Nitrogen Utilization Efficiency in Canola Cultivars at Grain Harvest

• Published in: Plant and soil 2006-05, Vol.283 (1-2), p.299-307
• Main Authors: Svecnjak, Z, Rengel, Z
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biological and medical sciences; Biomass; Brassica napus var. napus; Canola; Crop harvesting; Crop yield; Cultivars; Dry matter; Fundamental and applied biological sciences. Psychology; harvest index; harvesting; Leaves; Nitrogen; nutrient use efficiency; oil crops; Plant biomass; Plant roots; Plants; Seed productivity; Seeds; soil nutrients; soil-plant interactions; Soils; Stems
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-006-0020-5

Canola (Brassica napus L.) cultivars with improved nitrogen utilization efficiency (NUE) at grain harvest are of interest to growers to reduce fertilizer inputs. Our objective was to determine whether cultivar-specific responses in NUE (seed yield per N accumulated in the whole plant) could be related to the differences in dry matter and N partitioning among various plant parts. Four spring canola cultivars were grown in a glasshouse under the conditions of low and high N supply. When compared to high-N treatment, deficient N conditions resulted in a similar decrease in dry weight for all cultivars, averaging 46% for shoot, 47% for root, and 45% for dropped leaves. The reductions in N concentrations at low-N compared to high-N treatment were much smaller and averaged 15% for shoot, 16% for root and 10% for dropped leaves. Although significant variations occurred for dry weight, N concentration and N uptake in various plant sections, all cultivars accumulated a similar amount of N in total plant biomass at harvest. However, significant differences in plant biomass, seed yield and consequently, NUE existed because more N-efficient cultivars Eyre and Charlton produced larger seed yields than less N-efficient cultivars Pinnacle and Rainbow. No consistent variations in N concentration in various plant parts could be established among tested cultivars. Thus, cultivar-specific responses in NUE were mainly attributed to the differences in the root-to-shoot ratio and harvest index. N-efficient Eyre produced seed yield similar to the highest yielding Charlton, though it had the smallest plant dry weight of all cultivars. In contrast, N-inefficient Rainbow had the largest plant biomass, but produced the smallest seed yield because of its lowest harvest index and the highest root-to-shoot ratio. The absence of cultivar×N treatment interactions indicated that cultivars performed similarly for plant biomass, N uptake and seed yield across two contrasting N supplies. Canola cultivars significantly differed in NUE despite a similar amount of absorbed N in plant biomass; more N-efficient cultivars outyielded less N-efficient ones primarily because of cultivar-specific variations in the root-to-shoot ratio and harvest index.