Differences In Nitrogen Efficiency Among Potato Varieties And Their Physiological Mechanisms

Excessive application of nitrogen fertilizer is very common in potato production,which not only makes the low nitrogen fertilizer utilization efficiency of potato,but also brings serious environmental risks.Breeding nitrogen-efficient varieties is the main way to solve this problem.In this study,potato genotypes widely collected in the northern area were used as the test materials,and normal nitrogen application and nitrogen-free treatments,were set.Through two years of field experiment,different nitrogen efficiency of potatoes were classified based on the yield.Physiological characteristics of nitrogen absorption and utilization in potato varieties with different nitrogen efficiency types were compared and for mechanism exploring.The following main findings were obtained:1.Based on the average yield of 20 potatoes collected under nitrogen and no nitrogen fertilizer conditions,four nitrogen efficiency types were divided: double high,low nitrogen and high-efficiency,double low,high nitrogen and high-efficiency type,including 8 for double high and double low types,and 2 for two other types,respectively.2.A further study were perforemed with double high type(Jizhang 12),double low type(Mc Cann),high nitrogen high efficient type(Huasong 7),low nitrogen high efficient type(Qingshu 9)as test materials.It showed that total root length,total root surface area,total root volume exhibited significant positive correlation with plant nitrogen accumulation and nitrogen absorption efficiency.Developed roots laid a foundation for double high type potatoes to obtain more nitrogen.Under nitrogen application the dry matter accumulation of double high type was the highest,which was 102.99%,30.62% and 35.31% higher than that of double low type,high nitrogen efficient type and low nitrogen efficient type,respectively;and the nitrogen absorption efficiency was the highest,reached 84.42%.The dry matter accumulation of double low type was half of that of double high type,and the highest nitrogen absorption capacity was only 48.41%;The high nitrogen efficient type has a strong dry matter accumulation ability under normal nitrogen supply conditions,and there is no difference in nitrogen absorption efficiency between the high nitrogen efficient type and the double high type;The dry matter accumulation of low nitrogen efficient type was 6.45%,52.61% and 51.01% higher than that of double high type,high nitrogen efficient type and low nitrogen efficient type respectively without nitrogen application,and the nitrogen absorption efficiency reached 79.49%.3.Under no nitrogen supply and normal nitrogen supply,the yield of double high type was 48.32%,27.59% and 20.31% higher than that of double low type,high nitrogen efficient type and low nitrogen high efficient type respectively.Under the condition of no nitrogen supply,the nitrogen transport efficiency from stems and leaves of double high type was the highest,13.58%,26.56% and 76.70% higher than that of double low type,high nitrogen high efficient type and low nitrogen high efficient type respectively.The low nitrogen high efficient type had the lowest contribution rate of nitrogen transport in stems and leaves to tubers,56.07% lower than the double high type.Double high nitrogen utilization efficiency is the highest;The nitrogen use efficiency of double low type was4.07% lower than that of double high type;The nitrogen use efficiency of double high type was higher than that of nitrogen efficient type,which was 24.55% higher.The nitrogen use efficiency of the low nitrogen high efficient type was the lowest,which was only 70.55%of the double high type.4.The nitrogen absorption efficiency of four types showed as high-efficiency type,double-high type > low-nitrogen and high-efficiency type> double-low type,while the nitrogen use efficiency of the four types of genotypes is as follows: double high type,double low type > high-nitrogen high-efficiency type > low-nitrogen high-efficiency type.