Selection and breeding for yield and adaptation to environmental conditions often changes a number of characteristics of crops, and may influence the value of seed for animals. A series of experiments was conducted to evaluate the effect of breeding and growing conditions on the structure and degradability of lupin seed coats. Breeding has had significant influences on both seed size and seed coat structure of lupins. For instance, cultivars of Lupinus angustifolius released in 1987 and 1988 tended to have smaller seeds with a thicker seed coat than those released in 1971 (P < 0.05). Selection for soft seeds has resulted in a reduction of seed coat thickness in L. angustifolius. Hardseeded and roughseeded lines of L. cosentinii had thicker coats (P < 0.05) than softseeded and smoothseeded, respectively. The main contributor to the thick seed coat of hardseeded lines was a layer of cells known as the hourglass layer, which is located between the outer palisade and inner parenchyma. Anatomical analysis revealed that the soft seed coat tended to have short and round cells, whereas the hard seed tended to have long cells in the palisade layer. Smooth seeds had round cells in the subpalisade, but rough seeds had long cells in this layer. Although the seed coats of lupins contained about 80% crude fibre, with L. cosentinii and L. pilosus having more fibre than L. angustifolius, the fibre in lupin seed coats was highly digestible by sheep.

While it has been reported that leaves of subterranean clover are less digestible than stems, there is a lack of information on the variability of nutritive value of plant parts of subterranean clover. To determine the variation in nutritive value of leaf, petiole, stem and burr, an experiment with 26 cultivars of subterranean clover was conducted at Shenton Park Field Station, Perth, Western Australia. The cultivars were divided into 3 maturity groups according to flowering time and each cultivar was sown in blocks comprising 4 replicates. The plots were grazed by sheep at 2-weekly intervals. Plants were sampled at the vegetative stage before grazing and after the cessation of flowering. Dry matter digestibility (DMD) and nitrogen concentration of leaves, petioles, stems and burrs were determined. At the vegetative stage, there was no difference in DMD (P>0.05) among plant parts for most cultivars, and leaf had the highest (P<0.05) nitrogen concentration (4.8–5.4%). After the cessation of flowering, leaf had the highest DMD and nitrogen concentration (P<0.05). The DMD of plant parts differed significantly among cultivars (P<0.05). There was a slight decrease in DMD over time for leaves and a significant decrease in DMD for stems and petioles. These results suggest the main objective of grazing management of subterranean clover swards should be to increase the proportion of leaf material in the swards and that selection of leafy varieties by breeding could improve the late season digestibility of subterranean clover. Such management and breeding strategies would have value when the cultivars are in mixed pastures or used with supplements in summer.

The size and composition of pasture legume seedbanks were estimated from 2 surveys on a 460-km west-east transect of the wheatbelt of Western Australia. Survey 1 (in spring) sampled naturalised legumes, and survey 2 (in summer) measured the amount and botanical composition of legume seed from selected sites. Seedbanks were examined in greater detail on 2 farms in the higher rainfall part of the wheatbelt. Survey 2 revealed that mean seedbank size of the poorest 40% of sites (those with 5200 kg seed/ha) was 61 kg/ha, and that 72% of seeds were naturalised clovers. In contrast, the best 60% of sites (those with >200 kg seed/ha) averaged 533 kg seed/ha, of which only 35% was naturalised clover seed, the remainder in both surveys being mainly subterranean clover (Trifolium subterraneum). Mean seed bank size (kg/ha) varied from 359 (survey 2) to 587 (survey 1) and, in both surveys, was poorly correlated with long-term mean annual rainfall and a number of soil parameters. On the 2 farms, seedbank size ranged from 300 to 345 kg/ha (in spring) and from 650 to 740 kg/ha (in summer). Trifolium glomeratum (cluster clover) and subterranean clover were the most widespread species in both surveys. They were present at 35 and 30 of the 57 survey sites, respectively, and at both farms. Most of the subterranean clover collected was cv. Geraldton (22 of 30 sites), the next most frequent cultivar was Dwalganup (6 sites). The currently recommended cultivar, Dalkeith, was found at only 5 sites. Several other legumes including T. tomentosum (16 sites), T. suffocatum (8 sites), Medicago truncatula (7 sites), T. hirtum (4 sites), and M. minima (4 sites) were common, while M. littoralis, M. polymorpha, T. dubium, T. cernuum, T. cherleri, and T. carnpestre were found at single sites. With few exceptions, these are naturalised species and were characterised by flowering times about 20 days later than sown legume cultivars, and seed sizes < 1 mg. The value of these widespread annual legumes to agricultural productivity and sustainability needs to be quantified and their adaptation to wheatbelt farming systems assessed.

The nutritive value of 26 cultivars of dry, mature subterranean clover was evaluated at Shenton Park, Perth, Western Australia. The cultivars were divided into 3 maturity groups according to flowering time and each cultivar was sown in blocks comprising 4 replicates. The plots were grazed by sheep at 2-week intervals during the growing season. Dry mature plant material and soil were sampled in summer to examine the effect of grazing and cultivar on seed yield and nutritive value of feed residues. Cultivars heavily grazed in spring had a low herbage mass. There was no difference in seed yield and seed weight between heavily and lightly grazed cultivars. Dry matter digestibility and mineral content of dry residues was inconsistent for the 2 grazing treatments. The dry matter digestibility of dry, mature subterranean clover ranged from 40 to 56%, with a wide range of crude fibre, nitrogen and mineral content for the 26 cultivars. While most minerals in the dry residues were above the requirement for sheep, 7 cultivars had a zinc content less than the maintenance requirement for sheep. There was an imbalance for all cultivars in calcium: phosphorus with a range of 4–10: 1. Concurrent estimates on the yield and composition of seed indicated that seed can be resource of minerals for grazing animals in summer. Most cultivars had a seed yield over 100 g/m2 with that of 9 cultivars being over 130 g/m2. Seed was rich in nitrogen, sodium, phosphorus, potassium, magnesium, zinc and copper, and poor in sodium, calcium and manganese. However, there were no cultivars with an appropriate ratio of calcium and phosphorus. The imbalance in nitrogen and sulfur was a result of high nitrogen content with the ratio ranging from 19: 1 to 29: 1.

The effect of grazing intensity and cultivar on plant morphology was examined with 26 cultivars of subterranean clover during the growing season. The cultivars were grown in 3 groups (early, mid, and late) according to their flowering time and grazed under 2 grazing intensities (heavy and light) at a 2-weekly interval. Heavy grazing delayed flowering time by only about 2 days for early and late maturity cultivars without influencing flowering duration. Late and mid maturity cultivars had more (P< 0.05) branches, petioles, and leaves with shorter branches under heavy grazing than under light grazing, whereas early maturity cultivars did not show any significant differences in the numbers of plant parts under the 2 grazing intensities. The effect of grazing intensity on the proportions of plant parts was small over all cultivars, indicated by a 2 percentage unit increase in the proportions of leaf in September, burr in October, and stem in November by heavy grazing. There was a large cultivar variation in flowering duration, and the numbers, lengths, and proportions of plant parts. The ranges of flowering duration were 24–66, 26–66, and 31–76 days and of branch length after cessation of flowering were 12–20, 6–14, and 5–14 cm for the early, mid, and late maturity groups, respectively. The late maturity group had more branches, leaves, petioles, and stems, and the early maturity group had less with the mid maturity group being intermediate. The variation in the proportions of plant parts among cultivars was not related to flowering time or flowering duration.