Agroforestry systems provide smallholder farmers with opportunities to broaden their income base. However, as planting trees can come at the cost of reduced crop yield because of competition for resources, farmers need to understand the consequences of tree growing on crop productivity. This paper explores the impacts of Acacia auriculiformis on agricultural crop productivity during the first three cropping seasons in Gunungkidul, Java, Indonesia; maize then soybean was planted in each season. We also sought to understand whether water competition was a factor in determining productivity in this agroforestry system, as this environment is characterised by a long (~ 6-month) dry season. A randomised complete block design with five replications was used, with three treatments, monoculture A. auriculiformis trees, monoculture agricultural crops, and an agroforestry plot that combined the trees and crop. At the final measure, at age 27 months, the trees were 7.4 and 6.9 m in height and 7.2 and 7.1 cm in diameter in the monoculture and in the agroforestry systems respectively, and treatment had no significant effect on the tree height or diameter. Grain yield of soybean was not affected by treatment in any of the three growing seasons, but both grain and stover yields of maize were significantly lower in the agroforestry system than in the monoculture in the third growing season. Differences in soil water deficit, and pre-dawn and mid-day leaf water potentials in A. auriculiformis and soybean were generally not significant between treatments in all three growing seasons. land equivalent ratios for the A. auriculiformis agroforestry system decreased from the 1st to the 3rd growing seasons but remained > 1.3. As fertilizer was applied it was assumed that there was no nutrient limitation. It was therefore concluded that tree shading was primarily responsible for reductions in productivity, and that this affect was greater on maize than soybean grain yield.

中文翻译：

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印度尼西亚爪哇的金合欢与农业种植相结合，提高生产力

农林业系统为小农提供了扩大收入基础的机会。然而，由于资源竞争，种植树木可能会以降低作物产量为代价，农民需要了解树木生长对作物生产力的影响。本文探讨了金合欢对印度尼西亚爪哇古农基杜尔前三个作物季节的农作物生产力的影响；玉米然后大豆在每个季节种植。我们还试图了解水竞争是否是决定该农林复合系统生产力的一个因素，因为这种环境的特点是漫长（约 6 个月）旱季。使用五次重复的随机完整区组设计，三个处理，单一栽培 A. auriculiformis 树，单一栽培农作物，以及结合树木和作物的农林业小区。在最终测量时，在 27 个月大时，单作和农林复合系统中的树木高度分别为 7.4 和 6.9 m，直径分别为 7.2 和 7.1 cm，并且处理对树高或直径没有显着影响。在三个生长季节中的任何一个季节，大豆的籽粒产量都不受处理的影响，但在第三个生长季节，农林复合系统中玉米的籽粒和秸秆产量均显着低于单作。在所有三个生长季节，A. auriculiformis 和大豆的土壤水分亏缺以及黎明前和中午叶水势的差异在处理之间通常不显着。A.土地当量比率 auriculiformis 农林业系统从第 1 到第 3 个生长季节下降，但仍保持 > 1.3。当施肥时，假定没有养分限制。因此得出的结论是，树木遮荫是导致生产力下降的主要原因，而且这种影响对玉米的影响比对大豆谷物产量的影响更大。