IMPACT OF TILLAGE AND ARBUSCULAR MYCORRHIZA INOCULATION ON CHARCOAL ROT AND YIELD OF MAIZE UNDER SEMIARID CONDITIONS

Abstract

Conservation tillage promotes agricultural soil sustainability and the inoculation of arbuscular mycorrhiza fungi (AMF) enhances crop growth and yields. In this study, single and combined effects of tillage systems and inoculation of AMF on charcoal rot (Macrophomina phaseolina) incidence and severity, and grain yield in maize (Zea mays L.) were determined. The study was conducted in semiarid dryland conditions. Three factors with different levels were tested in maize hybrid ‘Pioneer 3025W’®: four tillage systems (moldboard or conventional tillage, subsoil-bedding, shred-bedding and no-tillage); two fertilization levels (inoculated seeds with AMF Glomus intraradices, and fertilization rate of 60N-40P-00K); and three years of evaluation (2003 to 2005). Chlorophyll leaf index (CI), incidence (IM) and severity (SM) of M. phaseolina, arbuscular mycorrhizal colonization (AMC), and grain yield (GY) were determined. No tillage showed the lowest charcoal rot (IM and SM), but also the lowest GY. Tillage systems did not affect AMC of maize. Inoculation was similar to chemical fertilization in CI, IM, SM and GY, although with increase of AMC on mycorrhization treatment. The highest values CI, lesser IM and SM, and highest GY were found in 2004 due to the highest rain fall (460 mm) compared to 2003 (230 mm) and 2005 (125 mm). Results indicate that conservation tillage is a strategy to reduce charcoal in maize crop, although associated with grain yield losses, respect to conventional tillage.