K. Kamali; Gh. Zehtabian; tayybe Mesbahzadeh; M. Arabkhedri; Hossain Shohab Arkhazloo; A. Moghadamnia
Abstract
Introduction: Soil quality is an essential indicator for sustainable land management that generally depends on soil physical, chemical and biological properties. Due to the multiplicity of soil properties, the number of variables is usually reduced to a minimum set by statistical methods, which reduces ...
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Introduction: Soil quality is an essential indicator for sustainable land management that generally depends on soil physical, chemical and biological properties. Due to the multiplicity of soil properties, the number of variables is usually reduced to a minimum set by statistical methods, which reduces study time, decreases monitoring cost for sustainable use of agricultural lands. The aim of this study was to introduce the most effective soil characteristics of agricultural lands in Mohammadshahr plain, Karaj, to prevent the descending trend of soil quality.
Materials and Methods: In this study, four farms and orchards which were different in terms of crop type and irrigation system were selected and evaluated with Integrated Quality Index (IQI) and Nemero Quality Index (NQI). In both indicators, the characteristics affecting soil quality are combined in the form of a mathematical model and presented as a numerical quantity. For this purpose, first 12 soil profiles were described, followed by sampling from topsoil (surface layer) and sublayers (weighting average for the depths) and testing 17 soil characteristics affecting its quality. In the next step, both indicators were calculated using two different sets of soil properties. The first category, the Total Data Set (TDS), included all measured soil characteristics, and the second group, the Minimum Data Set (MDS), included the most important properties affecting soil quality. The Principle Component Analysis was implemented to select the MDS. Soil properties were scored to calculate IQI and NQI. For this purpose, a function was defined for each soil feature to standardize all scores between zero and one. Weighting various soil quality properties was also performed by calculating the common variance of the variables, which was obtained by factor analysis method.
Results and Discussion: Calculation of IQI and NQI indices showed that the topsoil samples were in grade III and sublayer samples belonged to grade IV with major limitations due to lack of profile development, organic carbon deficiency, salinity and high gravel. Four and six items out of 16 variables were identified effective for topsoil and sublayers, respectively. The IQI index based on TDS was more accurate and sensitive than the NQI index for soil quality assessment, as more features are considered for TDS. In the IQI index, both the weight of attributes and their scores are effective, while in the NQI index, only the attribute score is considered. On the other hand, the coefficient of determination between the TDS and MDS for topsoil and sublayer samples was 0.55 and 0.56% for IQI model, respectively, and 0.48 and 0.16% for NQI model, respectively. In other words, the determination coefficients showed the reliability of using the MDS instead of TDS in both IQI and NQI models. In the MDS, mean weight diameter (MWD) showed the highest effect on the surface layer and percentage of gravel had the greatest impact on the soil quality of the sublayer.
Conclusion: Although TDS took into account all soil properties and showed a slightly higher coefficient of determinations with both soil quality indicators, the MDS obtained similar results to the TDS with only about half of the properties. In the MDS, the features with an internal correlation is eliminated rendering it more cost effective. The results of this study assist decision-makers to choose better quality management and soil sustainability strategies while decreasing the monitoring cost.
abdolmajid liaghat; masoud Pourgholam amiji; pourya mashhouri nejad
Abstract
Introduction: With due attention to the limitation of water resources in Iran and specific geographical conditions of the country, using modern methods of irrigation with low water usage is inevitable. By applying suitable management in water system, soil and plant, while increasing product, we can establish ...
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Introduction: With due attention to the limitation of water resources in Iran and specific geographical conditions of the country, using modern methods of irrigation with low water usage is inevitable. By applying suitable management in water system, soil and plant, while increasing product, we can establish a sustainable agriculture. Today, subsurface irrigation systems are used in various methods around the world, especially in the countries encountering water shortage. One of the newest methods is applying sponge plastic pipes such as tuporex which is installed in the area of plant root. Then, water with the pressure of 0/6-2 atmosphere flows inside it and by exuding, it dampens the area.
