| The production mode of“oil-vegetable dual-use”refers to both picking the stalk as a edible vegetable and harvesting seed for edible oil,which is an important way to exert the multifunctional use of rapeseed.This mode can not only significantly improve planting efficiency,but also effectively promote the development of rapeseed industry.At present,the nutrient uptake rule and yield formation mechanism of the interaction between“oil-vegetable dual-use”density and nitrogen fertilizer are not well studied in China.The planting mode of rapeseed with low density transplanting is mainly used in production,which is difficult to take advantages of increasing yield and efficiency of’“oil-vegetable dual-use”.In this study,a two-year field experiment was carried out in Beibei District of Chongqing City with double-low rape“Yuyou 28”as the material.A two-factor split-plot experimental design was adopted.The planting density was set as the main area,with three density levels D1(15×10~4 plants/hm~2),D2(30×10~4 plants/hm~2),D3(45×10~4 plants/hm~2).The nitrogen fertilizer applied level after bolting was set as the sub-area,including N0(0 kg N/hm~2),N1(40 kg N/hm~2),N2(80kg N/hm~2).By investigating the effects of interacting between density and nitrogen fertilizer on yield composition,photosynthetic characteristics,nitrogen and phosphorus uptake,dry matter accumulation,moss yield,planting efficiency,yield and quality of rapeseed after stalk-picked,the better density and nitrogen topdressing amount for“oil and vegetable dual-use”rapeseed production were determined.The main research results are as follows:1.Density and nitrogen fertilization had significant effects on agronomic traits and photosynthetic characteristics of oilseed rape in all periods after stalk-picked.Under the same density,plant height,root neck diameter,effective branch number,first branches height,effective siliques number per plant,1000-grain weight and seeds number per silique showed an increasing trend with the increase of nitrogen application level,while taproot length had no obvious change.Under the same nitrogen application level,the plant height,root neck thick,taproot length,effective branches number,effective siliques number per plant and 1000-grain weight of rape decreased significantly with the increase of density,but the branch height and seeds number per silique had no significant change.Under the same density,the net photosynthetic rate of individual rape was significantly promoted by increasing nitrogen fertilizer after stalk-picked.For example,in 2020-2021,the net photosynthetic rate per plant at flowering period under D2N1 and D2N2 treatments increased by 14.17%and 10.58%,respectively,compared with D2N0 treatments.Under the same nitrogen application level,increasing the density could significantly inhibit the net photosynthetic rate per plant after stalk-picked.For example,in 2021-2022,the net photosynthetic rate per plant under D2N1 and D3N1 treatments decreased by 15.06%and 24.11%,respectively,compared with D1N1.After stalk-picked,the stomatal conductance and transpiration rate of rape leaves at flowering period were significantly increased with the increase of nitrogen fertilizer level.For example,in 2021-2022 annual experiment,the silique peel area index of D2N1 and D2N2 treatments increased by 30.95%and34.26%,respectively,compared with D2N0.Under the same nitrogen fertilizer level,chlorophyll content,leaf area per plant and pod stage area per plant showed a decreasing trend with the increase of planting density,but leaf area index and silique peel area index increased significantly.For example,in 2020-2021 annual experiment,the leaf area per plant under D2N1 and D3N1 treatments was significantly reduced by22.35%and 47.32%,respectively,compared with D1N1,but the leaf area index was significantly increased by 55.29%and 58.04%,respectively.2.Appropriate density and nitrogen application can improve the accumulation of dry matter and nitrogen and phosphorus in rapeseed after stalk-picked.At the same density,the root dry weight,stem dry weight,leaf dry weight,horn dry weight and total dry weight of population rapeseed in different periods after stalk-picked showed a raising trend when increasing the nitrogen fertilizer application.For example,in2020-2021,the total dry weight of rapeseed was significantly increased by 14.42%and14.79%at maturity stage in D2N1 and D2N2 