Evaluación del contenido de nitrógeno durante el crecimiento del cultivo de cebolla mediante sensores para determinaciones rápidas

Onion (Allium cepa L.) is one of the main vegetable crops in Uruguay, and its yield depends largely on proper nitrogen (N) management. However, traditional nutritional diagnostic methods, such as laboratory analysis, are limited by their cost and response time. In this context, this final degree project aimed to generate knowledge to improve nutritional management in onion crops, enhancing production and reducing the risk of environmental impact. The use of a rapid method for determining nitrate content in sap using the LAQUAtwin sensor was evaluated, correlating its results with those obtained through laboratory analysis, while also studying the effect of different nitrogen doses on physiological and yield variables in two onion varieties (Armonía CRS and Pantanoso del Sauce CRS).

The experiment was conducted at the Centro Regional Sur (Progreso, Canelones) during the 2022 growing season, under a factorial design with two cultivars and three nitrogen fertilization levels. Physiological indicators such as leaf area index (LAI), bulbification index, total and marketable yield, and nitrate concentration in different plant tissues (leaf, stem, bulb, and root) were evaluated. In addition, nitrogen use efficiency and the relationship between sensor and laboratory measurements were analyzed.

Results showed positive and significant correlations between the rapid sap test and laboratory nitrogen determinations, demonstrating that the LAQUAtwin sensor is a useful tool for nitrogen diagnosis in onion crops. Nitrogen doses affected physiological variables and yield, with the best responses observed at intermediate doses. The cultivar Armonía showed higher nitrogen use efficiency and better physiological performance than Pantanoso. This approach could be extended to other horticultural crops in intensive production systems, contributing to more efficient and sustainable agriculture.