Allelopathy in upland rice in Brazil

Rice (Oryza sativa L.) is staple food for more than 50% world population and is grown in two ecosystems (upland and lowland). Upland rice refers to rice grown on rainfed, well drained soils, without surface water accumulation, without regular water supply and not bunded. It is mainly grown in Asia, Africa and South America. Brazil is the largest producer of upland rice in the world. The yield of upland rice is lower than lowland rice due to abiotic and biotic stresses. In Brazil, upland rice is mainly grown on Oxisols (acidic pH and poor fertility). Rice Blast disease, drought and monoculture (3–4 years) are responsible for its low yield. Allelopathy is also assumed to be responsible for this yield reduction. Adopting appropriate crop rotation and keeping land under pasture are important management strategies for sustainable production of upland rice. Additionally, developing cultivars resistant to allelochemicals is also fundamental strategy to improve the upland rice yield on allelochemically degraded soils.