The Physiological Mechanism Of High Water And Nitrogen Use Efficiency For Wheat Intercropping Sunflower In Hetao Irrigation District

For the main intercropping mode and the situation of shortage on water resource in Hetao irrigation area, the experiment systematically researched the plant morphological characteristics, the photosynthetic characteristics, matter accumulation, water and nitrogen use efficiency, yielding characteristics of intercropping wheat and sunflower under the different irrigation and nitrogen application.and revealed the physiological basis of high water and nitrogen use efficiency for wheat intercropping sunflower. The main conclusions arc as followed:Water consumption during the whole growth season increased significantly with the increasing irrigation rates, while water use efficiency (WUE) decreased significantly with the increasing irrigation rates under different irrigation treatments of the wheat intercropping sunflower mode.Compared with the conventional full irrigation treat, intercropping yield and economic benefits of irrigating water 3 times during the whole growth period were higher,but the total water consumption were lower, and WUE increased by more than 30%, achieved the target of water-saving and high-yielding.Plant growth of the intercropping wheat and sunflower was obviously promoted under irrigation and nitrogen application.The leaves’SPAD, Fv/Fm value of water-saving irrigation treatment fell slowly during the later growth stage, thus high photosynthetic efficiency of leaves were remained. The light interception rate of upper part of interplanting group was inceased and light leakage losses of lower part was decreased to coordinate the light condition in the group by increasing the amount of nitrogen application appropriately under water-saving treatment. The higher green leaf area and photosynthetic potential was maintained of later growth period due to the leaf slow declining during filling stage of wheat and sunflower, improving grain filling rate significantly. Dry matter accumulation and population growth rate of later growth period of wheat and sunflower under water-saving irrigation treatment was higher than conventional irrigation treatment and moderate nitrogen treatment performed highest. Leaf area index, photosynthetic potential, the population growth rate,dry matter accumulation and economic yield were significantly positive correlation after flowering of wheat and sunflower.The relationships between ecnomic yield and the amount of nitrogen application and WUE and the amount of nitrogen application showed single peak curve change under two irrigation treatments.Compared with the normal irrigation, crop’s spike numbers per mu increased and grain number per spike and grain weight decreased of wheat, and grain weight per set and grain weight per hundred decreased and seed setting rate increased of sunflower under the water-saving irrigation.There was no significant difference in the yield between the two irrigation modes, but WUE was improved significantly.The amount of nitrogen absorption increased accordingly, but efficiency use of nitrogen decreased significantly with the increasing of nitrogen application. lndexes of efficiency use of nitrogen and total nitrogen rate showed significantly negative correlation. Therefore, in order to achieve water saving, fertilizer saving and higher yield of wheat intercropping sunflower in Hetao plain,the proper nitrogen rate for wheat was 219-229.5kg/hm2 in jointing stage by combining with the first water. The proper nitrogen rate for sunflower was 156-163.5kg/hm2 in flowering stage by combining with the firstwater.