2019 ASHS Annual Conference

Partial root zone drying (PRD) is an irrigation method that utilizes alternating, localized water applications to produce a staged, simultaneous, wet/dry cycle between the two halves of a root system. The goal of PRD is to increase water use efficiency (WUE) by stimulating certain drought stress related responses in the plant. This study investigates the primary effects of a PRD regimen on drip-irrigated, field-grown ‘Pawnee’ pecan [Carya illinoinensis (Wangenh.) C. Koch] in south central New Mexico, USA, where the pecan production area is rapidly growing while the availability of water resources is declining. Comparisons of photosynthesis (Ps), stomatal conductance (g_s), midday stem water potential (Ψ_smd) measurements and various yield factors were made in the 2018 growing season between five irrigation treatments, including PRD applications at both 100% and 75% of estimated evapotranspiration (ET) levels. Results did not indicate a strong response to PRD treatments over a single season. Variations in Ps, g_s, Ψ_smd and measured yield factors were all relatively small, with only a single PRD treatment incorporating a 25% deficit during the earliest growth stage showing minor improvements in yield and average nut weight (4.67% and 4.18%, respectively) over the control. Further research will determine if PRD effects on WUE become more pronounced over time and if there are carry-over effects of PRD on return bloom or nut production.