Abstract
Coffee litter and the rain that occurs after the application of pre-emergence herbicides impact on their leaching and weed control effectiveness. The objective of this study was to evaluate the leaching and control effectiveness of indaziflam, applied on coffee litter, and under simulations of different amounts of rainfall. Two experiments in greenhouse were conducted with the application of indaziflam (0.1 kg of active ingredient - a.i. - ha-1), in a completely randomized design. The first involved the leaching of the herbicide using Urochloa plantaginea as a bioindicator, in a 8 x 4 factorial arrangement, with eight depths in the PVC column (0-0.05; 0.05-0.1; 0.1-0.15; 0.15-0.2; 0.2-0.25; 0.25-0.3; 0.3-0.35; 0.35-0.4 m) and four amounts of straw (0; 1; 3 and 5 t ha-1), this factor was isolated for rainfall simulations (10, 20 and 40 mm). The second experiment tested the effectiveness in controlling U. plantaginea, in a 4 x 3 factorial arrangement, with four amounts of litter (0; 1; 3 and 5 t ha-1) and three amounts of rainfall (10, 20 and 40 mm). Both experiments had four repetitions and controls without application of the herbicide. In leaching, a greater effect of indaziflam was found at a depth of 0-0.05 m, and the higher the simulated rainfall, the greater the phytotoxicity observed in U. plantaginea, with 39.75%, 52.50% and 92.06%, for rainfall amounts of 10, 20 and 40 mm, respectively. U. plantaginea showed high susceptibility to control by the herbicide indaziflam, and the lowest control, 82%, was observed when indaziflam was applied on 5 t ha-1 with simulation of rainfall at 10 mm. The increase in the amount of litter on the soil surface, combined with lower amounts of rainfall can reduce the leaching of indaziflam and the control of U. plantaginea.
Highlights
Weed infestation in coffee plantations can cause interference with coffee crop, affecting crop management in relation to: (1) interference with the harvesting process; (2) photosynthetic apparatus of coffee plants and (3) direct competition for resources within the same space (Dias; Alves; Lemes, 2005; Carvalho; Alves; Bianco, 2013; Ronchi; Silva, 2003; Ronchi; Silva, 2014; Oliveira; Freitas; Vieira, 2009; Da Silva et al, 2019).Among the main forms of weed management in coffee cultivation, we have the use of herbicides, the pre-emergence ones provide control of germination flows, reducing the number of post-emergence herbicide applications (Ronchi; Ferreira; Silva, 2014).In this context, indaziflam is a pre-emergence herbicide option in coffee crop, which presents the mechanism of action to inhibit cellulose biosynthesis (Tompkins, 2010)
2.2 Obtaining and preparing coffee litter Coffee litter used in the present study was removed from a coffee plantation in full production, variety Catuai Vermelho, transplanted in September 2001, with an average productivity of 50 bags ha-1, belonging to the Bela Vista site located in the city of Ibitiúra de Minas, in the state of Minas Gerais (MG)
In the application directly to the soil (0 t ha-1), the presence of the herbicide was observed to the depth 0.35-0.40 m, but the percentages of U. plantaginea phytotoxicity showed a gradual reduction as the depth increased, with averages greater than 80% only until the depths of 0.1-0.15 m
Summary
Among the main forms of weed management in coffee cultivation, we have the use of herbicides, the pre-emergence ones provide control of germination flows, reducing the number of post-emergence herbicide applications (Ronchi; Ferreira; Silva, 2014) In this context, indaziflam is a pre-emergence herbicide option in coffee crop, which presents the mechanism of action to inhibit cellulose biosynthesis (chemical class “alkylazine”) (Tompkins, 2010). Because of these physical and chemical characteristics, indaziflam is classified as lipophilic, and should be positioned in the rainy season, with applications in humid and clod-free soil, directed between the rows of the coffee crop through a directed jet at the pre-emergence of weeds (Rodrigues; Almeida, 2018) In this context, indaziflam applied on coffee litter can result in less transport of the herbicide to the soil, resulting in its low availability in the soil solution, and in the reduction of leaching and effectiveness in controlling weeds
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