Potential of slash-and-mulch system with legumes to conserve soil attributes and macrofauna diversity in Eastern Amazon

Abstract

Slash-and-burn agriculture has been practiced for thousands of years in the tropics and is sustainable in conditions of low population density, and long fallow. However, the population increase leads to intensification, and consequently the reduction of fallow, productivity, and sustainability. Then, public and private institutions with farmers, are seeking alternatives to replace this farming system. The slash-and-mulch technique for smallholder farmers is widespread in Central America and has the potential to be transferred to other regions. Nonetheless, little information is available about its potential for the eastern Amazon. The soil macrofauna is associated with soil quality and agricultural sustainability as it plays a key role in the provision of ecosystem services. Higher taxa of this fauna are often used to evaluate soil management, given that they are influenced by land-use and produce a fast response. Therefore, this study evaluates the short-term effects of the slash-and-burn or the slash-and-mulch system, after different durations of fallow on the composition, density, and diversity of the soil macrofauna higher taxa and selected physical and chemical attributes. Results are compared to old-growth forest and secondary forest fragments. The slash-and-mulch fields had soil fertility attributes similar to slash-and-burn and macrofauna diversity and composition were similar to forests. In particular, functional groups like ecosystem engineers or predators augmented with slash-and-mulch and were efficient indicators of land-use change. Despite its scarcity and their very high fragmentation, old-growth forest small remnants do conserve a more diverse and abundant soil invertebrates community of saprophages and predators, therefore their conservation is of utmost importance. This is the first study to show the potential of the slash-and-mulch system in this region to enhance the resilience of the smallholders' landscapes. Nonetheless, soil quality needs to be monitored to confirm the effective restoration of soil functionality and agriculture productivity.