JWSS - Journal of Water and Soil Science

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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.