JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2011 | Volume:12 | Issue:2|Papers Count:9

Irrigation management, soil tillage method and fertilizer management play important roles in increasing crop yield and water and solute movement in the soil profile. The present research was conducted to study the effects of a no-tillage system and nitrogen fertilizer on the mineral nitrogen movement and soil moisture under optimum irrigation conditions. The study was conducted at Safiabad Agricultural Research Center in silty clay loam soil and a warm, semi-arid climate. Two methods of corn seedbed preparation, including conventional tillage (CT) and no-tillage (NT) at three nitrogen levels (150, 225, 300 kg per hectare) were implemented. The nitrogen source was urea and was applied through fertigation in three equal splits at first irrigation, four-leaf and flowering stages. Nitrate and ammonium were measured before and 10 days after fertigation and after harvesting at 30 cm depth increments down to 120 cm. Inflow and outflow rates, soil moisture before and after irrigation, and bulk density were measured. The results indicated that no significant difference was observed between soil bulk density at the initial, middle and end of the cropping period for both tillage systems. The greatest moisture level was observed in the upper soil layer (0-20 cm) under NT (about 3%) for all pre-irrigation measurements. Inflow and outflow rates indicated that NT increased applied water and decreased runoff for every irrigation as a result of residues accumulated in the furrows. Nitrate concentration in the 0-30 cm soil layer for the two tillage methods was significantly higher than for the other layers (P<0.01). No significant differences were found between soil nitrate concentration and nitrate movement in soil layer for both tillage systems. Thus, nitrogen fertilizer application in the NT system with direct drilling on wheat residue is recommended at the same level recommended for CT. The levels of NH4-N in pre- and post-fertigation applications were generally low than the NO3-N level and no significant differences were found in the soil layers for both tillage systems.

Synthetic envelopes have been found to be highly effective filters for numerous applications and are currently replacing gravel envelopes. The growth of petrochemical and textile industries in Iran offers the possibility of manufacturing these products domestically. The objective of this study was to assess the mineral clogging potential of two non-woven synthetic envelopes (pre-wrapped loose materials, PLM) manufactured in Iran in comparison with similar imported envelopes. Two physical permeameter models designed according to ASTM D-5101 were used to carry out a series of permeability tests on varying envelope types. The study was conducted on soil and water provided from the Khorramshahr area, Khouzestan province, in southern Iran. A distinctive aspect of this research is the use of highly salt-affected drainage water (EC=22.2 dS/m and SAR=26.27) in contrast to nonsaline water (EC=0.78 dS/m) and Khoramshahr saline-sodic soil (EC=169.3 dS/m and SAR=45.18). Permeability tests were done at five hydraulic gradients (1, 2.5, 5, 7.5 and 10). Variations in discharge, hydraulic conductivity and gradient ratio (GR) were measured and investigated statistically in fully randomized factorial experiments. The results indicated that the greater the salinity, the lower the hydraulic conductivity and flow discharge rate for all envelope samples. The average hydraulic conductivity for domestic products 1 and 2 decreased 19% and 28%, respectively, in comparison to the imported envelope for non-saline water. For saline water, these percentages reached 28% and 33%, respectively. The gradient ratio revealed that the imported sample was not sensitive to mineral clogging. However, the two domestic specimen gradient ratios were greater than that for the imported envelope for the application of saline and non-saline water.

This research studied the addition of hull-less barley and wheat malt flour on the qualitative parameters of semi-voluminous bread (form, softness, porosity, upper and under surface characters, chewing capability, aroma, taste, hardness). A completely randomized design was used with 3 treatments (control, use of malted wheat, use of barley flour) in 4 replications. A sensory evaluation and the hardness of the breads were evaluated after baking. The sensory evaluation showed significance differences (p<0.05) among the breads. The bread containing hull-less barley malt flour had the highest scores for most parameters. Also, a staleness test at 0, 24, 48 and 72 hours of storage showed significance differences (p<0.05). Staleness for samples containing both malt flours was retarded. Adding hull-less barley malt flour had a greater retarding effect for staleness after 3 days of storage.

Irradiation is known to inhibit waste in stored garlic. Treatment time and optimum irradiation dosage are two key factors in achieving the least waste in this process. These two factors were investigated on white ecotype bulbs from Hamedan, Iran that were irradiated after harvest for 30 and 45 days using fast electrons at dosages of 0, 25, 50, 75, 100, and 150 Gy. Different properties of the garlic were measured bimonthly over eight months of storage under both cold and uncontrolled conditions. The results showed that sprouting was observed only in non-irradiated cloves and irradiated cloves showed no signs of external sprouting. Weight loss for non-irradiated bulbs was greater than for the irradiated cloves. The minimum weight loss for cold storage was less than 1% per week at dosages of 50 Gy and higher. For uncontrolled storage, this minimum was achieved at dosages of 75 Gy and higher after 300 days. Total pyruvate, particularly up to 120 days of storage, increased sharply and there was no significant difference between them at the end of storage. While the firmness of irradiated cloves at the end of storage was not significant, the greatest firmness was observed for cold storage at dosages of 50 Gy and higher. For the uncontrolled conditions, this was measured at 75 Gy and higher. During storage, both color change and non-enzymatic pyruvate increased. More change was observed during irradiation at 45 days after harvest than at 30 days. Consequently, it concluded that for garlic bulbs in cold storage, 50 Gy is the optimum dosage of irradiation and, for uncontrolled conditions, 75 Gy is optimum. For both storage conditions, irradiation for 30 days after harvesting seems to be the most suitable period.

