Yields from Rice Plants Cultivated under Tree Canopies in Rainfed Paddy Fields on the Central Plain of Laos

Many trees are left uncut in the paddy fields of many villagers in central Laos. Yields of rice in rainfed paddy fields interspersed with trees in central Laos were investigated in relation to shading and soil fertility from trees. Grain yield of rice plants cultivated in close proximity to tree trunks (CTP) was higher than that of the plants cultivated far away from the tree trunks (FTP) in 5 fields but lower in 7 fields. The effects of individual trees on rice yield varied among trees of the same species over the course of the three-year study period. No relationship was observed between the changes in photosynthetic photon flux density (PPFD) due to interception by the tree and the ratio of grain yield of CTP to that of FTP. A significant negative relationship was observed between grain yield of FTP and the ratio of grain yield of CTP to that of VIP, suggesting that yield of CTP under some trees is not lower than that of FTP when the latter was low.