Orchard salinity influences almond production before the signs of toxicity show up in trees, UC Cooperative Extension farm advisor David Doll, Merced County, told a crowded room at last year’s Almond Conference, in December. Increasing levels of salt in orchard soils make almond trees “work harder for water” and divert energy away from crop production.
Salts come from three general sources: irrigation water, fertilizers, or they are naturally present in soils.
“Salt levels within soils should be determined with preplant sampling, and modifications should also be made before planting if levels are found to be moderately high,” Doll said. “In cases of high salinity, trees should not be planted.” The majority of issues that arise after planting are the result of low-quality water that allows salts to accumulate in the root zone.
Sample Soil and Water
It is important, therefore, to regularly sample both soil and water sources to detect salt accumulation in the soil and to manage buildup by adding water to move salts away from the roots, as well as amending soils and water to correct specific problems.
Soils should be sampled down to a depth of 5 feet at about 12-inch intervals, pulling multiple samples within each block. Sampling should take place at the end of the irrigation year, in October, and again following a leaching program to determine if the program achieved the desired correction. Regular water sources, such as wells, should be sampled once or twice a year, and variable sources, such as canals, should be sampled more frequently, depending on general quality.
Leaching, the most effective way to remove salt accumulation near the roots, should ideally be conducted during the dormant season, and amendment strategies should be determined at that time for the coming year.
Calcium Amendments
“If you haven’t done that by early December, review sampling analysis with your certified crop adviser [CCA], and talk to them about the use of calcium-containing amendments in your water and calculating an in-season leaching fraction,” stated Doll.
Doll noted that all salinity is not the same, and there are differences in managing salinity in the water compared to salinity in the soil, as well as for specific soil types. For more information on managing salinity in fine or sandy soils, refer to the Salinity Management link on UC Cooperative Extension’s Almond Doctor website, TheAlmondDoctor.com.
Doll added that there are distinct varietal and rootstock susceptibility differences, with peach-almond rootstocks displaying higher salinity tolerance, and varieties such as Fritz showing signs of toxicity earlier than other varieties, serving as a “canary in the coal mine.”
More information on rootstock and varietal differences can also be found on The Almond Doctor website.
View Doll’s conference presentation, “Managing Orchard Salinity During and After Drought,” online at the Almond Board of California website, Almonds.com/ConferencePresentations.
