In many African countries, including Zambia, actual crop yields are still much lower than the potential yields. Increasing agricultural productivity to reduce food insecurity is a major concern for many policy makers and governments.
Despite efforts such as subsidies on fertilizers, crop productivity has marginally increased in Zambia. This has been attributed to: (i) low soil fertility and (ii) blanket fertilizer recommendations limited to Nitrogen (N), Phosphorus (P) and Potassium (K) for an entire country ignoring soil heterogeneity. In addition, crop production may be limited by other nutrients than N, P and K, such as Calcium, Magnesium, Sulphur, Copper, Zinc, Molybdenum, Manganese and Boron. With climate change, yields could further be negatively affected. Currently, there is little knowledge on crop yield responses to applied multiple nutrients under variable environments. This holds especially for the long-term effects since nutrient additions change soil nutrient availabilities and their interactions in time, which in turn affect crop yields.
Aim of the project
The main objective of the project is to enhance the understanding of soil nutrient interactions and their dynamics, to improve crop productivity in the face of climate change in Zambia. This will be a contribution towards developing appropriately sustainable water and soil nutrient management practices in Zambia.
To assess short-term and long-term crop yield responses to inputs of multiple nutrients by combining multiple-nutrient omission trials with model-based approaches. Scientifically sound nutrient omission pot and field experiments will be carried, using maize as the study crop, being an important crop in Zambia. Nutrient omission trials are a good tool for nutrient assessments in the short- to medium term. The quantities applied per omission treatment will be a function of target crop yield, mean element concentrations in crop type, expected nutrient use efficiencies and available soil nutrients. Long term impacts of the multi-nutrient additions on soil quality will be assessed with the adapted dynamic soil model VSD+. Long term yield response to water- and nutrient inputs will be calculated with WOFOST. The crop simulation will be adjusted to suit local conditions and run with biased corrected climate data from Global Climate Models.
Using five Global Circulation models and the WOFOST crop model, climate change impacts on maize yields in Zambia were assessed at a 0.5° × 0.5° spatial resolution for RCP 4.5 and RCP 8.5 scenarios for the near (2035-2066) and far future (2065-2096) in comparison with a reference period (1971-2001). The risk of crop failure in western and southern regions was estimated to increase due to dry spells and heat stress while crops in the northern regions will be threatened by flooding or waterlogging due to heavy precipitation. The simulated decline in the water limited and water- and nutrient limited maize yields varied from 15-20% in the near future and from 20-40% in the far future, mainly due to the expected temperature increases. Optimizing management by adjusting planting dates and maize variety selection can counteract these impacts by 6-29%. The existing gaps between water limited and nutrient limited maize yields are, however, substantially larger than the expected yield decline due to climate change. Improved nutrient management is therefore crucial to boost maize production in Zambia. More information is given in Siatwiinda, S.M., I. Supit, B. van Hove2, O. Yerokun , G.H. Ros and W. de Vries, 2021. Climate change impacts on rainfed maize yields in Zambia under conventional and optimized crop management. Climatic Change 167:39. https://doi.org/10.1007/s10584-021-03191-0