Characteristics of nitrogen, phosphorus and potassium uptake and accumulation of potato in Ningxia

【Objectives】Characteristics of nitrogen (N), phosphorus (P) and potassium (K) uptakes of potato plants have been researched worldwide, but few did in Ningxia region.There are not necessary parameter for potato formula fertilization technology, resulting in blind fertilization in production practice. Therefore,characteristics of absorption and accumulation of N, P, and K nutrients were studied according to soil condition of potato planting bases in Ningxia for providing a scientific basis for the potato precise fertilization.【Methods】Field experiments were conducted in potato bases in four counties of Ningxia in 2012. The fertilizer applying rates were made in accordance with the local recommended fertilization. 70% nitrogen fertilizer, total farmyard manure and phosphorus and potassium fertilizers are basal applied, and 30% nitrogen are topdressed at the budding period of potato. Plant samples were collected to test fresh weights and dry matters of different organs at different growth stages. The contents of N, P, and K in roots, stems, leaves and tubers were determined after the plant samples were dried at 70℃. The dry matter accumulation of N, P and K was calculated.【Results】1) The amount of dry matter accumulation increases with potato growth period and can be modeled as a Logistic curve. The accumulated amounts of dry matter at the seedling, tuber formation, tuber bulking and starch accumulation stages account for 5%, 20%, 40% and 35% of total cumulative amount, respectively. 2) The nitrogen contents in potato plant decrease with potato growth and the coefficient of variation is high. The phosphorus and potassium contents in potato plant increase first and then decrease with potato growth, but the coefficients of variation are low. Thehighest contents of nitrogen and phosphorus are in leaves, while the highest potassium content in stems. 3) The absorptive amounts of N, P and K at the seedling stage account for about 11%, 6% and 8% of the total amount in the whole stages, about 28%, 23% and 31% at the tuber formation, and about 36%, 39% and 41% at the tuber expansion stage, and about 25%, 31% and 20% at the starch formation.The accumulation amounts of N and P in tubers account for more than 60% of the total accumulation at the maturity period and K about 50%. 【Conclusions】Under the tested soil condition, the accumulated amounts of dry matter and absorptive amounts of nutrients (N, P and K) by potato are different in different growth stages and potato organs.The accumulation of dry matter and absorption of nutrients of potato are in accordance with Logistic curves,showeing obvious stage characteristic for nutrients absorption. The nutrient absorption at the tuber expansion stage is the largest, and those at the tuber formation and starch accumulation stages are low. The ratios of N, P and K uptakes in roots, stems and leaves in the totaluptake decrease with growth stage, while the ratios of uptakes of N, P and K in tubers increase, and the accumulated amounts of nutrients in tubers at the maturity account for more than half of the total nutrients in whole plant.