How Much Water Does An Almond Tree Need

Summary of Academy of California inquiry on irrigation management for almond trees nether drought conditions

For maximum growth, yield, crop quality and orchard longevity almonds trees should exist supplied with water to run into their total water requirement. There are some disease concerns with hull rot nether total water conditions which can be addressed with moderate water stress during hull split up. (Teviotdale et al. 2001) If water availability is express, growers can react by applying irrigation h2o when copse are well-nigh sensitive to stress and by taking measures to minimize water losses that occur during irrigation events. Supplying less water than the copse can potentially use reduces soil h2o availability, causes tree water deficits, and reduces transpiration. Encompass crops, depending on the coverage and the time of the flavour in which they are grown can increase the orchard water utilize by up to 30% . Cover crops should be removed when h2o is in express supply (Prichard et al. 1989).

Water deficits affect almond orchards not simply in the twelvemonth in which stress occurs, simply also in the post-obit seasons. By and large, nut size is reduced in the get-go season of significant h2o stress. Because water stress also reduces vegetative growth and potentially decreases productivity per unit awning volume, nut load tin exist reduced in subsequent years (Lampinen et al. 2007). Recent inquiry indicates some stages of almond fruit growth are more sensitive to water stress than others. Understanding these stages permits growers to withhold h2o while minimizing damage to copse and to current and subsequent crops.

Early on season stress

H2o stress affects more tree and crop development processes during the early season - from leaf out through shoot growth and evolution of final and lateral buds. During this catamenia, rapid vegetative development is necessary for awning development and fruiting positions for the post-obit flavour. (Goldhamer et al. 2006) (Prichard et al. 1994) In improver, orchard h2o use during this time is low compared to summer demand, reducing potential h2o savings from an early on-season deficit irrigation strategy.

Fruit growth and developement

Basics undergo a rapid growth phase early in the fruit growth and development period and are sensitive to water deficits during this time. However, copse tin tolerate drought stress fairly well during the two months prior to harvest, allowing for the successful utilise of deficit irrigation strategies during this period. (Shackel et al. 2004). Providing less than the full water requirement to cause moderate h2o stress during this menstruum, will take little influence on kernel weight. Still, severe water stress in the months leading up to hull split will reduce kernel weight and significantly reduce hull spliting. A 1-inch irrigation prior to hull dissever will mitigate the h2o stress impacts and will improve hull dissever and reduce the number of hull-tights. (Prichard et al. 1994) If drip irrigation is used, peradventure less irrigation can provide the same benefit, but this has not been proven in the field.

Post harvest stress

The outcome of water deficits during the postharvest period are substantially affected by 1) pre harvest water deficits and 2) the quantity of water use over the rest of the season. Bud differentiation tin continue through mid-September. Moderate stress during this menses will take little effect on subsequent twelvemonth'south nut numbers, but astringent stress during bud differentiation has been found to dramatically reduce fruit set the following jump (Goldhamer et al. 2006). In early harvest (early August) districts, particularly with early varieties, more of the high water use flavor remains after harvest. This increases the necessity for postharvest irrigation. Subsequently harvest (north State) districts and later varieties have a slightly shorter postharvest period which occurs at a fourth dimension of lower crop h2o demand. These factors reduce the risk of moderate water deficits causing bud differentiation problems (Prichard et al. 1994).

Tree response to postharvest stress tin exist influenced past the type of irrigation organisation used, and the previous irrigation management. Low volume systems with limited soil h2o reserves tin result in severe h2o deficits very apace after irrigation cut off. In the southern San Joaquin Valley where harvest is before than in the north, or with drought-sensitive varieties, postharvest irrigation is a necessity. Deep rooted, surface irrigated copse may accept plenty pre-harvest deep moisture remaining to behave them through the critical period of bud differentiation. This all depends on the irrigation management occurring pre-harvest.

