Cover crop management and mulching to reduce root rot losses on Hass avocados in São Paulo, Brazil

• Grant number: 10/20366-1
• Support Opportunities: Regular Research Grants
• Start date: March 01, 2011
• End date: May 31, 2013
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Simone Rodrigues da Silva
• Grantee: Simone Rodrigues da Silva
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated researchers: Francisco de Assis Alves Mourão Filho

Abstract

Avocado is grown in the North, Southeast and South of Brazil, being the State of São Paulo the main producer, followed by the States of Minas Gerais, Paraná, Rio Grande do Sul and Ceará. Fresh avocados are mostly consumed by the internal market, where large, low-oil, green fruit cultivars are preferred. Nonetheless, the production of the export cultivars such as 'Hass' and 'Fuerte' has significantly increased in the State of São Paulo, leading to an expressive growth of Brazilian avocado exports, with positive effects on foreign currency incomes and employment. Despite of the outstanding edaphic and climatic conditions for avocado production in Brazil, the expansion of this crop is limited by its high susceptibility to root rot caused by Phytophthora cinnamomi. The application of mulches on the soil surface is one of the strategies to reduce the damages caused by the disease, by increasing root density and the level of antagonists to the pathogen in the shallow soil layers. The objective of this study is to evaluate different strategies for cover crop management between the rows of an avocado grove, with the aim of supplying mulch to reduce the incidence of P. cinnamomi, by improving the tree sanitary and nutritional conditions, with positive effects on fruit yield and size. The trial will be installed in a commercial grove planted with 'Hass' avocado, in the county of Limeira, São Paulo State, with predominant cover crops of Brachiaria ruziziensis and Brachiaria decumbens between the tree rows. A completely randomized block design will be utilized, with 5 treatments (cover crop managements), 4 replications and 5 trees per plot, with 3 evaluated trees. The following treatments will be evaluated: 1) No mulch applied between tree rows nor on the row zone (unmulched control); 2) Unmulched soil between the rows, with mulch applied on the row zone twice a year; 3) Two mulch applications on the row zone, obtained by sowing the cover crop between the rows twice a year with lateral windrower; 4) Four mulch applications on the row zone, obtained by sowing the cover crop between the rows four times a year with lateral windrower, and 5) Mowing the cover crop between the rows with a standard windrower four time a year, without mulch deposition on the tree rows. Nutritional and sanitary plant conditions will be assessed, as well as the vegetative and root growth and fruit yield. Cover crop biomass between rows will be also analyzed, as well as chemical and biological soil properties. Data will be submitted to analysis of variance and means will be compared by the Tukey test (P<0.05). The results obtained with this project will provide important technical information for avocado crop management under the conditions of the São Paulo State. (AU)