Abstract:Radiation use efficiency (RUE) is critical for improving crop yield. The object was to explore the influence of limited irrigation and nitrogen rates on the canopy light interception rate, RUE and yield of maize under border irrigation in salinization irrigation district and realize the efficient utilization of water and nitrogen. A field experiment was conducted in Hetao Irrigation District (HID). The experiment referred to the local conventional irrigation and nitrogen amounts in HID, which had three irrigation amounts (W1, 150mm;W2, 225mm;and W3, 300mm, which was the local conventional irrigation amount) and three nitrogen amounts (N1, 172.5kg/hm2;N2, 258.8kg/hm2;and N3, 345kg/hm2, which was the local conventional nitrogen application amount), meanwhile, interactive experiments were carried out. The leaf area index (LAI), leaf inclination angle (MFIA), photosynthetic active radiation and biomass of maize were measured at the tasseling-filling stage, and soil water and salt contents and the final yield were also measured at the same time. To investigate the mechanism of maize yields in salinization farmland, the correlation analysis and path analysis methods were used. Main conclusions were as follows: the light interception rate (F) of maize was significantly affected by irrigation at the tasseling-filling stage in salinization farmland. At the same nitrogen application rate, the F of W3 and W2 levels were higher than that of W1 level, but the difference of F between W2 and W3 was not significant;the RUE of maize was significantly （P<0.05) affected by irrigation, nitrogen and interaction effects in salinization farmland. Especially, at grain filling stage, RUE was increased with the increase of irrigation and nitrogen rates, but the promotion of RUE had inhibition growth effect when excessive irrigation or nitrogen application was conducted. The RUE of maize was significantly improved with the moderate reduction of irrigation and nitrogen application rate;maize yields were significantly （P<0.05) affected by irrigation and nitrogen in salinization farmland. Moderately reducing irrigation volume and nitrogen rate had no significant effect on maize yields. The yield of W2N2 treatment was 4.01% and 3.91% higher than those of W3N3 and W3N2 treatments （P>0.05), respectively;correlation analysis showed that the yield was positively correlated with LAI, leaf area duration (LAD) and the light interception rate (F) during filling stage. Path analysis showed that LAI had the greatest effect on yield mainly through LAD and F. The RUE had the greatest direct contribution to yield and biomass accumulation, LAI, LAD and F contributed indirectly to yield through RUE;compared with the rest of treatments, the conditions of soil water and salt were obviously improved by W2N2 treatment at the late growth stage of maize in salinization farmland, which was beneficial to promote the development of canopy and increase photosynthetic productivity. The W2N2 treatment with small MFIA and large LAI was beneficial to enhance the light interception rate and area of photosynthesis during the late growth stage. Especially, at late grain filling stage, the LAI and LAD of W2N2 treatment were 7.15%~42.24% and 5.95%~37.60% higher than the rest of treatments, respectively, the decreasing rate of LAI was 37.35% and 53.49% lower than those of W3N3 and W3N2 treatments, respectively, which can construct proper canopy structure, keep high photosynthetic performance and increase biomass accumulation. Thus, W2N2 treatment was beneficial to the improvement of RUE. The RUE of W2N2 treatment was 18.61%~66.93% higher than those of the rest of treatments. Finally, W2N2 treatment achieved the highest yield. In conclusion, the W2N2 treatment had the advantages of saving water and nitrogen, high yield and RUE, as a water and nitrogen management mode, it was very suitable for maize planting in salinization farmland in HID.
