Sweet potato (Ipomoea batatas) is a highly nutritious root crop suitable for human food. Therefore, the development of technology for increasing sweet potato yield is necessary. The purpose of this research was to find out which cultural practices (soil preparation and plant spacing) increased the yield and quality of sweet potatoes grown in unused / abandoned paddy field condition. The experimental design was a split plot, in randomised blocks, with four replications. The main plots were two tillage types: (1) rough ploughing followed by one regular ploughing, and (2) rough ploughing followed by two regular ploughings. The sub plots were four spacings: 50 x 30, 50 x 50, 100 x 30 and 100 x 50 cm. The results showed that different tillage methods did not significantly affect vine length, chlorophyll content, leaf area, yield and chemical composition of sweet potato tubers. However, the treatment of rough ploughing followed by one regular ploughing significantly resulted in higher dry weight accumulation. Different spacings, had significant effects on chlorophyll content, leaf area, tuber weight and numbers of sweet potato tubers; the spacing of 50 x 30 cm gave the best results. Interactions between tillage method and spacing were significant for tuber width and length, tuber weight, protein and crude fibre. The rough ploughing followed by two regular ploughings combined with a spacing of 100 x 30 cm gave the maximum width and length of tubers; while rough ploughing followed by one regular ploughing with a spacing of 50 x 50 cm gave the maximum tuber weight, protein content and crude fibre. The results indicated that rough ploughing followed by one regular ploughing with a spacing of either 50 x 30 or 50 x 50 cm (50 cm between rows and 30 or 50 cm between plants) is a suitable technology for sweet potato grown in abandoned paddy fields.