Effect of K application method on K absorption and yield of sweet potato

【Objectives】 Potassium is particularly important for starch tuber yield of sweet potatoes. In this research, different potassium application methods were tested in sweet potato in Jiaozhou City and Jimo City.【Methods】 Two kinds of soils, Shajiang black soil in Jiaozhou City and aeolian sandy in Jimo City, were used in the experiment, and four treatments were designed: K0(CK, no potassium fertilizer),K1(all potassium basal applied),K2(half potassium fertilizer as basal and half as top dressing at the ridged covered stage)and K3(all potassium fertilizer top dressed at ridge covered stage).【Results】 Three potassium applications significantly increased the biomass, nutrient uptake and yield of sweet potatos. Compared with K3 and K1 in Shajiang black soil, the yield of K2 was increased by 18.7% and 10.4%. The yields differences between K3 and K1 were not significant. In aeolian sandy soil, the yield of K2 was increased by 35.3% and 17.3% compared with K3 and K1, The yield in K1 was significantly higher than that in K3. The highest yield achieved in K2 was significantly higher than in K1 and K3 in both the two tested soil types. Compared with K1, K2 significantly improved the tuber growth rate, accumulation of potassium at late growing stages(115 days to 150 days), potassium harvest index, potassium day accumulation rate, partial productivity, potassium efficiency and potassium agronomic efficiency. Compared with K3 and K1, the potassium apparent use efficiency in K2 was increased by 12.5% and 8.8% in Shajiang black soil, 13.9% and 13.2% in aeolian sandy soil, respectively. Under the same way of potassium application, the accumulation of nitrogen and potassium, the biomass and yield of sweet potatoes in shajiang black soil were higher than in aeolian sandy soil, but the potassium day accumulation rate and potassium use efficiency in aeolian sandy soil were higher than in shajiang black soil.【Conclusions】 Half potassium as basal dressing and half as top dressing at the ridge covered stage is an appropriate method in aeolian sandy soil.