Abstract Improving management practices of cocoa (Theobroma cacao L.) cultivation especially under future climate change requires knowledge of yield gaps and their determining factors. In this study, we assessed yield gaps and their determining factors through multiple regression modelling in smallholder cocoa agroforestry systems in Ghana along a climatic gradient. The studied zones referred to as dry, mid and wet with annual rainfall of 1200, 1200–1400 and 1400–2000 mm respectively, represent established “climate suitability zones” across the cocoa belt of West Africa, where 70% of the global cocoa is produced. Data was collected from 150 cocoa farmers and their plantation across the zones. Information about socioeconomic and management characteristics was collected through interviews. In each plantation, soil characteristics and cocoa plantation properties were recorded. Yield data for three consecutive years (2012/13–2014/15) and soil properties (0–30 cm layer) were analysed. Yield gap was estimated as the difference between attainable yield (AY) and actual farmers yield (FY) in each zone based on the approach of maximum farmer yields determined from survey. Average farmer and attainable yield of 211 and 645 kg ha−1 year−1 in the dry, 477 and 1174 kg ha−1 year−1 in the mid and 999 and 2125 kg ha−1 year−1 in the wet zone were recorded, respectively. Relative yield gaps were significantly larger in the dry (67%) than the wet zone (53%). In the dry zone with significantly older farmers (average age of 64), increasing labour cost (use of hired labour) significantly reduced yield gap. Contrary, increasing labour cost significantly increased yield gap in the mid zone where plantations were significantly larger. Yield gap increased significantly with increasing farmer age (54 years) in the mid zone but decreased significantly with farmer age (47 years) in the wet zone. Significant positive relationship between plantation size and yield gap was observed in both mid and wet zones. Soil available phosphorous (P) and fungicide use significantly reduced yield gap in the dry and mid zones. Finally, quantity of pesticide, proportion of hybrid cocoa plants and number of trainings received by farmers significantly reduced yield gap in the wet zone. In the dry zone, closing the yield gap against the climate risk might be unlikely. Transformation into more drought resistant systems such as cashew might be promising. However, in the mid and wet zones, labour availability for effective management of large plantations might be the major barrier for intensification, which needs to be addressed by intervention strategies.

中文翻译：

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加纳小农可可系统产量差距的变化以及沿气候梯度的主要决定因素

摘要 改进可可 (Theobroma cacao L.) 种植的管理实践，尤其是在未来气候变化的情况下，需要了解产量差距及其决定因素。在本研究中，我们通过对加纳小农可可农林业系统沿气候梯度的多元回归模型评估了产量差距及其决定因素。研究区被称为干、中和湿，年降雨量分别为 1200、1200-1400 和 1400-2000 毫米，代表了西非可可带上已建立的“气候适宜区”，其中 70% 的全球可可是产生。数据是从 150 名可可种植者及其整个区域的种植园收集的。通过访谈收集有关社会经济和管理特征的信息。在每个种植园，记录了土壤特征和可可种植园的特性。分析了连续三年（2012/13-2014/15）的产量数据和土壤特性（0-30 cm 层）。根据调查确定的最大农民产量的方法，将产量差距估计为每个区域可达到的产量（AY）和实际农民产量（FY）之间的差异。平均农民和可达到的产量为 211 和 645 kg ha-1 year-1 旱区，477 和 1174 kg ha-1 year-1 中期和 999 和 2125 kg ha-1 year-1 湿区， 分别。干区 (67%) 的相对产量差距明显大于湿区 (53%)。在农民明显年龄较大（平均年龄为 64 岁）的干旱地区，劳动力成本的增加（雇佣劳动力的使用）显着缩小了产量差距。相反，劳动力成本的增加显着增加了种植园明显更大的中部地区的产量差距。产量差距在中部地区随着农民年龄（54 岁）的增加而显着增加，但在湿区随着农民年龄（47 岁）的增加而显着减小。在中湿区均观察到人工林规模与产量差距之间存在显着正相关关系。土壤有效磷 (P) 和杀菌剂的使用显着降低了干旱和中部地区的产量差距。最后，农药用量、杂交可可植物比例和农民接受的培训次数显着缩小了湿区的产量差距。在干旱地区，针对气候风险缩小产量差距可能不太可能。转化为更耐旱的系统，如腰果，可能是有希望的。然而，在中湿区，