JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2003 | Volume:4 | Issue:14|Papers Count:6

In dry land areas, tillage practices should be involved soil and water conservation in addition to land preparation. In the most dry land cold areas Iran, tillage practices usually are performed in soil with high moisture content especially for plant crops during spring. Performance of tillage practices under high moisture content in soil with high clay percent and low organic matter leads to compact soil and it damages soil structure. This study was conducted in Maragheh Research Station on a clay loam soil for 3 years to determine the effect of subsoiling on soil moisture conservation and wheat grain yield in dry land conditions with this assumption that deep tillage might increase water use efficiency and wheat grain yield. There were used treatments with three subsoiler shank spacing (50, 75 and 110 cm) and one treatment without subsoiling in Randomized Complete Block Design (RCBD) with four replications. Soil bulk density and soil moisture content were measured between two subsoiler shanks in 10 cm soil depth. Subsoiling decreased soil bulk density and increased soil moisture content. The highest reduction of soil bulk density in 0-40 cm soil depth was measured at shank spaces of 50 and 75 cm. Soil moisture content and wheat grain yield increased by 15% and 21% respectively, with using subsoiler at 75 cm shanks spaces in comparison with treatment which was not used subsoiler.

Deflection-meter is a vane inserted in the direction of flow vertically. It is hinged out of water and could swings freely. Flow forces exerted on the vane, divert it from vertical position. This diversion is a function of flow characteristics and vanes geometry, which could be considered as an indicator of flow velocity and discharge. In this research hydraulic relations of rectangular deflection meter-for measuring average flow velocity in canals with rectangular and different and different trapezoidal cross sections are derived. Sixty percent of measured data are used for derivation of relations, and forty percent of data are used for calibration. Using these relations with measuring deflection angle and flow depth, average flow velocity and discharge could be determined. Results of this research show that, vane width has no significant impact on the relations. For rectangular canal a linear relation for vane theoretical velocity and average flow velocity exists. Therefore velocity coefficient is constant and equal to 0.82 two forms of structures head loss is calculated in terms of ratio of upstream and downstream head difference to the upstream head, and head loss coefficient of upstream velocity head. Maximum head loss for rectangular section observed was 3.2% and head loss coefficient was 2.46. for trapezoidal cross sections nonlinear relation between vane theoretical velocity and average flow velocity are derived. The relations show that vane velocity coefficient is variable with respect to the flow velocity. Maximum head loss in the range of 4-45 l/s, were around 1.2%, 2.1% and 2.8% and head loss coefficients were around 1.77, 0.05 and 0.31.

Loofa (loofa cylindrica) is a dried plant of the Aubergine family and the physical structure and specific characteristics of this plant, such as chemical, heat and microbiological stability, makes it a suitable carrier for the immobilization of microbial cells. This plant grows in the warm and humid areas in the north and south of Iran and has high porosity (75-84%) as well as low density (0.13-0.039 g/cm3) and compared to other existing carriers such as polyurethane foam, is very suitable for cell immobilization. However, the high specific volume of the pores in the structure of this carrier, in the range 16/48-19/2 g/ cm2, means that only cell flocs can be significantly entrapped inside the pores. In this study Loofa was used as a carrier for the immobilization of Sacharomyces cerevisae cells used in the production of ethanol from carbohydrate substrates. Since these cells do not have the ability to flocculate, chitosan, a cationic material, was used to induce the flocculation of S. cerevisae cells. The results showed that a concentration of 8 miligram per gram of cell results in 92% cell flocculation in a period of 1 hour. At this concentration, 60% of the cells where immobilized in the Loofa carrier in a period of two and a half hours with an initial inoculum of 0.1 gram cells per gram of Loofa. The use of such immobilized cells for the production of ethanol from a synthetic medium increased the productivity of ethanol production two folds compared to when free cells where used. However, during the course of the ethanol production process the concentration of free cells increased signifying the release of the yeast cells from the Loofa support. Addition of chitosan at specific points during the fermentation was shown to decrease this rate of cell release but also resulted in a decrease in the productivity of ethanol production which was attributed to the inhibitory effect of chitosan on the fermentative activity of S. cerevisae cells. Investigating the use of lower chitosan concentrations or the use of other non-inhibitory flocculents id suggested for future work.

One of the main problems in micro-irrigation systems is existence of suspended solids in irrigation water and consequently clogging of emitters. Thus, studying performance of water refinement unit is essential, especially when low quality water is used. Central control unit, which is responsible for filtration of water in micro-irrigation system, is the main factor for success or failure of the system. Most experts consider water filtration until as heart of micro-irrigation system, due to its importance. This study was conducted to investigate and evaluate the performance of sand and disk filters in central control until, in situation using low physical quality (High organic matter) water for irrigation. The amount of suspended solids in refined water was measured under different pressures. Also, variations of pore size diameters due to sand disturbtion after back washing were estimated in sand filters. The results of this study showed the possibility of clogging in some emitters in micro-irrigation system, in spite of presence of sand filter. Also, the results showed that sand layers are disturbed in sand filters after back washing. The disruption of sand layer would affect pressure loss, the amount of suspended solids in passed water and the operational time. Finally, the results of this study indicated that the performance of disk filters were much better than sand filters in aspect of refined water physical quality and easy washing.

The properties of soils affected by salinity and processes involving degradation of soil structure have been partly recognized. However, the effects of saline and sodic condition on physical and mechanical properties of soils, have been studied to a lesser extent. In this research, the effects of electrical conductivity (EC) and sodium adsorption ratio (SAR) on soils possessing various amounts of organic matter were assessed under laboratory conditions. The soils were collected from the Dasht -e-Naz of sari region in the north of Iran, contained a uniform clay type, predominantly Illite. The major difference of the soils was their amount of organic matter content. The treatments consisted of solutions with given EC and SAR (two levels of ES;0.5and 4 dS/m and three levels of SAR; 0 , 5 and 15 ) with increase of SAR, the wet aggregate stability (WAS) decreased and the amount of dispersible clay (DC) increased .In similar SAR, treatments with higher EC exhibited lower DC. The order of average aggregate stability of soils were; virgin soils > soils under continuous cultivation of Festuca >soils under intensive cultivation with regular crop rotation>soils under continuous cultivation of Agropyron. The variance analysis of data showed significant differences (at 1%) between soil types, sampling depth, and SAR.