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Questions and answers

What is the soil?

The definition of soil essentially depends on the focus of the approach, that is, the views on its use, or the study to be conducted. In soil science, it is a collection of natural, three-dimensional, dynamic bodies; consisting of solid, liquid, and gas parts; formed by mineral and organic materials; containing live matter; and occupying the largest portion of the Earth's mantle's continental breadths. It can be vegetated in and by nature and occasionally modified by anthropic interference. It is product of the weathering on a parent material, whose transformation occurs within a given relief, climate, biome and through time. Other definitions with other meanings can be found in the Brazilian Soil Classification System (SANTOS et al.,Sistema Brasileiro de Classificação de Solos, 2013a).

How are soils formed in nature?

The soil is formed as a result of the effect of active environmental factors such as the climate and organisms, on the parent material, in a given landscape and for a period of time. As a consequence, the soil undergoes successive stages of evolution, from the initial stage in which the parent material is weathered until a balance is reached, a maturity stage when its distinct trait no longer changes in the course of time. In a broad analysis, it can be said that soil genesis is based on two distinct stages: Stage A - Deposition and/or accumulation of the parent material (substratum), which represents the base for the formation, development and evolution of different soils. Stage B - Formation and differentiation of soil horizons (pedogenesis), which represent the joint or isolated action of physical, chemical and biological mechanisms on the parent material, whose intensity is conditioned by formation factors and which will bring forth different formation processes. The combination of such mechanisms and factors promotes or delays the differentiation and evolution of soil horizons, that is, the expression of formation processes, giving birth to different soils.

How are soils classified in Brazil? 

Soils are classified according to the Brazilian Soil Classification System, which consists of a classification based on morphologic and genetic characteristics described in soil horizons, contemporized in a system of taxonomic keys. The national system classifies soils in six different levels, each of which corresponding to a degree of generalization or detail, as follows: Order, Suborder, Major Group, Sub-group, Family, and Series (still in discussion). The full system including all soil types is published in the book Brazilian Soil Classification System (SANTOS et al., Sistema Brasileiro de Classificação de Solos, 2013a).

Which factors lead to soil degradation? 

There are many factors that lead to soil degradation, not only in rural areas but also in the cities. For example: deforestation; wildfires; slash and burning; excessive soil tilling downhill, monoculture over too much time; fertilization in wrong doses and without following recommendations from chemical analysis; indiscriminate use of agrochemicals; construction of residences and building in areas that are subject to collapse; garbage disposal in unsuitable places, endangering the environment and the health of the population.

How can I make the soils more productive? 

With regard to improving soil fertility to make it more agriculturally productive, it is necessary to correct pH and toxic aluminum levels (lime and/or gypsum), apply mineral fertilizers (urea, superphosphate, potassium chloride, micronutrients), organic fertilizers (poultry litter, manure, green manure with legumes) or organic-mineral fertilizers. It is important to stress that before making these procedures, it is necessary to commission a soil fertility analysis in specialized accredited laboratories. This principle is valid for any soil type or class, in any region of Brazil.

What is composting? 

Composting is a process of preparing a natural fertilizer, humus, from organic residue - animal droppings, mulch, leftover fruit and vegetables, among other materials. Such residue is mixed and piled so as to form compost heaps or stacks, which undergo management and monitoring according to technical principles.

How are soils classified in Brazil?  

The country's soil classification is under the Brazilian Soil Classification System (SiBCS), which classifies the soils at six different levels: Order, Suborder, Major Group, Subgroup, Family and Series. Brazil's Soil Map, updated based on SiBCS (Embrapa, 2006), distinguishes 13 major soil classes that are representative of Brazilian landscapes. To learn more about each of those classes, access the section Soils of Brazil

Check 200 questions and answers in the book "Soils for all", Solos para todos.