Materials and Method: For this purpose, in this study number of 12 concrete lysimeters with the dimension of 2×2×1/25 m was used to investigate the effect of vegetation (mulch) on the efficiency of water consumption and product function for corn, salt accumulation as well as the amount of nitrate wash on soil profile under two permeable subsurface irrigation and surface irrigation. For irrigation, a body of water with salinity of 4 ds/m was used. The plan includes two main treatments (permeable subsurface and surface irrigation) and two sub-treatments (mulch and without mulch) withfactorial experiment in a randomized complete block design with three replications at the College of Agriculture Research Campus, Tehran Universityof technology Located in Karaj, Iran in 2010. Surface irrigation was performed based on the moisturein the soil and permeable subsurface irrigation was performed per dayas much water as was consumed.. Lysimeters soil is prepared from farm soil and through examination, its appearance special weight was registered to be 1.4 gr per cm3 equals to 1400 kg per m3. The amount of nitrogen fertilizer (Urea) was applied on the lysimeters according to the region convention, was 300 kg per hectare (120 gram per each lysimeter(. A half of this amount was used at the time of cultivation and another half was used for the plant 60 days after cultivation; because the amount of water given in this type of system is higher.On the other hand due to the lack of vegetation, the significant amount of evaporated water and water productivity have decreased.
Results and Discussion: Results disclosed that the subsurface irrigation system has important effect in decreasing consumed water (58% with mulch and 40% without mulch) and increasing crop yield (46% in seed corn yield, 50% in forge yield and 12% in weight of one thousands seed corn) in comparison with the surface irrigation system. As well as the subsurface irrigation has prevented lower soil layer from contamination and being salty by decrease salt and nitrate leaching. Besidespresence of mulch in lysimeterhas shown important role in decreasing water consumption and seed corn yield. The important thing is that the highest yield in two type of performance, was recorded in subsurface irrigation treatment with mulch (TM) and this subject is so important when we remind that (TM) treatment had the least amount of water uses. Itmeans that with the least amount of water consumed the highest amount of product was obtained among the treatments.On the other hand, surface and non-mulching (SO) irrigation is expected to have the lowest yield per unit water consumption.
Conclusions: Also in both subsurface irrigation with preamble tube and surface irrigation system, existence of mulch caused to decrease salt concentration to 40% and 30% in soil surface respectively which makes it suitable for the areas facing water shortage. It can be concluded that, existence of mulches in the both subsurface irrigation with permeable tube and surface irrigation system causing water saving 13 and 23 percent, respectively and the rate of saving water in surface irrigation system with presence of mulch has also increased. Thus, it is recommended that some of the plant residuals, like mulch remain on the ground after harvest. The subsurface irrigation with permeable tube system has been prevented from washing nitrate to the depths of the soil. As a result, the environmental pollution caused by nitrate losses in this system is minimal and this system saves fertilizer. Also the concentration of salt solution in the soil profile in subsurface irrigation system was significantly lower than the salt concentration in surface irrigation. As a result in areas that use the saline water for irrigation, the subsurface irrigation with preamble tube confirm better function than surface irrigation system and use mulch can increase yield and reduce leaching.
M.M. Heidari; S. Kouchakzadeh
Abstract
Introduction: Unsteady flow in irrigation systems is the result of operations in response to changes in water demand that affect the hydraulic performance networks. The increased hydraulic performance needed to recognize unsteady flow and quantify the factors affecting it. Unsteady flow in open channels ...
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Introduction: Unsteady flow in irrigation systems is the result of operations in response to changes in water demand that affect the hydraulic performance networks. The increased hydraulic performance needed to recognize unsteady flow and quantify the factors affecting it. Unsteady flow in open channels is governed by the fully dynamic Saint Venant equation, which express the principles of conservation of mass and momentum. Unsteady flow in open channels can be classified into two types: routing and operation-type problems. In the routing problems, The Saint Venant equations are solved to get the discharge and water level in the time series. Also, they are used in the operation problem to compute the inflow at the upstream section of the channel according to the prescribed downstream flow hydrographs. The Saint Venant equation has no analytical solution and in the majority cases of such methods use numerical integration of continuity and momentum equations, and are characterized by complicated numerical procedures that are not always convenient for carrying out practical engineering calculations. Therefore, approximate methods deserve attention since they would allow the solution of dynamic problems in analytical form with enough exactness. There are effective methods for automatic controller synthesis in control theory that provide the required performance optimization. It is therefore important to get simplified models of irrigation canals for control design. It would be even more interesting to have linear models that explicitly depend on physical parameters. Such models would allow one to, handle the dynamics of the system with fewer parameters, understand the impact of physical parameters on the dynamics, and facilitate the development a systematic design method. Many analytical models have been proposed in the literature, Most of them have been obtained in the frequency domain by applying Laplace transform to linearized Saint-Venant equations. The got transcendental function can then be simplified using various methods to get a model expressed as a rational function of s (the Laplace variable), possibly including a time delay. It is therefore important to develop simple analytical models able to accurately reproduce the dynamic behavior of the system in realistic conditions.
