Sodium and Potassium Fertilizer in Relation to Soil Physical Properties and sugar-beet yield

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Abstract
Summary: Despite much experimental evidence showing that sodium fertilizer increases sugar–beet yield and decreases need for potassium, there is resistance to its use on some soil types through fears of deterioration in soil structure. Twelve field experiments with sugar beet were made in Eastern England, testing all combinations of autumn and spring applications of 0, 150 and 300 kg Na/ha and 0, 83 and 333 kg K/ha. Fields were chosen with soils of loamy very fine sand, very fine sandy loam, sandy clay loam and clay loam textures. Micro–plot and controlled environment studies were also made with the same soils to examine effects of sodium on seedling emergence and growth.Visual assessments of soil physical state following sodium application revealed no effect in the year sugar beet was grown nor in the following spring when cereals were grown. Measurements of physical properties of soils treated with sodium suggested that applications of several times the recommended amounts of sodium fertilizer would not damage soil structure. However, sodium fertilizer increased the osmotic suction of soil solution which, under some circumstances, e.g. dry springs or giving the fertilizer close to the time of sowing, decreased germination and seedling growth. For this reason and not because it has a detrimental effect on soil physical condition, sodium fertilizer best given in the autumn or some weeks before sowing.