Root Vigor and Kinetic Characteristics and Nitrogen Use Efficiencies of Different Potato (Solanum tuberosum L.) Cultivars

In the present study, the root vigor and kinetic characteristics of nitrogen absorption in potato cultivars was investigated through sand cultivation and pot tests with nutrient solution. Four cultivars of potatoes, namely, Feiwuruita, Yunshu301, Liangshu97, and Chuanyu56 were grown in nutrient solution matrix cultures. The result showed that: (1) Nitrogen uptake rates differed significantly among cultivars with different nitrogen efficiencies; (2) cultivars with High nitrogen-utilization-rate showed significantly higher root vigor, the average root vigor values of cultivars with the high nitrogen-utilization were 115% at seeding stage, 53% at tuber-bulking stage, and 18% at mature stage, respectively, higher than those of cultivars with the low nitrogen-utilization; and (3) Root vigor varied according to growth stage and nitrogen supply i.e. cultivars with high nitrogen-utilization-rate showed enhanced root vigor at the seedling stage under low-nitrogen conditions, while cultivars with low nitrogen-utilization rate showed reduced root vigor at the tuber-bulking and mature stages under high-nitrogen conditions. The kinetic characteristics of nitrogen uptake differed significantly among cultivars: (1) In comparison with cultivars with the low, high nitrogen-utilization showed lower K-m and higher V-max values; (2) The K-m value for nitrate nitrogen uptake was higher than that for ammonium nitrogen uptake, especially in cultivars with low nitrogen-utilization, than those of ammonium nitrogen; (3) In cultivars with low nitrogen-utilization, the V-max value for nitrate nitrogen was lower than that for ammonium nitrogen; and (4) In cultivars with high nitrogen-utilization, the V-max value for nitrate nitrogen was the opposite. The study provides a basis for breeding high nitrogen-utilization cultivars, thereby improving the efficiency of nitrogen fertilization.