Desenvolvimento de sensor capacitivo helicoidal móvel para análise da distribuição de fertilizantes minerais sólidos

Abstract

Modern agriculture uses techniques and technologies that allow the increase of productivity and possible reduction of costs to the producer. Optimizing the use of inputs by applying precise and precise dosages, in keeping with the real needs of the soil, besides providing the necessary nutrients for the correct development of the crops, reduces the costs and environmental impacts caused by the incorrect use of products such as fertilizers and agrochemicals. The productivity efficiency of a system depends mainly on the technology that is used to it, and that, in turn, its good use depends on the amount of information available to better apply its resources. The main objective of this work was to develop empirically a capacitive sensor to identify absence, presence and variations in the distribution of solid mineral fertilizer. The developed sensor identified in all tests the absence or presence of fertilizers independent of the tested formulation, presenting a coefficient of variation of less than 10% representing homogeneity and low dispersion of the data in relation to the arithmetic mean. The highest errors expressed by the standard deviation - DVP occurred in dynamic state with the formulation 06-21-12 presenting values of 6.19 pF and 7.14 pF for the gravity and overflow mechanism respectively. In the identification of variations of the fertilizer distribution, the sensor identified the reduction of fertilizer flow in all experiments when the obstruction was imposed. For the formulation 00-00-60 the capacitance reduction was approximately 55% for the gravity loading mechanism and 58% for the transhipment dosing mechanism. The other formulations presented variations close to these. In the analysis related to the identification of the fertilizer formulation, only formulations 02-28-20 and 06-21-12 in the experiments performed with the transhipment dosing mechanism do not differ statistically from each other, and all other formulations presented a statistically significant difference by ANOVA and Tukey's test at 5% significance. Moisture had an influence on the dielectric permittivity of the tested fertilizer formulations 02-20-10 and 02-28-20, generating alterations in the sensor response, being more expressive in humidity levels of 6.33% and 7.56%, respectively, presenting capacitance increase in 493.60% and 385.51% in relation to the initial humidities of 1.66% and 2%.