Poor stand establishment of canola (Brassica napus L.) under flatland mechanized planting and crust-forming soil is a major problem for farmers in central Iran. Previous research there showed that irrigated cotton emergence on crust-forming soils under flatland planting can be significantly improved using a double-disk planter with zero-pressure press wheel tires and no crust-breaking. In that research, it was not clear whether the furrow opener or the press wheel caused the development of the crack line along the seed rows. In the present study, field testing was conducted in loamy soil to study the effects of two furrow openers (runner, double-disk) and four press wheels (zero-pressure pneumatic, V-shaped edge, single conical rib, open-center concave steel press wheels) on canola emergence using a randomized complete block design in a factorial arrangement (2×4) with four replications. Effective crack (crack line developed along emerging seedlings) percentage, stand establishment uniformity, percentage of emergence, and plant density before onset of winter were measured. The results showed that, for all parameters, the double-disk opener had significantly higher values compared with the runner opener. The press wheel had a significant effect on the effective crack percentage and the stand establishment uniformity index before the onset of winter. However, the other parameters were not significantly affected. Planters with a single-conical rib and open-center press wheels had the best effective crack percentage and lowest index of stand establishment uniformity. Based on the results from this study, the best planter for canola production for the soil and climate of central Iran is a double-disk planter with a single conical rib and open center concave steel press wheels. The single conical rib creates a v-shaped depression and the steel press wheels stabilize the depression. This creates a crack along the deepest line of the depression after flood irrigation and during soil shrinkage, causes creation of crack along the deepest line of depression.

In recent years, researchers have tried to develop robots for agricultural applications. Robots make it possible to reduce human exposure to pesticide application risk. The aim of this research was to develop an automated method of spraying of plants in greenhouses. A threewheel differential steering vehicle was designed and constructed to act as the greenhouse sprayer. Power was transmitted from two DC motors to two drive wheels through a gearbox and shaft system. A proportional controller was developed and tested to control the left and right motors, which navigated the aisles using information provided by ultrasonic sensors. After design and fabrication, the robot was tested on concrete surfaces at 0.15, 0.25 and 0.35 m/s inside a greenhouse along a U-shaped path 0.98 m in width. Spraying, safety and obstacle detection units of the vehicle were evaluated. The tests results showed that the average RMSE of the vehicle position was between 4.93 and 6.51 cm at different speeds. Increasing the speed increased the RMSE of the vehicle position. The performances of the safety and central station units of the vehicle were acceptable. The accuracy of the spray function was 99.47% and the no-spray function was 99.92%, which are acceptable for greenhouse applications.

An important biomechanical property of the rice crop for harvesting and post harvesting machines is the threshing, or requirement, force that detaches grain from panicle. This has a principal effect on the power requirements of threshers and combines, threshing efficiency and shattering loss. In this study, tension and pressure testing instruments and specialized clamps were used to measure the detachment force. This force was analyzed in Gilan province for three common paddy rice varieties (Hashemi, Khazar, Hybrid), three moisture content levels (12, 16, 23% w.b.), four speeds (5, 20, 35, 50 mm/min), three directions of force applied to the rice grain (parallel to grain, perpendicular to front of grain, perpendicular to side of grain) and three panicle areas (upper, middle, lower). A randomized complete block design was applied to analyze the data with five replications and the data means were compared statistically. The results of the analysis of variance showed that threshing force is significantly different in the tested varieties. The grain moisture content, direction of applied force, speed of applied force and selection location of spikelet (grain) on panicle also significantly affected the threshing force. The highest threshing force (2.62 N) was obtained for the Hashemi variety with a grain moisture content of 16% (w.b.) where the direction of applied force was parallel to the grain (tensile) at a speed of 35 mm/min to the upper portion of the panicle.

Engineering analysis for the design and modification of mechanical systems in grain harvesting and processing, including barley, depends on basic information about the physical and mechanical properties of the agricultural commodities. These properties vary significantly with the biological nature of agricultural materials under varying conditions (variety, shape, size, moisture content, etc.). This research project conducted 300 compression tests to extract two important parameters of grain strength and used statistical analysis to determine their effects. The results showed that variety and moisture content have significant effects on modulus of elasticity and contact stress (p<0.01), while the effect of grain size was not significant. Increasing moisture content decreased contact stress (linearly) and modulus of elasticity (S-shape curve). Accordingly, 17% moisture content (w.b.) was considered as the transition moisture in barley grain. Values greater than this caused the grain to be softer and values less than this made it more brittle. The range of maximum stress induced in the barley grain in the elastic range was 243 MPa at 25% MC to 2832 MPa at 10.2% MC. Maximum contact stress varied from 11.3 MPa to 455.4 MPa for different treatments.