Zinc foliar spray enhances growth, yield and economic return of cassava variety Kasetsart 50 production

Cassava is extensively cultivated in low fertility sandy soils in the Northeast Thailand. Low yield and economic return of cassava grown in this area is partly due to deficiency of micronutrients especially zinc (Zn). The objective of this study was to investigate the effects of foliar spray of Zn on growth, yield, quality and economic return of the cassava variety Kasetsart 50. Five treatments consisted of unfertilized control (T1), recommended fertilizer (formula (formula 15-15-15 at the rate of 313 kg ha-1) (T2), recommended fertilizer plus foliar spray of Zn at the rate of 6.25 kg ha-1 (2% Zn) (T3), recommended fertilizer plus foliar spray of Zn at the rate of 12.50 kg ha-1 (4% Zn) (T4) and recommended fertilizer plus foliar spray of Zn at the rate of 18.75 kg ha-1 (6% Zn) (T5). The treatments were assigned in a randomized complete block design with three replications. The crop was planted in a Korat soil series (loamy sand soil) under rainfed conditions. Data were recorded for soil chemical properties and plant growth parameters at 11 months after planting. The recommended fertilizer plus foliar spray of 2% Zn (T3) resulted in the highest fresh root yield (26.0 t ha-1), starch content (27.83%), and economic return over the fertilizer cost (960.0 USD ha-1), and the increases in fresh root yield, starch content and economic return over the fertilizer cost compared to T1 were 100, 54 and 69%, respectively. The results suggested that foliar spray of 2% Zn together with chemical fertilizer was effective in overcoming Zn deficiency in the loamy sand soils for cassava variety Kasetsart 50 production