Abstract
Detection of spatial variability of data that can improve crop management is a key factor for precision agriculture. In agriculture, there is a need for tools to assist farmers in decision-making about proper nutrient management, aiming to achieve their full productive potential. Based on that, this study aimed to (1) determine the spatial correlations between the chlorophyll index (CI) and the foliar levels of nitrogen, phosphorus and potassium (NPK) in the coffee crop using geostatistical tools; and (2) to evaluate the potential use of this index as a tool for site-specific nutrient management in an irrigated coffee field. For that, a study was carried out in a 2.1 ha area under arabica coffee cultivation in Paula Cândido, Minas Gerais State, Brazil. Samplings of the CI were performed in 1141 plants using a portable chlorophyll meter (SPAD-502). Regarding the NPK analysis, leaf samples from one of each 10 plants used to measure the CI were taken for chemical analysis (114 plants). Then, the data were submitted to descriptive and geostatistical analysis. For the spatial correlation analysis, the Moran Bivariate Global (I) and the Local index (Ixy) were used. The results showed a moderate correlation between the CI and N (0.500), showing the potential of the chlorophyll meter as a tool for site-specific nitrogen management in the coffee crop. Differently, the CI is not recommended for P and K management since they were not well correlated. Lastly, as a tool that performs indirect measurements, the results from the chlorophyll meter should be validated by field measurements to local calibrations.
Highlights
Brazil is the largest producer and exporter of coffee beans worldwide, accounting for 37% of the global production in the 2018/2019 season (USDA, 2020)
The satisfactory range (SR) of all attributes, was considered satisfactory for the cultivation of coffee in Viçosa (Minas Gerais State) according to the values established in the literature (Martinez et al, 2003)
Regarding the Skewness coefficient (Sk) that is a measure used to a measure used to demonstrate how and how much the frequency distribution deviates from the symmetry, the data distribution was classified as asymmetric on the right for the NPK (Sk > 0) and asymmetric on the left for the chlorophyll index (CI) (Sk < 0)
Summary
Brazil is the largest producer and exporter of coffee beans worldwide, accounting for 37% of the global production in the 2018/2019 season (USDA, 2020). When considering quantity and quality of the produced coffee, several factors can influence its production, among them, the nutritional status of the plant is of utmost importance for management strategies definition (Silva et al, 2010). The nutritional status of plants grown under irrigation and fertigation has been the subject of concern by coffee producers since the adoption of these systems has expanded in Brazil (Assis et al, 2015). Foliar analyses are important for detecting and correcting nutrient imbalances according to the crop demand. This information helps avoid nutritional deficiency problems that greatly affect the efficiency of fertilization and significantly reduce production (Silva et al, 2013). To make the data acquisition process more agile, the use of portable optical sensors is presented as an attractive approach
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