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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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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