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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Franz Niederholzer8 CommentsNovember 20, 2012Nutrient, Salinity, Soil

Broadcasting compost within Orchards

Compost spreaders are working in almond orchards in this area.  The addition of composted organic matter – often composted yard waste — to soil should generally benefit soil physical and chemical properties.  However, it isn’t a source of short-term plant available nitrogen.  Research by UC Davis specialists Tim Hartz and Jeff Mitchell has shown that composted yard waste, when mixed with sand and held under constant, optimum moisture and temperature (the optimum conditions for mineralization of organic nitrogen) produces a very little plant available nitrogen (2% of total nitrogen in the compost) in the short run (12-24 weeks).  When compost is broadcast on the soil surface and not incorporated, plant available nitrogen should be even less.  Dr. Hartz did conclude that manures and composts had value in long-term soil building in vegetable crop production, where those materials are incorporated into the soil.  [Untreated/uncomposted manure use in almonds is a food quality risk and not supported by the almond industry.] Why bring up compost use? Growers are willing to pay for it and seem happy with the results.  Here’s why.  If California agriculture ends up in a regulatory situation where nutrient budgets are required of growers, it should be recognized that the short term nitrogen benefits from composted yard waste are almost non-existent and the long term benefits are unknown. Previous entries on compost applications can be found here and here.

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David Doll3 CommentsSeptember 28, 2010Salinity

Soil Sampling and the Effectiveness of Leaching

Unwanted sodium, chloride, and boron ions can accumulate and cause damage to the almond tree. These ions are introduced into the rooting zone through irrigation, and will remain within the rooting zone until they are either removed by the plant or leached beyond the rooting profile. Where soil salinity is a problem, periodic soil sampling should be performed. This analysis will provide the information to determine if the salts are accumulating to a toxic level and if the applied leaching fractions are adequate. Samples should be taken from areas of the orchard showing uniformity in reduced growth or toxicity symptoms. At each sampling location, soil should be taken for each foot for the top five feet. Do not pool the soil to create a composite sample; rather, take enough samples to represent the growth differences within the orchard. The sample should also take into account the emitter patterns as differing locations may have differing salinity levels. The samples should be submitted to an analytical lab and tested for the salts of concern. Once the results from the analysis are received, the concentration of salts at the various depths can determine the effectiveness of the applied leaching fractions. If the soil salinitity levels are the lowest near the soil surface and increase with depth, leaching is occurring. This gradient is due to the relatively low salinity of the irrigation water, the movement of salts with the water as the water infiltrates the soil during an irrigation. In contrast, if the salt levels are the highest near the surface, and decrease with depth, no leaching is occurring. The leaching fraction must be adjusted to help move soils below the active rooting zone. Keep in mind that larger leaching fractions will result in more uniform salinity as depth increases. Inadequate leaching fractions will result in increases in

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David Doll8 CommentsSeptember 20, 2010Salinity

Water analysis and applying a leaching fraction for saline conditions

Written by: David Doll (UCCE Merced) and Daniel Sonke (Sureharvest, Inc). As discussed previously, sodium and chloride build-up in soils can cause crop loss by stunting plant growth. While much of the Central Valley has access to high quality surface irrigation water through irrigation districts, many almond orchards around the state have irrigation sources of variable quality. The first step in managing salinity is to know the source of salts. Water sources should be analyzed to determine the suitability for irrigation. Measurements of electrical conductivity (EC), sodium, calcium, and magnesium concentrations (cations), chloride, carbonate, bicarbonate, and sulfate concentrations (anions), pH, boron, and nitrate-nitrogen should be made. Most of these are standard.  Testing should occur on a regular basis since aquifer quality can change over time. Once the data is received from the test, the data should be checked for accuracy. First, the combined totals of all of the cations and the combined totals of all of the anions should be equal. Exclude boron and nitrate-nitrogen from these calculations. Next, if the EC is 5 dS/m or less, check to see if the sum of the cations is equal to 10 times the value of the EC. If these numbers are close, but not exact, the test is of good quality with all measurements made. If the EC and sum of cations are equal, most likely one of the cations/anions were estimated by subtraction rather than direct measurement. In the case of questionable quality, re-run the sample. Waters with ECs between 5 and 20 dS/m should use a multiplication factor of 12 instead of 10. Guidelines for water quality have been established to help identify excess salinity in water supplies. Estimating a 15% leaching fraction and the use of peach rootstocks (Nemaguard), the following table should be used as a guide to evaluate waters for suitable for irrigation

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David Doll11 CommentsSeptember 6, 2010Salinity

Salt Burn and Stunted Growth – How Almonds Respond to Saline Conditions

Some areas of California are prone to salt damage. Within Merced County, common salt affected areas include the Livingston/Atwater/Hilmar area. The soils in these areas are coarse (Sand to Loamy Sand) and, when irrigated with well water, accumulate high levels of sodium. In other places of California, which include areas of the San Joaquin Valley and Lower Sacramento Valley,  sodium, chloride, and boron can be problematic. Salt burn is typically identified by tissue analysis. This analysis can be through visual or analytical observations. Leaf sampling in Mid-July can be compared to UC critical values to determine the relative level of salt. Severe salt burn appears late in the summer, with leaf tips burning back. Trees severely affected can look golden in appearance and, in some cases, lose their leaves. Once salt burn is visually observed in the tree, considerable crop loss has already occurred. Annual leaf sampling can help determine if salt levels are increasing and if salt reduction strategies are needed (leaching, buffering water, etc.). Salts dissolved in the soil water reduce growth and yield by osmotic or toxic effects. Osmotic effects are the processes that most commonly reduce growth and yield. Within a root zone unaffected by high levels of salt, the concentration of ions are higher within the root than in the soil. Through the process of osmosis, water moves from the soil into the plant. As the salinity of the soil increases, the difference between the concentration of ions between the plant and soil decreases, slowing the rate of water movement by osmosis, making water less available to the plant. To prevent this from occurring, the plant responds by making more sugars or organic acids or accumulating salts, raising the concentration of salts in the root. These processes use energy that could of been directed to the crop,  reducing

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