Agroforestry can be an option of sustainable farming practices for upland communities. However, information of spatial and temporal variation in soil fertility and crop productivity along slopes, which can guide e.g. effective management, such as application of fertilizers, is limited. This study evaluated spatial and temporal variability in crop productivity and soil fertility along slopes in two different fruit tree agroforestry systems in upland areas of north-west Vietnam: (1) longan-mango agroforestry integrating longan (Dimocarpus longan L.), mango (Mangifera indica L.), maize (Zea mays L.), and guinea grass (Panicum maximum Jacq.), and (2) plum agroforestry integrating plum (Prunus salicina L.), maize, and guinea grass. The two systems were established on relatively steep slopes, 37 % and 65 % slope, respectively. Crop performance and soil fertility were measured in different positions relative to the fruit tree-grass rows over 4–5 years and compared with sole-crop maize. The results showed that maize height, grain yield, and leaf nitrogen (N) concentrations were significantly higher at the upslope than downslope side of tree-grass rows. For example, the grain yields were 30–35 % higher at the upslope than downslope side. Regarding soil fertility, there was a tendency that SOC, total N, total phosphorus (P), available P, and available potassium (K) were higher at the upslope than downslope side of tree-grass rows. Thus, the forage grass strips played an important role in trapping N and other nutrients, and enhanced nutrient use efficiency within agroforestry at the steeply sloping study sites. The maize performance and soil fertility in the areas mid-way between two tree-grass rows were comparable to those in sole-crop maize. The results of this study can provide guidance for farmers managing fruit tree agroforestry in north-west Vietnam or other regions with similar cropping, climate, and biophysical characteristics to implement more effective plot management practices on sloping land.

中文翻译：

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陆地农林业中作物生产力的时空变化及其与土壤肥力的关系


农林业可以成为高地社区可持续农业实践的一种选择。然而，可以指导有效管理（例如施肥）的斜坡土壤肥力和作物生产力的时空变化信息是有限的。本研究评估了越南西北部高地地区两种不同果树农林复合系统中作物生产力和土壤肥力沿坡土壤肥力的空间和时间变化：（1） 龙眼-芒果农林业结合龙眼 （Dimocarpus longan L.）、芒果 （Mangifera indica L.）、玉米 （Zea mays L.） 和几内亚草 （Panicum maximum Jacq.），以及 （2） 结合李子 （Prunus salicina L.） 的李子农林业， 玉米和几内亚草。这两个系统分别建立在相对陡峭的斜坡上，分别为 37 % 和 65 % 的坡度。在 4-5 年内，在相对于果树-草行的不同位置测量作物表现和土壤肥力，并与单一作物玉米进行比较。结果表明，乔草行上坡玉米高度、籽粒产量和叶片氮 （N） 浓度显著高于下坡侧。例如，上坡的粮食产量比下坡的产量高 30-35%。在土壤肥力方面，乔草行上坡的 SOC、全氮、全磷 （P）、速效磷和速效钾 （K） 呈高于下坡的趋势。因此，牧草条在捕获氮和其他养分方面发挥了重要作用，并提高了陡峭倾斜研究地点农林业中的养分利用效率。两行树草之间区域的玉米性能和土壤肥力与单作物玉米相当。 本研究的结果可为越南西北部或其他具有相似种植、气候和生物物理特征的地区管理果树农林业的农民在坡地上实施更有效的地块管理实践提供指导。