Continuing to use animal power instead of progressing to fossil-fueled mechanized power has saved millions of dollars in foreign exchange. In some systems, e.g., Southeast Asia, draught animal power has been partly or largely replaced by mechanical equipment. A number of other factors seem to be associated with the adoption of machinery, such as improvements in rural infrastructure, especially road construction, and raising educational standards. It should be noted that, in many countries, draught animals are not kept solely for traction. Draught animals also are crucial to manure production, which becomes increasingly important as fallow periods decrease and access to commercial fertilizers is limited.
Most soils lack sufficient native fertility to sustain efficient crop production.
McIntire et al. Smaling et al. Manure increased yields similarly to the best chemical fertilizer treatment on two of three soil types. More information on the contributions of animal agriculture to recycling plant nutrients and maintaining soil fertility is provided by Romney et al. In many countries, access to food is limited not by availability but by purchasing power.