Cyanogenic glucoside production in cassava: The comparable influences of varieties, soil moisture content and nutrient supply

Varieties and soil moisture content are the two agronomic factors mostly pointed out as influencers of cyanogenic glucoside production in cassava. The role of soil nutrient supply is however often overlooked or minimised, despite its known influence on cyanogenic glucoside production. A pot experiment was hence carried out to determine whether soil nutrient supply had an equal influence on cyanogenic glucoside production in cassava, as varieties and soil moisture content. The cassava varieties, Kiroba (a sweet cassava variety) and Salanga (a bitter cassava variety), were used in the experiment, together with three soil moisture treatments that respectively induced severe moisture stress, moderate moisture stress and no moisture stress (optimal soil moisture conditions where plants were kept well-watered). The soil nutrient treatments used depicted conditions of low, moderate and high nutrient supply and consisted of increased levels of N, P and K, applied at rates of 0-0-0; 0-0-25; 25-5-25 and 50-13-50 mg N-P-K/kg (depicting field based fertiliser rates of; 0-0-0; 0-0-50; 50-10-50 and 100-25-100 kg N-P-K/ha, respectively). Total hydrogen cyanide (HCN) levels in cassava leaves were used to indicate the effects of the three factors on cyanogenic glucoside production. The results of the study showed that nutrient supply had a significantly (p