Impacts of climate change on the yields of leguminous crops in the Guinea Savanna agroecological zone of Ghana

The impacts of climate change on crop yields are receiving renewed interest, with focus on cereals and staple crops at the regional and national scales. Yet, the impacts of climate variability on the yields of leguminous crops in the local context has not been explored. Thus, an in-depth understanding of climate change variability in the local context may support the design of locally relevant adaptation responses to current and future climate risks. This study examined the impacts of climate variables (annual rainfall, annual average temperature, rainfall indices (rainfall onset, rainfall cessation, and the length of rainy days), and the number of dry days) on the yields of leguminous crops (groundnuts, cowpeas, and soybeans) in the Guinea Savanna agroecological zone of Ghana during the period of 1989–2020. The data were analysed using Mann-Kendall's trend, Sen's slope test, correlation analysis, and Multiple Regression Analysis (MRA). The findings revealed that annual rainfall, annual average temperature, rainfall onset, rainfall cessation, and the length of rainy days, and the number of dry days all showed varied impacts on the yields of groundnuts, cowpeas, and soybeans. The trend analysis detected a marginal decrease in the amount of rainfall, rainfall onset, and the number of dry days from 1989 to 2020 (P ​> ​0.050). Annual average temperature and the length of rainy days substantially varied (P ​< ​0.050) from 1989 to 2020, showing an increasing trend. The findings also showed a marked upward trend for the yields of groundnuts, cowpeas, and soybeans during 2005–2020. The climate variables analysed above increased the yields of groundnuts, cowpeas, and soybeans by 49.0%, 55.0%, and 69.0%, respectively. The yields of groundnuts, cowpeas, and soybeans have been fluctuating with the variability of 30.0%, 28.0%, and 27.0% from 2005 to 2020, respectively. The three leguminous crops under study demonstrated unpredictable yields due to the variations of annual rainfall, annual average temperature, rainfall onset, rainfall cessation, the length of rainy days, and the number of dry days, which stressed the need for agricultural diversification, changing planting dates, using improved seed variety, and irrigation to respond to climate change. The results of this study implied that climate change considerably impacts crop production in the Guinea Savanna agroecological zone of Ghana, emphasizing the urgency of locally based and farmer-induced adaptation measures for food security and resilient agricultural systems.