S. Tofigh; D. Rahimi; H. Yazadnpanah
Abstract
Introduction Statistical models and numerical simulations have been widely used to detect relationships between the climate and crops. However, the influence of non-climatic factors (such as cultivar and fertilizer changes on yield crop needs to be eliminated. For this reason, dynamic crop models ...
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Introduction Statistical models and numerical simulations have been widely used to detect relationships between the climate and crops. However, the influence of non-climatic factors (such as cultivar and fertilizer changes on yield crop needs to be eliminated. For this reason, dynamic crop models include the SUCROS, Erosion Productivity Impact Calculator(EPIC), WOrld FOod STudies (WOFOST), Agricultural Production Systems sIMulator (APSIM), and Decision Support System for Agrotechnology Transfer (DSSAT) have been used in water, nitrogen and weather responses. Among these models DSSAT contains separate models for different crops and can quantitatively predict the growth and production of the annual field crops.
Materials and Methods: In this study, the data of Shahrekord Agricultural Meteorological Station and the data of Lysimeter Station were used to evaluate the correlation between the research results and Lysimeter data from Pearson correlation coefficient, and the RMSE, MAD and MSE are applied in order to calculate the error.
Results and Discussion: Lysimeter: The wheat evapotranspiration amount from the planting (20 of Octobers) to the harvest time (14 of July) is recorded as 611.24 mm. Precipitation during the winter is low but continuous and it is 127 mm that equivalent to the evapotranspiration at this time of growth. In the warm season, a quarter of the evapotranspiration is provided by rainfall. The average of winter evapotranspiration is 0.87 mm per day and in the growth season is 4 mm per day. Also from planting to harvest is 2.42 mm per day that is recorded its maximum 7.8 mm and its minimum 2.32 mm per day. The total amount of drained water during the growth is 76.04 mm that 8.8% of the total rainfall. It indicates that drainage water from the soil is low and irrigation has a high efficiency.
CERES-WHEAT: Wheat evapotranspiration amount during the growth period is 413.51 mm by FAO Penman-Monteith and 489.53 mm by Priestley-Taylor. Precipitation during the winter is low but continuous and it is 127 mm that equivalent to the evapotranspiration at this time of growth. In the warm season, a quarter of the evapotranspiration volume is provided through rainfall. The average of winter evapotranspiration based on the F.P.M and P.T methods are 0.86 and 1.23 mm/day and in the growing season 2.98 and 3.11 mm/day, respectively. During the experiment, the evapotranspiration average is 1.59 mm/day for the FPM method that the maximum is 6.61, and the minimum is 0.379 mm/day. This amount is 1.88 mm/day for P.T method which the maximum is 5.64 and the minimum is 0.45 mm per day. The total amount of drained water during the growing period is 106.3 mm, based on the F.P.M method and 90.2 mm based on the P.T method.
The correlation between farm data and the data obtained through the F.P.M method of CERES-Wheat model is 0.97, which for the P.T method is 0.92. The MAD, MSE and RMSE values obtained between the F.P.M method and farm data are 0.95, 0.95 and 1.57, respectively, and for the P.T method, 0.97, 1.47 and 1.21, respectively. With respect to correlation and MAD, MSE and RMSE value, it is found that the model is highly capable in simulating evapotranspiration and crop performance. Among the methods applied in determining evapotranspiration, the F.P.M method with high correlation and lower error value is more accurate than the P.T method.
Water Factor: From the day 177 to 216 is considered the most sensitive stage of plant growth. Based on DSSAT output over a 25-day period (196 to 216 days) the water available is severely depleted and the plant may experience drought stress. At this stage of the growth, water deficiency should be offset by increasing the time and the amount of irrigation.
Day 210 is the beginning time of the increase in evapotranspiration of the plant. During this period, the amount of water which is uptake from the soil was less than 1 time the plant demand. This period of stress was based on the FAO Penman- Monteith method between the 203rd and 210th days. During this period, the plant goes through its clustering and flowering stages, and water stress at this stage causes the growth of wrinkled and lean grain, resulting in reduced grain weight and reduced crop yield. Water scarcity must be compensate by increased irrigation.
