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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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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