Response of cassava Huay Bong 80 variety to rates of chemical fertilizer in Yasothon soil series

Abstract

The study on a response of cassava, Huay Bong 80 variety, to different grades of chemical fertilizer was carried out in Yasothon soil series (Typic Paleustult). Treatments comprised applied chemical fertilizer that contained different rates of NPK, having seven treatments. Fertilizer was applied when cassava was two months old and the plant was harvested at ten months of age while soil sample being collected at the harvesting time. The results revealed that cassava clearly responded to different grades of chemical fertilizer applied except for the case of starch content. The use of chemical fertilizer at the rate of 12-4-12 kg N-P₂O₅-K₂O/rai or 3:1:3 ratio significantly gave the greatest fresh tuber yield, starch yield and above ground biomass of 4.64, 1.31 and 1.70 t/rai, respectively. When two times of this ratio (24-8-24 kg N-P₂O₅-K₂O/rai) was applied, the yield decreased significantly which the amount obtained was not different from that gained the control. In a similar fashion, the ratios of 1:1:1 and 2:1:2 statistically gave higher yield when applied at the lower rate (8-8-8 and 8-4-8 kg N-P₂O₅-K₂O/rai) than when applied at the higher rate (16-16-16 and 16-8-16 kg N-P₂O₅-K₂O/rai).Among the plant nutrient concentrations, K in cassava tuber was highly correlated with yield cassava (r=0.61**).The application of chemical fertilizer helped to increase the concentrations and the uptake of nutrients in the plant as compared to no addition of chemical fertilizer. Nonetheless, increasing rates of NPK adversely decreased the amounts of these plant nutrients taken up by cassava. Soil property after growing cassava for one crop revealed that different grades of chemical fertilizer had no residual effect on soil pH but the applications significantly resulted in higher amounts of total N available P and K remained in the soils than did no addition of chemical fertilizer.