Taking stock of the Brazilian "zero-till revolution": A review of landmark research and farmers' practice

Two decades of extensive research and experimentation with zero-till methods has allowed "ideal" zero-till systems to emerge in Brazil, involving no soil turning, maintenance of a permanent vegetative cover, and rotations of both cash and cover crops. By exploiting rapid successions of suitable crops, for example, as well as through careful temporal and spatial planning, Brazilian examples show that it is possible to continuously cover soil, gradually increase soil organic matter (SOM) stocks, integrate livestock, move surface-applied lime through the soil profile, break compact soil layers, and reduce reliance on agrochemicals in zero-till, all under a variety of edaphic and climatic conditions, and levels of mechanization/farm sizes. Various such technologies and systems are reviewed in this chapter. However, we also note that among smallholder zero-till farmers, for example, the adaptations of "ideal" zero-till systems are manifold and complex, partial adoption of certain components and technologies rather than full adoption of zero-till systems being the norm. By examining farmers' experiences and practice, we ascertain that in many cases there is perhaps a divorce between the ideal, originating mainly from individual technology research on agricultural research stations, and farmers' reality, given the complexity of sociocconomical constraints facing the latter. We conclude that although there is a wealth of valuable zero-till experience and technologies precipitating from the Brazilian zero-till "revolution," numerous challenges in zero-till research, especially in respect to resource-poor smallholder farmers, still remain, and perhaps more holistic, participatory and adaptive on farm-research is necessary in future.