Southdown sheep no longer economical and smaller flocks averaged only 135 ewes apiece. The use of artificial fertilizers had gained ground, and the combine-drill, which sowed grain seeds and fertilizer together, rendered close-folding by sheep unnecessary. Gradually surrendering to basic arable farming changes, the Southdown became largely a grassland breed. During the interwar years, the United Kingdom was known for farm animal breeding, and pedigreed Southdowns were still being exported to most parts of the world, especially New Zealand. In 1937, the number of exported Southdowns reached 459 head. During the Great Depression, a severe and prolonged fall in the prices of
Avondale–Southdown Line an agreement with the NZ Transport Agency over a land swap needed for a realignment of the highway and railway corridors. Another proposal exists to connect the Onehunga Branch at Galway Street to the Avondale—Southdown line by building a tunnel under Onehunga Mall to meet Hugh Watt Drive (State Highway 20) before connecting to the proposed route at Hillsborough. In May 2007 the Auckland Regional Transport Authority (ARTA) announced that it had formed a study group with ONTRACK to investigate the feasibility and costs for the section between Captain Springs Road in Southdown and Hillsborough Road in Mount Roskill. Avondale–Southdown