جستجوی مقالات مرتبط با کلیدواژه « توزیع » در نشریات گروه « آب و خاک »

One of the principal methods to improve water productivity in irrigation network is to use the suitable distribution of water. In this research، the distribution of water in Doroodzan dam irrigation network was evaluated using 14 years of data (1996-2010). This irrigation network is located in northwest of Fars province and distributes stored water in Droodzan dam. Distribution of water between Hamoon، Ordibehesht، Left side Principal and Abarj canals was studied. Monthly distribution of water showed that in April and May، inflow in canals are high، in November they are low and in February there is no water in canals. The index of delivered water per unit area of land must be equal between canals. The lowest amount of this index was 0. 19 (l. s-1. ha-1) for Hamoon canal and the highest amount was 0. 37 (l. s-1. ha-1) for Abraj canal. The results showed that Hamon canal compared to others received less water per unit area and Abarj canal، received the highest amount of water per unit area. It was recommended that the water must be distributed between canals by equal amounts per unit area on volumetric basis based on crop water requirements.

Evaluation procedures have been developed for effective design and management of irrigation systems. Furrow irrigation is one of the main types of applying water in agriculture. In the present study, a new procedure for field evaluation of water distribution in furrow irrigation is proposed. For this purpose, application efficiency (Ea), water requirement efficiency (Er), deep percolation (DP) and tail water ratio (TWR) have been introduced based on the average of the non-dimensional infiltrated depth values in the four data groups. The relationships between coefficient of uniformity, CU and distribution uniformity, DU have been described by opportunity time values of each quarter and using the linear equation instead of infiltration function. The proposed method was compared to other procedures by 9 scenarios of field data with different discharges and lengths. The results show that the evaluation indicators of furrow irrigation depend on the hydraulic characteristics of the soil and the opportunity time. Also, there was no observed any significant difference on the suggested indexes values and classical performance indicators.

The effects of two different organic matters including compost and sewage sludge on the distribution of Cd, Pb and Ni in different fractions of two calcareous soils were investigated. The soil samples were treated with two levels of each organic material (0 and 2%). Heavy metals were added to soils at the rate of 10 mg kg-1 of Cd, 200 mg kg-1 of Ni and 400 mg kg-1 of Pb as nitrate salt. The samples were incubated for 12h, 20 and 40 days. After each incubation time, metals were fractionated by sequential extraction and analyzed for DTPA extractable form. Results showed that Pb and Ni were rapidly transformed from exchangeable to more stable fractions during the incubation intervals. In contrast, the amount of Cd in exchangeable fraction changed slightly and the considerable portion of Cd remained in this fraction. At the end of the experiment, the distribution percentage of Cd, Ni and Pb followed the order of carbonate>Fe-Mn oxide>exchangeable, Fe-Mn oxide>carbonate>organic matter, carbonate>Fe-Mn oxide>organic matter, respectively. There were almost no changes for the metals in the residual fraction. The effects of compost and sewage sludge on the distribution of studied metals in two soils were different. However, application of organic matter mainly resulted in the increased organic matter fraction and DTPA extractable forms of metals.

The application of fertilizer through irrigation water (fertigation) is an efficient and cost-effective method in which crop yield increases while potential environmental problems related to conventional application methods reduced. In this study, distribution uniformity of fertigation in different furrow irrigation regimes is evaluated, a numerical fertigation model established, calibrated and validated. Conducted experiments includ: injection of fertilizer only during the first half of the irrigation event (FH), injection during the second half (SH) and injection during the entire irrigation event (T). These options were conducted under free draining as well as under blocked-end conditions with two replications. All the experiments were conducted through cutback method. Potassium nitrate was used as fertilizer in the experiments. Distribution uniformity of low half (DULH) and low quarter (DULQ) of water and fertilizer was assessed to evaluate different fertigation scenarios. A sensitivity analysis approach was also performed to assess the effects of longitudinal dispersivity parameter on overland solute transport. The results show that DULH has significantly differs within the three application times (FH, SH, T). That shows injection in the second half of the irrigation event is more appropriate than injection in the first half and during the entire irrigation event as based on the results. The best case is injection in the second half of the irrigation event preferably starting before completion of the advance phase and in blocked-end conditions. Because in this case, solute losses due to runoff from the outlet is zero and also distribution uniformity is somewhat higher whereas in free-draining conditions fertilizer application during the first half of irrigation provide acceptable fertilizer uniformity and least losses due to runoff. Results of the model show that the best case would be injection in the second half of the irrigation event with blocked-end conditions. No significant difference was observed between distribution uniformity of free-draining and blocked-end experiments. It was found that dispersivity parameter doesn’t affect the fertigation uniformity. A value of 5 cm for dispersivity provided a reasonable fit to the experimental data.