Response Of Sunflower Canopy Senescence And Soil Structure To Subsoil And Increasing Density

Increasing density is one of the basic ways to achieve high yield of crops,but Increasing density intensifies the senescence process of sunflower individuals,and subsoiling can alleviate the canopy senescence caused by the increase of density.In this experiment,the senescence characteristics of sunflower were explored from the aspects of canopy senescence and photosynthetic characteristics under the conditions of different planting densities of 45 to 7500plants/ha,one typical sunflower(edible sunflower)variety and one oil sunflower(oil-type sunflower)variety.The results are as follows:1.Subsoiling significantly reduced soil compactness,bulk density,increased soil porosity and soil water content.subsoiling 45 cm can effectively improve the soil bulk density and soil three-phase of plant 0-40 cm,and subsoiling 30 cm can effectively reduce the soil bulk density and soil three-phase of 0-20 cm.2.Under different tillage methods and densities,leaf senescence in different layers of sunflower showed that the lower leaf was earlier than the middle leaf and the upper leaf,and the upper leaf was the slowest senescence rate.The senescence rate of leaves at low density was lower than that of high density,and the senescence of sunflower leaves was delayed by subsoiling and shallow rotation,and the anti-senescence property of sunflower was strongest when 45 cm was subsoiling.With the increase of density,the senescence rate of the canopy was accelerated.The fuzzy membership function value of canopy anti-aging showed that the content of malondialdehyde MDA in the leaves of shoot affected the senescence of plants.3.Under the same tillage pattern and different density,the photosynthetic characteristics,seed characteristics and senescence enzyme activities(superoxide dismutase,catalase,peroxidase)of sunflower decreased with the increase of planting density.LAI and MDA increased with the increase of density.Under the same density and different tillage methods,the light rotation of subsoiling improved the photosynthetic characteristics,seed characteristics and yield components of sunflower,improved the anti-aging ability of sunflower and improved the soil physical characteristics.The overall performance is:S1>S2>S3.4.There was a significant positive correlation between the maximum filling rate of sunflower seed and grain weight,and a significant negative correlation between the time when the maximum filling rate was reached and the grain weight.Under different tillage methods,the time of maximum filling rate of sunflower was the slowest in S1 treatment,followed by S3.5.Under different tillage methods,the yield components and seed characteristics of sunflower were significantly improved by deep loosening and shallow rotation,and the yield components and seed characteristics of sunflower decreased with the increase of density.Subsoiling can reduce the variation of sunflower seed characteristics and yield components caused by the increase of density.To sum up,although sunflower varieties have higher yield under high density conditions,they are mainly related to the growth of sunflower varieties.There was a higher LAL in the long process,but the increase of density accelerated the senescence of sunflower canopy and reduced the photosynthetic characteristics.Subsoiling reduced the difference of sunflower photosynthetic characteristics,seed filling rate,antioxidant enzyme activity and anti-aging coefficient between high and low density.The results showed that deep pine could effectively improve the "density" effect caused by the increase of density,increase photosynthetic characteristics,anti-senescence coefficient and reduce the number of dead leaves.