Deep tree roots take up soil nutrients and moisture that are out of reach of root crops. Trees shelter crops and soil surfaces from drying winds and intense sun. Tree-leaf mulch retains moisture in upper soil layers. Trees serve to continuously sustain rather than periodically rebuild soils. Fallow requirements are reduced, leaving more land in production at any one time.
Trees protect the soil and crops from damaging, erosive, and drying winds.
Tree roots bind soil, preventing down-slope erosion during rains. Tree leaf litter becomes organic humus that builds good soil structure. Trees draw nutrients from below crop root reach and then release them on the soil surface as leaves fall or branches are pruned. Trees provide habitats for animals and birds that eat crop pests and insects. Root and grain crops, tree nuts and fruits, fuelwood, posts, animal fodder, medicines, and livestock.