Evaluation of the Non-destructive Method Efficiency of Estimating Nitrogen Content in Jambu Plants Grown in Hydroponic System

Abstract

Jambu is considered a leafy vegetable with expressive relevance in the regions that compose the Brazilian Amazon. However, there are challenges regarding its cultivation, particularly for the nutritional management, since there is little technical information that allows an increase in the efficiency of its production. In this sense, nitrogen (N) gains prominence, since it is related to the increased yield and quality of leafy vegetables, therefore its monitoring of N content in plants is necessary. The objective of this study was to evaluate the efficiency of using the SPAD index to estimate the N content of jambu leaves, total chlorophyll concentration, as well as its relationship with dry mass accumulation due to the increase of nitrogen concentration in the nutrient solution. The design used was completely randomized with eight replications. The treatments were six nitrogen concentrations in the nutrient solution (11, 13, 15, 17, 19 and 21 mmol L -¹ ). After 21 days of transplantation, the SPAD index was measured. Then, these plants were collected to quantify the total chlorophyll, dry mass and nitrogen content. In general, the variables were explained by increasing linear models. There was a positive correlation between the SPAD index and the other characteristics evaluated. Based on the results, the best response at the concentration of 21 mmol L -¹ in the nutrient solution stands out. In addition, the SPAD index has potential to be used in the diagnosis of nitrogen status in jambu leaves.

Nitrogen Fertilization and Liming Improves Growth, Production, Gas Exchange and Post-Harvest Quality of Yellow Flower Jambu

“…The increase in the number of inflorescences due to the increased application of N in the soil is possibly related to the increase in nutritional demand due to the phenological stage of the plant, especially regarding the reproductive phase, as also observed in vegetables such as lettuce (Martins et al, 2009). Thus, it can be perceived that the growth variables of jambu are responsive to the increased availability of N and the application of limestone in the soil, due to the linear responses obtained, indicating that the plant can still express greater responses in higher concentrations of nutrients in the soil, especially N due to its importance in improving the growth, production and quality of jambu, as already demonstrated in other studies (Borges et al, 2014;Rodrigues et al, 2014;Aviz et al, 2020;Sampaio et al, 2020).…”

“…Similar to the results, Mantovani et al (2005) observed quadratic adjustment for productivity by cultivating different lettuce cultivars as a function of the increase in the N dose, i.e., they observed a reduction in the biomass of the aerial part of the plants from the 176 kg ha -1 dose of N. For jambu, in general, little work is observed regarding the effect of nitrogen fertilization on the productive performance of the crop (Borges et al, 2013;Aviz et al, 2020;Sampaio et al, 2020). Thus, Borges et al (2013) evaluating the effect of nitrogen fertilization on jambu with curral dung and urea, observed that the increase in the dose of these fertilizers in the soil promoted accumulation of fresh and dry mass from the aerial part, highlighting fertilization with urea that obtained better performance.…”

Teores de macro e micronutrientes em plantas de jambu cultivadas em ambiente protegido

“…Para Borges et al (2020a) pesquisas em relação a plantas de jambu vem crescendo, devido a necessidades de informações sobre suas ações benéficas a saúde. Apesar de sua grande importância ainda há escassez de informações técnicas acerca do seu cultivo, principalmente quanto suas exigências nutricionais (SAMPAIO et al, 2020), o que torna o processo de adubação quase que empírico.…”