treatments,respectively,compared to D2N0.For the same nitrogen application,the root dry weight,stem dry weight,leaf dry weight,horn dry weight and total dry weight of population rapeseed in different periods after stalk-picked exhibited a similar raising trend when increasing the density,and the promotion effect first increased and then decreased.For example,in 2020-2021,the total dry weight of rapeseed was significantly increased by 32.00%and 26.09%at maturity stage in D2N1 and D3N1 treatments,respectively,compared to D1N1.At the same density,the accumulation of N and P in stalk-picked rapeseed at maturity stage could be improved by the increasement of nitrogen application.However,excessive nitrogen application resulted in the decrease of P accumulation in mature rapeseed.In2020-2021,the accumulation of N increased by 5.77%and 9.54%while the accumulation of P increased by 7.59%and 4.79%for mature rapeseed in D2N1 and D2N2,respectively,compared to D2N0.For the same nitrogen application,the accumulation of both N and P could be significantly increased in stalk-picked mature rapeseed when increasing density.However,excessive density resulted in the decrease of N and P accumulation in mature rapeseed.In 2020-2021,the accumulation of N increased by 20.09%and 16.93%while the accumulation of P increased by 21.37%and 14.03%for mature rapeseed in D2N1 and D3N1,respectively,compared to D1N1.3.The Density and nitrogen application had significant effects on the yield and rapeseed quality after stalk-picked.Under the same density,the yield of rapeseed after stalk-picked showed a trend of first increasing and then decreasing when increasing the nitrogen application.In 2020-2021,the rapeseed yield of D2N1 and D2N3 treatments was significantly increased by 8.88%and 6.88%compared with D2N0,respectively.Similarly,the population yield of rapeseed after stalk-picked also showed a trend of increasing first and then decreasing when increasing the density under the same nitrogen application level.In 2020-2021,the rapeseed yield of D2N1 and D3N1treatments was significantly increased by 16.02%and 8.05%,respectively,compared with that of D1N1.With the increase of nitrogen application,the oil content,erucic acid content,linolenic acid content and glucosinol content of stalk-picked rapeseed showed a decreasing trend,while the protein content exhibited a continuous increasement.While with the increase of density,the oil content and erucic acid content of rapeseed showed an increasing pattern whereas the protein content showed a decreasing trend,but there was no obvious effect on the contents of glucosinolates and linolenic acid.When nitrogen fertilizer level and density increased simultaneously,the angle of collapse,collapse index,and incidence of botrytis disease in stalk-picked rapeseed removal kept increasing,leading to a decrease in stable yield.4.Suitable density and nitrogen application can improve the planting profit of rape after stalk-picked.After excluding the cost of fertilizer,the economic efficiency of stalk-picked rapeseed showed a trend of first increasing and then decreasing with the increase of nitrogen application level at the same density.In 2020 to 2021,the economic benefits of D2N1 and D2N2 were significantly increased by 1421.3 yuan/hm~2 and 881.79 yuan/hm~2,respectively,compared with D2N0.At the same nitrogen application level,the economic benefits of stalk-picked rapeseed showed a trend of increasing and then decreasing with the increase of density.In 2020 to 2021,the economic benefits of D2N1 and D3N1 treatments were significantly increased by25.20%and 14.37%,respectively,compared with D1N1.Notably,the maximum economic benefit of stalk-picked rapeseed occurred in D2N1 treatment in both 2021(27,061.87 yuan)and 2022(28,595.39 yuan).Moreover,the increased application of N fertilizer can increase the bias productivity of N fertilizer and decrease the N harvest index,leading to a decrease in the utilization of N fertilizer in stalk-picked rapeseed.Taken together,the D2N1 treatment that used a density of 30,000 plants/hm~2 and applied with 40 kg N/hm~2 after stalk-picked can significantly improve the yield and planting efficiency of stalk-picked rapeseed as well as reduce the occurrence of lodging and sclerotinia disease,which can serve as a useful technology for the“oil-vegetable dual-use”mode of rapeseed in Chongqing. |
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