Evaluation of long-term climate change impact on the growing season and water use of mature pecan in Lower Rio Grande Valley

Abstract

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 (Kc) over the study period was calculated using a developed regression model relating growing season Kc 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 (ETa). 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 ETa 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 ETa 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 ETa 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.