Weed biomass production and its potential use in pineapple crops in the north coast of Rio Grande do Sul, Brazil

Abstract

The objectives of this work were to identify and quantify the biomass production of weeds in order to improve its control and also to indicate those with potential use in benefit of soil and the pineapple culture. Two experiments were carried out in the field, in one same area, from Aug./97 to Oct./99 and from Mar./05 to Dez./05, at FEPAGRO, Litoral Norte, Maquiné-RS (lat. 29°54’ S, long. 50°19’, alt. 46 m, rain 1659 mm, in a Chernosolo Haplico Ortico typical). In both, the spontaneous plants were identified before planting (Aug./97 and Mar./05) and the weeds at three (Nov./97), five (Aug./05) and nine months later (Dec./05), dates when the biomass was quantified. Influenced by the season of the year, applied treatments and management of the soil and of the culture before the collections, in each date a certain group of species produced more biomass. In Nov./97, 93,4% of the total biomass were produced by Digitaria horizontalis (79,4%), Paspalum notatum (9.8%) and Ageratum conyzoides (4,2%); in Aug./05, 59,0% of the total corresponded to the production of Lolium mulfiflorum (24,6%), Paspalum paniculatum (22,0%) and Hypochoeris brasiliensis (12,4%); in Dec./05, 56,4% of the biomass originated from the productions of Digitaria horizontalis (26,5%), Eragrosfis planna( 15,6%) and Paspalum urvillei (14,3%). In the referred dates, the ten species that produced more biomass accumulated 18,25; 0,42 and 1,28 t/ha, and the five of larger production and that were identified more frequently (D.horizontalis, L. mulfiflorum, C. juncea, D. incanum and V. safiva) have potential to be used in benefit of the soil and of the pineapple crop.