| Rapeseed is not only one of the major edible oil sources for human beings,but also has important applications in the domain of livestock feeding and renewable energy.Compared with other crops,rapeseed accumulated larger amount of N but without higher nitrogen use efficiency(NUE).The limited NUE of rapeseed is resulted from unreasonable nitrogen fertilization strategies and low N uptake and utilization of rapeseed plants Therefore,clarifying the current status of soil nutrients in the rapeseed planting area,optimizing the fertilization strategy accordingly and screening rapeseed varieties with increased nitrogen uptake efficiency(NUpE)and nitrogen untilization efficiency(NUtE)are important pathways to elevate the NUE of rapeseed.In this study,a field investigation collecting 103 soil samples was conducted at the major areas for spring rapeseed production of eastern Qinghai Province.The concentrations of soil organic matter,total/available NPK and micronutrients were measured to analyse the current soil nutrient status and pertinent fertilization strategies were suggested.A local field experiment was employed to compare NUE among 14 rapeseed hybrids under two nitrogen levels(high nitrogen: 160 kg N /ha;low nitrogen: 0 kg N /ha).Differences of agronomic and nutritional traits among the rapeseed hubrids were also studied.We have obtained the main following results:(1)Based on the results of the soil samples,the average soil organic matter(SOM)and total N of spring rapeseed areas in Qinghai Province were 26.81 g/kg and 1.97 g/kg,respectively,the soil fertility was moderate to rich.The variation of soil available K was huge in different areas,the scaricity areas were mainly distributed within Huangzhong and Huzhu.The average soil boron concentration of the 3 studied counties was as low as 0.27 mg/kg,classifed as nutrient extremely deficiency.The concentrations of other micronutrients were rich except zinc deficiency in Huzhu.(2)Hufeng 010,Qingza 3,Qingza 2,Qingza 11 and Qinzayou 4 were spring rapeseed hybrids with high NUpE and yield under high N condition.Hufeng 010,Qingza 2,Qingza 5,Qinzayou 4 were hybrids with high NUpE and yield under low N condition.Under high N condition,hybrids with high NUtE and yield were Qingza 11 and Qinyou 558,while under low N condition Qingza 7 and Qinyou 558 showed high NUtE and yield.(3)The hybrids with high NUpE under both high and low N conditions were Hufeng 010,Qingza 3,Qinzayou 4 and Qingza 2,while Fengyou 737 always showed low NUpE among all hybrids.Longyou 10,Qingza 7,Qinyou 558 and Hongyou 88 were high NUtE spring rapeseed varieties,and Hufeng 010,Qingza 3 and Qingza 2 were low NUtE spring rapeseed varieties.(4)The positive correlations between biomass of each organ,N accumulation of each organ,number of the first valid branch,silique number per plant and NUpE were significant(p<0.05 or p<0.01).Under high N condition,the ratios of N accumulation in silique husk and stem and leaf were positively correlated with NUpE(p<0.05),while the proportion of seed N accumulation was negatively correlated with NUpE(p<0.05).The hybrids with high NUp E had higher shoot biomass,plant height,silique number per plant,and N accumulation in stem and leaf than hybrids with low NUpE.(5)Ratios of seed yield to shoot biomass and seed N to shoot N were significantly and positively correlated with NUtE.NUtE had significantly negative correlations with the proportion of stem and leaf biomass in shoot biomass,N content in different plant organs,N accumulation in silique husk and stem and leaf,ratio of silique husk N to shoot N and ratio of stem and leaf N to shoot N.Extremely significant positive relationships were observed between seed number per silique,1000-seed weight and NUtE under low N conditions.Silique number per plant was negatively correlated with NUtE under both high and low N conditions(p<0.05).Spring rapeseed hybrids with high NUtE had higher seed number per silique,1000-seed weight,ratio of seed yield to shoot biomass and ratio of seed N to shoot N than hybrids with low NUtE. |
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