it is driven by remarkable collaboration between farmers, the ministry of agriculture, and the conservation farming unit, a zambian nongovernmental organization. this sustainable farming incorporates 3 main elements. the first is minimal soil disturbance. conservation farmers like charles mwanyamba don't plow the land up. they make small holes year after year in the same places. this helps water permeate the soil and promotes the growth of beneficial natural tillers, like earthworms. the second is maintaining soil cover. in africa, people often sweep their fields clean, removing the natural crop residues, then make a pile of them and burn them. conservation farming teaches them to save this valuable mulch. covering the land stops evaporation, gives nutrients back to the soil, and protects the ground from the torrential rain that sometimes falls here. the third is to intercrop grains with nitrogen-rich legumes, like beans or peanuts, and eventually even trees. in this model field of the golden valley agricultural research trust north of the capital city lusaka, the trees fix nitrogen into th