Management and conservation of acid soils in the Savannahs of Latin America: Lessons from the agricultural development of the Brazilian cerrados

Full text: Acid-soil savannahs represent most of the remaining land suitable for agricultural development in the world. They are considered to be marginal lands as they have low inherent productivity for agriculture and are susceptible to rapid degradation. In Latin America the majority of these lands are found in the Brazilian 'cerrados' or savannahs. They were opened up for agriculture some 30 years ago and today they supply a considerable portion of the country's agricultural produce. The development pathway in the cerrados has shifted from extensive grazing on native grasslands to improved pastures and annual monocrops. More recently no-tillage systems have been introduced along with perennial crops and integrated crop-pasture systems. Monocultures of either grain crops or pastures have proved to be unsustainable under today's conditions and alternative production systems are being developed and implemented that incorporate improved production technologies and conservation of the natural resources. No-till, minimum till and integrated crop-livestock systems are proving to be successful in terms of farmer adoption. A number of variations in no-till systems have been developed mainly by farmers in response to climate and/or soil conditions. No-till systems are more productive and economical and are perceived to be more sustainable. However there is a need to elucidate the principles and functioning of these systems in order to assess their suitability for long-term sustainability of the marginal savannah lands. The challenges that remain to ensure that these lands are developed in a more sustainable manner include social, cultural and economic aspects, a favourable policy environment and a clearer understanding of sustainability, its measurement and how farmers perceive this concept. In this article we review the lessons learned from the 'cerrados' experience including the scientific breakthroughs made. The relevance of these lessons to other tropical acid soil savannahs is also discussed. Future research topics are highlighted that include the development of further crop options with tolerance to acid soils, a better understanding of water and nutrient cycles, the development of principles of soil organic matter and crop residue management and the biological management of soil fertility. (author)