Testing and scaling-up agroecologically based organic conservation tillage systems for family farmers in southern Brazil

Summary in the original language of the document

In southern Brazil several small farmers developed an innovative organic conservation tillage system (OCT) that does not depend on herbicides for weed control but relies instead on the use of cover crop mixtures (including various combinations of rye, vetch and raphanus) that leave a thick residue mulch layer on which traditional grain crops are directly planted, suffering very little weed interference during the growing season and reaching agronomically acceptable yield levels. Our research showed that the rye, fodder radish and vetch mixture effectively suppressed emergence of summer annual weeds in OCT systems. Because of the allelopathic effect of phytotoxins associated with the cover crops residues, farmers avoid toxic effects by placing crop seeds below the toxic layer (allelopathic zone) formed by the phytotoxins leached a short distance (5-10cm) from the mulch into the soil. In addition to weed suppression, residues also have positive effects on subsequent crops from increased soil quality parameters, improved crop nutrition, and in some cases suppression of soil-borne pathogens. Yields in most cases are 5-10% lower in OCT systems when compared to CT systems, but such differences are easily offset by the lower costs of production and the environmental benefits of OCT systems. In our trials the combination of grass and legumes enhanced biomass production and therefore mulch thickness, weed suppression, and organic matter inputs.