Effect of time and proportion of leaf harvest on pest, forage and root yields of sweetpotato (Ipomoea batatas L.) in the inland valley swamp and upland ecologies of Njala

Sweetpotato (Ipomoea batatas L)is a dicotyledonous root crop that belongs to the family Convolvulaceae that comprises about 50 genera and more than 1000 species. Ipomoea batatas is the only crop of major importance in the Convolvulaceae family [1]. The crop is native to Central and South America [2] and cultivated in over 100 countries of the world. Sweetpotato is extensively grown in tropical and subtropical regions particularly in Asia, Africa and the Pacific; with Asia and Africa continents accounting for 95% of total global production [3]. Sweetpotato is the fifteenth most important food security crop, and the third most important root and tuber crops, grown on 8.6 million hectares worldwide, with production and average yield of about 106 million tons and 12.2 t ha-1, respectively [4]. China is the major producer of sweetpotato in the world, followed in order by Nigeria, Tanzania, Indonesia, Uganda, Ethiopia, Angola, India, the United States of America, Vietnam and Madagascar [4].

In Sierra Leone, the crop ranks as the second most important root and tuber crops after cassava, and is cultivated in all the provinces [5]. Both the leaves and roots of sweetpotato are consumed in Sierra Leone. Leaf harvesting from sweetpotato during its vegetative growth is common inmost parts of the country. The harvested leaves are either used for vegetable or for fodder. Leaves harvested for livestock feed involves plucking the fully expanded mature leaves [6], whereas the immature leaves are used for human consumption. According to Kiozya et al. [7] leaf harvesting in sweetpotato reduces root yield by 43%. Moreover, Masumba [8] also noted that harvesting of a certain number of leaves from root crop reduces photosynthates thereby contributing to reduction in root yield. Despite the dual-purpose potentiality of the leaves and roots of sweetpotato in contributing to food and nutrition security, no comprehensive study has been done on the effects of leaf harvest frequency and intensity on the growth and yield of sweetpotato. Even though earlier works by Kiozya et al. [7] suggests that leaf harvesting in sweet potato reduces root yield by 43%; and by Masumba [8] that increased leaf harvest intensity decreases photosynthate translocation to the roots thereby contributing to reduction in root yields, these are yet to be tested using different genotypes, ecologies and leaf harvest intensities and frequencies in Sierra Leone.

The identification of dual-purpose leaf harvest frequency and intensity with optimum economic forage and fresh root yields contributes to increasing food and feed production and productivity that meet the demands of various actors in the sweetpotato value chain. The identification of the leaf harvest frequency and intensity with optimum economic forage and fresh storage root yields also facilitate ready availability of planting materials, food and feeds, thereby contributing to increased food production and productivity. Thus, the main aim of the study was to investigate the effects of leaf harvesting time and proportion on Cylas puncticollis infestation, forage yield, fresh storage root yield and related attributes of sweetpotato grown in the inland valley swamp and upland ecologies of Njala. The specific objectives were to: (i) assess the effect of leaf harvest intensity and frequency on Cylas puncticollis infestation in sweetpotato; (ii) assess varietal response to leaf harvest intensity and frequency in sweetpotato; (iii) determine the effect of leaf harvest frequency and intensity on the forage yield of sweetpotato; and (iv) determine the effect of leaf harvest frequency and intensity on fresh storage root yield of sweetpotato.