New photo-film: mapping soil diversity in Tanzania

The second ''photo-film'' of a  two-part series, "The Ground Beneath Your Feet," launched this week during Global Soil Week, where the International Centre for Tropical Agriculture (CIAT) in partnership with the International Fund for Agricultural Development's (IFAD) is highlighting the importance of soil, whilst debating the latest science and technology as well as methods for preserving this vital natural resource. 

In Lushoto, Tanzania, a cluster of ''climate-smart villages'' supported by  Climate Change and Food Security's (CCAFS) nestle in the stunning Eastern Arc Mountains, stretching between Tanzania and Kenya. The richly diverse landscape is a biodiversity hotspot with its sloping hillsides supporting a wide range of agricultural produce - from vegetables, beans, sugarcane and cassava to agroforestry.

But this diversity of crops takes a toll on the soils in which they are grown. Sloping land is becoming exposed to increasing rainfall, which is washing precious top soil away. Without replacing nutrients in the soil, or better management of the  soils on the steep slopes, Lushoto’s diversity will likely disappear.

Soil health is measured through indicators such as organic carbon. In Lushoto, carbon per kilogram of soil can vary massively between 15 and 150 grams within 10 kilometers. Designed originally by the 
World Agroforestry Centre, the Land Degradation Surveillance Framework has been updated and implemented globally by CIAT and regional partners, such as IFAD's Adaption for Smallholder Agriculture Programme (ASAP), to map the landscape and show variability in dynamic soil properties.
Using this framework, a biophysical baseline of key soil and land health information across the landscape can be mapped. It can show what crops can grow, where, and how well. By pinpointing what soil type farmers have on their farms, researchers can then advise farmers on inputs and management strategies to improve soil health and overall agricultural productivity.

Scientists are now linking soil health data with household survey data on cropping diversity, perceptions of climate change, and gender. Together with socio-economic data, it allows them to better understand and address farming system constraints. Lab tests help further identify soil nutrient quantities such as nitrogen content, building up a rich map of the soil.