Osmotic pressure of the soil solution: determination and effects on some glasshouse crops.

Abstract

In a factorial experiment, calcium sulphate, sodium chloride and potassium nitrate were added to a loamy sand soil in various quantities. The experiment was carried out in an unheated glasshouse. The salt status of the soil was determined with the aid of different method of aqueous extraction. The results were correlated with the osmotic pressure of the soil solution. A close correlation was obtained with the conductivity of the saturation extract. Crop yields were correlated with the conductivity of the saturation extract and with the osmotic pressure of the plant sap. The correlation with the conductivity of the saturation extract was generally highest. With tomatoes, a clear relationship was found between the conductivity and the incidence of blotch on the fruits. In lettuce, there was a clear relationship between conductivity and the occurrence of tipburn. The yield reduction of some crops was significantly greater after the application of sodium chloride than after potassium nitrate. Apparently, this was caused by specific ion effects. The desirable salt level, the salt distribution in the soil and the determination of the osmotic pressure of the soil solution for routine soil-testing purposes are discussed. The curvilinear relationship between the salt level of the soil and the incidence of tipburn may be explained by the calcium uptake of the crop. (Abstract retrieved from CAB Abstracts by CABI’s permission)