Irrigation is expanding in the tropics and could make an important contribution to the intensification of production in those tropical areas where a dry season limits productivity. A study was carried out to characterize irrigation performance and the yield gaps of a tropical irrigation scheme that covers more than 41 000 ha in northern Costa Rica. The study covered a 5-year period, from 2014 to 2018. The performance indicator relative irrigation supply (RIS) ranged between 2.48 and 3.78, values higher than those typically observed in schemes of temperate areas, but in the low range of those documented in the tropics. Despite the excess of water usage, it was found that there were farms with water shortages, especially in the canal tails during the dry season, but there was also damage caused by excess of water in the rainy season. The potential yield of the two main crops (rice and sugar cane) was determined with the AquaCrop simulation model. Actual yields were determined via a farmers' survey that also inquired about irrigation management issues. Yield gaps were determined for each of the two sectors that make up the irrigation scheme (South and West canals). The mean yield gap of rice in the South Canal sector (3.34 t ha⁻¹) was smaller than that of the West Canal sector (4.84 t ha⁻¹). The highest yield gap of rice occurred in the rainy season in the West canal sector. The yield gap of sugar cane in the West canal sector was significantly larger than that in the South canal sector (170 and 148 t ha⁻¹, respectively). A farmers' survey, combined with an examination of soil maps, revealed that poor drainage through the heavy soils that predominate in the West canal sector is one of the main causes of the large yield gap, in both rice and sugar cane. While users are relatively satisfied with the provision of irrigation water and its cost, several opportunities (e.g. water delivery, amount of fertilizer in sugar cane, water supply and irrigation system on farms) for improving scheme performance and for closing the yield gaps are discussed.

中文翻译：

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评估热带环境中的灌溉计划绩效：哥斯达黎加瓜纳卡斯特计划*

灌溉在热带地区正在扩大，可能对旱季限制生产力的热带地区的生产集约化做出重要贡献。对覆盖哥斯达黎加北部超过 41 000 公顷的热带灌溉计划的灌溉性能和产量差距进行了一项研究。该研究涵盖了从 2014 年到 2018 年的 5 年期。绩效指标相对灌溉供应 (RIS) 介于 2.48 和 3.78 之间，高于温带地区方案中通常观察到的值，但在记录的低范围内热带地区。尽管用水过量，但发现有农场缺水，特别是在旱季的运河尾部，但也有因雨季用水过多而造成的损害。使用 AquaCrop 模拟模型确定了两种主要作物（水稻和甘蔗）的潜在产量。实际产量是通过一项农民调查确定的，该调查还询问了灌溉管理问题。确定了构成灌溉计划的两个部门（南运河和西运河）中的每一个的产量差距。南运河区水稻平均单产差距（3.34 t ha^-1 ) 小于西运河部门 (4.84 t ha ^-1 )。西渠段雨季水稻单产缺口最大。西运河部门的甘蔗产量差距明显大于南运河部门（170 和 148 t ha ^-1， 分别）。一项农民调查以及对土壤图的检查表明，西部运河区占主导地位的重土壤排水不良是水稻和甘蔗产量差距巨大的主要原因之一。虽然用户对灌溉水的供应及其成本相对满意，但讨论了改善计划绩效和缩小产量差距的几个机会（例如供水、甘蔗中的肥料量、供水和灌溉系统）。