Yield and quality of flue-cured tobacco (Nicotiana tabacum L.) as affected by calcium, magnesium, potassium and boron

Abstract

A field trial was carried out with flue-cured tobacco on a Shorrocks soil series at the Loskop research station. Different levels of K, Ca and Mg in the soil were obtained after two annual applications of these cations in the sulphate form. Averages for the three K levels in the top (300 mm) soil were 148,192 and 216 mg kg⁻¹. The three Ca levels averaged 646,706 and 835 mg kg⁻¹ and two Mg levels were 143 and 187 mg kg⁻¹. The pH (water) varied between 5,3 and 5,4. The highest Ca level produced greener leaves with significantly more chlorophyll and higher nicotine levels when harvested. Both Ca and Mg increased leaf mass interactively. The higher Mg level adversely affected the texture of the cured leaf which was aggravated by the higher Ca levels. A single foliar application of boron (1 kg B ha⁻¹) during the early flower bud stage increased the B content of the top leaves from 30,0 to 33,6 mg kg⁻¹ and improved their texture. K applications did not significantly affect yield or quality, possibly due to a relatively high natural K content of the soil.