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.

No abstract

Nayarit es el principal productor de guanábana (Annona muricata L.) a nivel mundial; sin embargo, no se reconocen variedades o ecotipos presentes en la entidad, la mayoría de la producción se realiza en árboles a pie franco. Así, se presentan resultados de una investigación preliminar sobre la caracterización de frutos de guanábana (Annona muricata L.) de Tepic, Nayarit. Se seleccionaron 13 árboles de ocho años de edad, de los cuales se cosecharon de cuatro a siete frutos entre junio y julio de 2014. La masa del fruto en la población varió entre 837.8 y 2513 g, la proporción promedio de pulpa, cascara y semilla fue de 71, 20.5 y 8.5%, respectivamente, en la población. Los frutos fueron elípticos en promedio, con un contenido de semillas entre 19 y 311. El color de la epidermis del fruto fue verde opaca y poco luminosa (h= 151.7 - 164.9, C*= 9.4-21.4; L*= 30.2 -45.8), la firmeza fue en promedio de 7.3 N, los sólidos solubles totales entre 7.1 y 14 °Brix, la acidez titulable promedio fue de 0.7 % y el pH de 3.6. El análisis de conglomerados formó 4 grupos. El grupo cuatro presentó el menor número de semillas (41) y mayor cantidad de SST (13.2 oBrix). Las variables masa, dimensiones y color de la cascara ayudaron a la separación de los grupos. Se determinó variabilidad en guanábana con potencial para obtener frutos para el mercado en fresco e industrial; así como para propagación de la especie.

El biocarbón es un material sólido poroso que se produce por la conversión termoquímica de materiales orgánicos en un ambiente limitado o en ausencia de oxígeno; tiene propiedades físico-químicas aptas para el almacenamiento a largo plazo de carbono y, potencialmente, mejora la fertilidad de los suelos. El objetivo del presente estudio fue evaluar la concentración nutrimental en biocarbón elaborado con cascarilla de arroz (Oryza sativa L.) y adicionado con ácido cítrico, maleico y propiónico al 5 y 10 % como catalizadores. El biocarbón se elaboró con la técnica de carbonización hidrotérmica a 200 ºC durante 19 h. Se determinó el rendimiento de biocarbón, concentración de materia orgánica y de N, P, K, Ca, Mg, Cu, Fe, Mn, Zn, Si y Na. Los mayores rendimientos de biocarbón (66 %) se obtuvieron cuando se añadieron los ácidos maleico y cítrico al 10 %. El mayor contenido de materia orgánica (71 %) se obtuvo con ácido maleico al 5 %. En general, los tres macronutrimentos con mayor concentración (mg kg-1) fueron Ca (4386-10,988), N (3067- 4467) y K (327-3530), mientras que los micronutrimentos con mayor concentración (mg kg-1) fueron Fe (77.1-238.3) y Mn (75.4-281.4), así como el elemento benéfico Na (92.8-160.0). Por sus características de rendimiento, concentraciones de materia orgánica y nutrimental, el biocarbón de cascarilla de arroz potencialmente se podría usar como mejorador de suelos agrícolas.

ResumenEl sistema poscosecha de los frutos de guanábana (Annona muricata L.) aún no está desarrollado completamente, por lo que existen diversos problemas durante el manejo de los frutos. El ablandamiento acelerado, durante el almacenamiento postcosecha, y su comercialización es un problema constante y de suma importancia. Los frutos de guanábana son del tipo climatérico, caracterizándose por su alta tasa de respiración y producción de etileno, aunado a una actividad enzimática alta y su sensibilidad al frío. Los periodos prolongados de almacenamiento aun no son posibles, debido principalmente a la alta susceptibilidad al daño por frio. La información científica al respecto es aun limitada y dispersa y aunque se ha realizado investigación al respecto, ésta ha sido insuficiente. En este documento se hace una recopilación de las investigaciones más importantes, especialmente en las generalidades del fruto, la respiración, producción de etileno, cambios de maduración, actividad enzimática y técnicas de almacenamiento postcosecha para extender la vida de anaquel del fruto. AbstractPostharvest system of the soursop fruits (Annona muricata L.) is not yet fully developed, so there are several problems during fruit handling. Accelerated softening during postharvest storage, and its commercialization is a constant and very important problem. Soursop fruits are of climacteric type, characterized by its high respiration rate and ethylene production, coupled with a high enzymatic activity and its sensitivity to cold. Long storage periods are not yet possible, mainly due to the high susceptibility to cold damage. Scientific information on this subject is still limited and dispersed and although research has been carried out on this subject, it has been insufficient. This paper compiles the most important researches, especially about fruit generalities, respiration, ethylene production, maturation changes, enzymatic activity and postharvest storage techniques to extend the shelf life of the fruit.

-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. Index terms: Spondias purpurea; bioactive compounds; antioxidant activity. ATIVIDADE ANTIOXIDANTE E PARÂMETROS FISICOQUÍMICOS DA AMEIXA MEXICANA "CUERNAVAQUEÑA" (Spondias purpurea L.)EM DIFERENTES ESTÁGIOS DE AMADURECIMENTORESUMO -A ameixa mexicana (Spondias purpurea L.) 'Cuernavaqueña' foi colhida em quatro estádios de amadurecimento com o objetivo de avaliar a concentração de compostos bioativos e capacidade antioxidante da polpa e do epicarpo. A maior produção de etileno (9,43 mL kg h -1 ) e concentração total de sólidos solúveis (23,9 ° Brix) foi observada no estágio totalmente maduro. A acidez titulável foi maior no estádio verde em comparação com outros estádios de amadurecimento analisados tanto na polpa (0,48%) como no epicarpo (0,32%). O epicarpo da ameixa totalmente madura apresentou o maior teor de fenóis totais (GAE 190 mg g -1 ), flavonóides (QE 214 mg g -1 ) e carotenóides (853 mg g -1 ) em comparação com outros estádios de amadurecimento. A capacidade antioxidante foi maior no epicarpo do fruto totalmente maduro em comparação com os outros estádios de amadurecimento: DPPH (1087 μM TE / 100 g), ABTS (1534 μM TE / 100 g) e FRAP (1764 μM TE / 100 g). Foram obtidas correlações significativas (r = 0,60 *** a 0,95 **) entre as concentrações de compostos bioativos e a atividade antioxidante. Termos para indexação: Spondias purpurea; Compostos bioativos; atividade antioxidante.