Effects of drip irrigation and nutritional values of potassium, silicon on the incidences and damages of diseases, insect pests and yield of rainy season cassava var Huay Bong 80

Abstract

A cassava field trial was conducted to assess effects of surface drip irrigation (SDI), chemical fertilizers (CF) and rice husk ash(RHA) on leaf-K and leaf-Si concentrations, fresh root yield, the incidences and damages of disease and insect pests intensities of cassava grown during wet season 2012 to 2013 in Nakornratsima province. At 6 and 9 months after planting, applications of SDI, CF and RHA markedly gave higher K and Si concentrations in cassava leaves than those of cassava grown under additions of CF and RHA. Potassium and Si concentrations in plant leaves at 6 months after planting did not significantly correlated with the incidences and damages intensi-ties of leaf brown spot disease and the incidences of pink mealy bug (PMB) and whiteflies(WF). Nevertheless, the negatively coefficient of determination values obtained tended to imply the enhancing roles of higher leaf-K and of leaf-Si contents on depressing the incidences intensities of PMB and WF. The pronounced - depressing effect of SDI on the incidence of PMB over the RF was also observed. Additionally, at 10 months after planting, higher contents of leaf-K and leaf-Si was also exerted tremendous effect on mitigating the incidence intensity of WF. Cassava grown under SDI markedly out yielded the rain-fed ones gave higher fresh root yield about 6,805 kg/rai. Application of CF and /or RHA also gave higher fresh root yield than those grown without CF and RHA. The application of RHA alone had significant effect on increasing fresh root yield of cassava. The best treatment combinations that produced the highest fresh root yield comprises the uses of SDI altogether with the CF grade 15-7-18 at 50 kg./rai, CF grade 0-0-60 at 25 kg./rai and RHA at 150 kg./rai.