ImprovImproving Yield and Quality of Kohlrabi Stems Growing under NaCl Salinity Using Foliar Application of Urea and Seaweed Extracting Yield and Quality of Kohlrabi Stems Growing under NaCl Salinity Using Foliar Application of Urea and Seaweed Extract

Abstract

Under unfavorable growth conditions, the swollen tuber-like stem (marketable part) of kohlrabi plant become woody and tough which reflected on reducing its revenue. Studies on the effect of salinity on growth and quality of kohlrabi stems are extremely limited. Consequently, an outdoor pot experiment was conducted to evaluate the effect of different levels of NaCl salinity (0, 1000, 2000, 3000, 4000, 5000 and 6000 ppm) on the growth attributes of kohlrabi. Results of the preliminary experiment indicated that kohlrabi is a moderate salinity sensitive plant, where growth of the stem significantly reduced after exposing to NaCl at 3000 ppm, whereas the high reduction in growth of both leaves and stems recorded when the applied concentration of NaCl is equal or more than 4000 ppm. NaCl salt as a source of salinity stress was applied at 0 and 4000 ppm in the subsequent main experiment to study the promotive effect of urea and seaweed extract on enhancing the growth and quality of kohlrabi plant under salinity conditions. The concentration of foliar application treatments were four levels for urea (0, 5, 10 and 15 g/l) and two levels of seaweed extract (0 and 0.5 g/l), in addition to their combinations. Application of NaCl at 4000 ppm reduced leaf f.w, leaf area, leaf area index, photosynthetic pigments and total soluble sugars (TSS), which in turn reflected on the reduction of stem f.w, as quantitative trait. In addition to that, salinity has a negative effect on the quality of kohlrabi stems, through increasing firmness value and fibre %. These negative effects of salinity on quantity and quality traits of kohlrabi plant disappeared when urea as individual applications or combined with seaweed extract were applied to the plant as foliar treatments. Moreover, most foliar treatments enhanced the stem f.w, whereas reduced firmness values and fibre %. Application of combined treatment of seaweed extract at 0.5 g/l + urea at 15 g/l maximized the quality and yield of kohlrabi swollen stems under stressed or non-stressed conditions.