Pecan is a major crop in the Lower Rio Grande Valley (LRGV), New Mexico. New Mexico is currently the largest pecan producer in the United States. Pecan is also considered a major water user which can consume as much as 1200–1300 mm of water during the growing season. Climate change can have significant potential impact on the water requirement of pecan as well as its productivity and cost of production. This study evaluates the climate change effects on the duration of growing season (DGS) and water requirement of pecan in LRGV over the period of 1901–2019. Temperature data for the study period was used to identify the DGS. Hargreaves–Samani model was used to calculate reference evapotranspiration (ET₀). Daily crop coefficient (K_c) over the study period was calculated using a developed regression model relating growing season K_c to cumulative growing degree days (GDD). The Mann-Kendall and Sen’s methods were applied to determine if there was a significant positive or negative trend in the DGS, ET₀, and actual evapotranspiration (ET_a). Statistical results showed a decreasing trend in the DGS over 1901–1950 whereas an increasing trend in the DGS was detected for the period of 1950–2019. Like the DGS variations, decreasing and increasing trends for both seasonal ET₀ and ET_a were observed for the first 50 years and the rest of the period with 99% confidence level, respectively. Results showed an increase of 124 mm in seasonal ET_a between 1950 and 2019. The study showed that climate change effects in LRGV have been occurring for the study period, continuous increases in both DGS and ET_a may bring changes in crop water requirement, and economics of pecan production as well as other horticultural challenges such as insufficient chill period for flowering, increased vivipary, and delayed or prolonged harvest.

山核桃是新墨西哥州下里奥格兰德河谷（LRGV）的主要农作物。新墨西哥州目前是美国最大的山核桃生产国。山核桃也被认为是主要的用水户，在生长季节可能消耗多达1200-1300毫米的水。气候变化可能会对山核桃的需水量及其生产力和生产成本产生重大潜在影响。这项研究评估了1901年至2019年期间气候变化对LRGV中山核桃生长时间（DGS）和山核桃需水量的影响。研究期间的温度数据用于鉴定DGS。使用Hargreaves–Samani模型来计算参考蒸散量（ET ₀）。日作物系数（K _c）是使用发达的回归模型将研究季节K _c与累积生长天数（GDD）相关联来计算的。应用Mann-Kendall和Sen方法确定DGS，ET ₀和实际蒸散量（ET _a）是否存在显着的正或负趋势。统计结果表明，在1901年至1950年期间DGS呈下降趋势，而在1950年至2019年期间DGS呈上升趋势。像DGS的变化一样，在最初的50年和该时期的其余时间内，观察到季节性ET ₀和ET _a的下降趋势和上升趋势，其置信度分别为99％。结果显示季节性ET增加了124 mm_a在1950年至2019年之间。研究表明，在研究期间，LRGV一直在发生气候变化影响，DGS和ET _a的持续增加可能带来作物需水量的变化，山核桃生产的经济性以及其他园艺挑战例如寒冷的时期不足以开花，活动性增加，收获延迟或延长。