In Indonesia, management practices that reduce soil fertility could be limiting cocoa (Theobroma cacao L.) production. To address this, we investigated the effects of fertilizers and organic amendments comprising different combinations of NPK + urea, dolomite, and manure-based compost on soil properties and cocoa productivity. We extended an existing field experiment in South Sulawesi, Indonesia, to assess these treatments’ effects on cocoa trees from the age of 2.9 years to 7.4 years. The treatments were first applied 5 months after planting and subsequently twice a year. Soil analyses were performed before planting, after 3 years, and finally after 7 years. Productivity was assessed yearly between the age of 3.5 and 7.4 years. The highest yields were obtained from the plots receiving compost, although the yield benefits diminished over time. Inorganic fertilizer alone doubled the yield compared to the control, while the yields with compost and compost + fertilizer were three times that of the control. With dolomite alone, the yield cumulated over 4 years was 41% higher than the control. The positive effect of compost on cocoa yields can potentially be attributed to (1) physical changes increasing soil water availability, (2) the chemical improvement of nutrient availability, and (3) biologically, by promoting the activity of beneficial organisms. The application of dolomite increased soil pH, Ca, and Mg contents. Soil organic carbon greatly declined in the composted treatments, even though 10 kg of compost was applied per tree per year, probably because of the low C:N ratio of the compost. Future studies should assess different fertilizer formulations and combinations with organic inputs and explore the mechanisms by which compost promotes cocoa productivity.

中文翻译：

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肥料、堆肥和白云石对印度尼西亚苏拉威西岛可可土壤和生产力的中期影响

在印度尼西亚，降低土壤肥力的管理做法可能会限制可可（可可树L.) 生产。为了解决这个问题，我们研究了肥料和有机改良剂（包括 NPK + 尿素、白云石和基于粪肥的堆肥的不同组合）对土壤特性和可可生产力的影响。我们在印度尼西亚南苏拉威西扩展了一项现有的田间试验，以评估这些处理对 2.9 岁至 7.4 岁可可树的影响。种植后 5 个月首次施用处理剂，随后每年施用两次。土壤分析在种植前、3 年后和最后 7 年后进行。生产力在 3.5 至 7.4 岁之间每年评估一次。最高产量来自接受堆肥的地块，尽管产量收益随着时间的推移而减少。与对照相比，仅无机肥的产量增加了一倍，而堆肥和堆肥+肥料的产量是对照的三倍。仅使用白云石，4 年累积的产量比对照高 41%。堆肥对可可产量的积极影响可能归因于 (1) 物理变化增加了土壤水分的利用率，(2) 养分利用率的化学改善，以及 (3) 生物学上，通过促进有益生物的活动。白云石的施用增加了土壤的 pH 值、Ca 和 Mg 含量。即使每棵树每年施用 10 kg 堆肥，堆肥处理中土壤有机碳也大大下降，这可能是因为堆肥的 C:N 比低。