[Effects of water and nitrogen coupling on grain yield formation and nitrogen accumulation, transportation of oil flax in dryland].

A completely random split zone experiment with irrigation as main plots and nitrogen application rate as sub-plots was carried out to examine the optimal water-nitrogen coupling mode for oil flax planting in dryland. There were three irrigation levels, no irrigation (0 m3·hm-2, I0), irrigation at 1200 m3·hm-2(I1200) and at 1800 m3·hm-2(I1800); and three nitrogen application rates, no nitrogen (0 kg N·hm-2, N0), 60 kg·N hm-2(N60) and 120 kg·N hm-2(N120). We investigated nitrogen accumulation content at different growth stages, nitrogen transport characteristics after anthesis, grain yield and nitrogen utilization efficiency of oil flax. Results showed that the coupling effects of water and nitrogen application on nitrogen uptake in different organs, nitrogen accumulation during different growth stages and grain yield of dry land oil flax varied greatly. Under no irrigation, nitrogen application was beneficial to stem nitrogen absorption at anthesis and maturity stages, but 120 kg N·hm-2 inhibited it at different irrigation levels. At the 1200 m3·hm-2(I1200) irrigation level, foliar nitrogen content at anthesis stage increased first and then decreased with increasing nitrogen rates, and N60 increased foliar nitrogen content by 11.0% and 28.9% respectively compared with N0 and N120. At the 1800 m3·hm-2(I1800) irrigation level, nitrogen application increased foliar nitrogen content at maturity stage, with that in N60 and N120 treatments being 39.7% and 26.9% higher than N0, respectively. The effects of water-nitrogen coupling on nitrogen accumulation in different growth stages of oil flax was mainly shown after budding stage. Under the same irrigation level, N60 promoted and N120 inhibited nitrogen accumulation in each stage after budding. Nitrogen application increased nitrogen transport rate and contribution rate of leaves and stems under I1200 and I1800. The coupling of I1800 and N60 significantly increased the number of effective capsules per plant and grain yield of oil flax (6.6%-22.8%), which was a suitable water-nitrogen coupling management mode in this area.