Evaluation of Penman-Piche method to estimate reference evapotranspiration in Uberaba, MG

Objetivou-se, no presente trabalho, realizar a comparação do método de determinação da evapotranspiração de referência, Penman-Monteith com o método de Penman-Piché, que utiliza medidas de evaporação pelo evaporímetro de piche. Analisou-se o período de janeiro de 2003 a dezembro de 2008, trabalhando-se com dados diários de temperatura do ar, radiação solar, umidade relativa e velocidade do vento, coletados em uma estação meteorológica automatizada, localizada na Fazenda Experimental da Uniube, MG. Para a comparação dos métodos de estimativa de evapotranspiração de referência foram utilizados: coeficientes de correlação (r), índice de concordância de Willmott (d) e o índice de confiança (c), que é o produto entre "r" e "d". Concluiu-se, no trabalho, que é possível estimar a evapotranspiração de referência de maneira satisfatória através da evaporação medida pelo evaporímetro de piche, quando se obtiveram coeficientes de correlação acima de 0,90. Nos meses de baixa umidade relativa do ar a ETo estimada pelo método que considera as medidas do evaporímetro de piche, apresenta redução na precisão, com valores de "r" de 0,70; 0,78 e 0,70, respectivamente para os meses de junho, agosto e setembro da série estudada.The present research aimed to accomplish a comparison between the reference method of estimation of evapotranspiration, Penman-Monteith, considered as the standard method by FAO, with Penman-Piché method, which uses measurements of the evaporation from the Piché's evaporimeter. The period from January 2003 to December 2008 was analyzed considering daily data of air temperature, solar radiation, relative humidity of air and wind speed, which were collected with an automatic weather station, located in the Experimental Farm of University of Uberaba, in Uberaba, in the State of Minas Gerais, Brazil. Correlation coefficient (r), Willmott agreement index (d) and confidence index (c), which is the product between "r" and "d", were used in the comparison between reference evapotranspiration estimated by Penman-Monteith (ETpm) and Penman-Piche (ETpi). It was concluded that it is possible to estimate the reference evapotranspiration in a satisfactory manner through the evaporation measured by the Piche's evaporimeter. In the months of low relative humidity of air, the evapotranspiration estimated by the method which considers the measures of Piche's evaporimeter shows reduction in precision, with "r" values of 0,70; 0,78 and 0,70, respectively for the months of June, August and September of the studied series.Consórcio Brasileiro de Pesquisa e Desenvolvimento do Caf

A Multicriteria Model for Estimating <i>Coffea arabica</i> L. Productive Potential Based on the Observation of Landscape Elements

Understanding a crop’s productive potential is crucial for optimizing resource use in agriculture, encouraging sustainable practices, and effectively planning planting and preservation efforts. Achieving precise and tailored management strategies is equally important. However, this task is particularly challenging in coffee cultivation due to the absence of accurate productivity maps for this crop. In this article, we created a multicriteria model to estimate the productive potential of coffee trees based on the observation of landscape elements that determine environmental fragility (EF). The model input parameters were slope and terrain shape data, slope flow power, and orbital image data (Landsat 8), allowing us to calculate the NDVI vegetation index. We applied the model developed to coffee trees planted in Bambuí, Minas Gerais, Brazil. We used seven plots to which we had access to yield data in a recent historical series. We compared the productivity levels predicted by the EF model and the historical productivity data of the coffee areas for the years 2016, 2018, and 2020. The model showed a high correlation between the calculated potential and the annual productivity. We noticed a strong correlation (R2) in the regression analyses conducted between the predicted productive potential and the actual productivity in 2018 and 2020 (0.91 and 0.93, respectively), although the correlation was somewhat weaker in 2016 (0.85). We conclude that our model could satisfactorily estimate the yearly production potential under a zero-harvest system in the study area

Influence of deficit irrigation on accumulation and partitioning of sugarcane biomass under drip irrigation in commercial varieties

Studies of sugarcane varieties grown under water-restrictive conditions are necessary because climate changes may result in insufficient rain for agriculture and selecting or breeding drought-tolerant cultivars will become more and more important. This study aimed to quantify the accumulation and partitioning of biomass, as well as water use efficiency of commercial sugarcane varieties under different soil water availability conditions throughout the growing season. The study was conducted during two cropping cycles in Southeast Brazil (22.7 °S, 47.6 °W). Four soil moisture availability regimens were set up to provide 100, 75, 75* and 50% of the water demand of eight commercial varieties of sugarcane (CTC15, CTC17, RB867515, RB92579, RB931011, RB966928, IAC5000, and NCo376). The total aboveground biomass was measured in both crop cycles. Our results indicate that two Brazilian varieties (CTC15 and CTC17) and one South African variety (NCo376 - Canegrow DSSAT reference), increased their water use efficiency when grown under an irrigation deficit of 75% of normal, without yielding less biomass. We did not observe any change in sucrose content under controlled water deficits; however, the studied varieties showed different biomass partitioning: RB966928 had the largest biomass fraction allocated in the stalks (0.59), while IAC5000 showed the lowest fraction (0.51). We verified that the harvest index for sucrose was not altered by reduced irrigation, but that its variability was attributed to the genotype inherited from traditional breeding programs. Thus, we conclude from these results that increased sugar yield per unit area is only possible nowadays by increasing sugarcane biomass productivity under highly efficient irrigation conditions to minimize the loss of yield from water stress