Produção de mandioca com manejo sustentável das plantas infestantes

Abstract

Cassava production in Amazonas deserves to be highlighted due to its great historical, social and economic importance. The interference caused by the competition between weeds and cassava is an important limiting factor of its production. Despite the importance of this crop, there are still few studies aimed at the sustainable weed management and food security in the Amazon region. Thus, this study had the objectives of evaluating productivity, pesticide residues and soil attributes due to the weed management in cassava. Two experiments were conducted at the Experimental Farm – FAEXP of the Federal University of Amazonas, located at km 38 of the BR 174 highway, Manaus, Amazonas, from 2017 to 2020. The first experiment was carried out in a randomized complete block design with five treatments and five repetitions. The treatments were i) biological control with two species of cover plants (Brachiaria ruziziensis and Mucuna pruriens), ii) chemical control, iii) mechanical control, and iv) treatment with no weed control. The cover crops characteristics evaluated were dry weight, the percentage of cover, and rate of decomposition of plant residues. The soil bulk density and total porosity were determined. The contamination of the storage roots was evaluated based on the analysis of glyphosate residue. The second experiment was carried out in a randomized block design with six treatments and four replications. The treatments were i) biological control with three cover species (Brachiaria ruziziensis, Canavalia ensiformis and Mucuna pruriens), ii) chemical control, iii) mechanical control and iv) treatment with no weed control. Brachiaria ruziziensis presented more dry weight and higher percentage of cover compared with M. pruriens. The physical properties of soil were unaffected by any treatment evaluated. There was no detection of glyphosate and its metabolite, aminomethylphosphonic acid (AMPA), in any treatment evaluated. The treatments with chemical and mechanical weed control provided the highest yields, followed by B. ruzizienis and C. ensiformis. Cover crops improved soil properties. The use of B. ruziziensis and C. ensiformis may be an alternative for sustainable weed management in the Amazon ecosystem.