Evaluation of AquaCrop Model in Simulating Yield and Water Use Efficiency of Three Corn Hybrids under Hot-Dry Climatic Conditions

Nowadays, crop simulation models have a key role in crop growth and yield estimation, production planning, production economy and identifying strategies for crops supply. In this research, AquaCrop model was calibrated and evaluated for three corn hybrids; (DC 370, ZP 677, and SC 704) under different levels of water supply (non stress, mid stress, and severe stress) and nitrogen rates (0, 120, 180, and 240 kg N/ha). For model validation, normalized root mean square error (nRMSE) and determination of coefficient (R2) were used. Result showed that the model simulated grain yield of corn hybrids with high precision. Simulation precision decreased with increasing drought stress. The lowest nRMSE (7.5%) and highest R2 (0.93) were obtained from ZP 677 hybrid. The model simulated corn biological yield with more deviation percentage than grain yield. However, it´s variation trend due to variation in drought stress level or nitrogen fertilizer predicted well according to field experiment. nRMSE ranged from 6.8 and 10.9, while R2 varied from 0.82 to 0.92. AquaCrop model simulated the variation of water use efficiency of corn hybrids with reasonable accuracy, so that it´s value increased with increasing drought stress and nitrogen fertilizer application, while, model outputs in most situations were lower than measured values. The best model validation result (nRMSE=6.4% and R2= 0.93) obtained from ZP 677 hybrid. According to the results were obtained, AquaCrop model can be applied with high reliability for simulating corn yield under similar climatic regions of this experiment

Determination of Suitable Cultivar and N-topdress Rates in Corn Planted After Wheat Harvest

In order to find suitable cultivar and N-topdress rates in corn planted after wheat harvest, a field experiment was conducted in Isfahan University of Technology Experiment Farm located at Shervedan, Falavarjan in 1994. The experiment design was a split plot with a randomized complete block arrangement and four replications. Main plots were four N-topdress rates (0, 90, 180, and 270 kg/ha) and the subplots were three corn hybrids (S.C.I08, S.C.301, and D.C.370). N-topdress rates had no effect on the stages of plant development (50% emergence, transition, pollination and physiological maturity). Also there were no significant effects on the number of leaves per plant, LAI, plant height and plant dry weight measured at pollination stage for different N-topdress rates. As expected, plant development stages differed among hybrids except that of time until 50% emergence. Differences in the number of leaves per plant, LAI, plant height and dry weight of plant measured at pollination stage were highly significant among hybrids. D.C. 370 had the highest values for all of these characteristics. Dry matter accumulation during growing season increased as the N-topdress rates were increased for the hybrids. Also N-topdress rates x hybrid interaction was significant for biological yield. Grain yield, number of seeds per ear, 100-seed weight and biological yield were affected by N-topdress rates and hybrid. Higher grain yield of D.C. 370 can be attributed to greater number of seeds per ear. The results of this study suggest that D.C. 370 with 90 kg/ha N-topdress rate can be used after wheat harvest in Isfahan

Effects of Organic and Chemical Fertilizers on some Quantitative Traits and Anthocyanin of Roselle under Zabol conditions

