Fababean (Vicia faba) in Australia's northern grains belt: canopy development, biomass, and nitrogen accumulation and partitioning

Abstract

The growth and yield of fababean (Vicia faba) in temperate environments has been well described; however, information is lacking on the response of the crop to the higher temperature and radiation conditions of subtropical regions. Our aim in this study was to quantify fababean canopy development, radiation interception, radiation use efficiency, biomass partitioning, and nitrogen (N) accumulation and partitioning in a subtropical winter environment and to investigate if parameters describing these processes were consistent between temperate and subtropical regions. Two of the most important factors effecting growth patterns and yield in the field are crop density and water supply. Thus, 2 field experiments were conducted at Lawes, south-eastern Queensland, over 2 seasons, the first concentrating on the effect of plant density and the second on varying water deficit, both using the widely adapted cv. Fiord.

Main-stem nodes appeared at the rate of one node every 54 degree-days (base temperature 0˚C), with no effect of plant density. With the addition of each main-stem node, plants produced a constant 5.22 leaves per node until the start of grain-filling, at which time assimilate became limiting. High plant density decreased both the number of leaves produced and the size of individual leaves on later formed branches. Radiation use efficiency values of 1.03–1.29 g/MJ were determined for plants grown under well-watered conditions, with a lower value (0.83 g/MJ) for a partly irrigated crop. The measured radiation extinction coefficient was 0.73 for leaf area index values ranging from 0.4 to 7.5, pooled across experiments and treatments. Leaf and stem were partitioned in equal proportions until pod set, and the root : shoot ratio was c. 0.8 at the beginning of pod set. The rate of increase in harvest index (HI) during pod filling was 0.012/day, except under fully irrigated conditions in 1999, when HI was much reduced, possibly due to pod shedding.

Parameters such as the extinction coefficient, partitioning between leaf and stem, and rate of main-stem node appearance appeared to be quite conservative in response to density and water deficit, and were within the range of published values from temperate and Mediterranean environments. This is an encouraging outcome and suggests that it should be possible to simulate growth and yield of fababean across the diverse climate zones in which the crop is grown in Australia by using a single simulation model.