Critical leaf S concentration and S requirement of stevia grown in two different soils of Bangladesh

Abstract

Sulphur is one of the essential nutrients for plant growth, protein and chlorophyll biosynthesis and can be supplemented by inorganic fertilizers like gypsum. To examine the effects of S on the growth, leaf biomass yield, S content and uptake and to estimate minimum S requirement and critical leaf S concentration of stevia, an experiment was conducted in the net house of the Department of Agricultural Chemistry, Bangladesh Agricultural University during March to July 2012 in two different soils of Bangladesh. Six levels of S (0, 10, 20, 30, 50 and 80 kg ha^-1) were applied. Plant sampling was done at 15, 30, 45 and 60 days after planting (DAP) to measure plant height, number of branches and leaves, dry weight of leaves, leaf area and leaf S concentration. All the studied parameters of stevia plant were significantly affected by different levels of S. The highest values of the parameters except S concentration were obtained from 30 kg S ha^-1 and the lowest from S control. Sulphur application increased leaf dry yield at harvest by 54 to 573% in acid soil and 75 to 545% in non-calcareous soil, respectively over control. The growth of the plant was rapid at the later stages (30 to 60 DAP). Leaf S content was directly proportional with the increased levels of S. Critical S concentration to achieve 80% of the maximum production of stevia leaf was estimated to be ca 0.125 and 0.137% in the leaves of stevia plants grown in acid and non-calcareous soils, respectively. The minimum amount of S for maximum leaf biomass production in the plants grown in acid and non-calcareous soils was also estimated to be ca 40 and 45 kg ha^-1, respectively. The overall results suggest that farmers can be advised to apply S @ 40 kg ha^-1 in acid soil for getting 80% production of stevia leaf under the agro- climatic conditions of Bangladesh Agricultural University.