Research On The Potentiality Of Increasing Densities Of Dry Land Oil Flax (Linum Usitatissimum L·) In Different Nitrogen Applications

"Longya Hybrid No.1" was chose as experimental material in our research. Under field conditions, effects of planting density on dry matter production, fertilizer-nitrogen use efficiency, non-structural carbohydrate and yield of oil flax in different nitrogen applications were studied. The main results were as follows:(1)The leaf area per plant, leaf area index and chlorophyll content of oil flax showed a sigenificant unimodal curve under different nitrogen applications and planting densities. In the same nitrogen application level, inceasing plant densities could reduce the area per plant and increase the leaf area index. With the growth stages advancing, leaf area of oil flax increased with nitrogen applications increasing in the same planting density after flowering stage due to increased collective competition, and then, leaf area index of oil flax was highest under high nitrogen of high density treatment. Under the same nitrogen application level, photosynthetic potential of increasing planting density increased in every growth stage;total photosynthetic potential of oil flax increased by 13.59%~100.27% in the whole growth stage when the planting density was changed from 4.5 millon per hectare to 10.5 million hectare.(2) The contents of WSC of oil flax in different organs at the maturation stage for the different treatments were lower than that at the flowering stage, while the starch contents had an opposite law. Increasing fertilizer applications reduced the total amount of non-structural carbohydrate and the amount of NSC of transportation of the vegetative organs of oil flax before flowering, but increased the amount of NSC of transportation of the vegetative organs of oil flax before flowering. When the nitrogen applications were between 0 kg/ha to 75kg/ha, the starch content of oil flax leaves and non-grain organs decreased with nitrogen applications increasing at the flowering stage, while the contents of starch of stems had an opposite law. Under high nitrogen applications, increasing planting density decreased the WSC content of leaves and increased the WSC content of stems and non-grain organs; and then, the NSC content of leaves and stems were promoted, but, the content of NSC of non-grain organs showed no significant effect. The main contribution of NSC to grain was after flowering. The contribution rate of the NSC of vegetative organs to the NSC of grain of oil flax increased with density increasing after flowering when the nitrogen applications were 75 kg/ha and 150 kg/ha, and the contribution rate increased by 28.46% ~ 48.40% at thelower density.(3) The amount of dry matter accumulation per plant and per unit of oil flax increased with the growth stages advancing at the different nitrogen applications and seeding density plant.When the planting density was 10.5 million plants/ha, increasing nitrogen applications could increase dry matter accumulation per plant of oil flax before flowering. At the levels of no nitrogen application and nitrogen application of 75 kg/ha, the amount of dry matter accumulation per plant under the treatment of 4.5 million plants/ha was higher significantly than the treatment of 10.5 million plants/ha, which increased respectively by 33.33%,11.63% and 50.65%, 52.24%; In the same level of nitrogen application, increasing planting density could increase group dry matter accumulation. Oil flax dry matter allocation volumes of grain were lowest at the maturation stage in high planting density for single plant, and the performance of group showed an opposite trend. At three levels of nitrogen application,increasing planting density could increase transportation volumes of storage assimilates in vegetative organs before flowering, which increased respectively by 71.46%, 43.06% and49.31%; Under the same planting density, increasing nitrogen application could reduce transportation volumes of storage assimilates in vegetative organs before flowering. When the nitrogen application was 75 kg/ha, the contribution rate of storage assimilates to grain of oil flax after flowering was higher significantly other treatments under the treatment of high planting density, which increased respectively by 5.69% ~ 31.85%.(4) Under different nitrogen applications, increasing seeding density could increase aboveground amounts of nitrogen accumulation of oil flax at the different growth stages;When the nitrogen application were 75 kg/ha and 150 kg/ha, increasing seeding density enhanced the amounts of nitrogen accumulation flowering and ratios of nitrogen accumulation between the flowering stage and seeding stage, which increased by55.15%~70.89% and 58.98%~73.28%. Increasing nitrogen application made the nitrogen absorption efficiency decrease by 46.00%~67.58%, while increasing planting density increased nitrogen uptake efficiency. Increasing planting density could increase nitrogen storage then re-transportation of the vegetative organs before flowering, while increasing nitrogen application increased the amounts of nitrogen accumulation after flowering.Nitrogen utilization efficiency of oil flax under the condition of increasing planting density increased respectively by 23.52% and 21.54% compared with the treatment of low plantingdensity.(5) The grain yield, effective numbers of capsule per unit, grain numbers and thousand-grain weight of different treatments showed a significant positive correlation. In the nitrogen application of 150 kg/ha, increasing planting density increased grain yield of oil flax and reduced its harvest index, namely, the planting density increased from 7.5 million plants/ha to 10.5 million plants/ha, and the grain yield increased by 12.39%, then, the harvest index reduced averagely by 18.18%. Under our experimental conditions, the optimal combination between planting density and fertilizer for oil flax were respectively 150 kg/ha and 10.5 million plants/ha.