Materials and Methods: Changes in water demand can create transient flow in irrigation networks. The Saint Venant equations are the equations governing open channel flow when unsteady flow propagates. In this research, the finite volume method using the time splitting scheme was employed to develop a computer code for solving the one dimensional unsteady flow equations. Considering stationary regime and small variations around it, the Saint-Venant equations around initial condition was linearized.
The Laplace transform is applied to the linearized saint venant equations, leading to an ordinary differential equation in the space variable x and parameterized by the Laplace variable s. The integration of this equation lead to a transfer matrix, and gives the discharge Q*(x, s) at any location with respect for the upstream discharge. This matrix is coupled with the downstream boundary condition and developed an equation that solved using Simpson integration algorithm. It should be noted numerical solution of developed equation is easier than solving fully dynamic saint venant and is less sensitive to the spatial step and the researcher simply writing code.
Results and Discussion: Froud Number (F), variation of inflow discharge (ΔQ/Q), and dimensionless parameter of KF2 in which K is the kinematic flow number, are effective factors on accuracy of developed equation. In order to determine the effect of the factors on accuracy of presenting formula, several simulations were performed using numerical model. The presented formula and numerical model were compared for 10, 20 and 30 percent discharge variation and error calculated, the maximum error increases with increasing ΔQ/Q.
To assess the importance of Froud Number and KF2, also several simulations were carried out, the results showed that the maximum error in the development equation for various Froud Number and KF2>1, is less than 3.8 percent.
Conclusion: Using Laplace transform to the saint venant equations and with respect to upstream and downstream boundary a formula for routing discharge presented. Investigation of the applicability range of presenting formula and cognitive effective factors on accuracy is necessary. So, the finite volume method using the time splitting scheme was employed to develop a computer code for solving the one dimensional unsteady flow equation. Then some tests of unsteady flow were simulated and verified the equations. The results showed that the maximum error increases with decreasing KF2 and increasing the rate of sudden changes of discharge. The maximum error in the presented formula for all tests with KF2>1, less than 3.8 percent.
M.A. Mousavi Shalmani; A. Khorasani; N. Pirvali Bieranvand; M. Noori Mohammadiye; A. Eskandari; S.M. Mohati
Abstract
Nitrogen (N) is the most usually used crop nutrient which represent importance of the efficient use of nitrogen fertilizers. At this study, the optimum fertilizer application pattern by using of 15N isotope technique in different irrigation systems and the influence of the fertilizer application time ...
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Nitrogen (N) is the most usually used crop nutrient which represent importance of the efficient use of nitrogen fertilizers. At this study, the optimum fertilizer application pattern by using of 15N isotope technique in different irrigation systems and the influence of the fertilizer application time on amino-N accumulation in roots has been investigated. The experimental design was a randomized complete block (sampling method) design with four main treatments (irrigation methods) and three replications (unit area 144 m2). Irrigation treatments include: T1; surface drip fertigation, T2; sprinkler fertigation, T3; sprinkler irrigation T4; furrow irrigation. In the middle of the each plot an area about 1- 2 m2 (15 plants) was allocated as isotopic sub plot. Results indicated that the least tendency to utilize the fertilizer sources was related to the fertigation treatments. Despite the highest root weight, treatment T2 is not recommended to use. The method of application of fertilizers in treatment T3 lead on to the highest nitrogen uptake efficiency and pure sugar. The method of application of fertilizers in T1 and T2 increase the rate of α-amino acid N in the sugar beet roots and decrease their quality. Treatment T4 produced relatively high quality roots that confirm the method of application of fertilizer in treatment T3. In the weather condition of central Iran, during the sugar beet growing season, the application of fertilizer should be begun 45 days after sowing seeds and must be completed within one month. Occurrence of isotopic fractionation phenomenon cause that the average percentage of labeled nitrogen fertilizer (Ndff %) in underground and aerial parts of the plant considered to be 20.1 and 16.1% respectively.
