JWSS - Journal of Water and Soil Science

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The effects of three levels of soil moisture content (8-10, 10-12 and 12-14% d.b.) and three levels of plowing depth (15, 20 and 25 cm) on draft, specific draft and drawbar power requirement of a 7-shank chisel plow in a clay loam soil were investigated. The experimental design was a randomized complete block design with a 3×4 factorial. The effect of plowing depth on all of the parameters mentioned was highly significant. Implement draft and drawbar power requirement both increased with plowing depth, whereas a decreasing trend of specific draft with depth was observed. Soil moisture content had no significant effect on draft and specific draft of chisel plow in the range of moisture contents studied, though both parameters were minimized at 10-12% m.c. At this moisture level, the drawbar power requirement showed a significant reduction comparing with the other two moisture levels. This indicated that the soil was close to its optimum friability at this moisture content. Soil penetrometer readings, taken before and after plowing, indicated the existence of a hardpan from about 8 to 20 cm below the surface which was broken by chisel tines, but another hard layer formed under the plowing depth by the chisel points. Comparison of the results from the present study with those from the previously published works on chisel plow draft at similar plowing depths showed that the values obtained for draft and specific draft were acceptably close to those previous investigators. Also, a comparison with the findings of Loghavi and Moradi on moldboard plow draft under similar conditions confirmed the reports of previous investigators to the effect that a chisel plow requires approximately one-half of the draft of a moldboard plow with the same working width and depth.

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The effects of three levels of soil moisture content (10 - 12, 13 - 15 and 16 - 18% d.b.) and three levels of plowing depth (15, 20 and 25 cm) on draft, specific draft, and drawbar power requirements of a 3 - bottom disk plow and on soil pulverization and inversion in a clay loam soil were investigated. The experimental design was a randomized complete block design with a 3 × 3 factorial. Except in soil inversion, the effect of soil moisture on all of the performance parameters mentioned, was highly significant. Mean values of draft, specific draft and drawbar power requirements and clod mean weight diameter were minimized at 13 - 15% and 16 - 18% soil moisture contents, respectively. The effect of plowing depth was highly significant only on draft and drawbar power requirement of disk plow, in such a way that the mean values of these two parameters were significantly increased with plowing depth, while specific draft showed only a mild decreasing trend. In order to provide a quantitative index to express the degree of soil pulverization by tillage implements, a tractor-pulled rotary sieve was designed and fabricated. With this apparatus, in-field determination of soil clod mean weight diameter (MWD) following plowing was possible. The results showed that the effect of soil moisture content on MWD was highly significant, such that, plowing at 10-12% moisture content produced the largest clods, whereas the effect of plowing depth on MWD was not significant. The decreasing trend of MWD with soil moisture content persisted to the highest moisture level studied (16 - 18%), in which the average clod MWD (33.8 mm) was about 72% smaller than those formed at 10-12% moisture content. The effects of plowing depth and soil m. c. on soil inversion by disk plow were not significant and the overall soil inversion was about 54% which was in agreement with those reported by other researchers.

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Wheat as a main food source is partly lost in different ways such as planting, harvesting, storage and even in consumption processes. This calls for attention to reducing these losses through application of the results from agricultural research, use of new farming practices, improvements in management system and repair and renewal of farm machinery. The present study considers the design, development and evaluation of a new pneumatic air reel system as a replacement for the conventional mechanical reel. To evaluate the new system, laboratory and field tests were conducted.

 In the laboratory tests, the air velocity was measured along the fan outlet width at a 10 centimeter interval from the outlet to 40 centimeters away from it, and corresponding curves of air velocity distribution along the fan outlet width were drawn. On the basis of the results, 13 fans were calculated to be required on the cutting platform of a 14-foot (4.3 meter) combine. The results from the field tests of mechanical and air reels show that grain losses of air reel during harvesting are less than those of the mechanical reel because the air reel has no mechanical contact with the crop and applies less shock on plant stem than the mechanical reel. According to the results, grain losses increased linearly with increasing fan speed. In addition to the change of fan speed (2247, 2503, 2860, 3218 and 3932 RPM), three air discharge directions of 10, 20 and 30 degrees from horizontal line were examined. According to the data analysis in Randomized Complete Block Design (RCBD) through Tukey’s procedure (15 treatments and 6 samples in each treatment), there were significant differences between grain loss at these directions and mechanical reel at a level of 5%. A wind direction of 20 degrees and fan speeds of 2503 to 2860 RPM are recommended.

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In this study tractive efficiency (TE) of MF285 and U650 tractors during moldboard plowing were evaluated and compared. Field experiments were conducted at the Experimental Station, College of Agriculture, Shiraz University, using a randomized complete block design with a 3*3 factorial. The soil was sandy clay loam with an average moisture content of 18% b.d. from zero to 30 cm depth. Test treatments were combinations of three tractor types or conditions (U650, MF285 liquid ballasted and MF285 with no liquid or weight ballast) and three levels of plowing depth (10-15 cm, 15-20 cm and 20-25 cm). Plowing speed was kept constant at about 4 km/h throughout the experiment. The measured or calculated parameters included: tractor drawbar pull and rolling resistance, drive wheel slip and tractor tractive efficiency. Statistical analysis of the test results showed that the primary difference between the tractor types or conditions was in their wheel slip, such that the average wheel slip of U650 was lowest (12.6%) while that of unballasted MF285 was highest (27%) and was reduced to 17.7% with liquid ballasting. Also, while growth of unballasted MF285 wheel slip with increasing plowing depth was drastically high (11% to 48%), that of U650 was quite moderate (9.7% to 16.5%). Analysis of the calculated values of TE showed that there was no significant changes in the TE of U650 with increasing plowing depth and that with an average of 73.8%, it had a desirable performance. The TE of unballasted MF285 that was over 75% at shallow plowing, dropped to 46% with increasing plowing depth, while water ballasting improved the decreasing trend of TE with plowing depth and raised its minimum value to about 63%. The overall results of this study showed that unballasted MF285 tractors had desirable TE only at shallow plowing and that for medium and deep plowing, U650 or water ballasted MF285 tractors should be used.

