الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The digging harvesting machine was modified and tested to perform the effect of harvesting speeds on harvesting qualities such as sweet potato lifting, un-lifting, damaged, un-damaged, soil adhesion on tuber surface and machine productivity. These indicators were evaluated under condition of medium at El Dakahlia Governorate (Belqas), Egypt. A lot of experimental field were conducted on sweet potato and carrot harvesting under three different levels of separator length (450, 700 and 1200mm); reciprocated cam with link length of 180, 210 and 240 mm and three forward speeds (3.6;, 5.1 and 7.2km/h) under digging Nose share.. The obtained results concluded that the maximum value of sweet potato lifting efficiency was 97.14% recorded at 3.6 km/h harvesting speed and reciprocated cam with link length of 180mm. (At reciprocated cam with link length of 180mm, increasing forward speed from 3.6 to 7.2 km/h decreased the un-lifted of 2.74; 1.26 and 1.19 times at separator length of 450, 700 and 1200mm respectively.) Generally, increasing harvesting speed increased sweet potato damage and decreased un-damage percentage. For example, at reciprocated cam with link length of 180mm, increasing forward speed from 3.6 to 7.2 km/h increased mechanical damage from 2.80 to 3.85% and decreased un-damage from 97.12 to 96.15% at separator length of 450mm. The harvesting forward speed strongly affected soil adhesion on sweet potato surface. By increasing forward speed from 3.6 to 7.2 km/h decreased soil adhesion on sweet potato surface under all treatments except at reciprocated cam with link length of 180mm. The cost of harvesting was 420.6 L.E. / hectare. For sweet potato and carrot, by using the digger at optimum conditions from (forward speed, share shape, separator length and link length reciprocating). Meanwhile, the manual harvesting per hectare for sweet potato and carrot needs 15 labors for six hours was costing 825 L.E/hectare. That means that the machine reduced the percentages of costs to approximately half for sweet potato and carrot respectively.