AGRICULTURAL RESEARCH
Year:2006 | Volume:6 | Issue:3|Papers Count:8

A zero-inertia model was developed for furrow irrigation simulation with constant spatial intervals and effectiveness of wetted perimeter (Zero-Inertia Model, Wetted Perimeter Variable; ZIWPV model) using an explicit scheme. The code of the computer program remains simple and its teaching and learning will be easy, if the explicit scheme is used. The wetted perimeter is assumed as a function of flow section area. However, the depletion phase has not been simulated by previous models in which explicit schemes have been used, it has been simulated in this model. The model result was validated against the experimental field data and the spatial intervals size was investigated on simulation of advance phase of ZIWPV model. The advance phase was also simulated well with large spatial intervals. Applying the small sizes of spatial intervals make the results get closer to actual data. However, the model may behave unstable on advance phase. Also, it was found that the final results of model are not sensitive to time and space interval sizes. Therefore, the solution of zero-inertia models with explicit schemes can be used well to simulate furrow irrigation.

Because of water requirement increase, the efficiency of irrigation water must improve especially in areas with limited water resources. In order to improve physical performance of hydraulic systems, some efforts have been done, but the lack of fiscal resources is the main problem for performance improvement of irrigation networks. Therefore, the proper management of system is the practical method for efficiency improvement. One of the major sources of water loss in irrigation canals is unsteady flow. Water delivery and distribution schedules are one of the sources of unsteady flow in irrigation networks. In this research, for quantifying operational performance, unsteady flow in E1R1 canal of Dez irrigation network is simulated using ICSS hydrodynamic model. Performance indicators are determined under two conditions of operation and non-operational of structures and 6 hours water delivery. The results show that using hydrodynamic model and analysis of unsteady flow can quantify operation performance of irrigation canals. Furthermore the application of suitable operation instruction in response to unsteady flow can improve the performance of the system.

In order to study the effect of planting arrangement and plant density on yield and growth indices of grain corn (three way cross 647 hybrid) under redroot pigweed competition a field experiment was carried out at Kabotar-Abad experimental station, agricultural research center of Esfahan in 2003. Treatments were arranged in a factorial split experiment based on RCBD with three replications. Factorial arrangement of corn densities (74000 and 111000 plant ha-1) and planting patterns (single row, rectangular twin row and zigzag twin row) formed the main plots. Sub-plots were referred to pigweed densities (0, 4, 8 and 12 plant per m of row). Results showed that leaf area index (LAI), total dry matter accumulation (TDM), crop growth rate (CGR), and grain yield of corn decreased by presence of red root pigweed. All variables in higher corn density were more than low corn density and reduction of LAI, TDM, CGR and grain yield of corn under pigweed competition decreased with increasing corn density. Among different corn arrangements, twin row planting and especially zigzag twin row increased all corn traits, in such a manner that twin row planting arrangement decreased the pigweed competition effect on these traits.

In this study, 9 sprinkle irrigation systems including 3 wheel move, 3 classic and 3 big gun systems were evaluated as samples in East-Azarbayjan Province. Uniformity coefficient, actual and potential application efficiencies were determined in each case. For the fields under study, the potential application efficiencies varied from 69.3% to 78.5% for the wheel move systems, from 48.2% to 73.5% for the classic systems and from 40% to 56.5% for the big gun systems. The average actual application efficiencies of wheel move, classic and big gun systems were 65.8%, 52.7% and 47.9%, respectively. Under low wind speed conditions and actual operation of the systems, average uniformity coefficients for wheel move, classic and big gun systems were 85.9%, 73.8% and 64.4%, respectively, and the distribution uniformity of low quarter were equal to 79.3%, 63.5% and 51.5%, respectively. The results of one of the experimental site showed that the reduction of 25% in lateral spacing would approximately result in 25% increase in uniformity coefficient and 21% and 33% increase in distribution uniformity based on half and one fourth of low observation data, respectively. Under low wind conditions and soil texture of clay loam, the performance of wheel move system was better than the performances of classic and big gun systems. Also, the performance of the classic system was better than the performance of big gun system.

