Mineral nitrogen and salicylic acid rates and their effects on yield, quality and alternaria blight incidence in cabbage

Abstract

Cabbage is the main vegetable grown largely in Adarkabrunso/Adeito in the Bosome Freho District in the Ashanti region of Ghana. Lower yields and quality due to Alternaria blight and inappropriate use of fertilizers are setbacks in its production. A study was conducted to assess cabbage yield, quality and resistance to Alternaria blight under different rates of mineral nitrogen fertilizer and salicylic acid in 2019. Oxylus cabbage variety was planted in a randomized complete block design with six treatments: control (NPK (0-0-0) kg/ha), NPK (30-60-60) kg/ha, NPK (60-60-60) kg/ha, NPK (90-60-60) kg/ha, NPK (90-60-60) kg/ha+ 0.25 mM SA and NPK (90-60-60) kg/ha+ 0.5 mM SA which were replicated four times. Of the parameters studied, leaf area, leaf number and circumference of cabbage heads were significantly different whilst cabbage yield, Alternaria blight and pest resistance, number of folded and unfolded leaves were not significant at 5 % probability level. However, treatments (NPK (90-60-60) kg/ha and NPK (90-60-60) kg/ha + 0.5 mM SA gave an equal yield of (50.9 t ha-1) and resisted the Alternaria blight most. NPK (60-60-60) kg/ha induced better leaf area (6.847 m2) and number (19.875). Control plots (NPK (0-0-0) kg/ha) were more resistant to pests, treatments with salicylic acid (NPK (90-60-60) kg/ha + 0.5 mM SA and (NPK (90-60-60) kg/ha + 0.25 mM SA induced better leaf folding and circumferences (56.95 & 55.05 cm) respectively, Control (NPK (0-0-0) kg/ha) and (NPK (30-60-60) kg/ha) controlled unfolded leaves in cabbage. Meanwhile treatments with highest nitrogen rate NPK (90-60-60) kg/ha stood tall interms of yield, quality, cost and resistance to Alternaria blight in cabbage compare to NPK (90-60-60) kg/ha + 0.5 mM SA.