CONSERVATION AGRICULTURE WITH TREES (CAWT)

Conservation Agriculture with trees (CAWT) harnesses and combines the synergies of rapid improvement of livelihoods from conservation agriculture with the longer-term but sustained crop productivity and environmental resilience derived from “fertilizer and high value trees”. CAWT derives its strength from the complimentary principles of Conservation Agriculture and Agroforestry. Conservation Agriculture with trees is poised to revolutionalize the way farming is practiced in Africa and other parts of the world.

CAWT is based on five important principles;

i) minimizing soil disturbance,

ii) maintaining land/soil cover,

iii) practicing crop rotation,

iv) good agronomic management practices,

v) incorporating nitrogen fixing trees and high value trees (e.g. fruit, medicinal and timber)

1. Minimum soil disturbance

Whether the farmer is using a hand hoe or sophisticated equipment, tilling the soil is costly in terms of labour and fuel. Organic matter is the substrate for soil life. In addition to disrupting biological processes, tillage also exposes the soil to loss of carbon through rapid mineralization of organic matter (due to an increase of oxygen content in the soil) as well as soil loss through water and wind erosion. In CAWT practices, only the spots where seeds are sown need to be prepared. This leaves the rest of the land intact. Minimum tillage enhances soil biodiversity and allows soil organisms to perform the task of tilling the soil, and this process can be called "biological tillage," which also enriches the soil in the process.

2. Permanent soil cover

When soil is exposed, it is vulnerable to sun baking and wind/water erosion. Soil cover is necessary and may be achieved with use of crop residues, fertilizer trees and other legumes. In CAWT, crop residues are left on the land to serve as mulch. To reduce greenhouse gas emissions crop residues should not be burnt at all. Fertilizer trees and cover crops can also be grown in rotation or between rows of crops to smother weeds, increase activity of soil fauna and reduce soil compaction. The fertilizer trees also shade the land during the dry season, thereby reducing soil surface temperatures.

3. Crop Rotation

Crop rotation helps to interrupt the propagation of crop pests between subsequent crops while also helping to diversify food crops.  A well balanced rotation involving cereals and legumes (e.g. maize and beans) can reduce pest build-up and increase the diversity of beneficial organisms that maintain the “checks and balances” in terms of insect pests, disease and weed control.

4. Good management practices

Smallholder farmers are often skilled in crop management. However, they need quality seed and useful information on weather conditions. With appropriate timing of planting, weeding and overall efficiency of crop management, they can minimize crop failures. The spacing and management of trees is another important consideration. Trees spaced and managed optimally will provide the necessary nutrients to maximize crop productivity. The control of pests and weeds is crucial in minimizing production and post harvest losses.

5. Incorporating nitrogen fixing trees

Growing legume trees helps to improve soil fertility through the fixation of atmospheric nitrogen, thus enriching the soil with nitrates. With appropriate selection of tree species and good management we can substantially reduce the requirement for inorganic fertilizers. In addition to this, incorporating pruning materials (leaves and litters) of these nitrogen fixing legumes in the soils enables better retention of water as well as increasing the content and efficiency of fertilizer use. Pruning materials used as mulch also reduce the soil temperature, thereby enabling a better build up of soil fauna that helps crop productivity. Therefore, the integration of tested trees into farming practices (Agroforestry) has the potential to sustain land productivity in addition to providing useful tree products such as firewood and fodder