Conclusion: Comparison of model calibration results and farm data indicates that there is a high correlation between farm data and model output. The error between the model results and the Lysimeter station data is low. Among the methods used to calculate the evapotranspiration in the model, FAO Penman- Monteith method is the highest correlation and the lowest error value with the farm experiments and results. In general, the results indicated that the CERES-Wheat model has a high ability to simulate evapotranspiration and wheat yield. Regarding observed data for crop irrigation program indicates that farmers' performance in managing the amount of water needed for the crop at various stages of the growth was not optimal. Consequently, drought stress was observed for developmental and mid-growth stages. The DSSAT simulation indicated that the optimal irrigation management adjusts the time and value of irrigation water according the actual evapotranspiration and water requirement would significantly improve irrigation water use.
foroogh abbasi teshnizi; M. Kouchakzadeh; F. Abbasi
Abstract
Water for agriculture is one of the most important factors in arid and semi-arid areas and municipal wastewater treatment is an important resource for this purpose. Therefore, potential of transfer contaminations is a serious problem regarding use of treated wastewater for agriculture. Due to the risk ...
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Water for agriculture is one of the most important factors in arid and semi-arid areas and municipal wastewater treatment is an important resource for this purpose. Therefore, potential of transfer contaminations is a serious problem regarding use of treated wastewater for agriculture. Due to the risk of transfer contaminations through the use of wastewater, the study of transfer microbes in soil in recent decades has been of interest to researchers. In the present study, the transfer of bacteria fecal coliform was investigated in a lysimeter and the HYDRUS-1D model was used to simulate water flow and the fecal coliform in the soil. For calibration of the model and estimating the model input parameters, soil hydraulic and transport parameters, were inversely estimated. Results represented that the HYDRUS-1D with reasonably accurately simulated the outlet flow. To simulate the transfer of the bacteria in the soil, one site sorption model, two kinetic sites model (particle transport using attachment/detachment) and one kinetic site model were used. In the simulation of bacterial transfer, one site sorption model was selected as the proper model for this study. One site sorption model estimated solid-phase growth coefficient ( ) about sextuple more than liquid-phase. It showed that deposited cells had a higher division rate compared with the cell in liquid-phase. The calibrated model was used for surveying the effect various irrigation intervals and irrigation times on bacterial transfer. The results showed that by increasing irrigation times, more bacteria leached out from the soil. Also by increasing irrigation intervals, more bacteria observed in the soil profile, due to favorable environmental conditions and food for the bacteria growth. According to the results, the best interval and irrigation times were one day and four hours, respectively.
M. Shakarami; S. Marofi; Gh. Rahimi
Abstract
Introduction: Arid and semi-arid areas are confronting increasing water shortages. In these regions of the world, planners are being forced to consider other water sources that could be used economically and effectively to promote further development. Wastewater is the only potential water source, which ...
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Introduction: Arid and semi-arid areas are confronting increasing water shortages. In these regions of the world, planners are being forced to consider other water sources that could be used economically and effectively to promote further development. Wastewater is the only potential water source, which will increase as the population grows and the demand on freshwater increases. Composting municipal solid wastes (MSW) and sewage sludge is a good way to reduce the amount of wastes generated in densely populated areas. Municipal solid waste production in Asia in 1998 was 0.76 million tons per day, with an annual growth rate of 2- 3% in developing countries and 3.2- 4.5% in developed countries. (MSW) compost is increasingly used in agriculture not only as a soil conditioner but also as a fertilizer. Despite the growing interest in wastewater and compost usage, excessive application of them may have some harmful effects such as human health problems, runoff and leaching of nutrients to surface and groundwater, undesirable chemical constituents, pathogens, accumulations of heavy metals in plants and soils, negative environmental and health impacts. So, using of wastewater and compost application should be under controlled conditions that minimize health risks of agricultural products.
