JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2010 | Volume:11 | Issue:1|Papers Count:9

Tillage and press wheel weight play an important role in seedling emergence, crop establishment and growth. An optimal combination of tillage implements and suitable press wheel weights should increase grain yield. This study investigated the effect of tillage systems and press wheel weights on dry land wheat (Triticum aestivum L.) seedling emergence and grain yields in Izeh, Khuzestan Province. Cone index and emergence rate were also recorded. A split factorial complete block design was applied with four tillage treatments including no-tillage, conventional tillage (moldboard plow+disk) and reduced tillage (two disk passes, chisel plow + disk). The seeding treatments included independent and two-axle press wheel drill at three levels (4, 5 and 8 kgcm-1) of press wheel width. The results indicated that reduced tillage (two disk passes) produced a higher and faster rate of emergence and the highest grain yield (1961.7 kgha-1). The independent press wheel drill decreased the cone index and increased the seedling (28%) and rate of emergence (54%) more than other treatments. This seeding machine yielded 2202.9 kgha-1 grains with greater 1000 grain weight compared to other planters. The results suggest that reduced tillage (two disk passes) and the independent press wheel drill are more effective than other treatments (p£0.01) for wheat production under the dry land conditions similar to those of Izeh.

Soil compaction is a major problem in many parts of the world. The determination of soil compaction profiles requires fast sampling systems to keep pace with the change in soil moisture condition over time. Soil cone penetrometers are commonly used for this purpose. A tractor-mounted soil cone penetrometer was designed and fabricated with multiple probes and the ability to determine cone index values in crop rows. The multiple probe penetrometer, composed of mechanical, hydraulic and electrical components, can evaluate soil strength conditions to a depth of 45 cm. The mechanical section comprised a frame to support the other sections of the unit and was mounted to a tractor using three-point hitches. Hydraulic power was used to force the probes into the soil. Using a data logger, data was collected from the load cells and depth sensors and sent to a computer to develop the cone index curve. To evaluate the penetrometer, the soil cone index was measured under two soil conditions (stubbly and plowed) and two soil moisture levels (before irrigation and after irrigation). The penetrometer was then tested and evaluated in comparison with a hand-pushed penetrometer under the same test conditions ata 15 depths. The coefficient of correlation between the hand-pushed and tractor-mounted penetrometers for stubbly and plowed soil was determined as R2=0.98 and R2=0.98 (before irrigation) and R2=0.96 and R2=0.97 (after irrigation), respectively. The t-test revealed that the cone index was not significant for the tractor-mounted and hand-pushed penetrometers at 5% confidence levels. Thus, the tractor-mounted penetrometer can be used for soil strength measurement with high confidence.

The effects of soil tillage methods and residue management were studied at Miandoab Agriculure Station during 2003-2005. The experiment design was split block with the main plots devoted to residual management strategies (burning residue, crushing residue by disk, no treatment). Subplots were tillage methods (moldboard plowing to 20-25 cm in fall, moldboard plowing to 20-25 cm in spring, moldboard plowing to 20-25 cm in both spring and fall). Other operations were identical in all treatments. The soil cone index, percent of residue crushing, percent of residue inversion, percent of seed emergence, crop yield, percent of sugar, depth of root development and percent of soil organic carbon were measured. Results showed that tillage and residual management had no significant effect on seed emergence, percent of sugar, bulk density and soil cone index. Tillage management had a significant effect on yield and depth of root development. Fall plowing and fall-spring plowing treatments produced higher yields and root development (15%, 11%) than did the spring plowing treatment. Results also showed that soil organic carbon after harvesting was higher (14%) for the crushed and no treatment categories than for the burned residue treatment. Burning residue is not recommended, because this strategy had no positive effect on the parameters and, in some cases, reduced root yield and soil organic carbon. Water productivity in moldboard plowing at 20-25 cm in the fall treatment was higher than for the other treatments. Water productivity based on root yield was 4.32, 3.47 and 3.66 kg/m3 for fall plowing, fall-spring plowing and spring plowing treatments, respectively.

In this research, the positive mixing length and trajectory characteristics of a buoyant jet was investigated. Jet flux is dependent on parameters such as initial velocity, port diameter, concentration of jet and flow conditions in the receiving fluid. A buoyant jet fluid governing equation with relevant logical assumptions was used to drive the required dimensionless functions using dimensional analysis. A physical model was built to evaluate the function of these parameters. Testing was done at varying velocities, concentrations and initial port diameters. The length of the falling jet trajectory was analyzed as the ratio of trajectory length to port diameter versus relative trajectory elevation. The results showed that increasing jet diameter and jet momentum had a significant effect on jet trajectory. Increasing jet fluid density caused a density gradient between the jet and receiving fluid and a change in the buoyancy forces involved which had a major influence on the length of the falling jet trajectory. Hence at a given density, increasing the diameter from 5-8 mm or 8-15 mm decreased the densimetric Froude number 30-40% for different velocities and the ratio of the length of positive flux buoyancy to port diameter decreased 20-35%. Findings showed that doubling the increase in density decreased the length of positive flux buoyancy 5-20%.

