Lettuce tipburn as related to the cation contents of different plant parts

Abstract

The effects of various cations on the incidence of tipburn in lettuce were studied. For that purpose lettuce was grown in soil in an experiment in which two concentrations of various salts were added to the irrigation water. The quantities of the salts were selected in such a way that the total ion concentrations were the same for all the salts,i.e. 25 and 50 mmol.l−1. The tipburn levels were assessed visually and at harvest, crop samples were collected from various parts of the plants and analysed for sodium, potassium, calcium and magnesium. The application of sodium bicarbonate in the irrigation water had a significantly greater effect on the fresh weight of lettuce than the other salts. There were no significant differences between the effects of the other salts. The greater effect of sodium bicarbonate may be attributed to sodicity. The relationship between the results of the tipburn assessments and the cation contents of the various plant parts were examined in different ways. The highest correlation coefficients were obtained with multiple linear regression equations in which calcium, magnesium and sodium were included as independent variables. The correlation coefficients for the analytical results of the various plant parts ranged between 0.88 and 0.91. The correlation coefficients for the analytical results of the various potassium was used instead of sodium as the third independent variable. This is probably the result of the fact that sodium and potassium were highly correlated in the crop analyses.