The experimental site was located at Hombolo Agricultural Research Institute (ARI) in Dodoma Region about 58 km North-East of Dodoma Municipality at latitude 05☄5′ S and longitude 35★7′ E. The central zone comprising Dodoma and Singida regions is located between latitudes 6° and 06☀8 S and longitudes 34☃0′ and 35☄5′ E. Specifically, the study used APSIM crop simulation model to investigate how rainfall variability may affect yields of improved sorghum varieties based on long-term historical rainfall and projected climate. This study, therefore, used the APSIM model to simulate sorghum growth and yield patterns over the current (baseline) climate under existing soil conditions and local management practices across selected locations in semiarid central Tanzania.
Apsim sorghum simulator#
The Agricultural Production System sIMulator (APSIM) is able to simulate growth and yield under different management practices and has been used by several studies under semiarid environments (e.g., ). A combination of field experiments and computer simulation models could be an appropriate option to comprehend the biophysical (climatic and soil conditions) factors and their interactions affecting crop yield and productivity. These contrasting results suggest the need for undertaking location specific analyses of rainfall trends to ascertain contentious assertions on the same. Some rainfall analyses have shown decreasing trends (e.g., ) associated with decreases in the number of rainy days, while others have revealed neither abrupt changes nor trends. Moreover, alongside such studies, analyses of rainfall trends are deemed necessary to understand the vulnerability of semiarid regions to historical and projected future conditions. Thus studies are essential which would combine long-term period and multiple locations (spatial-temporal analysis) under variable rainfall and soils to elucidate sorghum varieties’ performance. Moreover, over the past years concerns have grown on increased rainfall variability across seasons resulting in large yield variability and thus becoming an apparent determinant on the performance and adaptation of sorghum varieties. Thus being short lived, the ensuing experiments do not permit derivation of robust conclusions about yield performance and adaptation of sorghum varieties over a long-term period. Results from the previous experiments on improved sorghum varieties show that grain yields vary among varieties and across locations and seasons. Although short-term field experiments provide data with high degree of accuracy, they suffer from the failure to capture the interannual variability due to environmental conditions. Tegemeo, contrary to the results by Saadan et al. Previous short-term field experiments at different locations and seasons, both on-farm and on-station, obtained higher grain yields, for instance, (2.65 t ha −1) and (2.58 t ha −1) for var. Nonetheless, sorghum plays a significant role in fighting hunger and food insecurity in central Tanzania.įew long-term field experiments exist with sufficient detail in space and time to enable an understanding of variability in sorghum production due to dynamics in soil, nutrient, varieties, management, and weather processes and their interactions. According to a review by Keya and Rubaihayo sorghum ranks fifth after maize, cassava, rice, and wheat as staple in Tanzania. Sorghum ranks second in importance after maize in Africa with a mean yield of 0.8 t/ha from a cultivated area of about 24 million hectares. Moench) is an important and widely adapted small-grain cereal grown in the tropics and subtropics and a staple food grain in food-insecure regions of Asia, Africa, and Central America. We conclude that, in the event where harms imposed by moisture stress in the study area are not abated, even improved sorghum varieties are likely to perform poorly. Simulation results for future sorghum response, however, show that impacts of rainfall variability on sorghum will be overridden by temperature increase. Further analyses of simulated sorghum yields based on seasonal rainfall distribution indicate the concurrence of lower grain yields with the 10-day dry spells during the cropping season. The study confirmed that rainfall variability indeed affects yields of improved sorghum varieties. Analyses of historical rainfall indicate a mix of nonsignificant and significant trends on the onset, cessation, and length of the growing season. This study used the parameterized APSIM crop model to investigate how rainfall variability may affect yields of improved sorghum varieties based on long-term historical rainfall and projected climate. Rainfall variability has a significant impact on crop production with manifestations in frequent crop failure in semiarid areas.