16 Aug, 2021
David Doll3 CommentsAugust 16, 2021Irrigation, Salinity

Post-harvest Leaching Fractions to Manage Soil Salinity

Drought years are tough. Limited water supplies create several challenges that impact the current and future year’s crop. Several articles have been constructed to help manage almond orchards with limited water supplies, but as harvest starts, focus needs to shift to post-harvest management of the orchards. Many orchards relied on groundwater at some point through this year. This may have been sourced directly from a well on the property, or from wells within an irrigation district. Groundwater often contains elevated levels of salt, in particular sodium and chloride. These salts accumulate in the soil from the irrigations that occur during the season. Due to almond roots generally excluding salts, salt levels within the soil could climb as high as 10-15 times the concentration of the irrigation water within a single season. These higher levels of salt will impact growth and productivity as well as lead to tissue toxicity and leaf loss. To manage these salts, they need to be removed from the active rootzone of the tree. Salinity management for various soil types have been described previously for sandy and finer texture soils. These programs rely on winter leaching to reduce the salinity levels within the active rootzone of the tree. This process, however, can be improved by taking actions in the post-harvest to increase soil moisture levels. At this time of year, a leaching fraction should be added to each water applications to increase soil moisture levels. An increase of 15-20% of the irrigation duration should be sufficient. This additional water will refill the soil profile during this period, increasing the effectiveness of leaching by winter rains. The value of applying a leaching fraction in the post-harvest is greater than leaching fractions applied earlier in the season. This is due to the irrigation practices associated with harvest – a

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David Doll3 CommentsOctober 18, 2015Salinity

Salinity Management for Fine Textured Soils

AUTHORS NOTE: The following article discusses salinity management considerations for FINE TEXTURED SOILS (e.g. loams, silts, and clays). This is a follow-up to the previous article, “Salinity Management for Sandy Soils.” For the most part, this article describes issues with the WEST SIDE of the San Joaquin Valley. NOT ALL SOILS ARE THE SAME. Please note that the following guidelines may need site-specific adjustments. Starting with the soil, we often use the term cation exchange capacity (CEC), which is the amount of cations (positively-charged ions like sodium, magnesium, calcium, potassium, etc.) that can bind to the soil particle surface. In fine textured soils across the State, CEC values can be very high, with values ranging between 15-40 meq/100 g of soil. Generally, sandy loams are in the teens through 20s, and silts and clays are in the 30s to 40s. This CEC value is important as it indicates the amount of cations the soil particles can hold. The higher the CEC, the more cations that stick to the soil, preventing them from entering the soil water (soil water is the amount of water that is held between soil particles – it is what the tree drinks), reducing salt exposure to the roots of the tree. Regardless of the CEC, once the soil is saturated with cations, the excess will stay within the soil water. As soil salinity increases, the tree’s roots salt exposure is increased. High soil salinity affects the osmotic movement of water, and this impacts the tree roots’ uptake of water (e.g. essentially making the tree work harder for water), leading to eventual toxicity. Salt toxicities within fine textured soils can vary based on the element involved. Chloride toxicity can occur rapidly, showing up within a year or two when applying poor quality water. This is due to chloride being an anion, and due

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David Doll11 CommentsOctober 10, 2015Salinity

Salinity Management for Sandy Soils

AUTHORS NOTE: The following article discusses salinity management considerations for SANDY SOILS (e.g. sands, loamy sands). A follow up post will be made for finer texture soils (loams, silts, and clays). For the most part, this article describes issues with the EAST SIDE of the San Joaquin Valley. NOT ALL SOILS ARE THE SAME. Please note that the following guidelines may need site-specific adjustments. During low rainfall years, salt burn often shows up in sandy soils. This salt burn is a combination of accumulation of sodium within the soil, the use of well water, and the low exchange capacity of the soil. Starting with the soil, we often use the term cation exchange capacity (CEC) which is the amount of cations (positive charged ions like sodium, magnesium, calcium, potassium, etc.) that can bind to the soil particle surface. In the sandier areas on the east side of the San Joaquin Valley, CEC values can be quite low, with values less than 10 meq/100 g of soil. To put that in perspective, sandy loams are in the teens through 20s, silts and clays are in the 30s to 40s. This value is important as it indicates the amount of cations the soil particles can hold. The higher the CEC, the more cations that stick to the soil, preventing them from entering the soil water (soil water is the amount of water that is held between soil particles – it is what the tree drinks), reducing exposure to the roots of the tree. Regardless of the CEC, once the soil is saturated with cations, the excess will stay within the soil water. As the soil salinity increases, the tree’s roots have a greater exposure impacting them by affecting the osmotic movement of water (e.g. essentially making the tree work harder for water) and  eventual toxicity.

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David Doll10 CommentsNovember 14, 2014Salinity

Soil Salinity and Leaching for Almonds

An earlier post discussed proper soil sampling methods. By now, those results should have been received and reviewed. Almond trees are relatively sensitive to sodium, chloride, and boron. Yields are impacted when average root system salinity increases above 1.5 dS/m, with research indicating a 19% decrease in potential yield with every 1.0 dS/m increase. This yield reduction is due to the osmotic effects of the salts, which basically makes the tree “work harder” for water reducing growth and vigor. If excess salts continue to accumulate within the rooting zone, trees will ultimately uptake the salts and cause tissue toxicity. The salts of primary concern are sodium, chloride, and boron. A leaching program should be implemented when EC of the entire rooting depth exceeds 1.5 dS/m or sodium, chloride, and boron exceed  an exchange saturation percentage of 5%, 5 meq/l, and 0.5 mg/l, respectively.

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David Doll6 CommentsSeptember 29, 2014Salinity, Soil

Fall soil sampling for salinity management

The harvest season is winding down, and in the next few weeks many orchards will be receiving their last irrigations. After the final irrigation of the season, growers should conduct soil sampling to determine any potential issues with sodium, chloride, or boron. These salts are “imported” onto the farm through fertilizers and soil amendments, with the largest amount coming through irrigation water. There are several videos online that go through the procedure of collecting a soil sample. Here is a link to an article containing this series. When soil sampling for salinity management, varying depths of soil must be collected to determine where the salts have accumulated. Suggested depths are in one foot increments (down to four five feet), but 18 inch increments may also be used. If dealing with soil infiltration issues, it may be of value to sample the top 6″ to determine if there is a soil imbalance.

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Joe Connell0 commentsJuly 4, 2014Horticulture, Nutrient, Salinity

Leaf analysis and salinity monitoring

Written by Joe Connell, Butte County Farm Advisor Leaf analysis for the full range of nutrients is best done in July when nutrient levels in leaf tissue are stabilized. Published July critical values established for almond by U.C. researchers can help guide you in your fertilization practice.  Analysis can reveal specific nutrient deficiencies or can alert you to developing trends when results are compared from one year to another.  Keeping trees in the adequate zone for nitrogen can save on fertilizer costs by helping to avoid over fertilization. 

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David Doll3 CommentsMarch 24, 2014Irrigation, Salinity

Well Water Analysis to ID Salinity Issues

There will be an increase reliance on groundwater for 2014. Wells that have been typically relied on to subsidize water allocations are now providing the primary source of water for the drought stricken almond orchards. If using a well, it is important to sample the water. Sampling will determine the characteristics of the water such as dissolved salts, pH, and major cations and anions. Sampling should be performed regularly, and more frequently if well performance or pumping depth has changed. 

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