David Doll0 commentsMarch 7, 2021Horticulture, Irrigation

Drought and Almonds: Spring Considerations

The current drought conditions faced by California will impact the agricultural industry. Annual precipitation, snowpack, and reservoir conditions are well below average for this time of the year. Although there is some rain in the forecast, future rain and snowfall amounts are hard to predict. Furthermore, spring storms tend to come in warmer temperatures, leading to more rain but less snow at lower elevations. Although we cannot control the weather, there are things we can do to improve the use of water resources. These practices will improve the use efficiency of on-farm water resources. They also include strategies to help capture more water from spring rain events. Lastly, implementing practices now will provide on-farm data for future mitigation strategies as the Sustainable Groundwater Management Act (SGMA) comes into full enforcement. Start timing. Most farm operations begin to irrigate too early. This occurs even in low rainfall years. Stem water potential (SWP) or other plant-based monitoring systems are strongly recommended to help determine start timings in the spring. With SWP, recommendations are to wait to at least 2 bars more negative than baseline (remember, SWP is read in negative numbers). This will most likely lead to an irrigation timing around early- to mid-April, depending on leaf-out date. A study demonstrating this method was established in a ‘Butte’/’Padre’ located near Delhi, CA in a very sandy soil. The trial was established in the drought year of 2014-2015 and continued through 2017. Within this study, the delayed start to the irrigation did not impact yield in comparison to the grower standard. The dates for the first irrigation were between April 22nd – 26th, for all three years. Since ‘Butte’ and ‘Padre’ are later leafing cultivars, I suspect that ‘Nonpareil’ and other earlier leafing cultivars will be 1-2 weeks earlier. This delay saved between

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David Doll0 commentsJanuary 29, 2020Horticulture, Irrigation

Influence of water availability on orchard spacing and development

Orchard canopy coverage has been shown to correlate with yield. As canopy size increases, more sunlight is intercepted by the leaves. This leads to the production of more energy that can be directed to the tree, leading to more growth, and therefore more crop. Correlation of intercepted light at mid-day (PAR) and kernel yield per acre. Research conducted by Lampinen, et al. What is often forgotten is the most critical to canopy development: water. Without access to water, tree canopy growth will slow or stop due to the reduction of gas exchange and photosynthesis, leading to smaller canopy size. Water is generally limited within an orchard system by either supply (e.g. reduced access to irrigation water) or delivery issues (e.g. irrigation engineering or water infiltration issues). To complicate this even further, water availability is not necessarily simply the amount of irrigation water available per area of orchard. It also takes into account rainfall that has been stored within the soil, general water availability, system engineering and distribution uniformity, and water infiltration rates. Limitations in any of these will lead to a reduction of the tree’s available water. Work by researchers in California has shown the correlations of canopy coverage with yield. This research was performed by gathering the amount of light intercepted at mid-day and comparing it to measured yields within orchards in California. This work has identified that high-producing orchards tend to alternate around 50 kernel lbs for every 1% of light intercepted, giving a theoretical maximum yield of 5000 lbs/acre.  Since it takes water to develop the canopy, this correlation can be also be extrapolated to water use: every percent of the tree’s water needs met will provide roughly 50 kernel lbs of crop in California’s growing conditions. An orchard with >80% light interception requires full irrigation to

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David Doll4 CommentsAugust 22, 2014Irrigation

Water Stress and Varietal Differences

A few visits and emails have highlighted differences in leaf drop patterns observed across varieties within an orchard. Full rows of trees will have yellow leaves that drop in time, characteristic of water stress while other varieties appear unaffected. These “in-field” observations suggest that almond varieties respond differently to the amount of water applied. For example, the variety ‘Monterey’ and ‘Aldrich’ have been observed to show signs of stress before ‘Nonpareil’ trees even though crop load is similar. In these cases, these trees may undergo severe leaf drop while ‘Nonpareil’ appears unaffected.

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