4.2.1. Spontaneous vegetation
For farmers who applied semi-direct and conventional production systems, the appearance of spontaneous vegetation during the fallow period was the most important soil quality indicator, because the soil can get ‘natural benefits’ from the vegetation. More spontaneous vegetation results in a reduced use of inorganic fertilizer because the biomass is considered a natural organic fertilizer. Besides, the farmers believe that the decomposing vegetation increases the ‘fat’ of the soil (organic matter), maintains soil friability and soil water content, promotes earthworms and micro-organisms, and provides protection against erosion.
Looking at the appearance of spontaneous vegetation, farmers decide (each year) to apply supplemental inorganic fertilizer (usually based on nitrogen) or to postpone this action until the next annual cropping season. If they decide to apply inorganic fertilizer, they base this on soil chemical analysis. According to the farmers, if the spontaneous vegetation is dark, green and well developed in terms of plant height they assume their fields to be good for the following crop without needing soil chemical analysis to determine if additional fertilization is necessary. Thus, spontaneous vegetation is considered to contribute to soil quality and, consequently, to sustainable farming. As commented by a farmer in the second round of individual interviews: “If a field can always sustain much spontaneous vegetation during the fallow period, it means that the soil is going to keep its own life for my grandchildren.” (Reinaldo Zaikowisk). A second farmer added: “The soil health of tomorrow is like the health of a person; it depends on today's eating habits.” (Adolfo Westphal).