<i>Effects of damaged seedlings on the growth and yield of sweet potato</i>

Abstract

Abstract. Sweet potato seedlings are soft, thin and tangled, which restrict the development of mechanical sorting and transplanting technology. Sweet potato planting depends extensively on manual labor with low production efficiency. But if sweet potato seedlings were planted mechanically, some physical damages might happen easily such as missing leaves, damaged leaves and broken seedlings. Till now, it is not clear to what extent these physical damages will affect the growth of sweet potato seedlings and yield of sweet potato. In this study, sweet potato seedlings named Longshu 9 were planted in small raised bed using three-leaf planting method, and sweet potato growth and yield were analyzed by field testing. The results showed that survival rate of seedlings with damaged leaves, seedlings with damaged stems, normal seedlings were 94%, 85% and 100%, respectively. Number of young roots was almost same and irregular, but total length of young roots varied greatly between different treatments. Total length of young roots for damaged seedling was shorter than that of normal seedlings. Tubers, stems and leaves grew early and quickly for normal seedlings, and total weight increase of stems, leaves and tubers were 4.45g, 3.88g, 5.18g for damaged leaves, damaged stems and normal seedlings, respectively. Between three treatments, tubers yield differed significantly and had regularity. Compared with normal seedlings, yield of seedlings with damaged leaves was reduced about 11.3%, and yield of seedlings with damaged stems was reduced about 22.8%. In conclusion, damaged sweet potato seedlings have little or no effect on number of young roots and tubers, but damaged leaves and stems have a significant effect on survival rate, root burgeon, leaves and stems growth, and tubers yield. The more serious the damage is, the more severe the impact is. This research provides a theoretical and experimental basis for mechanical sorting and transplanting of sweet potato seedlings.