4.2. Important soil quality indicators
From the group discussions it appeared that out of the 11 soil quality indicators named in the first individual interviews, only
soil colour, earthworms, soil organic matter and soil friability were unanimously considered by farmers as significant indicators of soil quality, with soil colour as the most important one. Farmers could not decide on the order of importance of these four indicators because they considered all to be interrelated. According to farmers’ comments, if the soil is darker it will contain more clay, more organic matter, produces amore abundant spontaneous vegetation, contains more earthworms and other organisms. Consequently, friability and root development would be better and yields higher. However, to get to know which indicators are important in decision-making, a second round of individual interviews was made. Farmers were (again individually) asked which of the 11 soil quality indicators named by all farmers involved in the study was useful to
their management decisions. Out of the four indicators mentioned earlier, only soil colour was considered important for decisionmaking, while two other ones were now highlighted: spontaneous vegetation and rice plant development. Additionally, they stated that their usefulness depended on the production system used, and on the type of decision to be made, i.e., day-to-day management or buying and renting land, as explained below.
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 formygrandchildren.” (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).
4.2.2. Development of the rice plant
Farmers who practice the pre-germinated system cannot evaluatethe quality of their soils by looking at the spontaneous
vegetation during the fallow period as their soils are too degraded (because, as they perceive it, the soil’s ‘fat’ is lost by soil preparation) to support much growth of the spontaneous vegetation and also because the fallow is shorter as they start to prepare the soil earlier. So these farmers have no idea of soil quality before soil preparation and planting rice. Soil quality is only assessed by observing developmentdevelopment of the rice plant in terms of colour, height, root development
and numbers of tillers.
4.2.3. Soil colour
If farmers want to buy or rent land, soil colour is the most important indicator. They assume that black soil has a high potential
production because of the characteristics (qualities) mentioned earlier and, therefore the soil has a high economic value.
4.3. The use of local soil knowledge in (development of sustainable) land management Farmers are conscious of the fact that soil quality varies from field to field because of inherent soil characteristics and the strong influence of management. Farmers are also aware of soil degradation and its association with land management. Most soil degradation in the region is observed in the pre-germinated production system. Farmers believe that rotation of irrigated rice with soya bean increases soil fertility, ‘softens’ the soil and results in better weed control.1 To improve soil quality, some farmers use fallowing and
cattle grazing for 2–3 years. Many farmers said that grazing cattle adds manure to the field, crop residues add organic matter to the soil, roots that remain in the field increase water-holding capacity of the soil and, as a result, soil life is diversified.
However, they consider that these options are limited to only a small part of the farmers, i.e., those who have relatively much land or money. The majority of these farmers adopt the conventional production system and some of them use the semi-direct system. They do not depend on just one plot of land for survival; they can divide their land in order to produce rice, soya bean or keep a field under fallow. So they spread the risk of crop failure and at the same time maintain soil fertility for rice production. Most of the small farmers are located on poor soils, in low-lying areas, where it is almost impossible to produce soya bean because of poor drainage. For rice, they are bound to use the pre-germinated system with long periods of inundation. Farmers observe that because of this, soil quality decreases, making it much more acid, and leading to iron toxicity, compaction and reduction of soil life.