Response Of Grain Filling Characteristics,Quality Formation And Yield Of Sunflower To Water And Nitrogen Coupling

To reveal the regulatory role of irrigation N application on sunflower growth and seed filling and the specific effects of irrigation N application on yield and quality formation,edible sunflower(Longkui 27)was studied in 2021 and 2022 in the dry crop area of Wuchuan at the northern foot of the Yin Mountains in Inner Mongolia in the northern agro-pastoral mosaic zone using a split-zone experimental design with three irrigation patterns as the main factors and three N application levels as the secondary factors.The main results were as follows:1.Irrigation and nitrogen application had a significant effect on the yield of sunflower,and irrigation mainly increased the yield by increasing the 100-grain weight(the average100-grain weight of W1 and W2 increased by 2.06 g and 3.18 g,respectively,compared with no irrigation).Nitrogen application increased the yield by increasing the 100-grain weight and increasing the number of disks(the average 100-grain weight of N1 and N2 increased by 1.85 g and 1.72 g,and the number of disks increased by 72 and 100,respectively,compared with no nitrogen application).Optimizing water and nitrogen management can increase crude fat content and the proportion of unsaturated fatty acids.2.Richards model can accurately simulate the dynamic process of sunflower aboveground dry matter accumulation.Nitrogen application made sunflower enter the rapid increase period of dry matter accumulation in advance.Compared with no irrigation treatment,irrigation at seedling stage and squaring stage delayed the time to enter the rapid increase period but the accumulation rate was higher,and irrigation at flowering stage and filling stage delayed the end time of the rapid increase period.3.More irrigation is more conducive to the accumulation of dry matter in various organs of sunflower,but not conducive to the transport of dry matter.Nitrogen application increased the dry matter accumulation of sunflower organs.Irrigation and nitrogen application promoted the production of photosynthesis in leaves after anthesis by increasing the dry matter accumulation of sunflower stems and leaves,thereby increasing yield.Dry matter transport has little effect on yield,and the improvement of yield mainly depends on the better photosynthetic production of leaves after flowering.Although the grain yield under better water and nitrogen conditions is high,its economic coefficient is often low,which may be an important factor limiting the further increase of yield.4.Richards equation is also suitable for simulating sunflower grain filling.The grain filling process was mainly affected by irrigation.Although irrigation reduced the duration of grain rapid growth period,it increased the grain filling rate.In general,irrigation increased grain weight.Irrigation and nitrogen supply affected the absorption and utilization of a large number of nutrients in grains,and ultimately affected the accumulation of nitrogen,phosphorus and potassium in grains.5.With the increase of irrigation,the total uptake of NPK in the aboveground part of sunflower showed an upward trend,but the physiological utilization efficiency and harvest index of NPK showed a downward trend,which indicated that drought stress improved the transport of NPK and made sunflower use of limited NPK resources to create more dry matter.Excessive nitrogen application exceeded sunflower nitrogen demand.Sunflower filling stage has a certain nitrogen demand and appropriate nitrogen application does not meet the nitrogen demand of sunflower filling stage.6.Nitrogen application significantly increased the yield of sunflower.The agronomic efficiency and nitrogen use efficiency of moderate nitrogen application were higher,which were 1.14 times and 0.91 times higher than N2,respectively.The yield of sunflower without irrigation is very low,but its water use efficiency is high.Under the condition of W2,there are many ineffective irrigations that are not used by sunflowers,resulting in the irrigation efficiency of W1 being 53.73%higher than that of W2.Considering the three factors of water saving,fertilizer saving and high yield,W1N1 nitrogen application and irrigation strategy(nitrogen application rate:135 kg/hm~2,irrigation amount:900 m3/hm~2)was recommended.