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A 4x4 factorial experiment with a completely randomized design with three replications was conducted separately on two major pistachio varieties, Ohady and Kaleghoochy, to investigate the effects of shaking amplitude and frequency on pistachio nut and cluster detachment. Four levels of shaking frequencies used for Ohady were 5, 7.5, 10 and 12.5 Hz, while those of Kaleghoochy were 7.5, 10, 12.5 and 15 Hz. Four levels of shaking amplitude for Ohady were 20, 40, 60 and 80 mm, while those of the Kaleghoochy were 40, 60, 80 and 100 mm. Analysis of variance and mean comparison showed that the effects of shaking amplitude and frequency on pistachio nut and cluster detachment were significant on both varieties. It was found that in Ohady, at frequency of 12.5 Hz and amplitude of 80 mm, the maximum effective nut detachment occurred. But considering the need to limit both yield loss and limb damage to 5% and minimizing the power requirement of the limb shaker, applying shaking amplitude of 60 mm and frequency of 10 Hz, which detaches 95% of the nuts, is considered as the most suitable combination of shaking amplitude and frequency. Also, at amplitude of 80 mm and frequency of 12.5 Hz, the highest percentage of cluster detachment occurred. Here again, by considering limb damage and power requirement, applying shaking frequency of 12.5 Hz at 60 mm amplitude with 69% cluster detachment was selected as the most suitable combination. In Kaleghoochi, at amplitude of 100 mm and frequency of 15 Hz, nut detachment was 100%, while the need to limit limb damage and power consumption, the combination of 60 mm amplitude and 15 Hz frequency with 97.2% nut detachment was selected as the most suitable one. For cluster harvesting of Kaleghoochy, shaking amplitudes of 60 and 40 mm and frequency of 12.5 Hz with cluster detachment of 75 and 69 percent, respectively were selected as the most suitable ones. The average ratio of tensile force required for removing pistachio nut to its weight (F/W), and the ratio of tensile force required for removing pistachio cluster to its weight (V/W), which could be considered as an index of ease of detachment, were measured 6.2 and 37 for Ohady and 9 and 37.8 for Kaleghoochy, respectively. Finally, we may conclude that by applying the suitable combination of shaking amplitude and frequency, shake harvesting of pistachio could be practiced successfully.

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Tractive efficiency and fuel consumption of Massey Ferguson (MF399) and John Deere (JD 4230) tractors during plowing with moldboard plow were evaluated and compared. The tests were conducted at the Experimental Station, College of Agriculture, Shiraz University, in a field with sandy clay soil at average moisture content of 18% d. b. from zero to 30 cm depth. A randomized complete block design with a 4 3 factorial was used in three replications. The treatments consisted of two types of tractors, MF399 and JD 4230, each at two levels of axle load (standard and liquid ballasted) and three levels of plowing depth, shallow (15-20 cm), medium (20-25 cm) and deep (25-30 cm) using a semi-mounted 4-bottom moldboard plow. In all treatments, the tractor engine speed was set at rated rpm (2000 and 2200 for MF399 and JD 4230, respectively) and forward speed was kept constant at about 4.5±5 km/hr. The measured and calculated parameters included: drawbar pull, rolling resistance, wheel slip, tractive efficiency and fuel consumption. The results indicated that tractive efficiency of MF 399 in deep plowing increased from 36.5% to 53% with ballasting the drive wheels, even though the improved traction was not comparable to that of JD 4230 (64%) at the same plowing depth. However, at ballasted condition it is comparable to JD 4230 at shallow and medium depth plowing due to its lower fuel consumption. Using ballasted JD 4230 for shallow depth plowing is not economically justified due to the excessive fuel consumption and may cause soil compaction due to the lower than optimum wheel slippage. Generally, using MF399 is recommended for lower draft and JD 4230 for higher draft tillage operations. Otherwise, MF399 will encounter severe reduction in tractive efficiency and excessive increase in fuel consumption and JD 4230 will cause soil compaction.

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In the conventional methods of herbicide and fertilizer application, a substantial amount of toxic chemicals is sprayed or broadcast into the furrows, which is later washed away by irrigation water and may contaminate ground water, human and animal environment. If herbicide and fertilizer application could be limited to the most needed parts of the field rather than overall broadcasting, the mentioned problems could be alleviated and the application efficiency could also be increased by reducing the consumption rate. In an attempt to achieve this goal, a combination cultivator capable of simultaneously performing cultivation practices such as weed control (mechanical + chemical), fertilizer application and pest control was developed and evaluated. This machine was able to perform band spraying (fungicide, insecticide and herbicide) and mechanical cultivation (within-the-row weed killing, furrow reforming and hilling) simultaneously and properly. The combination cultivator was able to reduce herbicide consumption up to 66%.