Effects Of Nitrogen And Potassium Fertilizer Rates On Yield And Nutrient Utilization Of Rapeseed Varieties In Different Ages

Variety replacement is a key factor driving the rapid development of our country’s rapeseed industry.In the past 70 years,our country’s rapeseed varieties have achieved a leap from cabbage type to double-low and high-yield rapeseed.In the breeding process,the yield,quality and disease resistance characteristics of rapeseed are often concerned,while nutrient use efficiency is neglected.Fertilization is an important guarantee for high and stable rapeseed yield.Improving the nutrient use efficiency of rapeseed can reduce the rates of chemical fertilizers and provide support for the green development of rapeseed.In order to clarify the changes of rapeseed nutrient efficiency,10 varieties from 1950-1960s,1970-1980s,1990-2010s,and2010-2020s were selected to study the application of nitrogen and potassium fertilizers through field experiments with different nitrogen and potassium fertilizer rates.The effects on the yield,nutrient use efficiency and quality of the main planting varieties in the Yangtze River Basin in different years,in order to provide a reference for the cultivation of high-yield,high-quality and high-efficiency new varieties of rapeseed.The main results are as follows:（1）Effects of nitrogen fertilizer rates on yield and nutrient utilization of rapeseed varieties in different agesNitrogen fertilizer application significantly increased rapeseed yield.When the nitrogen fertilizer rates exceeded 270 kg/hm²,the effect of increasing yield was not significant.The nitrogen fertilizer response trends of varieties of different ages were similar,but there were differences among varieties of different ages.With the advancement of breeding years,the yield showed an increasing trend,and the yield of varieties from 2010-2020s was the best.Further,from the perspective of yield component factors,there were significant differences in the number of siliques per plant and 1,000-grain weight of varieties of different ages,but the differences in the number of grains per silique were not significant.Nitrogen fertilizer application can reduce the differences in yield and yield components among varieties,and tap the yield potential of rapeseed.With the increase of nitrogen fertilizer rates and the advancement of breeding years,the harvest index of varieties in different ages showed an upward trend.The nitrogen content of rapeseed in different ages was slightly different,and the difference of nitrogen content was concentrated in the nitrogen content of grain.The nitrogen content of early varieties was higher than that of modern varieties,but the nitrogen content of stem and horn shell had no significant difference between varieties of different ages.Nitrogen fertilizer rates significantly increased the nitrogen accumulation in rapeseed shoots,but the differences in shoot nitrogen accumulation of rapeseed in different ages were not significant.The apparent nitrogen utilization rate and agronomic utilization rate of the varieties of different ages reached the maximum when the nitrogen application rate was 180-270 kg/hm²,which were51.9%-69.8%and 11.3-12.9 kg/kg,respectively.There was no significant difference in the apparent nitrogen use efficiency and agronomic use efficiency among the varieties of different ages.There were obvious differences in quality traits among varieties of different ages.With the advancement of breeding years,the oil content,oleic acid,linoleic acid and protein content of rapeseed all increased,while the content of erucic acid and glucosinolate decreased significantly.The application of nitrogen fertilizer significantly affected the quality of rapeseed.With the increase of nitrogen fertilizer rates,the oil content,oleic acid and linoleic acid content of different varieties showed a downward trend,while the content of protein,erucic acid and glucosinolate increased significantly.（2）Effects of potassium fertilizer rates on yield and nutrient utilization of rapeseed varieties in different agesPotassium fertilizer application significantly increased rapeseed yield.When the potassium fertilizer rates exceeded 120 kg/hm²,the effect of increasing yield was no longer significant if the application continued to increase.The differences between varieties in different ages were large,and the yield increased significantly with the advancement of breeding years,and the application of potassium fertilizer narrowed the differences between varieties.With the increase of potassium fertilizer and the advancement of breeding years,the harvest index of rapeseed varieties in each age showed an upward trend.With the increase of potassium fertilizer rates and breeding age,the potassium content of stems and horn shells of varieties of different ages increased to different degrees,but had little effect on the potassium content of grains.Potassium fertilizer rates significantly increased the potassium accumulation in various parts of rapeseed at maturity,which was concentrated on the stem and angular shell.The above-ground potassium accumulation between varieties of different ages increased significantly with the advancement of breeding years,and the above-ground potassium accumulation of varieties in 2010-2020s was significantly higher than that in1950-1960s.The agronomic utilization rate of potassium fertilizer of varieties of different ages reached the maximum under K₃₀ treatment,ranging from 13.92 to 21.16kg/kg,and there were differences among varieties of different ages.The agronomic utilization rate of potassium fertilizer of varieties from 2010-2020s was higher than that of early varieties.There were obvious differences in quality traits among varieties of different ages.With the advancement of breeding years,the oil content,oleic acid and linoleic acid contents of rapeseed all increased,while the contents of erucic acid and glucosinolate decreased significantly,and the protein content did not change significantly.Potassium fertilizer application had no significant effect on the oil content of cultivars of different ages.The contents of protein,oleic acid and linoleic acid increased,while the contents of erucic acid and glucosinolate decreased significantly.