβλητή διατομή

Crop growth simulation models require robust ecophysiological functionality to support credible simulation of diverse genotype × management × environment (G × M × E) combinations. Most efforts on modeling the nitrogen (N) dynamics of crops use a minimum, critical, and maximum N concentration per unit biomass based empirically on experimental observations. Here we present a physiologically more robust approach, originally implemented in sorghum, which uses the N content per unit leaf area as a key driver of N demand. The objective was to implement the conceptual framework of the APSIM sorghum nitrogen dynamics model in APSIM maize and to validate the robustness of the model across a range of G × M × E combinations. The N modelling framework is described and its parameterisation for maize is developed based on three previously reported detailed field experiments, conducted at Gatton (27°34'S, 152°20'), Queensland, Australia, supplemented by literature data. There was considerable correspondence with parameterisation results found for sorghum, suggesting potential for generality of this framework for modelling crop N dynamics in cereals. Comprehensive model testing indicated accurate predictions at organ and crop scale across a diverse range of experiments and demonstrated that observed responses to a range of management factors were reproduced credibly. This supports the use of the model to extrapolate and predict performance and adaptation under new G × M × E combinations. Capturing this advance with reduced complexity compared to the N concentration approach provides a firm basis to progress the role of modelling in exploring the genetic underpinning of complex traits and in plant breeding and crop improvement generally

Evaluation of Maize (Zea mays L.) Hybrids Thermal Time Requirements of Different Soil Fertility in the Arid Climate of Kerman

In order to evaluate phenologic and thermal time response of three maize hybrids (KSC 704, Maxima and TWC 604) in different rates of nitrogen (0, 92, 220 and 368 kg ha-1), a two-year experiment was laid out as a randomized complete block design with a factorial arrangement of treatments and three replications in 2014 and 2015. Results showed that nitrogen and genotype had a significant effect (p<0.01) on leaf appearance rate, phenology and grain yield of maize hybrids. In both years, nitrogen stress postponed the tasseling, silking and physiological maturity occurrence in hybrids and increased their thermal time requirements, but this effect was more severe in the second year. The thermal time required for all of the phenological stages of hybrids showed significant increase only in control treatment, compared with other N rates and there was no significant difference among other N rates from this viewpoint. Significant yield benefits of KSC 704 and Maxima compared to TWC 604 was observed. Among the studied hybrids, Maxima is recommended due to the shorter growing season duration, lower thermal time requirement and faster germination rate under N stres

Study on the Efficacy of Some Current Herbicides for Control of Resistant and Susceptible Canarygrass (Phalaris spp.) Biotypes to Acetyl CoA Carboxylase (ACCase) Inhibitors

Abstract \ud Two separate greenhouse experiments were conducted in the greenhouse facilities of the Iranian Plant Protection Research Institute, Tehran, to study the efficacy of some herbicides to control of resistant and susceptible P. minor and P. paradoxa biotypes. In each experiment, resistant and susceptible biotypes were treated separately by 19 herbicide treatments. Treatments included 10 ACCase inhibitors, 6 Acetolactate Synthase (ALS) inhibitors, prosulfocarb, flamprop-M-isopropyl, isoproturon plus diflufenican and a non-sprayed control. To evaluate the effects of treatments, different characteristics including percent damage based on EWRC scores at 15 and 30 days after spraying, percentage of survived plants after spraying relative to before spraying, and percentage of dry weight and wet weight of individual plants relative to control were studied. Results showed that the susceptible biotypes of P. minor were best controlled by clodinafop propargyl and pinoxaden at 450 ml/ha while pinoxaden at 450 ml/ha and cycloxydim were best options for control of the resistant biotype. Among ALS inhibitors, iodosulfuron plus mesosulfuron could control susceptible and resistant biotypes of P. minor very effectively and semi-satisfactory, respectively. Iodosulfuron plus mesosulfuron and sulfosulfuron plus metsulfuron could remarkably reduce the wet weight of individual plants compared to control so that the plants were not damaging any more. Among other herbicides, isoproturon plus diflufenican could control the susceptible and resistant biotypes semi-satisfactory and very effectively, respectively. \ud \ud Keywords: Herbicide resistance, ACCase inhibitors, ALS inhibitor

Modelling the nitrogen dynamics of maize crops – Enhancing the APSIM maize model

Crop growth simulation models require robust ecophysiological functionality to support credible simulation of diverse genotype × management × environment (G × M × E) combinations. Most efforts on modeling the nitrogen (N) dynamics of crops use a minimum, critical, and maximum N concentration per unit biomass based empirically on experimental observations. Here we present a physiologically more robust approach, originally implemented in sorghum, which uses the N content per unit leaf area as a key driver of N demand. The objective was to implement the conceptual framework of the APSIM sorghum nitrogen dynamics model in APSIM maize and to validate the robustness of the model across a range of G × M × E combinations. The N modelling framework is described and its parameterisation for maize is developed based on three previously reported detailed field experiments, conducted at Gatton (27°34′S, 152°20′), Queensland, Australia, supplemented by literature data. There was considerable correspondence with parameterisation results found for sorghum, suggesting potential for generality of this framework for modelling crop N dynamics in cereals. Comprehensive model testing indicated accurate predictions at organ and crop scale across a diverse range of experiments and demonstrated that observed responses to a range of management factors were reproduced credibly. This supports the use of the model to extrapolate and predict performance and adaptation under new G × M × E combinations. Capturing this advance with reduced complexity compared to the N concentration approach provides a firm basis to progress the role of modelling in exploring the genetic underpinning of complex traits and in plant breeding and crop improvement generally