The main objective of the present study was to modify the vegetable transplanter to become suitable for transplanting and fertilizing sweet potatoes under Egyptian conditions. The performances of transplanting and fertilizing units were evaluated during transplanting operation of sweet potatoes. The performance of fertilizing units was evaluated and tested using four angle of metering device position of 0^o, 15^o, 30^o and 45^o (0, 0.262, 0.523 and 0.785 rad.) at four values of speed ratio (R) of fertilizing unit (0.92, 1.25, 1.57 and 2.14). On the other hand the performance of modified transplanter was also evaluated using four different values of transplanter speed ratio (l) of 0.73, 1.0, 1.25 and 1.52. Results indicated that the speed ratio range of fertilizing unit (R) from o.92 to 1.25 and position angle of metering device of 30^o (0.523 rad.) below the horizontal position gave the best results of standard deviation, coefficient of variation and coefficient of uniformity. The results also showed that the best values of crop yield, void hills, field efficiency, fuel consumption and power requirements were 10.8 Mg/Fed., 3.5 %, 82.9 %, 3.93 l/h and 16.99 kW ,respectively, at the optimum transplanter speed ratio of 1.0.  The increase of modified transplanter speed ratio from 0.73 to 1.52 tends to increase the longitudinal and transverse scattering from 2.02 to 6.19 cm and from 0.98 to 2.95 cm, respectively. Also, the results revealed that the mechanical transplanting and fertilizing operation of sweet potatoes by using modified transplanter recorded the minimum value of cost (32.96 LE/fed.), compared with manual transplanting and fertilizing operation (140 LE/Fed.)