Balanced below- and aboveground growth improved yield and water productivity by cultivar renewal for winter wheat

1. Test name: Balance aboveground and underground growth through winter wheat variety renewal in 2017-2020 to improve yield and water productivity2. Data collectors: Zhang Xiying, Chen Suying, Shao Liwei, Li Haotian, Li Lu, Liu Na3. Test data year: 2017-20204. Test site: Luancheng Agricultural Ecosystem Test Station, Chinese Academy of Sciences (37 ° 50 ′ N, 114 ° 40 ′ E, altitude 50.1m)5. Research objectives:(1) In the context of unstable climate and decreasing water resources, meeting the growing population's food demand is a major challenge. The main way to solve the above problems is to improve crop production efficiency and resistance to adversity by improving planting technology and varieties.(2) Through environmental regulation or genetic improvement, the sensitivity of crops to water deficit can be reduced, and the yield potential of crops under water limited irrigation can be improved.6. Test design:(1) The experiment was conducted at Luancheng Agricultural Ecosystem Experiment Station of Chinese Academy of Sciences, and the data included the relevant data of winter wheat growth season in 2017-2020. The field water holding capacity of 0-20cm topsoil in the test plot is 0.24g/kg, the withering humidity is 0.09g/kg, the organic matter is 21.7g/kg, the total nitrogen is 1.2g/kg, the available nitrogen is 108.1m/kg, the available phosphorus is 28.3mg/kg, and the available potassium is 113.2mg/kg.(2) The varieties used in this study were popularized in different years from 1970's to 2010's, and were widely planted locally after promotion, including Jimai 7 promoted in 1976, Jimai 26 promoted in 1988, Jimai 30 promoted in 1992, Shi 4185 promoted in 1999, Kenong 199 promoted in 2006, and Shimai 22 promoted in 2013. In 2017-2020, about October 15 of each year, 30 seeds will be randomly selected and evenly sown in each barrel. After sowing, the soil surface of barrel planting shall be covered with 1cm thick fine sand to reduce soil evaporation. During the three leaf period of winter wheat, there are 20 seedlings per tube. The total amount of irrigation in winter wheat growth period is set as high irrigation level (HW) 320mm, medium irrigation level (MW) 240mm, and low irrigation level (LW) 180mm. A total of 18 treatments were set for 3 irrigation levels and 6 winter wheat varieties. Each treatment has four replicates, and 72 barrel plants are arranged in the field. The barrel planting of different treatments was arranged randomly.7. Measurement and method of indicators:(1) Phenology and leaf photosynthesis of winter wheat growth season in 2017-2020: During the three growth periods of winter wheat in 2017-2020, regularly monitor the start and end of all key growth periods of barrel planting. Take management measures consistent with the surrounding farmland to prevent pests and weeds from affecting crop yield. In the jointing and filling stages of winter wheat, four fully developed flag leaves in each barrel were randomly selected, and the photosynthesis rate (Pn) in the middle of the leaves was measured by the CO2 gas exchange system (LI-6400, LI-COR Inc., USA) from 10:00 to 14:00 local time in sunny weather.(2) Biomass, grain yield and yield factors: When harvesting in the three winter wheat growing seasons from 2017 to 2020, cut the aboveground parts of each barrel planted plant along the ground level, measure the plant height and spike number of each treatment of winter wheat manually, air dry the crop samples to constant weight, and weigh them to obtain the total aboveground biomass. Use a thresher to separate straw and grain, weigh to get the grain weight (the average moisture content of the grain is 13%), and measure the total number of grains through an automatic grain counting machine. The average value of four replicates was taken for the yield of each treatment, and the average environmental yield was calculated as the average value of the grain yield of six wheat varieties under each water treatment. Harvest index (HI) is calculated as grain weight/total aboveground biomass.(3) Measurement of soil water content and root system at harvest time: after harvesting the aboveground part of winter wheat in each growing season, the PVC pipe is excavated from the field and divided into 20 cm sections from top to bottom. Take about 100g soil sample from each section and put it into an aluminum box, and measure the soil water content by drying method. The rest of the soil segments are put into fine mesh bags for washing to extract root samples, and the samples are dried in an 80 ℃ oven to determine the dry weight. The root weight density (RWD) is calculated as the sectional root weight/sectional soil volume, the total root weight is the sum of the root weights of each soil layer, and the root shoot ratio (RS) is calculated as the total root weight/aboveground biomass. In this study, root efficiency (RSE) is defined as the grain yield corresponding to unit root weight.(4) Winter wheat yield and yield components: when winter wheat is mature, determine the number of ears in each barrel, harvest each barrel separately, thresh with a thresher, record the air dried yield (water content is constant at 13%), and determine the 1000 grain weight. After harvest, the aboveground part was tested, the grain number per spike, grain weight and aboveground biomass were measured, and the harvest index was calculated.(5) Evapotranspiration and water productivity during growth period: Evapotranspiration (ET) during growth period of winter wheat is calculated by the following formula: ET=P+I+SWD+CR-R-D. ET is the total evapotranspiration during the growth period (mm); P is precipitation (mm); I is irrigation amount (mm); SWD is soil water consumption (mm); CR is the amount of water that rises from the soil through the capillary to the root zone (mm); R is surface runoff (mm); D is the amount of soil infiltration in the root zone (mm). Under the test conditions of this study, the values of P, D, R and CR are zero. Winter wheat yield level water productivity (WP) is calculated as grain yield/evapotranspiration during growth period.(6) Statistical analysis and drawing: Microsoft Excel 2021 (Microsoft, Redmond, USA) and IBM SPSS Statistics 26.0 (IBM, Stanford, USA) are used for data analysis and drawing. The average values of four replicates in each treatment were used to analyze the correlation between different plant physiological parameters. When the homogeneity test of variance was successful, the least significant difference (LLW) test was performed (P<0.05).