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.
QTL for Main Stem Node Number and Its Response to Plant Densities in 144 Soybean FW-RILs
