Pruning strategies for reducing crop suppression and producing high quality timber in smallholder agroforestry systems
2007
m.g bertomeu
In the Philippines, smallholder farmers have be come major timber producers and trees planted on farms are an important source of raw material s and income for them and for the local timber industry. The smallholder mode of timber produc tion has several advantages over traditional reforestation. The frequent and intensive tend ing operations (land cultivation, weeding and fertilization) for annual intercrops improve tree survival and growth. Intercropping reduces tree establishment and weeding costs because these are charged to annual crop production. The cropped alleys between tree lines f unction as effective firebreaks. However, the planting of timber trees in association with light-demanding annual cr ops often leads to a drastic suppression in crop production as a result of competition for both above- and below-ground resources. With few exceptions, the most common timber trees promo ted for farm forestry have been reported to decrease yields of associated crop s. Therefore, concerns have been raised over the sustainability and suitability of tree farming for resource-poor far mers. Branch pruning e ffectively reduces light interception by the tree canopy, and thus prolongs the number of years that annual crop production can be practiced. However, to minimize crop yi eld suppression, farmers often practice intensive pruning annually before planting annual crops. Intensive pruning may enhance crop yield, but it is incompatible with commercial timber production because the growth rate and quality of the overstorey timber trees are severely reduced. This paper reports the results of on-farm trials conducted to assess the effects of four pruning levels on maize gr ain yield and also on tree growth and form. Plots consisted of three rows of the timber tree Gmelina arborea planted at 1 x 10 m with maize planted in the 10 m alleys during seven cropping seasons. The study shows that high pruning intensity (retaining a live crown ratio of 20 â?? 30%) results in significantly higher maize grain yields but reduced tree diameter. In economic terms, these higher maize grain yields are not enough to compensate for the costs of pruning and the lower market value of smaller-diameter timber. Therefore, if crop production is a priority, tree farmers should plant timber species that are less competitive or plant trees at low de nsities in other farm niches away from crops
显示更多 [+] 显示较少 [-]M.G Bertomeu, 'Pruning strategies for reducing crop suppression and producing high quality timber in smallholder agroforestry systems', Paper presented at the IUFRO International Conference on'Improving Triple Bottom Line Returns from Small-Scale Forestry', held in Leyte, Philippines 17-21 June 2007, 2007
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