Nitrogen (N) is an essential nutrient for plant growth and development and is especially important in the production of high quality leafy green vegetables. In this experiment, leaf N concentration, chlorophyll concentration (Chl) and weight above fresh matter (AFM) of romaine lettuce (Lactuca sativa L. var. longifolia) were estimated by correlations between in situ SPAD and atLEAF readings. Lettuce was grown in high tunnels during 42 days and was irrigated at five nitrogen levels: 0, 4, 8, 12 and 16 mEq·L-1 of NO3-, based on the Steiner nutrient solution. The N concentration, Chl concentration and AFM were determined in the laboratory, while SPAD and atLEAF readings were measured in situ weekly. SPAD readings had high, positive and significant linear correlations with N (R2 = 0.90), Chl (R2 = 0.97) and AFM (R2 = 0.98); atLEAF readings had a similar linear correlation with N (R2 = 0.91), Chl (R2 = 0.92) and AFM (R2 = 0.97). Besides, SPAD and atLEAF readings had high, positive, and significant linear correlation (R2 = 0.96). Thus, SPAD and atLEAF meters can be used to non-destructively and accurately estimate the N status of lettuce, in a reliable and quick manner during the crop production cycle. In addition, atLEAF is currently more affordable than SPAD. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

Crop segmentation is an important task in Precision Agriculture, where the use of aerial robots with an on-board camera has contributed to the development of new solution alternatives. We address the problem of fig plant segmentation in top-view RGB (Red-Green-Blue) images of a crop grown under open-field difficult circumstances of complex lighting conditions and non-ideal crop maintenance practices defined by local farmers. We present a Convolutional Neural Network (CNN) with an encoder-decoder architecture that classifies each pixel as crop or non-crop using only raw colour images as input. Our approach achieves a mean accuracy of 93.85% despite the complexity of the background and a highly variable visual appearance of the leaves. We make available our CNN code to the research community, as well as the aerial image data set and a hand-made ground truth segmentation with pixel precision to facilitate the comparison among different algorithms.

The maturity of two selections of soursop (G1 and G2) from Nayarit, Mexico, was evaluated under environmental conditions at 22°C and refrigeration at 15°C stored for 6 and 8 days, respectively. Maximum CO₂and ethylene values were present on the fifth and sixth day. The fruits exposed at 15°C had a significantly lower weight loss (5%) and showed no chilling injury. The firmness of two selections decreased more than 90%. The concentration of TSS increased to 5.3 to 15°Brix, and the titratable acidity was higher for fruit stored at 22°C. The highest concentration of phenols was recorded on the fourth day of storage at 22°C. The enzymatic activity of PPO was increased from physiological ripening to consumption ripening for both treatments. The two selections stored at 22°C registered the highest level of PME activity at ripeness. Shelf life was increased by up to 8 days (4 days at 15°C plus 4 days at 22°C) without causing chilling injury or alterations in the ripening process of the fruits. No significant differences were observed between the two selections evaluated; postharvest handling was considered to be similar; however, it would be advisable to evaluate other technologies combined with refrigeration.

The development of new postharvest technologies, which prolong useful fruit life and are also biodegradable, has promoted the use of edible coatings, prepared based on polysaccharides obtained from nonconventional sources, such as the starch and pectin in banana fruits. The objective of this study was to evaluate the effects of coatings based on starch and pectin from ‘Pear’ banana, as well as chitosan applied to ‘Ataulfo’ mango fruit. Coverings with 1 % starch and others with 1 % pectin were applied by immersion to mango fruits at physiological maturity; fruits were then stored for 12 days at 10 ± 2°C, plus another 9 days at 22 ± 2°C. The assessed variables were: weight loss (%), color (L*, a*, b*), firmness (kgf∙cm-2), total soluble solids (°Brix), and titratable acidity (%). ‘Ataulfo’ mango fruits covered with starch from ‘Pear’ banana (Musa ABB) showed greater firmness (3.34 kgf∙cm-2) and a high content of total soluble solids (16.96 °Brix), compared to the control fruits (2.26 kgf∙cm-2 and 15.8 °Brix, respectively); this coating extended the postharvest period to 21 days. The edible coatings did not affect the cuticle color of ‘Ataulfo’ mango fruits and retained their typical yellow color

Determinations of nitrogen (N) and chlorophyll (Chl) by destructive methods are precise but time-consuming and frequently expensive. The objective of this study was to determine the relationship between SPAD, atLEAF, and MC-100 readings with the concentrations of Chl, N, and fresh matter (FM) in basil 'Nufar'. In addition, we determined the relationship of the N concentration with fresh matter (FM). The plants were irrigated with five levels of N (0, 4, 8, 12, and 16 mEq·L-1 of NO3) based on a modified Steiner solution for 42 days after transplant. Plants were evaluated weekly with SPAD, atLEAF and MC-100 portable chlorophyll meters in the greenhouse, while fresh matter and the concentration of chlorophyll and N were determined in the laboratory using conventional techniques. The relationship between SPAD readings, Chl, N, and FM was strong, positive, linear, and significant, with correlation coefficients (R2) between 0.94 and 0.98. For atLEAF and MC-100 readings, R2 values were 0.96 to 0.99 and 0.96 to 0.99, respectively. The relationships between SPAD, atLEAF and MC-100 readings were strong, positive, and significant, with R2 values of 0.98. Similar behavior was shown by the relationship of N concentration and FM with R2 of 0.88. With these results, we conclude that SPAD, atLEAF, and MC-100 can be used to estimate the nutrient status of N in a non-destructive, rapid and reliable manner during basil production.

Mexican plum (Spondias purpurea L.) ‘Cuernavaqueña’ was harvested at four ripening stages, with the aim of evaluating the concentration of bioactive compounds and antioxidant capacity in the pulp and the epicarp. The highest ethylene production (9.43 mL kg h-1) and total soluble solids concentration (23.9 °Brix) was observed in the fully ripe stage. Titratable acidity was higher in green stage compared to other analyzed ripening stages in both pulp (0.48 %) and epicarp (0.32 %). Fully ripe plum epicarp presented the highest content of total phenols (GAE 190 mg g-1), flavonoids (QE 214 mg g-1), and carotenoids (853 mg g-1) compared to other ripening stages. The antioxidant capacity was higher in the epicarp of the fully ripe fruit compared to the other ripening stages: DPPH (1087 µM TE /100 g), ABTS (1534 µM TE/100 g), and FRAP (1764 µM TE/100 g). Significant correlations (r = 0.60 *** to 0.95 **) between bioactive compounds concentrations and antioxidant activity were obtained.