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
Southdown Motor Services Corporation was reached, splitting mileage and receipts on a 57:43 share, Southdown being the minority. This often had the result, at the end of the year, that buses from one operator would be put onto routes of the other to balance the mileage. The driver/conductor would not change, thereby working on a 'foreign' vehicle. This replaced an earlier agreement dating from 1931 involving protective fares on Southdown routes within the city. The co-ordination of services, dubbed Portsmouth Area Joint Transport Services, lasted until deregulation in 1986. After the war, Southdown started its first overseas tours with a 17-day tour to