Abstract
ABSTRACT: The aim of this work was to demonstrate a detailed study of the controlled release of the herbicide Tebuthiuron (TBH) encapsulated in microparticles of calcium alginate (Ca-ALG), to evaluate the phytotoxicity in different concentrations of herbicide (4, 6 and 8 g L-1), and their correlation with the depth of leaching using bioindicator plants. The Ca-ALG microparticles were prepared from the crosslinking of sodium alginate by Ca++ containing varied amounts of TBH supplied in calcium chloride (CaCl2) aqueous solution. The results showed that TBH herbicide, when encapsulated, leached to shallow depths relative to the conventional, non-encapsulated herbicide (which moved to a depth of 40-50 cm). The concentration of 4 g L-1 was the one that leached most in the PVC columns, but its mobility did not exceed 30 cm of depth. The results of the dry mass corroborated with the phytotoxicity results of the bioindicator plants, evidencing the mobility of the conventional herbicide in the soil at depths around 40 and 50 cm, while the herbicide encapsulated in the Ca-ALG microparticles did not show leaching beyond 20 -30 cm deep. The encapsulation of TBH in Ca-ALG microparticles can thus be considered as a more eco-friendly technology, reducing the leaching process and consequently soil contamination.
Highlights
Agriculture uses large amounts of pesticides to reduce productivity losses caused by biotic agents
Among the phytosanitary products regularly used in agriculture are herbicides, which are regularly used for weed control
Especially 2013 was consumed 902.408 tons of commercial product, the total amount of pesticides sold in Brazil increased relative to consumption in 2012, corresponding to 367.778 tons of active ingredient (Ferreira and Vegro, 2015) and it has an important application in agricultural productivity, it is found in worrisome quantities in superficial water bodies and can generate serious environmental impacts (Grillo et al, 2012)
Summary
Agriculture uses large amounts of pesticides to reduce productivity losses caused by biotic agents. Among the phytosanitary products regularly used in agriculture are herbicides, which are regularly used for weed control. The TBH (N- {5- (1,1-dimethylethyl)-1,3,4-thiadiazol-2-il} -n, n’dimethylurea), an inhibitor of photosystem II, has a long residual effect in the environment and a half-life of approximately 360 days. This herbicide is applied in pre-emergence in the cultivation of sugarcane, and used for control of mono and dicotyledonous species. As its final destination is the soil, according to Fontes et al (2004), Wang et al (2008), Tomco et al (2010) and Faria et al (2016), it is subject to processes such as leaching, volatilization, photodegradation, chemical and microbiological decomposition, surface runoff
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