فصلنامه تحقیقات مهندسی کشاورزی
سال چهاردهم شماره 2 (تابستان 1392)

Water harvesting in agriculture mobilizes rainwater in a catchment area (usually non-productive) to benefit growing plants in a target area. This brings water available to the target area closer to crop water requirements so that economical agricultural production can be achieved, improving rainwater productivity. To investigate micro-catchment water harvesting (MCWH), a field experiment was conducted from 2000 to 2006 in East Azarbaijan in northern Iran using a split-split plot factorial design with five replications. Thetreatments comprised two MCWH patterns (small basins and semi-circular bunds); three catchments sizes of 25 m2 (5×5, R = 2 m), 49 m2 (7×7, R = 2.85 m) and 81 m2 (9×9, R = 3.7 m); three runoff area treatments (natural; cleaned and smoothed; cleaned, wetted and compacted); and two-infiltration areas (natural, soil mixed with polymer at 1 kg/tree) for two new almond varieties. Agronomic characteristics, product growth, threshold runoff and crop yield estimates were examined. The results were compared with farmed fields (traditional and irrigated) and showed that the tree survival rate was about 35%-55% for irrigated farmed fields and 100% for the MCWH site. The use of a polymer had no significant effect on water retention. Although a small basin (9×9) and runoff area that were compacted using a polymer gave better results for the survival, growth and productivity of almonds, a small basin (7×7) compacted without a polymer isrecommended based on the economic analysis. Threshold runoff was 2.5-3.5, 3.5-4.5 and 4.5-5.5 mm for the natural, cleaned and smoothed, and cleaned, wetted and compacted conditions, respectively. During the 2006 season, the fruit yield was estimated to be 3 kg/tree, totaling 612 kg/ha for the recommended treatment. For the farm fields, the optimal treatment combined required at least 1-2 irrigations during the summer.

The self-purification capacity of rivers is a function of time, space, nature, intensity of the pollution load and the condition of the river bed. Evaluating a river self-purification rate requires determination of the dissolved oxygen levels. The level of pollution and oxygen shortages at critical points along the river should be investigated. In the other words, the estimation of river contaminants is based on the selfpurification capacity. The Streeter-Phelps method is a well-known approach for evaluating the level of dissolved oxygen in a river and it can be restricted to ignore advection and dispersion terms. It is possibleto model the self-purification process knowing the aquatic parameters and pollutants. In this paper, the basic Streeter-Phelps equation has been analytically solved. Advection and dispersion terms have been included in the equation to increase the accuracy of the predictions. The new equation was then modeled using FTCS, Upstream, Lax & Wendroff, and QUICKEST numerical methods. A 2 km section of the Pasikhan River was chosen for field testing and the required water samples were taken and lab tested forDO, BOD5, NO3 and PO4. The analytical and numerical results for predicting dissolved oxygen were compared with the field data. The results showed that all numerical predictions were in good agreement with the measured data, but the Upstream method showed the best results. Furthermore, the results indicated that the numerical methods performed better than the Streeter-Phelps base model. This may have been caused by the addition of the advection and dispersion terms to the Streeter-Phelps base model.

Three varieties of Iranian rice were evaluated in the paddy (Tarom, Khazar, Fajr) for the cooking, textural, and pasting physicochemical properties during 18 months of storage under ordinary conditions. Testing was done for were amylose, cooking time, elongation, water uptake, and solid loss. A texture analyzer and Rapid Visco Analyzer were employed to determine hardness and pasting properties. All experiments were repeated every three months for 18 months and in three replications. Amylase was determined only for the first month. Solid loss decreased significantly over the 18 month for all varieties. The hardness of the cooked rice increased for all varieties, but was only significant for Khazar. The most significant change in the pasting properties was that the peak viscosity increased initially there was decreased. There was an initial increase in breakage followed by a decrease. In Tarom and Khazar varieties, the setback initially increased and then decreased and, in Fajr, it was initially constant and then decreased.

Corresponding Author: Academic member, Agricultural Engineering Reaserch Department, Isfahan Agricultural Research Center, Isfahan, Iran. P. O. Box: 81785-199. E-mail: orangtaki@yahoo.com Received: 11 June 2012, Accepted: 29 December 2012In Iran, onion plants are currently broadcast over the majority of onion fields and weeding and harvesting are done manually by seasonal workers. At harvest time, 40 worker-days are required to onion dig just one hectare. This cost could be saved if the operation could be carried out by machine. Rear-mounted diggers can only be implemented if 40 cm spacing between rows is allowed for each tractor wheel, which results in a 20% decrease in yield. This research evaluated the feasibility of using front-mounted implements to digrows of crop bulbs of the same width as the tractor and to dig only two narrow bands in front of the tractorwheels. Treatments included installing a rod weeder (rod digger) with attached wind rowers in front of the tractor and a rod-digger at the rear of the tractor. Furrowers were attached in front to dig bulbs located in front of the tractor wheels. The feasibility of the treatment applications was evaluated in preliminary field tests where machine performance indices were measured. The effect of machinery treatments and leaftopping before digging on loss and mechanical damage were tested in a typical onion farm in Isfahan province. The results showed that the working depth of the rod digger installed in front of the tractor without a draft control system was not consistent and damaged 8% of bulbs mechanically. Moreover, insufficient maneuverability of the tractor and a percentage of slippage of the drive wheels were other restrictions to application of the front-mounted rod digger. Connecting the rod digger to the rear linkage of the tractor and using two furrowers in front of the tractor wheels was the only configuration for use of such implements in densely planted onions. In this configuration, using foreword tines like moldboard furrowers in front of the tractor was not easy without the use of a draft control system because of the non-uniformity of the working depth. Disk plows worked at a relatively uniform depth without the need for a draft controller; slippage and maneuverability of the tractor were also satisfactory. A comparison of the two furrowers in front of the tractor showed that the disk-type furrower caused less loss to the outer layer of the onion bulbs. The drawback to this type was a 4% loss from cut bulbs that emerged in front of the vertical cutting edge of the disk. If just a 20 cm space is provided on the either side of the planted band, a disk furrower attached in front and a rod digger in the rear of a tractor is the recommendable configuration for onion digging under the tested conditions.