Aboveground and belowground competition between intercropped cabbage and young Eucalyptus torreliana

There is growing incentive for farmers in the uplands of the Philippines to develop agroforestry systems rather than strictly vegetable farms due to an increasing market demand for timber. Farmers view intercropping young timber crops with annual crops as advantageous, based on the assumptions that the small trees will not deprive the vegetable crops of adequate light or nutrients, and that the tree crops will thrive with the nutrient inputs and weed control used in the intercropping system. This paper reports on a study of these assumptions that assessed both above- and below-ground competition between the tree species Eucalyptus torelliana and a cabbage crop. The test plots were located in the uplands of Mindanao, the Philippines. The impact of intercropping on cabbage yields varied according to the proximity of the cabbage row to the tree, suggesting above ground competition for light and below ground competition for moisture. There did not appear to be detrimental competition for nutrients; intercropping increased overall nitrogen efficiency. Further research is needed to investigate the tradeoffs between reduced crop yields and increased nutrient efficiency and to explore management strategies that will reduce the negative competition impacts of intercropping.