Analysis of Biophysical Variables in an Onion Crop (<i>Allium cepa</i> L.) with Nitrogen Fertilization by Sentinel-2 Observations
2022
Alejandra Casella | Luciano Orden | Néstor A. Pezzola | Carolina Bellaccomo | Cristina I. Winschel | Gabriel R. Caballero | Jesús Delegido | Luis Manuel Navas Gracia | Jochem Verrelst
The production of onions bulbs (<i>Allium cepa</i> L.) requires a high amount of nitrogen. According to the demand of sustainable agriculture, the information-development and communication technologies allow for improving the efficiency of nitrogen fertilization. In the south of the province of Buenos Aires, Argentina, between 8000 and 10,000 hectares per year<sup>−1</sup> are cultivated in the districts of Villarino and Patagones. This work aimed to analyze the relationship of biophysical variables: leaf area index (LAI), canopy chlorophyll content (CCC), and canopy cover factor (fCOVER), with the nitrogen fertilization of an intermediate cycle onion crop and its effects on yield. A field trial study with different doses of granulated urea and granulated urea was carried out, where biophysical characteristics were evaluated in the field and in Sentinel-2 satellite observations. Field data correlated well with satellite data, with an R<sup>2</sup> of 0.91, 0.96, and 0.85 for LAI, fCOVER, and CCC, respectively. The application of nitrogen in all its doses produced significantly higher yields than the control. The LAI and CCC variables had a positive correlation with yield in the months of November and December. A significant difference was observed between U250 (62 Mg ha<sup>−1</sup>) and the other treatments. The U500 dose led to a yield increase of 27% compared to U250, while the difference between U750 and U500 was 6%.
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