Almond Orchard Management

Author : Tara Ann Seely
Publisher :
ISBN 13 : 9780355763782
Total Pages : pages
Book Rating : 4.7/5 (637 download)

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Download or read book Connecting Physiological and Agronomic Responses of Almond Orchards to Drought Stress written by Tara Ann Seely and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Almonds are California’s second leading agricultural commodity and comprise 10% of state agricultural water use. Recently, the almond industry has faced increasing pressure for its intensive use of water in almond production. Adopting water-efficient irrigation practices for almonds is critical in light of California’s 2012-2016 drought and projections of more severe droughts in the future. The objective of this work is to determine the effect of continuous deficit (T1), control (T2), and surplus (T3) irrigation treatments on orchard yield and tree physiology, and to ascertain the way in which tree response to water stress is linked to field-level agronomic productivity. We also investigate how irrigation treatment affects depth of water uptake and the use of stored soil water by almond trees by using soil moisture measurements and water isotope sourcing of [delta]2H and [delta]18O. Irrigation treatments were replicated from 2013-2016 in three orchards spanning the latitudinal production range of almonds in California (~35° N to ~40° N) in Kern, Merced, and Tehama counties. Physiological parameters of stem water potential (SWP) and intrinsic water-use efficiency (iWUE) derived from [delta]13C isotopes were combined with agronomic measurements of yield, kernel weight, and irrigation water productivity (yield per unit water applied) to connect tree response to water stress over multiple scales. Stem water potential (SWP) reflected seasonal water stress in T1 treatment in all three orchards, but iWUE increased due to water stress in T1 treatment in Tehama and Merced only. Almond yield varied widely across orchards and decreased only moderately under deficit irrigation in Tehama and Merced, although yield in Tehama may have been limited by other resources in addition to water. Interestingly, trees in Kern did not increase iWUE in response to water stress, but yield in Kern decreased the most due to deficit irrigation. Results indicate that physiological mitigation of water stress (i.e. by increased iWUE due to stomatal regulation of transpiration) can buffer agronomic losses in yield at the orchard scale. Additionally, limitations on the physiological ability of almond trees to increase iWUE may be linked to thresholds of high yield and small kernel size. On a regional level, climatic differences between study sites did not play a significant role in orchard response to treatment. However, orchards significantly differed in soil texture and soil water holding capacity. Within orchards, there was no statistically significant difference in the amount of stored soil water used by trees under different irrigation treatments. Depth of water uptake by T1 irrigated trees was either equivalent or shallower (i.e. close to the irrigation source) to T2 and T3 irrigated trees. Temporally, T2 and T3 irrigated trees shifted water uptake to deeper layers between May and July, while T1 irrigated trees displayed less plasticity in depth of water uptake. Over three years, surplus irrigation (T3) only increased yields up to 7% by using 6-12% more water. Deficit irrigation (T1) saved between 17-24% of water and decreased yields between 1- 16%, depending on the orchard. We conclude deficit irrigation can be a useful strategy to reduce water use in almond orchards across the state with minimal reduction in yield. However, the variability in responses to deficit irrigation indicates site-specific differences in soil texture, tree spacing, and management characteristics are important considerations when designing irrigation strategies.