**1. Introduction**

The global demand for food will grow considerably in the coming years due to the increasing global population that is supposed to reach 9 billion people by 2050. The agriculture practiced in the tropics has key importance on food supply for much of the current global population and may become even more important for future generations.

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The soils in most of these tropical environments have high acidity and aluminum toxicity, and are rich in oxides and poor in nutrients. Therefore, the use of lime and fertilizers accounts for a large part of the agricultural production cost. Thus, to increase the environmental and economical sustainability of these environments, it is important to make rational use of fertilizers and find viable alternatives to maintain a good physical, chemical, and biological soil characteristics.

We highlight the use of green manures and crop residues as practices that can help maintain or increase the productivity capacity of the soils, since they act as conditioners of the physical, chemical, and biological characteristics. Since the ancient Greeks, Romans, and Chinese, the humanity wisely used fresh organic matter as green manures in order to maintain the land productivity, and even today, this practice has been used with the same purpose. Meanwhile, crop residues were "a problem" for many years in agriculture. The removal and/or burning of residues were common practiced used in order to accelerate its degradation in conventional tillage. The expansion of no‐till system, from the 1970s, presented several benefits by conserv‐ ing and managing residues of annual crops, especially at medium and long term. The culti‐ vation of perennial crops also presented major recent changes, such as management of weeds between plants, not using fire in renewing and especially the use of processed residues.

In this chapter, we present some of the benefits of management of green manure and crop residues, mainly the nutrient supply potential for crops of economic interest. Initially, we discuss the factors that most influence the fresh organic matter decomposition and nutrient mineralization in tropical areas. Subsequently, we discuss the concept of green manure, its management, the amount of nutrients potentially accumulated and their advantages and disadvantages. In the last part, we present examples from the main crops grown in the tropics. Regarding the annual crops, we focused on legumes with greater economic impact, since they are the first crops to be planted in rotation or succession managements. Regarding perennial crops, we present the contribution of the main crop residues and the processing of sugarcane, coffee, and eucalyptus.