• Developing a Deficit Irrigation Strategy

Crop Water Use

Almond water apply begins when the leaves develop and shoot growth begins. Concurrent with canopy evolution, the climatic demand increases, driven by longer days and college temperatures and depression humidities as the season progresses. Both of these factors upshot in a seasonal h2o use starting at a low level, peaking in mid-season and falling as flavour ends. Sources of water available to trees include: soil-stored moisture (including frost protection water applications if the root zone is less than field capacity when applications are made), any in-season rainfall captivated by the soil, and applied irrigation water. These all combine to make up one's mind the total seasonal h2o available to the orchard.

Mature conventionally spaced almond trees in the Southern Sacramento Valley can utilize about 41- 44 inches of h2o in an average year of unrestricted water use. Loftier-density orchards, long pruned orchards, or those with a cover crop can have even college use. . Soil moisture monitoring demonstrations in more than 40 almond orchards in Kern Canton indicate that seasonal water employ in the southern San Joaquin Valley may be as loftier as fifty - 54 inches (Sanden 2007). Figure 1 shows a typical water use pattern for fully irrigated and a deficit irrigation government for almond in the Manteca area.

The moderately deficit irrigated orchard used (in a combination of soil supplied and irrigation h2o) 28 inches of water or almost 34 % less than the total potential orchard.

Water Deficits

H2o deficits occur when the climatic water demand exceeds the water absorbed past the roots. Equally the soil becomes depleted of readily available moisture, water uptake by the roots lags backside water utilize causing plant stress in the mid to tardily afternoon. This pocket-sized crop water deficit has little event on the crop yield. However, as soil water becomes increasingly difficult to extract water stress increases. One style to measure "tree stress" is to apply a portable pressure bedroom to measure "midday stem water potential". To use this technique a few leaves from representative copse are first covered with an opaque plastic bag while still on the tree. The covers need to remain on the leaves at least 10 minutes afterwards which they are detached and the the water potential measured using the pressure sleeping room (Fulton et al. 2001). The pressure chamber measures the amount of pressure needed to force water out of the leaf petiole, indicating copse water status. http://fruitsandnuts.ucdavis.edu/General_Management/The_Pressure_Chamber,_aka_The_Bomb.htm

A Moderate H2o Stress Strategy

From the previous give-and-take it tin be ended that tree water utilise from leafage out through mid June should not exist compromised. From mid June through harvest, reductions up to 50% of total h2o utilise have been successfully used to reduce orchard water utilise with merely minimal reductions in kernel weight. It is important to supply the trees with water nearly hull split to avoid hull-tights.

There are diverse approaches growers can have to manage express h2o supplies depending on what types of irrigations scheduling tools interest or are available to them. A simple method is to reduce irrigation run fourth dimension or lengthen irrigation intervals to obtain the desired percentage of irrigation reduction in applied water. In a iv-twelvemonth study investigating pre-harvest, mail service-harvest, and uniform deficit irrigation for the entire flavor, the best results were achieved when h2o applications occurred at a uniform deficit rate across the season relative to full potential ingather ET. The uniform deficit rate does not mean a uniform irrigation amount across the season (eastward.g. 1.5 inches each calendar week), only rather a uniform (e.g. 85%) reduction of full ET for each period. Deficit irrigation rates of 55%, 70%, and 85% were tested with the 70% and 85% irrigation reduction treatments showing little yield loss compared to the full ET treatment. (Goldhamer et al. 2006) The 70% and 85% uniform across the flavour deficit treatments experienced fiddling early on flavor stress, probable because stored soil wet supplemented the applied irrigations.

Some other arroyo that is likely an improvement over the approach outlined above is to schedule irrigations using periodic pressure level sleeping accommodation readings and irrigate when midday stem water potential reaches a pre-determined threshold stress level (see Figure below). This method effectively extends the irrigation interval, but the interval is adamant by tree water status rather than the calendar. Irrigations should be in the volume of a normal set every bit performed with a full irrigation authorities. In a deficit irrigation study conducted on mature almond in the Manteca, CA a only prior to irrigation threshold value of -20 to -22 bars midday stalk water potential start in June resulted in 34% less tree h2o consumption and no significant influence on yield for the four-year measurement period. (Prichard et al. 1994) Information technology should be noted that a reduction in vegetative growth was measured in this treatment, indicating that use of this threshold for a longer-term strategy (more than than 4 years) may reduce yields by reducing nut numbers. The impacts of stress on a developing tree awning is much more detrimental as opposed to the impacts on a canopy that has already reached information technology's full volume.

