Risk assessment by sowing date for barley ( Hordeum vulgare) in northern Ethiopia

Abstract

Risks of dry and wet sowing methods of rainfed barley were evaluated in northern Ethiopia. The evaluation was based on yield simulation using a validated AquaCrop model. Risks of failure (false start) were assessed by taking biomass threshold levels (<0.1 t ha −1) from defined early, normal and late sowing by farmer's and depth criterion over long-term (21–41 years) climate observation. The study verified that false start increased over the study area in the order from southwest to southeast and northeast. The risk level due to false start by farmer's criterion ranged from 5 to 37%, 9 to 37%, and 9 to 19% for early, normal and late sowing, respectively, whereas the false start risk by depth criterion ranged from 14 to 29% for early; 14 to 24% for normal; and 5 to 23% for late sowing. The long-term simulated average yield across the stations ranged from 0.8 ± 0.8 to 1.5 ± 0.7 t ha −1 for early, 0.9 ± 0.7 to 1.6 ± 0.5 t ha −1 for normal and 0.8 ± 0.7 to 1.7 ± 0.6 t ha −1 for late sowing when farmer's criterion was applied whereas the corresponding average yield when depth criteria was applied ranged from 0.8 ± 0.6 to 1.5 ± 0.6 t ha −1 for early, 0.6 ± 0.6 to 1.6 ± 0.7 t ha −1 for normal and 0.4 ± 0.4 to 1.7 ± 0.4 t ha −1 for late sowing. The result suggested that risks of false start reduced and barley yield relatively improved when normal/late sowing was applied based on farmer's criterion or when early/normal sowing was applied based on depth criterion. In most of the cases, stations situated southwest of the catchment were characterized by early onset and late cessation (longer length of growing period) whereas stations situated towards the northeast, northwest and southeast are more characterized by normal or late onset and early or normal cessation (shorter growing period). In general, yield reduced from west to east mainly due to the effect of onset and cessation of rain. This study also showed that weed infestation was prevalent when early sowing was applied. Thus to minimize the risk of false start and to reduce cost of weeding, sowing should be scheduled after sufficient moisture is ensured during which especially grass weeds would emerge before sowing so that the emerged weeds could be plowed over.