Responses Of Canola Genotypes Differing In Nitrogen Efficiency To Nitrogen Fertilizer

It will be helpful for revealing the mechanism of N uptake and utilization by canola and support N-efficient-cultivar breeding and N management of canola to investigate the differences between canola genotypes differing in nitrogen efficiency and its responses to N fertilizer. Based on the prophase screening by our research team, two canola genotypes(No. 13 and 4) significantly differing in N uptake efficiency were grown in pots under different N rates(0,0.05,0.1,0.15,0.2gN/kg). The N efficiency,nutrition characteristics, agronomic traits and other physiological characteristics were compared. The results show as following:1. Range from 0 to 0.2gN/kg, N efficiency and N uptake efficiency of two canola genotypes decreased with N rate increasing while N utilization efficiency increased in the lower N rate range and then decreased in the higher N rate. N efficiency and N uptake efficiency of N-efficient genotype was more sensitive to N rate than that of N-inefficient genotype. The difference of N efficiency and N uptake efficiency between different genotypes was greater when less N fertilizer was applied.2. The results indicated that no significant genotypic difference in N uptake responses to N rate was found. However, they were different in various growth stages. In seedling stage and bud stage, N accumulation in aboveground part of both N-efficient and N-inefficient genotypes increased and then decreased with the increasing of N rate while they increased steadily from flowing stage to pod developing stage. At maturity stage, N accumulation in whole plant and in various sections increased when N fertilizer rate increased. For both genotypes, N concentration of aboveground part had increase trend with the rising of N rate from seedling stage to pod developing stage. However, there was small increase in seedling stage and it tended to expand in the following stage. At maturity stage, N concentration of various parts decreased slightly and then increased slightly with the rising of N rate. No significant genotypic difference in N distribution in plant responses to N rate was found, either. For both genotypes, N harvest index was enhanced due to the application of N fertilizer. Ratio of N in root, stem to N in whole plant tended to reduce with the rising of N rate while ratio of N in seed to N in whole plant was opposite. Genotypic differences in N uptake were different in various growth stages. There was no significant difference in N accumulation in aboveground part between two genotypes from seedling stage to pod developing stage while N-efficient genotype had greater N accumulation in whole plant and various sections than N-inefficient genotype at maturity stage. N-efficient genotype had higher N concentration of aboveground part than N-inefficient genotype from seedling stage to flowing stage while N concentration differences between them depended on N rate. N distribution in different parts of canola varied between two genotypes. N harvest index of N-efficient genotype was slight higher than N-inefficient genotype. Ratio of N in root to N in whole plant of N-efficient genotype was higher than N-inefficient genotype while Ratio of N in stem was lower.3. N-efficient genotype and N-inefficient genotype showed similar trend that grain yield, roots biomass, shoot biomass, total biomass, percentage of different parts biomass in whole plant biomass, silique number per plant, 1000-seed weight, height, the fist valid branch height and primary branches number fluctuated with the increase of N rate. N-efficient genotype had higher grain yield, roots biomass, shoot biomass, total biomass, percentage of root biomass in whole plant biomass, percentage of stem and leaves biomass in whole plant biomass, percentage of grain biomass in whole plant biomass, root to shoot ratio, harvest index, silique number per plant, seeds per silique, height, primary branches number and stem diameter than N-inefficient genotype, while it had lower percentage of silique wall biomass in whole plant biomass, 1000-seed weight and the fist valid branch height than N-inefficient genotype. However, the differences varied according to N rate.4. There was no response of the SPAD value to N rates from seedling stage to bolting stage. It was increased as N rates increased at florescence stage. The SPAD value of N efficient genotype was significantly higher than N inefficient genotype under different N rates from seedling stage to florescence stage.5. The P and K accumulation per plant was increased as N rate increased. There was no response of P and K content to N rates at harvest time. The P and K accumulation, K content per plant of N efficient genotype was significantly higher than N inefficient genotype, but P content was only showed under lower N rates.