Effect of Leaf Priming Removal Level and Fertilization Rate on Yield of Tobacco in Zimbabwe

Abstract

Tobacco (Nicotiana tabacum L .) is one of Zimbabwe’s most valuable crop. It accounts for about 26 % agricultural gross domestic product and 61 % of agricultural exports. It is therefore important to work towards continuously improving its yield and quality. Leaf priming removal could improve the yield and quality of flue-cured tobacco. A field experiment was carried out at Kutsaga Research Station to investigate the possibility of improving yield and quality of cured leaf by removing the lower leaves (primings) and applying additional nitrogen to the remaining leaves. The experiment was laid out as a split plot experiment in a randomized complete block design with three replications. A plant spacing of 1.2 m between rows and 0.56 m within rows was used. All recommended agronomic practices in flue-cured tobacco production were observed except that 0, 2, 4 and 6 lowest leaves were removed and discarded at 6 weeks after planting. A supplementary ammonium nitrate side dressing was applied at topping at a rate of 0, 5, 10 and 25 kg N/ha. The removal of 4 leaves plus the addition of 10 kg N/ha at topping resulted in a 22.42 % increase in income above that obtained from the control. However, removal of 4 leaves plus excessive amounts of N (25 kg/ha) resulted in very large leaves but the saleable yield was lower than that from the control or other plots with the same priming removal level plus less additional N. The addition of 25 kg N/ha when only 2 leaves were removed produced the highest saleable yield and recorded 19.67 % yield increase above the control. Addition of 10kg N/ha when 4 leaves were removed resulted in 19.04 % yield increase above the control. The latter however had a better grade index. It was also noted that the removal of 4 leaves plus an extra 10 kg N/ha at topping and the removal of 2 leaves plus an additional 25 kg N/ha at topping resulted in a substantial increase of the saleable yield for all reaping groups. Removal of priming leaves plus the addition of supplementary nitrogen did not increase leaf expansion. It did not lower yields but it improved the quality of the cured leaf and this resulted in better income basing on the gross margin of the expanded project. It is therefore concluded that the removal of the lowest 4 leaves plus an addition of an extra 10 kg N/ha neither lowers yield nor quality but brings with it income benefits to the farmer.