Abstract
The frequent tank mixing of phytosanitary products, adjuvants, and foliar fertilizers highlights the lack of information which sustains decisions about what products can be mixed for spray application. Thus, the aim of this study was to evaluate the physical and chemical characteristics of fungicides, herbicides, and insecticides in combination with some adjuvants on the Brazilian market. The experimental design was completely randomized and spray mixes of the phytosanitary products: fungicide (azoxystrobin+benzovindiflupir), herbicide (diamônio salt of N-(phosponomethyl)) or insecticide (fenpropathrin) were evaluated in combination with adjuvants (mineral oil base, foliar fertilizer or lecithin + propionic acid), and in two application rates (95 and 52 L ha-1); all with four replications. Surface tension, electrical conductivity, pH, dynamic viscosity and density of spray mixes were evaluated. The adjuvants presented characteristics capable of significantly altering the physicochemical properties of the phytosanitary spray mixes, and thus, alter the biological effectiveness and efficiency of the spray applications. However, its effects are also dependent on the phytosanitary product added to the spray mix, which makes general recommendations a difficult task. The greatest pH reduction, as well as the greatest increase in electrical conductivity, were caused by the adjuvant lecithin + propionic acid. All phytosanitary products and adjuvants studied, associated or not, resulted in a reduction in the surface tension of the spray mix in relation to water. The magnitude of change of density and dynamic viscosity promoted by adjuvants was lower than the other characteristics evaluated.
Highlights
The mixture of phytosanitary products, adjuvants and foliar fertilizers for crop spray is a topic of interest for professionals in animal and plant production, and ecology, and with the legalization of this practice (BRAZIL, 2018) it became a theme that needs to be better studied and discussed
The physical and chemical characteristics of the fungicide, insecticide and herbicide spray mixes showed differences for all the variables analyzed (Table 3, 4 and 5), demonstrating that the spray solution is significantly affected by the addition of adjuvants
Changes in pH may interfere with the biological effects of phytosanitary products as demonstrated by Cunha and Alves (2009)
Summary
The mixture of phytosanitary products, adjuvants and foliar fertilizers for crop spray is a topic of interest for professionals in animal and plant production, and ecology, and with the legalization of this practice (BRAZIL, 2018) it became a theme that needs to be better studied and discussed. The improvement of application techniques depends on several factors, such as the knowledge of the environmental conditions at the time of application (low relative air humidity, high temperature, and wind speed above 10 m s-1 will negatively affect the efficiency of an application), the characteristics of each product and the physicochemical properties of the final phytosanitary spray mix. These properties can be altered by the phytosanitary product as well as by the adjuvants added. Among the main features that an adjuvant may present, there are the ability to change the time to drop evaporation, the size and the contact angle of the droplets, the area of leaf wetness and spreading of the product on the leaves, the electrical conductivity, pH and surface tension of the spray mix (MENDONÇA et al, 2007; CUNHA; ALVES, 2009; CUNHA et al, 2017)
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