| Due to the increasing labor costs,there has stimulated the intensification and large-scale production of rapeseed cultivation,leading to a rapid shift from traditional seedling transplanting to direct seeding in winter rapeseed production in southern China.Rapeseed seeds have relatively small grain weight,and different cultivation techniques have a significant impact on the seedling rate.In this experiment conducted during the 2020～2021 and 2021～2022 growing seasons,two rapeseed varieties,Ningza 1838(with a determined thousand-seed weight of 3.925 g and 3.913 g in respective years)and Qinyou 10(with a determined thousand-seed weight of 3.452 g and 3.446 g in respective years),were used as test materials.The experiment included two sowing depths of 2 cm and 3 cm,with and without soil compaction treatments.The study aimed to investigate the differences in seedling rate,seedling density,biomass accumulation,and allocation,as well as agronomic traits and grain quality under different sowing conditions.The main research findings are summarized as follows:1.The range of variation in seedling rate under different treatment conditions ranged from 37.08%to 44.11%.The average seedling rate for Ningza 1838(large-seeded variety)and Qinyou 10(small-seeded variety)across all treatments was 40.28%and 39.60%respectively,indicating a 1.72%increase in seedling rate for Ningza 1838 compared to Qinyou 10.Under non-compaction conditions,as the sowing depth increased,the seedling rate significantly increased.The average increase was 5.06%when comparing a sowing depth of 3 cm to 2 cm.Conversely,under compaction conditions,the seedling rate significantly decreased with an increase in sowing depth,with an average decrease of 9.61%.Under the condition of a 2 cm sowing depth with compaction treatment,the seedling rate was significantly higher than without compaction treatment,with an average increase of 13.54%.Under the condition of a 3 cm sowing depth,there was no significant difference in seedling rate between compaction and non-compaction treatments for the large-seeded variety Ningza 1838 in both years.For the small-seeded variety Qinyou 10,there was no significant difference between compaction and non-compaction treatments in the 2020～2021 growing season,while in the 2021～2022 growing season,the compaction treatment showed a significant decrease of 4.12%compared to the non-compaction treatment.2.The range of variation in seedling density during the seedling stage under different treatment conditions was between 28.45 × 104 and 38.15 × 104 plants/hm~2.The trends in seedling density variation,influenced by seed weight,sowing depth,and compaction,were consistent with those observed for seedling emergence rate.Under the same sowing rate of 3 kg/hm~2,the average seedling density for Ningza 1838 and Qinyou 10 in each treatment was 30.83 ×10~4 plants/hm~2 and 34.44×10~4 plants/hm~2,respectively,resulting in an 11.71%increase in seedling density for Qinyou 10 compared to Ningza 1838,which is a small-seeded variety.3.The correlation coefficients between seedling leaf area index and biomass accumulation,and seedling density were 0.944 and 0.948 respectively,indicating a highly significant positive correlation.However,the correlation coefficients between total biomass accumulation and yield during the ripening stage,and seedling density were 0.478 and 0.440 respectively,which did not reach a significant correlation level.4.Under non-compaction conditions,the total biomass accumulation significantly increased with an increase in sowing depth,with a 9.17%increase observed when comparing a sowing depth of 3 cm to 2 cm.Under compaction conditions,there was no significant difference in total biomass accumulation between the two sowing depth treatments for the large-seeded variety Ningza 1838.However,for the small-seeded variety Qinyou 10,as the sowing depth increased,the total biomass accumulation significantly decreased.The decrease was 4.66%when comparing a sowing depth of 3 cm to 2 cm.For Qinyou 10 under the condition of a 3 cm sowing depth,there was no significant difference in total biomass accumulation between compaction and non-compaction treatments.However,for all other sowing depth conditions,the compaction treatment showed a significantly higher total biomass accumulation compared to the non-compaction treatment.During the ripening stage,the proportion of dry matter allocation to roots and seeds increased with an increase in sowing depth under non-compaction conditions.Both compaction and non-compaction treatments showed an increasing trend in dry matter allocation to roots and seeds.Among them,the compaction and non-compaction treatments under the 2 cm sowing depth condition exhibited a larger increase in the proportion of dry matter allocation to roots and seeds.On average,across different years and varieties,the increase was 7.96%and 6.97%,respectively.The proportion of dry matter allocation to stems and branches showed an overall opposite trend to the proportion allocated to roots and seeds.The difference in the proportion of dry matter allocation to husks was relatively small among different treatments during the ripening stage.5.The average yields for Ningza 1838 and Qinyou 10 under different treatments were 3788.2 kg/hm~2 and 3766.0 kg/hm~2,respectively.Under non-compaction conditions,the yield significantly increased with an increase in sowing depth,with a 12.65%average increase when comparing a sowing depth of 3 cm to 2 cm.Under compaction conditions,there was no significant difference in yield between different sowing depth treatments.When comparing compaction and non-compaction treatments under the same sowing depth conditions,both showed an increase in yield.Among them,the compaction treatment resulted in a relatively large increase in yield after sowing at a depth of 2 cm,with an average increase of 21.42%across different treatments.pod numbers per hectare increased with an increase in sowing depth under non-compaction conditions.Under compaction conditions,there was no significant difference in pod numbers per hectare between different sowing depth treatments for the large-seeded variety Ningza 1838.However,for the small-seeded variety Qinyou 10,pod numbers per hectare significantly decreased with an increase in sowing depth.Under the 2 cm sowing depth condition,the compaction treatment showed a significant increase in the pod numbers per hectare compared to the non-compaction treatment,with an average increase of 10.77%.Under the 3 cm sowing depth condition,there was no significant difference in the pod numbers per hectare between the compaction and non-compaction treatments for the large-seeded variety Ningza 1838.However,for the small-seeded variety Qinyou 10,the compaction treatment showed a significant decrease compared to the non-compaction treatment,with an average decrease of 4.03%.On average,the number of seeds per silique and 1 000-seed weight showed relatively high values under deep sowing and compaction treatments.6.There was no significant difference in plant height between different treatments within the same experimental year.However,there was a relatively large difference in the coefficient of variation between blocks.Under deep sowing and compaction treatments,the plants exhibited relatively uniform height distribution.The coefficient of variation for plant height was lower among different blocks under the 3 cm sowing depth and compaction treatment,ranging from 3.38%to 4.09%.On the other hand,the coefficient of variation was higher under the 2 cm non-compaction treatment,ranging from 5.92%to 6.40%.Similarly,the coefficient of variation for the number of pod per plant was lower under the 3 cm sowing depth and compaction treatment,ranging from 15.9%to 18.1%.Conversely,the coefficient of variation was higher under the 2 cm non-compaction treatment,ranging from 21.2%to 24.6%.The average oil content for Ningza 1838 and Qinyou 10 treatments was 45.12%and 42.51%,respectively.In different years,the highest oil content was observed under the 3 cm sowing depth and compaction treatment. |
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