Materials and Methods: This study was conducted in greenhouse of Bu-Ali Sina as a factorial completely randomized design to evaluate the effects of wastewater and compost on physical and chemical properties of soil. The factors included four types of watering: raw wastewater (W1), treated wastewater (W2) combined 50% of raw wastewater and fresh water (W3) and tap water (W4) and also four compost levels: 0 (C1), 40 (C2), 80 (C3) and 120 tha-1 (C4). Therefore, 16 treatments (W1C1 to W4C4) were considered for investigation. It is noted that Compost added and mixed just with top layer of the soil. 48 volumetric lysimeters were applied as Cultivation beds (26 × 30 × 30 cm). The soil had three layers: the upper layer (Clay texture), the middle layer (clay loam) and the bottom layer (sandy clay loam). After beds preparation, basil (Ocimum Basilicum) was planted in them. Due to the lack of an active wastewater treatment plant in the region, raw and treated wastewaters were transported from Kermanshah, the nearest city to Hamedan. Also, municipal compost was prepared from Kermanshah Compost Company.At the end of cultivation period, the soil samples (from 0-15 cm) were collected and the amount of physical (hydraulic conductivity, bulk and particle density and porosity)and chemical (nitrogen, phosphorus and potassium) properties were measured.
Results and Discussion: The results showed that the water quality has a significant effect on all parameters and the amount of compost has significant effect on all parameters except bulk density. But, the amount of all parameters (except hydraulic conductivity) was not influenced by interaction between water quality and compost levels. In all treatments, the range of hydraulic conductivity, bulk density, particle density and total porosity were varied between 23.82 to 35.61 mmh-1, 1.41 to 1.43 grcm-3, 2.51 to 2.57 grcm-3 and 42.88 to 45.19 %, respectively. Also the range of nitrogen, phosphorus, and potassium were varied between 0.06 to0.08 %, 14.64 to232.28mgkg-1,and 393.22 to519.84mgkg-1,respectively.Overall, the results indicated that using compost and wastewater increased hydraulic conductivity, porosity, nitrogen, phosphorus, and potassium of the soil in comparison to the control. Whereasbulk and particle density of soil decresed by using compost and wastewater (as a mixed material).
Conclusion: In this study, we investigated the effect of wastewater and compost on some of soil physical properties (hydraulic conductivity, bulk density, particle density and total porosity) and also some of chemical properties of soil nitrogen, phosphorus and potassium).The results showed that the use of wastewater and compost on soil physical condition has a positive effect.Wastewater and compost by improving the soil pore size distribution, decreased the bulk and particle density and increased porosity and hydraulic conductivity of the soil. The impact of wastewater and compost to improve the physical properties, commensurate with the level of wastewater treatment and composting rate in the soil. Also using the wastewater (raw wastewater, treated wastewater and combined 50% of raw wastewater and fresh water) and compost (40, 80 and 120 tha-1), compared to the control (fresh water and soil without compost), increased total of nitrogen, phosphorus and potassium of soil. But, due to the risks of soil salinity and nitrogen leaching, it is suggested that longterm exposure to wastewater and compost needs a careful practical management.
M. Ghaemi Baygi; mahmood raeini; M. Mousavi Baygi
Abstract
Evapotranspiration is one of the important elements of the hydrologic cycle in agricultural projects. Energy balance (the bowen ratio) is a method for estimating evapotranspiration of plant which is based on measurements of temperature and humidity gradients in two different heights of a plant. An experiment ...
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Evapotranspiration is one of the important elements of the hydrologic cycle in agricultural projects. Energy balance (the bowen ratio) is a method for estimating evapotranspiration of plant which is based on measurements of temperature and humidity gradients in two different heights of a plant. An experiment was conducted in agriculture faculty of Ferdowsi university of Mashhad by using three Lysimeter to estimate evapotranspiration of Gascogne wheat and the resulting were compared with direct method. Required data for measuring the amount of evapotranspiration using energy balance method was obtained throughout plant phenology with one hour intervals using energy balance (model 5200 – DIK) estimation device of evapotranspiration was daily calculated. The rate of daily evapotranspiration that obtained by using energy balance method amounted to 2.4 mm which is in a high correlation (0.98) with the Laysimeter result that was 2.4 mm. The range of Bowen ratio changes was between -1.5 to 1.9 during the day which the negative values occurs after sunset that is the sensible heat flux begins to decrease. The value of Boven ratio gradually increase so that it's maximum value between 8 AM to 9 AM, and then followed a decreasing trend until the afternoon.