Introduction: Roselle (Hibiscus sabdariffa L.) belongs to the Malvaceae family, and is an annual or biennial plant that cultivated in tropical and subtropical regions for its stem fibers, eatable calyces, leaves and grains. Roselle is resistant to relatively high temperatures throughout the growing and fruiting times. Continuous use of chemical fertilizers destroys the soil ecological balance, reduces soil fertility and groundwater pollution is caused. In contrast, organic fertilizers are very safe for human health and the environment. It is made by recycling organic material as plant and animals waste, and food scraps in a controlled process. Of the organic fertilizers can be noted to compost, vermicompost, cattle manure andhumic acid. The study was carried out in order to sustainable agriculture. The aim of this study was to investigate the effects of organic and chemical fertilizers on some quantitative traits and anthocyanin of roselle. Materials and Methods: The experiment was performed in complete randomized block design with ten treatments and four replications in research field of agricultural faculty, university of zabol. The treatments included T1: control, T2: NPK in a ratio of 2:1:1 (300 kg ha-1), T3: cattle manure (20 t ha-1), T4: compost (10 t ha-1), T5: vermicompost (5 t ha-1), T6: humic acid foliar in a ratio of 1.5 per thousands, T7: 50% of T2 and T6 , T8: 50% of T3 and T6, T9: 50% of T4 and T6 and T10: 50% of the T5 and T6. Five plants were chosen and an average of five plants was calculated as the single plant for measuring of variables that included the height, number of branches, stem diameter, shoot fresh weight, number of fruits per plant, fruit weight, number of seeds per plant, fresh and dry weights of sepals, inflorescence length, length and diameter of fruit. Method of Wagner has been used for the anthocyanin measurement. Results and Discussion: Results of this research showed that the application of different fertilizers increased the height, number of branches and stem diameter per plant in different stages of growth. Mean comparison showed that there were significant differences between the treatments and control in most traits, so that the maximum height, number of branches and stem diameter belonged to the treatment of organic and chemical fertilizer with humic acid (T8, T9 and T10). The highest number of fruits and seed yield per plant (41/98%) was obtained from the T9 treatment compared to the control. This result was corresponded with the results of other researchers in the roselle. The result showed that inflorescence length, length and diameter of fruit had the highest values by using the cattle manure + humic acid (T8); and so measured characters had the lowest values in control treatment. Effect of different fertilizer treatments on fruit fresh weight, fresh and dry weights of sepals had statistically significant differences. The highest and the lowest values of fruit fresh weight, fresh and dry weights of sepals were obtained from T9 treatment (compost + humic acid) and control treatment, respectively. Compost improves conditions for the plant growth. Humic acid stimulates the growth hormone and increases the absorption of nutrients by plant. So, with these reasons it seems that higher growth features and further calyx yield were achieved by applying compost + humic acid than other treatments. The effect of treatments organic and chemical fertilizers with humic acid on the amount of anthocyanin was higher compared with using them separately. Compost, vermicompost and cattle manure fertilizers are containing humic acid substances and humic acid (phenolic compound derivatives) is a precursor for the synthesis of anthocyanidin (flavonoid structure), therefore they correlated with the increasing anthocyanin in treatments organic fertilizers and chemical with humic acid. Conclusions: The results showed that all applied fertilizers treatments improved growth features, further calyx yield and anthocyanin amount, than the situation of non-use of fertilizer. Nevertheless, the effect of the treatments organic fertilizers with humic acid on vegetative growth, fruit and sepals yield and anthocyanin content per sepals was higher compared with using them separately and using chemical fertilizers. Therefore, to achieve maximum vegetative growth, fruit and sepals yield and anthocyanin content per sepals using treatments of organic fertilizers with humic acid were better than other fertilizer treatments in this research. Therefore, it seems that, in terms of sustainable production and the environmental protection of roselle, applications of organic fertilizers may be viable alternatives to chemical fertilizers

Performance evaluation of CERES-Maize in simulating maize yield and WUE under water and nitrogen managements in Northern Iran

Abstract The CERES-Maize model was tested in a Mediterranean environment in Iran for simulating the response of three maize hybrids (DC370, ZP677, and SC704) to water supply (full irrigation, mid drought stress, and severe drought stress) and nitrogen rates (0, 120, 180, and 240 kg N ha -1 ). Grain yields of maize hybrids were adequately simulated by the model (differences between simulated values and observations were less than 10%). However, CERES-Maize underestimated grain yield in most of situations. Mismatches between observations and predictions increased with water stress. CERES-Maize predicted grain yield of hybrids well (normalized RMSE = 10.7, 7.0, and 9.0%, respectively). CERES-Maize model simulated the variation of biological yield of maize hybrids equal to the average measured biological yield, although the model almost underestimated biological yields in response to different levels of water and nitrogen supply. Validation trials gave an nRMSE for DC370, ZP677, and SC704 of 8.8, 12.2 and 14.3%, respectively. The field experiment and model output results also revealed that decrease of irrigation application increased water use efficiency of maize hybrids due to higher grain yield per unit of water supplied. Also, increase of nitrogen fertilizer gradually increased WUE of all maize hybrids. For the model validation, the nRMSE for WUE of three maize hybrids was 7.91, 6.12, and 9.14%, respectively indicating that the CERES-maize model predict WUE of studied hybrids reasonably well. Obtained results suggested that the CERES-Maize model can be utilized to evaluate the effects of N and irrigation management on maize under same climatic conditions