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Soil quality, as a measure of the soil's capacity to function, can be assessed by indicators based on physical, chemical, and biological properties. Here we report on the assessment of soil quality in 21 rice (Oryza sativa) fields under three rice production systems (semi-direct, pre-germinated, and conventional) on four soil textural classes in the Camaquã region of Rio Grande do Sul, Brazil. The objectives of our study were: (i) to identify soil quality indicators that discriminate both management systems and soil textural classes, (ii) to establish a minimum data set of soil quality indicators and (iii) to test whether this minimum data set is correlated with yield. Twenty-nine soil biological, chemical, and physical properties were evaluated to characterize regional soil quality. Soil quality assessment was based on factor and discriminant analysis. Bulk density, available water, and micronutrients (Cu, Zn, and Mn) were the most powerful soil properties in distinguishing among different soil textural classes. Organic matter, earthworms, micronutrients (Cu and Mn), and mean weight diameter were the most powerful soil properties in assessing differences in soil quality among the rice management systems. Manganese was the property most strongly correlated with yield (adjusted r2 = 0.365, P = 0.001). The merits of sub-dividing samples according to texture and the linkage between soil quality indicators, soil functioning, plant performance, and soil management options are discussed in particular.

a b s t r a c tIn the recent past there has been increasing recognition that local knowledge of farmers can yield insight into soil quality. With regard to constraints and possibilities for the production of irrigated rice in the south of Brazil there is no documentation on local soil knowledge. The goals of this study were to answer the following questions: (1) Which soil quality perceptions do rice farmers have? (2) Which soil quality indicators are most important to them? (3) Do rice farmers use their knowledge about soil quality indicators when making soil management decisions and developing sustainable management? The study was carried out in the municipality of Camaquã-Rio Grande do Sul, Brazil. The research methods used included semi-structured interviews alternated with group discussions. Farmers named eleven characteristics as good indicators for soil quality: earthworms, soil colour, yield, spontaneous vegetation, soil organic matter, root development, soil friability, rice plant development, colour of the rice plant, number of rice tillers and cattle health. Out of these, three indicators were found to be useful in farmers' decision-making: spontaneous vegetation, rice plant development and soil colour. The potential use of local knowledge for maintaining soil quality and developing sustainable land management is discussed.

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