RESUMEN
The injudicious use of water and fertilizer to maximize crop yield not only leads to environmental pollution, but also causes enormous economic losses. For this reason, we investigated the effect of nitrogen (N) (N0 (0), N60 (60 kg ha-1), and N120 (120 kg ha-1)) at different irrigation levels (I0 (0), I1200 (budding 600 m3 ha-1 + kernel 600 m3 ha-1), and I1800 (budding 900 m3 ha-1 + kernel 900 m3 ha-1)) on oilseed flax in the Loess Plateau of China in 2019 and 2020. The objective was to establish appropriate irrigation and fertilizer management strategies that enhance the grain yield (GY) of oilseed flax and maximize water and N productivity. The results demonstrated that irrigation and N application and their coupling effects promoted dry matter accumulation (DMA) and non-structural carbohydrate (NSC) synthesis, and increased the GY of oilseed flax. The contents of NSC in various organs of flax were closely related to grain yield and yield components. Higher NSC in stems was conducive to increased sink capacity (effective capsule number per plant (EC) and thousand kernel weight (TKW)), and the coupling of irrigation and N affected GY by promoting NSC synthesis. Higher GY was obtained by the interaction of irrigation and N fertilizer, with the increase rate ranging from 15.84% to 35.40%. Additionally, in the increased yield of oilseed flax, 39.70-78.06%, 14.49-54.11%, and -10.6-24.93% were contributed by the application of irrigation and nitrogen and the interaction of irrigation and nitrogen (I × N), respectively. Irrigation was the main factor for increasing the GY of oilseed flax. In addition, different climatic conditions changed the contribution of irrigation and N and their interaction to yield increase in oilseed flax. Drought and low temperature induced soluble sugar (SS) and starch (ST) synthesis to resist an unfavorable environment, respectively. The structural equation model showed that the key factors to increasing the GY of oilseed flax by irrigation and nitrogen fertilization were the differential increases in DMA, EC, and TKW. The increases in EC and TKW were attributed to the promotion of DMA and NSC synthesis in oilseed flax organs by irrigation, nitrogen fertilization, and their coupling effects. The I1200N60 treatment obtained higher water use efficiency (WUE) and N partial factor productivity (NPFP) due to lower actual evapotranspiration (ETa) and lower N application rate. Therefore, the strategy of 1200 m3 ha-1 irrigation and 60 kg ha-1 N application is recommended for oilseed flax in semi-arid and similar areas to achieve high grain yield and efficient use of resources.
RESUMEN
Increasing water shortages and environmental pollution from excess chemical nitrogen fertilizer use necessitate the development of irrigation-nitrogen conservation technology in oilseed flax production. Therefore, a two-year split-plot design experiment (2017-2018) was conducted with three types of irrigation (I) levels (no irrigation (I0), irrigation of 1200 m3 ha-1 (I1200), and 1800 m3 ha-1 (I1800)) as the main plot and three nitrogen (N) application rates (0 (N0), 60 (N60) and 120 (N120) kg N ha-1) as the subplot in Northwest China to determine the effects of irrigation and N rates on oilseed flax grain yield, yield components, water-use efficiency (WUE), and N partial factor productivity (NPFP). The results show that I1800 optimized the farmland water storage and water storage efficiency (WSE), which gave rise to greater above-ground biomass. Under I1800, the effective capsule (EC) number increased significantly with increasing irrigation amounts, which increased significantly with increasing nitrogen application rate (0-120 kg ha-1). Both irrigation and nitrogen indirectly affect GY by affecting EC; the highest grain yield was observed at the I1800N60 treatment, which increased by 69.04% and 22.80% in 2017 and 2018 compared with the I0N0 treatment, respectively. As a result, both irrigation and N affect grain yield by affecting soil water status, improving above-ground biomass, and finally affecting yield components. In addition, I1800N60 also obtained a higher WUE and the highest NPFP due to a higher grain yield and a lower N application rate. Hence, our study recommends that irrigation with 1800 m3 ha-1 coupled with 60 kg N ha-1 could be a promising strategy for synergistically improving oilseed flax WUE, grain yield and yield components within this semi-arid region.
RESUMEN
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.