Abstract
Abstract Background: Competition with weeds and the lack of selective herbicides registered for birdsfoot trefoil crops affect their development and limit their productivity. Objective: This study aimed to evaluate selectivity of post-emergent herbicides for weed control in birdsfoot trefoil crops. Methods: Experiments were carried out in a greenhouse and on a field, in both vegetative and reproductive development stages of birdsfoot trefoil crops. Treatments were composed of post-emergent herbicides recommended for soybean, corn and garlic cultivation. Phytotoxicity (PHYTO), plant height (HEI), shoot dry matter (SDM) and root dry matter (RDM) were evaluated. Data were submitted to the analysis of variance and when means were significant, they were compared by the Duncan’s Test (p≤0.05). In order to determine post-emergent herbicides which were selective to the crop, those that provided PHYTO below or equal to 15% were recommended, since they did not significantly interfere with morphological variables HEI, SDM and RDM, by comparison with the control. Results: Unlike results found in the vegetative stage, birdsfoot trefoil plants were more tolerant to phytotoxic effects of herbicides imazethapyr, chlorimuron-ethyl, cloransulam-methyl and fomesafen in the reproductive stage. The variables were negatively affected by the herbicides bentazon, glyphosate and carfentrazone-ethyl, with PHYTO higher than 40% at 20 days after treatment in the vegetative stage. Conclusions: Herbicides imazethapyr, chlorimuron-ethyl and flumetsulam, when applied as post-emergent ones, regardless of the development stage of the species, are selective to birdsfoot trefoil crops, without affecting crop development, whereas herbicides cloransulam-methyl and fomesafen are not selective to them.
Highlights
Birdsfoot trefoil (Lotus corniculatus L.), which is a forage plant that belongs to the Fabaceae family, is known for its rusticity and adaptability to edaphoclimatic variations (Grant and Small, 1996)
Results of homoscedasticity and normality tests showed that data transformation was not needed for greenhouse and field experiments in any development stage
In the evaluation that took place 10 days after application (DAA), both ALS inhibiting herbicides imazamox and flumetsulam were the only ones that were selective to the crop; they did not differ from the control (Table 3)
Summary
Birdsfoot trefoil (Lotus corniculatus L.), which is a forage plant that belongs to the Fabaceae family, is known for its rusticity and adaptability to edaphoclimatic variations (Grant and Small, 1996). It is suited to sandy, clayish, poor and moderately fertile soils, but it exhibits good tolerance to acid, badlydrained, dry and low fertile soils (Ayala and Carámbula, 2009) Even though it is a rustic crop, it has problems in the establishment stage, such as slow plant growth and development (Formoso, 2011). In this period, the crop behaves as a weak competitor and is highly susceptible to the interference of weeds that limit its development as the result of competition for essential resources, such as water, light and nutrients (Carvalho et al, 2010). Conclusions: Herbicides imazethapyr, chlorimuron-ethyl and flumetsulam, when applied as post-emergent ones, regardless of the development stage of the species, are selective to birdsfoot trefoil crops, without affecting crop development, whereas herbicides cloransulammethyl and fomesafen are not selective to them
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