Changes of Sorghum bicolor landrace diversity and farmers' selection criteria over space and time, Ethiopia

Temporal and spatial changes in sorghum landrace diversity and distribution, field sizes, and farmers' selection criteria were studied in five agricultural landscapes in North Shewa and South Wollo, Ethiopia. The study was undertaken during 2000/2001 and 2011/2012 cropping seasons in order to ascertain the stability of a range of factors that support the maintenance of sorghum landrace diversity. The same farmers were interviewed and the same sorghum fields were surveyed during both cropping seasons to determine the changes over the 11-year period. Farmers' selection criteria increased significantly in all agricultural landscapes [Bati (P < 0.0001); Borkena (P < 0.0015); Epheson (P < 0.002); Hayk (P < 0.022); and Merewa Adere (P < 0.05)]. In Bati (P < 0.0081) and Merewa Adere (P < 0.0087), fields planted to sorghum landraces have increased significantly. Changes in field sizes in Epheson (P < 0.36) and Hayk (P < 0.237) did not show significant differences. The field sizes in Borkena (P < 0.0001) have decreased significantly due to population growth, land distribution policy, and seasonal variations followed by inter-and intra-species crop diversification. Sorghum landrace richness has increased significantly in Bati (P < 0.0001) and Hayk (P < 0.0001), marginally increased in Merewa Adere (P < 0.08). No significant changes have been observed in sorghum landrace richness in Borkena (P < 0.344) and Epheson (P < 0.24). In 2011/2012, 24 "generalist'' sorghum landraces (grown widely across three or more agricultural landscapes), and 53 "specialist'' sorghum landraces (restricted to certain microhabitats in one or two agricultural landscapes) were found. Landrace dynamics in response to farmers' selection criteria and environmental variations are explained.