A More than Severe Water Stress Strategy

A more severe strategy that reduces seasonal tree water utilise by l% requires that stress be imposed early on as well as mid to late flavour. Using this strategy, irrigations in April and May are withheld until trees reach a midday stem water potential of -12 to -14 bars. Using conventional sprinklers, a normal gear up time is used. If lighter applications are fabricated, more water is lost by evaporation. From June 1st through hull separate, midday stem h2o potential values should exist allowed to reach -twenty to -22 confined just prior to irrigation. This strategy will require a pre-harvest irrigation of about two inches with sprinklers-less with micros and drip--to ensure good hull separate. Annotation: this strategy reduces water use significantly but besides reduces nut weight the year it is used and the nut number in succeeding years. In the Manteca trial discussed above, it took 2 years of total irrigation for trees to recover. (Prichard et al. 1996)

A "Staying Alive" Drought Strategy

Less is known about this strategy since information technology is a rarely used selection. However, based on past drought conditions, trees may be kept alive with about a foot of applied h2o. This strategy does not consider growth and yield-just tree survival. This strategy is best conducted using a micro-irrigation organisation which maximizes water distribution and minimizes evaporative losses from irrigation. Using this strategy no irrigation is applied until water potential reaches -16 bars from leaf out through the end of May. Monitor stem water potential until the threshold is reached over again then echo the cycle. After June 1st, and for the rest of the season allow the stress to climb to -25 confined prior to irrigation. As a guide, try to merely retain the leaves on the tree. Good luck, every bit this is only a guide. Call up that following this astringent deficit strategy, it will take at least 2 years of total irrigation for the trees to recover to normal yields.

List of References

Fulton, A., Buchner, R., Giles, C., Olson, B., Walton, J., Schwankl, L., and K. Shackel. 2001. Rapid Equilibrium of Leafage and Stem Water Potential nether Field Conditions in Almonds, Walnuts, and Prunes. HortTechnology xi: 502-673.

Fulton, Allan. 2007. UC Research on Arrears Irrigation of Almonds. Column written for Merchandise mag publication.

Goldhamer DA, Viveros M, Salinias M. 2005. Regulated deficit irrigation in almonds: effects of variations in practical water and stress timing on yield and yield components. Irrig. Sci. 24(2):101-114.

Lampinen, Bruce, Ted DeJong, Steve Weinbaum, Sam Metcalf, Claudia Negron, Mario Viveros, Joe McIlvane, Nadav Ravid and Rob Bakery. 2007. Spur Dynamics and Almond Productivity. 35th Almanac Almond Industry Conference Proceedings, December. 5-6, 2007, Modesto, CA. Pp. 73-77.

Prichard, T.L., W.One thousand. Sills, Due west.Yard. Asai, L.C. Hendricks, C.L. Elmore. 1989. Orchard H2o Use and Soil Characteristics, California Agriculture, 43:4, 32 p. 23-25.

Prichard et al. 1994. Comprehensive Project Report, Project No. 93-H5 - Effects of Water Supply and Irrigation Strategies on Almonds. Written report to CA Almond Lath.

Prichard et al. 1996. Project No. 95-M7 - Residual Effects of Water Deficits and Irrigation Strategies on Almonds. Report to CA Almond Board

Sanden, B. Â 2007. Â Fall irrigation direction in a drought twelvemonth for almonds, pistachios and citrus. Â September Kern Soil and H2o Newsletter, Univ. CA Coop. Ext., Kern County. Â viii pp.

Shackel et al. 2004. Final Study (2004 and 2001 - 2004 summary): Deficit Irrigation Direction During Hull-Carve up. Report to the CA Almond Board.

Teviotdale BL, Goldhamer DA, Viveros M. 2001. Effects of arrears irrigation on hull rot disease of almond trees acquired by Monilinia fructicola and Rhizopusstolonifer. Plant Dis 85(4):399-403.