Effect of different nitrogen level on root morphology and nitrogen utilization of oil flax

In order to identify the effect of different nitrogen level on root morphology and nitrogen utilization efficiency of oil flax,a soil column experiment was conducted with 4 pure nitrogen application rate: without nitrogen( N0),low nitrogen( N1,78. 75kg·hm- 2),medium nitrogen( N2,105kg·hm- 2) and high nitrogen( N3,131. 25kg·hm- 2). Oil flax cultivar Longyaza 1 was used. Results showed that root growth was inhabited by nitrogen application in fir shaped period. However,root length,diameter,surface area and volume initially were raised by the increase of nitrogen,and decreased under N2 after squaring. Root distribution under 40cm- layer soil was increased under N2. Shallow roots increased under higher nitrogen( N3) application in late growth stage. Root-shoot ratio was gradually decreased along with the growth,but was significantly improved under N2 in late period.Under N2 treatment,grain yield reached the highest. After takeng into account of grain yield and nitrogen utilization,the nitrogen fertilizer rate of 105kg·hm- 2was recommended.