Decreasing crop loss is a way to achieve agriculture self-sufficiency. Many parameters affect the quality and quantity of rice loss, including the type of processing and grain moisture content. This study compared abrasive and blade (Engelberg) whitening systems for percentage of grain breakage and degree of milling. In addition, optimum milling moisture content was determined for both systems. The effect of two types of whiteners (abrasive and Engelberg) was investigated on rice quality for three rice cultivars (Sorkhe, Sazandegi and Tarom) at four moisture contents (14%, 12%, 10%, and 8%) using a factorial test based on a complete randomized block design with three replications. Percent of rice breakage, degree of milling, work capacity, and power consumption were measured for each treatment. The results showed that the effect of rice cultivar, whitener type, moisture content and their interactions caused significant differences at the 1% level. Sorkhe and Tarom rice cultivars had minimum and maximum rice breakage percentages, respectively. Rice breakage and degree of milling were lower for the abrasive whitener than for the Engelberg whitener. The sample with 14% moisture content had the minimum degree of milling and maximum rate of breakage. The optimum moisture contents for milling for Sorkhe, Sazandegi and Tarom rice cultivars by abrasive were 10%, 12%, and 10%, respectively. For the Engelberg whitener it was 10%, 12%, and 12%, respectively. Work capacity and power consumption were 1.7 and 3.43 times higher, respectively, for the abrasive system than for the blade system.

Water shortage in the agricultural sector is currently a major challenge in crop production. The more efficient water usage is that which increases yield without increasing water use. Thus, a determination of the water-yield relationship is essential. A field study was conducted to examine water-yield relations in three genotypes of soybeans, including optimum irrigation depth, a comparison of deficit and full irrigation, and the yield response factor (Ky) at Gorgan Research Station in the 2005 and 2006 growing seasons. Four irrigation treatments (W1, W2, W3 and W4) were identified according to their decline in irrigation caused by increased distance from the line source. Testing was based on a strip plot design and examined the effect of fixed irrigation rates on three cultivar treatments (SAHAR, G3, DPX) with four replications. Each irrigation treatment of each strip was divided into three cultivar treatments along the length of the laterals. Results indicated that the grain yield was affected by irrigation treatment and cultivars. The highest grain yield was obtained by treatment W1 (3306 Kg/ha) with the DPX cultivar (2905 Kg/ha). Under deficit irrigation scheduling, when effective rainfall (P) during the growing season is negligible, the optimum values for irrigation water (I) showed little difference between cultivars and were obtained at 430 mm. Under full irrigation, the SAHAR, G3 and DPX cultivars required 437, 467 and 523 mm of irrigation water and 550, 580 and 640 mm of applied water (I+P), respectively. Ky for SAHAR, G3 and DPX for the total growing season were 1.1, 1.06 and 0.92, respectively. The DPX cultivar had the lowest Ky (0.92) and, therefore, is a more suitable response to water deficit than were the other cultivars.

Size distribution and frequency of seeds in sunflower samples were investigated for three hybrid oily sunflower varieties (Hysun33‚ Progress and Euroflor) taken from four locations (Aliabad, Golidagh, Kalale and Kalpoosh in Golestan province). The samples were distributed into three groups (large, medium, small) using two screens 14-16 mm in length and 2.75 and 3.75 mm wide. The effects of seed size on the peroxide value, acidity, specific weight and refractive index was evaluated using a completely randomized experimental design with replications. A 8´3´2 factorial design (sunflower sample × seed size × kernel type) was adopted. Kalale Progress and Aliabad Hysun 33 samples had the greatest and least number of large seeds, respectively (p<0.05). The Golidagh Euroflor and Golidagh Hysun33 samples had the greatest and least number of small seeds, respectively (p<0.05). Large, medium and small seeds showed significant differences (p<0.05) in their refractive indices; medium seeds had the highest value and large seeds the lowest value (p<0.05). Whole and broken kernels showed significant differences (p<0.01) in their specific weight. There were significant differences (p<0.05) in the peroxide value of extracted oils. The oil content of Golidagh Euroflor, with the greatest percentage, was 61.6% greater than that of Kalpoosh Euroflor, with the lowest.  The results obtained and the effect of Achenes size on extracted oil quality showed that oils should be graded on the basis of their quality characteristics. This could be a guideline for oil refining operations, particularly hydrogenation and the production of oils for frying and salads.