Vol. 73 No: 2

Title:
Effects of Soil Applications of Potassium Sulphate on the Mineral Composition and Eating Quality of Stored ‘Conference’ and ‘Doyenné Du Comice’ Pears

Authors:
D.S. JOHNSON, T.J. SAMUELSON, K. PEARSON and J. TAYLOR

pp: 151-158

Abstract:
In a ten-year trial, withholding K fertilizer to ‘Conference’ and ‘Doyenné du Comice’ trees did not cause leaf K to fall to deficient levels. Soil application of potassium sulphate raised leaf K by up to 0.4% above the optimum level, and fruit K concentrations were increased by up to 20 mg 100 g^-1, and there was a slight yield increase in ‘Conference’ (but not ‘Comice’) pears in the latter years. Potassium application influenced the uptake of other minerals into leaves and fruit, and in particular reduced their Ca and B status. Although the tendency for a lower starch content in fruit from fertilized plots suggested an advanced state of maturity, this was contradicted by the lower soluble solids content, and higher firmness of K-rich fruits at harvest. In taste-panel assessments on fruit ripened for 5 d at 18°C after storage at -1 to -0.5°C, no consistent differences between fruit from fertilized and unfertilized plots were detected in terms of flavour, sweetness, firmness or juiciness. Chemical analysis, however, showed that K application occasionally lowered fruit sugar concentrations, and consistently increased acidity. Improvements in eating quality are unlikely to be gained from increasing K application to trees already adequately supplied with this nutrient.

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