Water Stress

In sub-Saharan Africa (SSA) food production is almost entirely rain-fed, yet variable rainfall and drought are common in many poor farming regions. Climate change is likely to increase constraints on agriculture due to increased flooding and longer periods of drought. While farmers cannot control rainfall, better soil and water management on farm landscapes, such as through mulching, cover crops or drip irrigation, could increase soil moisture and alleviate some of the impacts of climate variability on crop production. Irrigation could boost crop yields by at least 50% in Africa, although it penetrates just 6% of cultivated land. The potential for irrigation investments in SSA is highly dependent on geographic, hydrologic, agronomic, and economic factors.

To achieve better understanding of the dynamics in crop production systems, HarvestChoice uses the Spatial Evaluation Framework to simulate multidimensional impacts of rainfall variability and drought on crop production systems, using historical climate records as well as projected future climate data. Site-specifically simulated crop growth and production responses under a range of climatic and management scenarios (e.g., irrigation) help identify and measure vulnerability of different crop production systems. This information will be further used to support making a better choice of investments in cropping systems to stabilize production and minimize risks.

Soil Stress

The inherent characteristics of the soil, such as depth, texture, water holding capacity, drainage, organic matter and fertility - and their evolution in response to farming practices - are major determinants of the long-term sustainability of cropping systems. In Africa, many of the soils are ancient, highly weathered, highly erodible and inherently poor. Only about 16% of the total land area in Africa is “highly suitable” for agriculture. Smallholder farming practices and the inaccessibility of fertilizers further contributes to the degradation of soils as farmers are unable to replenish the soil with the nutrients they harvested. Rates of degradation are particularly high in densely populated areas with climates favorable for food production.

A farmer’s decision to purchase fertilizer generally depends on a variety of factors: farming and household characteristics, access to markets or ports, road infrastructure, poverty rates, and population stats. Policy and development professionals rely on these same indicators to measure the potential impact and cost-effectiveness of interventions at strategic locations. The Spatial Allocation Model (SPAM) layers data on crop area, yield and production of major food staple crops in SSA using a structured fusion of satellite imagery, sub-national crop statistics, population, prices, climate, terrain and soil (explore in Tools!). MAPPR provides easy access to over one hundred layers of high-resolution spatial data, including 13 soil indicators, for SSA.

Cropping system models are useful for assessing the potential yield of crops with or without certain types of constraints, such as soil nitrogen deficiency. HarvestChoice is currently investigating a number of such crop simulations to address production constraints on crops in SSA.

Topic Contacts