Assessment of maize crop water requirements and productivity under climate change in central and southern regions of Malawi

Abstract

The rapid population growth, poverty and climate variability have resulted into food insecurity in Malawi. The impacts of climate change on agriculture will add challenges to ensuring food security and poverty reduction in the country. This study aimed at assessing maize (Zea mays L.) crop water requirements (CWR) and productivity under climate change in agro-climatic zones of the central and southern regions of Malawi comprising the Lakeshore, Central plains, Shire valley and Southern highlands. CROPWAT model was used to estimate reference crop evapotranspiration. The data used include temperature, air relative humidity, sunshine duration, wind speed, rainfall and maize yields. The 1961-1990 period was used as baseline. A survey was conducted to identify planting dates and cropping patterns. Maize crop coefficients for each zone were calculated. The CCCM and UK89 climate model scenartos representing drier and wetter climates respectively were adopted. Yield response functions to crop water deficit (CWO) were established for each zone by regression analysis. The regression models were used to predict maize yields under climate change. The results show that CWO of 10mm may cause maize yield reduction of greater than. 178kg/ha. -The results also indicate that. Shire valley, Lake-s~ore and Central plains' have higher CWR of about 250-340mm per growing period while the Southern highlands have approximately 220mm. By the year 2050, CWR is likely to increase between 8% and 17%. Lakeshore areas are likely to experience the highest increase between 1~% and 17% while the Central plains are likely to increase the least up to 9%. Generally, irrigation water requ-irement is expected to increase between 20% and 73% for the regions. The Central plains are likely to have the highest increase in water deficit and the Southern highlands which currently have sufficient rain water for maize production are anticipated to experience water shortage. In all zones, the relationships developed between maize yields and CWO were statistically significant at P<O.05.The yield is likely to decrease but Significantly in the Lakeshore areas and Central plains with ranges of 10%-70% and 10%-15% respectively. The information from this study is useful for improving crop productivity through development of adaptation' measures to climate change.