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Agroforestry systems have been promoted as sustainable land-use systems for regions where shifting agriculture is the traditional predominant land-use. Although environmentally sustainable, agroforestry systems require investment to establish that may affect their economic sustainability. In the southern Yucatan Peninsula 47 agroforestry plots of two timber and 10 fruit tree species were established with 22 farmers in three communities covering two rainfall zones and five soil types. Some fruit trees had wide adaptability to different soil, rainfall and management conditions, e.g. Manilkara zapota; others were restricted to the best soil, rainfall management conditions, e.g. Persea americana. The Meliaceae timber trees responded little to rainfall and soil, but stem borer attack was markedly lower in less intensively managed systems. Level of system maintenance greatly affected costs, but also opportunities for intercropping and obtaining immediate income. All levels of managements had negative net present value (NPV) for the three-year establishment phase, but so does traditional maize production. Farmers preferred to inter-crop their agroforestry systems, but were often limited by site quality. Determining sustainable agroforestry options for farmers requires multiple decisions related to species adaptability to the site, farmer production objectives and farmer capacity to invest in different management strategies. One production technology did not fit all.  相似文献   
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优选出秦艽中龙胆苦苷的提取最佳工艺,采用正交试验法,以龙胆苦苷的质量分数为指标,考察了溶剂用量、提取时间、提取次数及提取温度对秦艽中龙胆苦苷提取率的影响,优选出合理的提取工艺。结果得知,蒸馏水用量为15 mL、提取时间为40 min、提取次数为2次、提取温度为40℃为最佳工艺条件,经验证性实验证明所优选条件可靠,适合秦艽中龙胆苦苷的提取。  相似文献   
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