Effects of Different Tree Species on Growth and Yield of Mung Bean (Vigna radiata (L.) Wilczek) Grown in Hedgerow Intercropping Systems in Sri Lanka

Reduction of crop yields due to resource competition from tree hedges is a serious drawback of hedgerow intercropping. This work quantified the competition of six potential hedgerow tree species ( Calliandra calothyrus , Desmodium ransonii , Flemingia congesta , Gliricidia sepium , Cassia spectabilis and Tithonia diversifolia ) on mung bean ( Vigna radiata ) grown as hedgerow intercrops at Pallekelle in the mid-elevational (367 m above sea level), subhumid (rainfall of 1400 mm year⁻¹) zone of Sri Lanka. Leaf area, total biomass and yield of mung bean in hedgerow intercrops showed a clear reduction closer to the hedgerows, whereas no such reduction was observed in a sole crop of mung bean. At 30 cm from the hedgerow, growth and yield of mung bean were significantly lower than in the sole crop, indicating significant competition from hedgerows. However, growth and yield of mung bean increased with increasing distance from hedgerows so that, at 150 cm, mung bean under Gliricidia and Desmodium showed significantly greater growth and yields than the control. In contrast, even the maximum mung bean yields under the rest of the species did not reach that of the control. The differences in competition with different hedgerow species are discussed in terms of variations between tree species in biomass production, quality of prunings and the possibility of root competition.