| Canola canopy structure could be changed by different agricultural practices, especially by sowing date, plant density, fertilizer rate and row-spacing configuration and other agricultural management practices. These practices could change the state of the canopy radiation distribution, regulating radiation use for population plants, and ultimately affect the canola seed yield.Two representative canola varieties in Yangtze River Basin were used in this study, and there were different sowing dates, plant densities and nitrogen rates. Measurements for photosynthetically active radiation interception dynamics were carried out for canola canopy with different row-spacing configurations under varied plant densities. Effects of different agricultural practices and their interactions on radiation utilization of canola and grain yield were studied in this research. The main findings are as follows:1. Different agricultural practices on canola canopy microenvironment have some moderating effect. Increasing canola plant density, there is an increasing trend in the temperature and humidity within the canopy, while decreasing CO2 concentration; wide-narrow row spacing ratio of cropping patterns is more conducive to increased temperature and humidity within the canopy. During the budding and flowering stage of canola, CO2 concentration and canopy temperature substantially increased in humidity with the delayed sowing date.2. Increaseing nitrogen rate within a certain range, early sowing and reducing the plant density could be in favor of canola individual plant growth and development. From 90 kg/ha to 270 kg/ha nitrogen, the number of green leaves each plant can increase by 5.4-19.5%(0.5-1.5 leaves), plant dry weight increased by 45.5%-74.8%; increasing plant density from 15 plants/m2 to 75 plants/m2, green leaves would reduce by 3.9-18.9%, plant dry weight reduce by 32.8%-70.5%, leaf dry weight reduce by 33.2% and 54%, bud dry weight decrease by 51.5% and 69.4%, pod dry weight reduce by 60.9% and 78.3%; compared with 15 September, with sowing date delaying 15, 30 and 45 days, the plant dry weight decreased by 16.5%, 41.1% and 54.2%; row-spacing configuration 20 + 40 cm(R2) increased the bud dry weight by 1.2%, 12.4% than 20 + 20 + 20 + 60 cm(R3) and 30 cm(R1), respectively; and R2 increased pods dry weight significantly by 13.4% and 13% compared to R3 and R1.3. Application of wide-narrow row arrangements could be in favor of the establishment of appropriate canola plsnt population structure under high-density planting. Density from 15 plants/m2 to 45 plants/m2 and 75 plants/m2, the whole growth period of the canopy area index(CAI) increased by 19.1% and 29.6%, respectively; increasing fertilizer rate from 90 kg/ha by 1-2 times, CAI is increased by 55.3% and 90.3%; Under the sowing date of September 30, the average leaf area index was 4.35, 26% higher than the date of October 30; The canola CAI of Huayouza 9 is 7.7 percent higher than Zhongsuang 11; CAI under wide-narrow row R2(20 + 40cm) in the plant density of 45-75 plants/m2 was significant increased. Increasing N 90 kg/ha will increase 1000 pods/m2, increasing 60 branches/m2, and pod layer length will increase by 7.5cm.4. The number of pods and yield per m2 could be increased with increaseing nitrogen rate and plant density and early sowing appropriately. Density from 15 plants/m2 to 45 plants/m2 and 75 plants/m2, yield increased by 4.1-5.3% and 8.3-8.8%, respectively, reduce the number of pods by 46.9-52.1% and 68.2-64.2%, grain weight increase by 0.4-1.1% and 0.7-1.8%. Compared with N06 yield increased by 5.3-8.8% with the fertilizer rate from N12 to N18, yield increase by 36.2-57.9% and 45.2-104%, and pod number will increase by 34.8-53% and 80.6-81%, seed per pod by 0.9-1% and 0.9-1.5%, 1000-seed weight by 3.6-4.3% and 2.1-2.9%; compared with B4,early sowing date of B2 increase yield by 15.7%-35.1%.5. Radiation use efficiency could be increased with increaseing nitrogen rate and plant density and early sowing appropriately. Density from 15 plants/m2 to 45 plants/m2 and 75 plants/m2, radiation capture increase by 10.8-12.3% in canola whole growth period; doubling the nitrogen rate could improve radiation capture by 8-12 percentage points. Under fertilizer rate of 270kg/ha nitrogen, radiation use efficiency is up to 2.16 g / MJ, increased by 26.7% and 16.7% higher than 90kg/ha and 180kg/ha; The relatively high RUE is the sowing date of September 30 and October 15(2.2 g/MJ); RUE in R2 are increased by 6.0% and 2.4% compared with R1 and R3; The RUE of Huayouza 9 is 24.6% higher than Zhongshuang 11.6. High-yielding plant population construction and agricultural practices recommendation. The combined effects of different agronomic pracitices on canopy plant population structure should reach 7760 pods per m2, 250 branches per m2, 36 cm of the pods layer, radiation interception rate of 75%, radiation use efficiency 2.05 g/MJ for the seed yield of 3000 kg/ha. Optimized agronomic measures are the sowing date of September 30 to October 15, planting density of 450,000/hm2, nitrogen rate of 270 kg/hm2, wide-narrow row spacing of 20 + 40 cm, which could be beneficial for improved canola seed yield and radiation use efficiency. |
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