The objective of this study was to investigate the combined influences of soil physical conditions (structure and texture) and organic manures application on the flow of E. coli through intact soil columns. The soil conditions consisted of intact columns (with height of 25 cm and diameter of 16 cm) of two soils: sandy clay loam and loamy sand. The manures were: cow manure, poultry manure and sewage sludge which were surface-applied at the rate of 10 ton ha-1 on dry basis. The manure-soil combinations were leached by tape water at the flux of 4.8 cm hr-1 (which was 0.12 of saturated hydraulic conductivity of sand clay loam soil) up to four pore volumes. A suction was applied by a vaccum pump on the beneath of the columns to preserve the steady-state flow during the leaching experiments. Aliquots of the effluent were sampled at different times during the experiment. The colony forming units of the samples were counted by plate count method. When the leaching was continued, the effects of soil and manure treatments became significant due to the impacts of manure effluents on soil physical and chemical properties. It is also related to the fact that some time is needed for the pollution plume to reach to the end of the columns. The preferential flow caused more pollution of effluent in the sandy clay loam soil when compared with the loamy sand soil. Among the manure treatments, poultry manure caused more significant effluent pollution. However, the differences between cow manure and sewage sludge were not significant in terms of E.coli concentration in the drain water. The impact of cow manure on bacteria transport was greater due to the higher amount of organic materials and soluble organics in comparison with the other manures. Overall, poultry manures are potentially important sources of pathogenic bacteria (e. g. E.coli) and soil structure has great role in this regard.

Transport of pathogenic bacteria that can potentially contribute to surface and groundwater contamination, is paraimportant. In spite of the widespread distribution of gypsic and calcisols in Iran, there is no information on the effects of lime and gypsum on bacteria transport phenomenon. This study was carried out to evaluate the influence of lime and gypsum on Pseudomonas fluorescents transport through sand columns under saturated steady state conditions. Four levels of lime: 0, 5, 10 and 20% w/w and three levels of gypsum: 0, 5 and 10% w/w were mixed with sand and arranged as a factorial design (completely randomized) with three replicates. The mixtures were poured into pyrex cylinders (with 20 cm height and 7 cm diameter) and steady-state water flow was imposed on the columns. Then, the influent was switched to a constant concentration (106 cfu ml-1) of Pseudomonas fluorescens. The leaching of the column was continued for five pore volumes (PV) and the bacteria concentration of the effluent was measured. Adding the lime and gypsum both affected the effluent concentration, significantly. The highest and the lowest pollutions of the drain water occurred in the pure sand columns and 20% lime treatments, respectively. Lime addition significantly decreased the bacteria transport through the columns. The impacts of lime and gypsum on effluent concentration were significant. The breakthrough curves could obviously represent the lowering of bacteria flux with lime and gypsum additions. Overall, the results demonstrated the high adsorptive and filtering capacities of carbonate and sulfate compounds which could reduce the bacteria transport and contamination of aquifers.

In this study 194 Fusarium isolates belonging to Martiella section were obtained from more than 150 soil and plant samples collected from different parts in Kermanshah, Hamadan and Kurdistan provinces. The soil samples were taken randomly from 15 – 25 cm depths and then transferred in plastic bags to the laboratory. Fusarium isolates were obtained on Nash and Snyder medium using soil suspension technique. Identification process was carried out using morphological features including colony characters (pigmentation and growth rate on PDA) and microscopic characters such as shape and size of conidiophores, conidia, chlamydospores and phialides. Microscopic features were studied and recorded 5-10 days after inoculation on CLA and SNA. This investigation resulted in identification of four species including: F.  solani,  F.eumartii,  F.  javanicum  and  F. caucasicum.  Among the identified species, F. caucasicum is new for the Mycoflora of Iran.

Wormwood, (Artemisia absinthium L.) is one of medicinal and fragrant plants belonging to the family of Asteraceae. In this research, the essence components of the field grown plants were analyzed in which then 20 compounds were recognized. The effect of nitrogen fertilizer (urea) on total essential oil and the amounts of a-Thujone and Chamazulene rate was studied. The amounts of fertilizer were 0, 50, 100, 150 and 200 Kg urea per hectare applied in two parts, one at the time of transplanting seedlings in the field and the second part, two months later. Essential oil was extracted using Clevenger-type apparatus, with water distillation system. Separation and measurement of a-Thujone and Chamazulene content was conducted by Gas-Chromatography and Mass Spectrometry (GC-MS). The rate of vegetative yield and dry matter were significantly increased due to nitrogen application. Nitrogen had no significant effect on essential oil, a-Thujone and Chamazulene content in spite of increasing the herb yield. Therefore increased plant foliage due to the use of nitrogen fertilizer (150 Kg/ha and more) caused an increase in the essential oil, a-Thujone and Chamazulene contents per plant but had no significant effect on the basis of dry weight.