How do farmers know when to plant their seeds? In Europe, farmers rely on high-quality weather data to determine optimal planting dates. In Africa, however, weather stations are scarce, resulting in poor rainfall predictions. This is particularly problematic for farmers in tropical regions, where start of the rainy season determines planting times. For centuries African farmers have relied on traditional methods to determine the onset of the rainy season. Yet, with climate change the predictable behavior of the season has become erratic. False starts have become common, where a few days of intensive rain (signalling the start of the rainy season) are followed by serious dry spells. African farmers need the same high-quality data as in Europe to adapt to a changing climate, protect them from false starts, and improve their crop yields and livelihoods.
The TU Delft and TAHMO (Trans-African Hydro-Meteorological Observatory) have launched a project with the Netherlands Embassy in Ghana to improve local weather data, help Ghanaian farmers get actionable information from it and with it foster a climate-smart horticultural sector in Ghana.
At FutureWater, we support the project by researching optimal planting dates for different crops that are commonly grown in Ghana, such as tomato, eggplants, and onions. The end goal is to supply farmers and extension officers with location-specific information on optimal planting dates for different horticultural crops.
Our methodology is inspired by Agoungbome et al. (2024) and their analysis of safe sowing windows in West Africa. We will evaluate three different approaches to determining planting dates: a rainfall-based strategy requiring 20mm accumulation with no subsequent dry spells, an agronomic onset requiring consecutive rainy days, and a model-based safe sowing window identifying dates that yield at least 90% of maximum potential.
We will use the FAO AquaCrop model to simulate crop growth under different planting dates over the past 30 years. By simulating over more than a hundred different planting dates per year, we will be able to assess the effectiveness of both traditional and weather-data informed planting strategies. Moreover, we can assess how optimal planting dates have already shifted in the past 30 years due to climate change, and how droughts affect optimal planting strategies.
This will also be the first time that FutureWater will use the open-source Python version of AquaCrop, developed by our former colleague Tim Foster. It will be exciting to see the accuracy of the AquaCrop model merge with the power of the Python framework. Where possible, we will also research how the AquaCrop OSPy model could be extended with more features from the original AquaCrop model, such as fertility stress simulation.
This project will not just explore new ground on sowing windows in Ghana, but it will also provide actionable information for Ghanaian farmers and help them better prepare for an already changing climate.
Agoungbome, S. M. D., ten Veldhuis, M.-C., & van de Giesen, N. (2024). Safe Sowing Windows for Smallholder Farmers in West Africa in the Context of Climate Variability. Climate, 12(3), 44. https://doi.org/10.3390/cli12030044
