Abstract
Sweetpotato [lpomoea batatas (L.) Lam] is a staple crop in many areas of the South Pacific, but little has been reported on its potential in multistrata system. In this experiment, it was grown as an intercrop between nine different species of leguminous hedgerows, and a control with no hedge. The aim was to determine whether addition of foliar mulch to sweetpotato could compensate for the competitive effects of shrubs, whether such mulch applications could halt yield decline in successive crops, and to test the performance of a range of lesser utilised shrubs with better known species. Hedge species varied greatly in performance, Acacia angustissima, Calliandra calothyrsus, and C. houstoniana producing greater quantities of foliage when pruned, which were then applied to the sweetpotato intercrop. Sweetpotato biomass did not differ between the two seasons, but in the second crop, tuber yields declined while vine production increased. Regression analysis showed that tuber and vine mass decreased as hedge foliage offtake increased, but K applied in mulch increased tuber mass and quality of N applied increased vine mass. In the second cropping cycle, tuber mass in rows closest to hedges increased relative to outer rows. It was hypothesised that this effect was due to the fertilizing effect of fine root and nodule die-back following pruning in rows closest to the hedges, in combination with a shortened hedge-pruning cycle.
