Sugarcane yields are known to decline with successive ratoon crops, a phenomenon termed ratoon yield decline (RYD), and the rate of decline is largely dependent on the environment in which the crop grows. An environment in sugarcane production is characterized by harvest season and soil type, and gaining an understanding on how these influence RYD, can assist growers manipulate them through best practices to attain longer profitable ratoon cycles. This study aimed to quantify the effect of harvest seasons and soil types on RYD for tons cane per ha per annum (TCHA), sucrose content (SUC%) and tons sucrose per ha per annum (TSHA). To achieve this, 15 year (2000–2014) commercial field data from four large growers of the Eswatini sugarcane industry with similar climatic conditions were analyzed using linear mixed models. Season, soil and season x soil effects had highly significant (p < 0.0001) effect on RYD for TCHA and TSHA. The order of importance for TCHA was season > soil > season x soil while for TSHA it was soil > season > season x soil. SUC% was not significantly (p > 0.05) affected by change in ratoon crop numbers, although there were indications of increase with increase in ratoon number. Early season harvests had the highest rate of cane yield decline (−3.33 TCHA) followed by late season (−2.30 TCHA), and mid season (−1.98 TCHA) had the lowest. Early (−0.33 TSHA) and late (−0.32 TSHA) season harvests had higher rates of sucrose yield decline than mid season harvests (−0.26 TSHA). Poor draining soils had a higher rate of cane yield decline (−2.92 TCHA) than moderate draining (−2.30 TCHA) and good draining (−2.43 TCHA) soils. Similarly, poor draining soils had a higher rate of sucrose yield decline (−0.38 TSHA) than moderate draining (−0.28 TSHA) and good draining (−0.25 TSHA) soils. There were larger variations in rates of yield decline for season x soil effects for TCHA (−1.70 to −3.98) and TSHA (−0.23 to −0.46) than the main effects of seasons and soils indicating the complexity associated with yield traits. The results of this study will inform sugarcane yield forecasting models to estimate yields of plant cane and ratoon crops for each soil class, adjusted for harvest seasons. Plant breeders can segregate environments according to their potential RYD and select genotypes for specific adaptations to optimize genetic gains. Growers on the other hand will be able to identify profitable ratoon numbers for each growing environment and schedule their replant programs accordingly.

已知甘蔗产量会随着连续的宿根作物而下降，这种现象称为宿根产量下降 (RYD)，下降的速度很大程度上取决于作物生长的环境。甘蔗生产环境的特点是收获季节和土壤类型，了解这些因素如何影响 RYD，可以帮助种植者通过最佳实践来操纵它们，以获得更长的盈利周期。本研究旨在量化收获季节和土壤类型对每年每公顷甘蔗吨数 (TCHA)、蔗糖含量 (SUC%) 和每年每公顷蔗糖吨数 (TSHA) 的 RYD 的影响。为了实现这一目标，使用线性混合模型分析了来自斯威士兰甘蔗产业的四个大型种植者的 15 年（2000-2014 年）商业田间数据，这些种植者具有相似的气候条件。季节，土壤和季节 x 土壤效应对 TCHA 和 TSHA 的 RYD 具有非常显着的 (p < 0.0001) 影响。TSHA 的重要性顺序是季节 > 土壤 > 季节 x 土壤，而 TSHA 的重要性顺序是土壤 > 季节 > 季节 x 土壤。SUC% 受宿根数量变化的影响不显着（p > 0.05），尽管有迹象表明宿根数量增加而增加。早季收成的甘蔗产量下降率最高（-3.33 TCHA），其次是晚季（-2.30 CHA），中季（-1.98 TCHA）最低。早期（-0.33 TSHA）和晚期（-0.32 TSHA）收获季节的蔗糖产量下降率高于中期收获（-0.26 TSHA）。排水不良的土壤的甘蔗产量下降率 (-2.92 TCHA) 高于中等排水 (-2.30 CHA) 和排水良好 (-2.43 CHA) 的土壤。相似地，排水不良的土壤的蔗糖产量下降率（-0.38 TSHA）高于排水中等（-0.28 TSHA）和排水良好（-0.25 TSHA）的土壤。与季节和土壤的主要影响相比，TCHA（-1.70 至 -3.98）和 TSHA（-0.23 至 -0.46）的季节 x 土壤效应的产量下降率变化更大，表明与产量性状相关的复杂性。这项研究的结果将为甘蔗产量预测模型提供信息，以估计每个土壤类别的植物甘蔗和宿根作物的产量，并根据收获季节进行调整。植物育种者可以根据其潜在的 RYD 隔离环境，并选择基因型进行特定适应以优化遗传增益。另一方面，种植者将能够为每个种植环境确定有利可图的再生树数量，并相应地安排他们的补种计划。