Early vigorous growth is a major factor influencing nitrogen uptake in wheat

A field trial, a lysimeter system study and a nutrient solution experiment were conducted to determine the genotypic differences in nitrogen (N) uptake among wheat (Triticum aestivum L.) genotypes differing in vigour of early growth. Plant growth and N uptake of Vigour 18, a breeding line with early vigour, and the commercial cultivars Westonia, Tincurrin, Camm and Janz were compared. Shoot biomass of Vigour 18 was higher than that of the other genotypes, except for Westonia at booting when 50 kg N ha^-1 was applied 3 d after wheat emergence. Vigour 18 had significantly higher efficiency of fertiliser-N uptake than the other four cultivars at tillering when 50kg N ha^-1 was applied. Fertiliser-N uptake efficiency at booting was similar in Vigour 18 and Westonia, but significantly higher than in three other commercial cultivars. Vigour 18 had higher root dry matter, root-length density and root surface area than Janz when examined in columns of soil. The greater root growth of Vigour 18 occurred across all soil layers to a depth of 0.6 m. Differences in total N uptake between Vigour 18 and Janz were apparent from tillering (Z14,22) to booting (Z19,24,49). Vigour 18 also had significantly higher shoot biomass and N uptake than Janz when grown in nutrient culture. Nitrate reductase activity (NRA) expressed on a whole-plant basis was higher for Vigour 18 than for Janz, and was related to total N uptake. However, NRA expressed on a per-unit-fresh-weight basis was not significantly different across the cultivars tested. It is concluded that vigorous early root and shoot growth in Vigour 18 was the main driving force for higher N uptake.