| Jujube-cotton intercropping system is one of major composit ecosystems in agriculture and forestry intercropping mode. However jujube trees could make shading effect, thus affect the yield and quality of cotton. N plays an important role in cotton growing stage, so it is an problem which require immediately solution to confirm appropriate N levels, improve N utilization, decline the negative effects to environment. As two of the most important growth factors, illumination shortage caused by intercropping and nitrogen interactively affect the production and distribution of material, and carbon and nitrogen metabolism. So studying on theeffects on different nitrogen levels of cotton and confirming appropraite N levels in jujube-cotton intercropping system to provide theory basis for making nitrogen management optimization and enhancing cotton yield and quality. The study are as follows:1. The ralation between photosynthetic rate(Pn) and nitrogen levels is quadratic curve, the Pn will not increase as well as certain nitrogen content has been reached. The intercellular CO2concentration (Ci) increased along with the net photosynthetic rate (Pn), stomatal conductance (Gs), the transpiration rate(Tr) reduced, it indicated that assimilatory power shortage caused by intercropping limited carbon assimilation. The Pn, Gs, Tr of leaves in close area were higher than far area under lower nitrogen levels, and the minimal fluorescence (Fo) risedin close area. It seemed that nutrigen levels had little effect on Fo and the maximum photochemical efficiency of photosystem II (Fv/Fm) when the cotton was shaded, and nutrigen level should be improved if higher quantum yield of electron transport (ΦPSII) was going to be increasing.2. The cotton dry matter and nitrogen accumulation in different treatments fit the Logistic equation. The beginning of speed nitrogen accumulation were3-4days earlier than thatof biomass. The N accumulation in close area from jujube were higher than far area underlower treatments (NOã€N30), and it had more N accumulation in higher nitrogen levels under unshaded treatment.3. Intercropping could improve cotton yield through boll numbers and boll weight of per plant in the condition of reasonable nitrogen levels. The close area needed less nitrogen than far area while reached higher yield. Appropriate nitrogen levels and management can alsoenhance cotton fiber quality, increase the length and intensity, and insur micronaire in good range, but it had no effect on fiber elongation or uniformity. Shading could decline fiber intensity, elongation, uniformity and micronaire. Compared with the above part cotton fiber, middle part needed more nitrogen, and unsufficient nitrogen mostly affected intensity and micronaie while excess nitrogen affected fiber elongation and uniformity. So intercropping and nitrogen levels make a big difference to above and below aparts in fiber quality.4. In conclusion, lower nitrogen levels in close area advanced carbon-nitrogen metabolismlevel and balanced the relation of the sink-source. It indicated that nitrogen fertilizer should be supplied more in enough illumination, but it was opposite in non-enough illumination to avoid excessive growing. In this experiment, the nitrogen application rate shoud among207kg/hm2～310kg/hm2... |
