Due to the worldwide water supply crisis, sustainable strategies are required for a better use of this resource. The use of magnetic water has been shown to have potential for improving irrigation efficacy. However, a lack of modelling methods that correspond to the experimental results and minimize error is observed. This study aimed to estimate the replacement rates of magnetic water provided by irrigation for lettuce production using a mathematical model based on fuzzy logic and to compare multiple polynomial regression analysis and the fuzzy model. A greenhouse study was conducted with lettuce using two types of water, magnetic water (MW) and conventional water (CW), and five irrigation levels (25, 50, 75, 100 and 125%) of crop evapotranspiration. Plant samples for biometric lettuce were taken at 14, 21, 28 and 35 days after transplanting. The data were analyzed via multiple polynomial regression and fuzzy mathematical modeling, followed by an inference of the models and a comparison between the methods. The highest biometric values for lettuce were observed when irrigated with MW during the different phenological stage evaluated. The fuzzy model provided a more exact adjustment when compared to the multiple polynomial regressions.

The objective of this study was to verify, through statistical analysis, analysis of variance by the F test, regression analysis and multivariate analysis, the behavior of the nutrient contents of the biofertilizer in the soil. For this purpose, different levels of doses of liquid swine biofertilizer were used to identify which variables had relevant statistical significance, among the variables, pH, organic matter, phosphorus, potassium, calcium, magnesium, hydrogen + aluminum, aluminum, base saturation, boron, copper, iron, manganese and zinc. The soil used was the Red Latosol type. The option to use swine biofertilizer in this experiment is due to the fact that in Brazil swine farming activity generates large amounts of waste that must be used in agricultural production. The experiment was carried out with 30 plots (500-gram pots each) stored and treated in a climate-controlled greenhouse at a temperature between 28°C and 31°C, in the microbiology laboratory of the Universidade Prof. Edson Antônio Velano - Unifenas, Alfenas Campus, in a completely randomized design - DIC, with 5 treatments and 6 replicates. The liming and field moisture maintenance period was 70 days. The treatments were conducted with swine biofertilizer collected at the Retiro School Farm of Unifenas in Alfenas - MG. The proportion of soil used was 40 m3, 80 m3, 160 m3, 320 m3 and 640 m3 per ha-1 corresponding to 10 ml, 20 ml, 40 ml, 80 ml, and 160 ml of biofertilizer respectively, plus the control plot that had no biofertilizer added and was called 0ml. The amounts of biofertilizer were adopted after the first chemical analysis of the soil and swine biofertilizer. The Sisvar 19 software was used to collect and determine the data, perform statistical analysis, analysis of variance using the F test, regression analysis, determination of the coefficient (R2), and others. The results of the analysis of variance showed that there was a significant effect on some nutrients as the doses of biofertilizer were progressively increased. Thus, as the doses increased, the levels of the soil's nutritional load also increased. Therefore, the use of swine biofertilizer improved the structure and physical and chemical characteristics of the soil. Therefore, several types of plants could be cultivated after incorporating swine biofertilizer into the soil, with legumes, vegetables, and perennial crops, especially fruit, standing out in this case.

Este trabalho teve como objetivo realizar um estudo de viabilidade econômica para implantação de um biodigestor anaeróbico analisando os cálculos do Tempo de retorno (payback), Valor presente líquido (VPL), Taxa interno de retorno (TIR) obtidos de uma planilha de Excel. A pesquisa foi de viés bibliográfico com estudo empírico por permitir incluir análises secundárias não consideradas em relatos anteriores. Os biodigestores anaeróbicos são tecnologias que podem auxiliar o produtor rural e o meio ambiente com a produção de biofertilizante para agricultura e biogás para aquecimento ou produção de energia elétrica. Para fazer cálculos de viabilidade econômica usou-se o investimento de R$ 44.500,00 feito pela Unifenas para montar o projeto do biodigestor. As receitas consideradas na análise financeira foram com base na saving de energia elétrica de R$ 2.225,00 por mês e a venda de biofertilizante, totalizando uma receita mensal de R$ 2.975,00. Após a análise de viabilidade econômica, fez-se uma comparação com um investimento em Letra de crédito Imobiliário – LCI para verificar qual investimento é mais viável. Assim, este trabalho mostrou que os dois investimentos são viáveis, porém, a implantação de um biodigestor se mostra melhor porque auxilia a questão ambiental.