Surface Accumulations of Nitrates and Other Soluble Salts in California Orange Orchards
1954
Harding, Robert B.
Information presented shows that in furrow-irrigated California orange orchards, as much as 3 tons of soluble salts per acre, representing 800 lbs. of nitrogen as well as other necessary plant nutrients, may accumulate in the upper 6 inches of the interfurrow ridges as a result of capillary conduction. These accumulations have little chance of being of benefit to the trees under present cultural practices. Factors controlling the rate of surface concentration of salts are rate of evaporation, amount of irrigation, kind and amount of soluble salts available as source material, type and shape of furrow, and soil texture and profile characteristics. Surface salt concentrations have been shown to be greater in orchards that are not tilled than in those that are tilled. Laboratory leaching studies indicate that when water is applied to areas of high salt concentration, the initial outflow is not so concentrated as may be suggested by analysis of the saturation extracts. These data also indicate that a considerable amount of water must pass through the soil before any apparent reduction in salinity of the leachate is obtained. From the information available to date, a number of suggestions are made regarding cultural operations which should be considered in this problem. Further study should be directed toward management practices which will lessen these surface concentrations.
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