Field trials were conducted in 2 seasons at 13 sites on neutral to alkaline soils in Western Australia, to compare the growth and seed yield of 6 winter grain legume species: field pea (Pisum sativum L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), lentil (Lens culinaris Medik), narrow leaf lupin (Lupinus angustifolius L.), albus lupin (L. albus). In a dry year (1991), overall site mean seed yield was highest for field pea (1.35 t/ha), then faba bean (1.22 t/ha) and narrow leaf lupin (0.85 t/ha). Chickpea, lentil line ILL5728, and albus lupin produced an average seed yield of 0.64 t/ha. Rainfall in 1992 was above average and seed yields of all species except field pea were higher than in 1991. Heavy rainfall in winter and spring caused transient waterlogging at several sites, affecting growth and seed yield of most species. Faba bean responded positively to the increase in rainfall and produced exceptional seed yields of >4 t/ha at 3 sites. Mean seed yield was highest for faba bean, at 2.87 t/ha, then narrow leaf lupin (1.19 t/ha), chickpea (1.1 t/ha), and field pea (1.0 t/ha). Field pea performed poorly at several sites due to its susceptibility to transient waterlogging and black spot disease (caused by Mycosphaerella pinoides). Albus lupin and lentil line ILL5728 produced similar seed yields (0.78 t/ha). Lentil cvv. Laird (1991) and Kye (1992) had low seed yields due to poor adaptation. Seed yield differences between species at various locations were not simply related to any soil chemical parameters or to depth to clay. On a calcareous soil of pH(CaC12) 8 at Dongara, the growth of narrow leaf lupin was severely affected and the crop failed. Days to flowering varied between species; faba bean was earliest to flower (76 days), then field pea. Faba bean and field pea (particularly in 1991) generally produced the most dry matter, both early and at final harvest. The relationship between seed yield and rainfall was complicated by transient waterlogging and fungal disease (e.g. black spot in field pea) at many sites. Seed yield was significantly positively related to final dry matter production but not to harvest index.
The effect of sowing rate (60–320 kg/ha) on the growth and seed yield of kabuli chickpea (cv. Kaniva) was assessed at 11 sites for 4 seasons in the cropping regions of south-western Australia. The economic optimum plant density and yield potential were estimated using an asymptotic model fitted to the data and calculating the sowing rate above which the cost of additional seed was equivalent to the revenue that could be achieved from the extra seed yield produced, assuming a 10 and 50% opportunity cost. On average for all sites and seasons, plant densities ranged from 10 plants/m2 when sown at 60 kg/ha to 43 plants/m2 when sown at 320 kg/ha. Assuming a mean seed weight of 400 mg and a germination of 80%, then on average 75% of viable seeds sown (or 60% of sown seeds) established as plants. The poor establishment rates are thought to be associated with reduced viability caused by mechanical damage, storage conditions, fungal infection in the soil, and unfavourable seed bed moisture and temperatures. In general, there was a positive relationship between sowing rate and seed yield. Seed yield increases at higher sowing rates were mainly associated with the greater number of plants per unit area. There were fewer pods per plant at higher sowing rates, but there were more pods per unit area. Changing the sowing rate had little effect on mean seed weight and the number of seeds per pod. The economic optimum plant density varied from 8 to 68 plants/m2, depending on the location, but the mean (27 plants/m2) was within the range currently recommended in southern Australia (25–35 plants/m2). Due to the low establishment rates observed in this study, we estimate a sowing rate greater (160–185 kg/ha) than currently suggested (110–160 kg/ha) to achieve this density. There was a strong relationship between economic optimum plant density and seed yield potential ( r 2 = 0.66, P <0.01), which allows an estimation of the most profitable sowing rate, depending on the seed yield potential of the site. For most crops yielding about 1.0 t/ha in southern Australia, a plant density of 25 plants/m2 is most profitable, while in higher-yielding situations (>1.5 t/ha) plant densities >35 plants/m2 will produce the most profit.
The influence of terminal drought on the seed growth of 3 chickpea (Cicer arietinum L.) genotypes was examined in a field experiment at Merredin, Western Australia. Tyson, a small-seeded desi cultivar, ICCV88201, a desi breeding line (sister line to the recently released Sona cultivar) with medium-sized seed, and Kaniva, a kabuli cultivar with large seed, were grown under rainfed and irrigated conditions. In the rainfed plots, leaf water potential had decreased from above –1.2 MPa to about –2.5 MPa and net photosynthesis from 21 to 29 µmol CO2/m2. s to below 10 µmol CO2/m2.s, by the time seed filling commenced. Rainfed plants had significantly fewer pods than irrigated plants, regardless of genotype. In rainfed plants average seed weight was reduced by 19, 23 and 34% and yield by 74, 52 and 72% in Tyson, ICCV88201, and Kaniva respectively. Individual pods were tagged at pod set on previously-selected representative plants and were weighed separately from the rest of the plant over 6 subsequent harvests so that the rate and duration of seed fill could be measured. Genotypic differences in the maximum rate of seed fill were found to exist in chickpea. In both irrigated and rainfed conditions, Kaniva had the highest maximum rate of seed fill followed by ICCV88201 and Tyson. Both the rate and duration of seed growth were reduced in the rainfed plants, regardless of genotype. Reductions in the dry weight of the pod shell suggest that the remobilisation of dry matter from the pod may contribute 9–15% of the seed weight in rainfed chickpea.