Search

Fast diagnostics from hyperspectral data and machine learning (ML) models to predict nitrogen (N) content and pigments in maize crop is a challenge to optimize nitrogen fertilization. Therefore, this field research identifies which ML algorithms accurately estimate nitrogen, chlorophyll, and carotenoid contents in maize crop leaves at different phenological phases using hyperspectral band data. The treatments were arranged in a factorial scheme having four N doses (0, 54, 108, and 216 kg ha− 1) combined with five leaf collection seasons at phenological stages V6 to V14. The ML models tested were artificial neural networks – ANN, decision tree adapted for prediction problems – M5P, REPTree decision tree, random forest - RF, polynomial support vector machine – SVMP, and ZeroR - ZR (control). Pearson correlations were estimated between in situ variables and those predicted by ML models. Spectral bands 530–550 nm and 690–750 nm are effective wavelengths as well as RF and SVM are effective models for the estimation of nitrogen and pigment contents. These methods can be applied in precision farming practices and assist in decision making for N management in maize crop.

Treatment with low temperatures can be used to quarantine mangoes against fruit-fly infestation. However, mangoes can develop chilling injury (CI) when stored at temperatures below 13 °C. We demonstrated that the immersion in polyol solutions can alleviate CI symptoms in 'Palmer' mangoes stored at 8 °C. These suggest that polyols can be used to reduce CI in mangoes during quarantine at low temperatures. Thus, we investigated the efficacy of applying 0.1% (v/v) glycerol, propylene glycol, or sorbitol to 'Palmer' mangoes subjected to cold treatment (1.0 °C) for 28 days. Mangoes were then ripened at 23 °C for 7 days.Among these polyols, sorbitol was the most effective in alleviating CI for up to 14 days of cold treatment. Mangoes treated with sorbitol showed lower levels of malondialdehyde (MDA) and hydrogen peroxide (HSorbitol can reduce the CI, but to an unsatisfying level, and it should be combined with other treatments storage at low temperature. © 2022 Society of Chemical Industry.

Pera-do-cerrado (Eugenia klotzschiana O. Berg) has a good appearance and adequate post-harvest shelf life. However, little information is available regarding its maturity stages. This study aimed at characterizing E. klotzschiana fruits harvested at three maturity stages (immature, physiological mature and ripe), in addition to evaluating the physical and chemical changes during storage at ambient temperature (24 ± 2 ºC and 75 % ± 5 % of RH) for up to 5 days. The ripe fruits had a higher fresh mass (98.03 g), width (5.61 cm) and ratio (5.37), and lower titratable acidity (1.27 %). In contrast, immature fruits showed a greener peel (101.32 ºh) and higher vitamin C content (11.23 mg 100 g-1). There was an increase in the fresh weight loss (3.05 %) and a decrease in the peel luminosity (67.09-57.12 L*) and vitamin C content (8.11-5.04 mg 100 g-1). However, the soluble solids (SS) values did not change during the 5 days of storage. A reduction in the titratable acidity (TA; 1.29-1.06 %) was also observed, which resulted in a higher ratio (3.81-5.84). In conclusion, E. klotzschiana fruits should be harvested ripe, as they present larger dimensions, better color, higher SS/TA (flavor) and are less acidic. RESUMO A pera-do-cerrado (Eugenia klotzschiana O. Berg) tem boa aparência e adequada vida útil pós-colheita. No entanto, existem poucas informações sobre seus estádios de maturação. Objetivou-se caracterizar frutos de pera-do-cerrado colhidos em três estádios de maturação (imaturo, fisiológico maduro e maduro), além de avaliar as alterações físicas e químicas durante o armazenamento à temperatura ambiente (24 ± 2 ºC e 75 % ± 5 % de UR), por até 5 dias. Os frutos maduros apresentaram maior massa fresca (98,03 g), largura (5,61 cm) e proporção (5,37) e menor acidez titulável (1,27 %). Em contraste, frutas imaturas apresentaram epiderme mais verde (101,32 ºh) e maior teor de vitamina C (11,23 mg 100 g-1). Houve aumento na perda de massa fresca (3,05 %), redução de luminosidade da epiderme (67,09-57,12 L*) e teor de vitamina C (8,11-5,04 mg 100 g-1). No entanto, os valores de sólidos solúveis (SS) não se alteraram durante os 5 dias de armazenamento. Também foi observada redução da acidez titulável (AT; 1,29-1,06 %), o que resultou em maior proporção (3,81-5,84). Em conclusão, frutos de pera-do-cerrado devem ser colhidos maduros, por apresentarem maiores dimensões, melhor cor, maior SS/AT (sabor) e serem menos ácidos.

Considering the lack of technical information on the water depth and nitrogen fertilization via fertigation in bell pepper cultivation, this work aimed to provide management data for its production in the northern region of Brazil. The experiment was carried out in a greenhouse at FEIGA / UFRA, with a 1.0 x 0.50 m spacing, in a randomized block design, with a 5 x 4 factorial scheme, with three replications. The treatments consisted of five water tensions in the soil (15, 25, 35, 45 and 65 kPa) and four nitrogen doses (0, 135, 265 and 395 kg.ha-1). There was no interaction between the factors of water tension in the soil and nitrogen doses for any of the variables analyzed. Height of plants, fresh shoot mass and dry shoot mass showed significant differences only for nitrogen doses. Predawn potential, showed significant difference for soil water tensions and nitrogen doses. Ahead of the conditions under which this work was carried out and the results obtained for the variables analyzed for the bell pepper cultivation in a protected environment, we found that the soil water tension of 15 kPa and the nitrogen dose of 265 kg.ha-1 were ideal for the crop.