SEED YIELD AND HARDSEEDEDNESS OF 2 AMPHICARPIC PASTURE LEGUMES (VICIA-SATIVA SSP ANPHICARPA AND LATHYRUS-CILIOLATUS) AND 2 ANNUAL MEDICS (MEDICAGO-RIGIDULA AND MEDICAGO-NOEANA)

Yields and hardseed breakdown of underground and aerial seeds in subte rranean vetch (Vicia sativa ssp. amphicarpa) and lathyrus (Lathyrus ci liolatus) and aerial seeds of Medicago rigidula and M. noeana were com pared at Tel Hadya, near Aleppo, in north Syria between 1990 and 1992. Underground and aerial seed and straw (mature herbage) yields were me asured at maturity in the first spring, and hardseed breakdown over th e following summer, autumn and winter. Regenerating herbage production was measured in the second spring. In the establishment year (299 mm rainfall) the medics produced twice as much straw as the amphicarpic s pecies. In contrast, seed yields were less than half: M. rigidula and M. noeana produced 412 and 110 kg/ha respectively, while subterranean vetch and lathyrus produced 1174 and 736 kg/ha. More than 95% of the t otal seed yield of the amphicarpic legumes was underground. Undergroun d seeds of the amphicarpic legumes were larger than aerial seeds, and almost 10 times as large as the medic seeds. Seeds of all species were > 90% hard when newly set in summer. At the first seasonal rains > 95 % of underground seed had softened, compared with 5 and 40% of the aer ial seeds of vetch and lathyrus respectively. The medics remained > 90 % hardseeded. In laboratory tests, embryo dormancy was observed in all species prior to the onset of first seasonal rains. For the amphicarp ic legumes, but not for the medics, embryo dormancy persisted into win ter. In the field, and after all germination events, 900-1430 seeds/m( 2) of subterranean vetch seed remained in the soil. This was considera bly more than expected, based on the low levels of hardseededness and embryo dormancy observed in the laboratory. The results suggest that d ormant seeds of the amphicarpic legumes need light to germinate. In th e second year (353 mm rainfall), regenerating M. rigidula produced 5.3 t/ha compared with 3.4 t/ha by the best subterranean vetch from appro ximately equal numbers of seedlings. The amphicarpic legumes germinate d later and over a more extended period than the medics, indicating th at they could become weeds in a cereal/pasture rotation. However, the results suggest that in drier areas or in drier years the vetches will compare favourably with the medics in most respects. Clearly, subterr anean vetch and lathyrus have great potential for pasture improvement in dry areas.