Área foliar, contenido de clorofila, y masa seca de raíces en palmas de aceite (Elaeis guineensis Jacq.) afectadas por el disturbio del plumero

El disturbio del plumero en palma de aceite se caracteriza por una anormalidad en el desarrollo del área foliar, el amarillamiento de las hojas jóvenes y el rayado clorótico longitudinal paralelo a la nervadura central. En esta investigación se determinó el área foliar de la hoja 17, el área foliar específica, los contenidos de clorofilas y la masa seca de raíces en una plantación de palma de aceite (Elaeis guineensis Jacq.) en la costa norte de Colombia con el objetivo de caracterizar los daños morfofisiológicos y cuantificar la severidad del disturbio. Para el análisis estadístico se realizó un modelo de regresión ordinal y pruebas de análisis de varianzas. Los resultados indicaron que la palma reduce su área foliar antes de que el disturbio sea evidente a nivel visual. Las hojas se vuelven más gruesas con menor contenido de clorofilas. También se presentó un aumento de la masa seca de raíces terciarias y cuaternarias en los grados iniciales. Esta variable disminuyó en los grados más severos del disturbio.

Study of the effects of glyphosate application on Collembola populations under controlled conditions

Glyphosate is the most widely used herbicide worldwide. However, the effects of this molecule on non-target populations are still a subject of study. The objective of this research was to determine the effect of the application of different glyphosate doses on variation in collembolan (springtail) populations. To accomplish this goal, samples of organic substrate that contained different collembolan populations were collected. Samples were taken to the laboratory and acclimatized for 48 hours. Glyphosate C14 was then applied to the samples in doses equivalent to 0 L ha-1, 2 L ha-1, and 4 L ha-1 under a completely randomized experimental design with three treatments and five replicates. Population counts were performed by implementing the flotation method at 0, 4, 7 and 11 days after application (DAA). We found that individuals were distributed in the families Isotomidae and Entomobryidae and divided into species of the genus Proisotoma (Börner), Lepidocyrtus (Bourlet) and Seira (Lubbock). A decrease in the number of arthropods between 40% and 60% was reported for the treatments with herbicide application at 4 and 7 DAA, showing a drop in the size of the community in those treatments in which the herbicide was applied compared to the control. However, no differences were observed between herbicide doses. Additionally, the presence of glyphosate C14 was demonstrated in dead individuals. This confirms a possible effect of the herbicide on some biological systems that led to a decrease in the size of the population.

Influence of some environmental factors on the feijoa (Acca sellowiana [Berg] Burret): A review

Climatic alterations affect the physiology, growth and production of the feijoa, a native plant to the higher zone between Brazil, Uruguay, Paraguay and Argentina. In Colombia, optimal growth temperatures are between 13 and 21°C (16°C). Very high temperatures (>32°C) affect pollination and fruit set, but low temperatures down to -4°C in adult plants do not cause significant damage. Thus, feijoa is a well-adapted plant to cold conditions since 3.04°C has been found as the base (minimum) temperature for the phase between flower bud and fruit set, while 1.76°C was measured as the base temperature for fruit development. The plant requires a minimum of 1000 hours of direct sunlight/year (optimum≥1500); the pyramidal form of the tree favors the entry of light into the crown organs. In the crown of a feijoa tree, trained with three branching levels of horizontal bent primary laterals, the outer middle quadrant produces the largest fruits, compared to those that grow in the upper quadrant. The reduced fruit growth is due to the excessive incidence of light (especially UV) and heat on these fruits on the periphery of the tree. In Colombia, altitudes between 1800 and 2700 meters above sea level (m a.s.l.) are adequate for growth and production of this fruit, while lower elevations favor the incidence of fruit flies. Precipitations between 700 and 1200 mm/year (max. 2000 mm) benefit the vegetative and reproductive performance of the tree, with an important drier season at the beginning of the reproductive season (flowering and fruit set). Due to the strength of its branches and the small, thick leaves, the tree is relatively wind resistant.

Gene action and heritability in bi-parental crosses of sunflower

A field experiment was conducted in the contrasting locations of Kafr-El-Hamam/Sharkia and Al-Arish/North Sinai agricultural research stations of the Agricultural Research Center in Egypt. We estimated the additive and dominance genetic variances, as well as heritability in the broad and narrow senses for sunflower yield and its attributes in the cross L350 x L355 using North Carolina Design-III. The magnitude of the additive variances for all studied traits at both locations in proportion to the phenotypic variances was larger than the dominance variances. The average degree of dominance was greater than the unit, as also confirmed by the high narrow-sense heritability for most of the studied traits. The genetic improvement may be achieved through the selection of genotypes with larger head diameter and heavier seed weight which also showed moderate to high values of narrow-sense heritability. Thirty-two sunflower backcrosses were grouped into eight distinct clusters/groups by canonical analysis.

Impact of biochar use on agricultural production and climate change. A review

Biochar is a solid material obtained from the thermal decomposition of biomass of diverse biological origins through a process called pyrolysis. Biochar has great potential for reducing greenhouse gas emissions, sequester carbon in the soil, rehabilitate degraded soils, and reduce dependence on chemical fertilizers in crops. It also improves the physical, chemical, and biological properties of the soil and has a positive effect on plant growth. Given these attributes, there is a growing interest for adopting its use in agriculture, soil and land reclamation, and climate change mitigation. The effects of biochar application can be neutral or positive and will be determined mainly by factors such as the origin of the raw materials, carbonization conditions, frequency of applications, the method of application and dosage. In this review, we offer a detailed examination of the origins of biochar and the technologies used for its production. We examine the various materials that have been used to produce biochars and how they affect their physico-chemical characteristics, and we describe their applications in agriculture and climate change mitigation. Finally, we list the guides that describe the standards for the production, characterization, and commercialization of biochar that seek to guarantee the quality of the product and the essential characteristics for its safe use.

Optimization of the extraction of antioxidant compounds from quinoa (Chenopodium quinoa Willd.)

Argentina contains a great biodiversity of natural foods such as quinoa that can be included in the human diet because of their nutritional characteristics and content of bioactive compounds. Among other properties, these bioactive have an antioxidant capacity that protects biomolecules from oxidant damage. Bioactive compounds contribute beneficially to diverse antimicrobial, anti-inflammatory and anti-carcinogenic physiological activities. The objective of this study was to optimize the parameters for the extraction of antioxidant compounds from quinoa: drying temperature of the grain, liquid/solid ratio (L/S), and ethanol concentration in the extraction solvent, based on an experimental design of three variables at three levels. A face-centered central composite design was used. The proposed levels were 40°C, 60°C and 80°C; 20:1, 30:1 and 40:1, and 30%, 50%, and 70% v/v of ethanol. Antioxidant capacity was determined by the capture of the DPPH free radical. The values obtained were from 16.3 mg to 161.5 mg of equivalent trolox (ET) 100 g-1 of quinoa. The maximum antioxidant capacity was obtained for the L/S ratio of 28:1, and the drying temperature of the grain was 58°C and 39% v/v of ethanol in the extraction solvent. The ethanol concentration was the most influential variable in the antioxidant compound extraction.

Compuestos antioxidantes en papa diploide: Efecto de la aplicación foliar de magnesio y manganeso

La papa es una buena fuente de compuestos con alta actividad antioxidante como los ácidos fenólicos, las antocianinas y los carotenoides, cuyos contenidos se pueden ver afectados por prácticas agronómicas como la fertilización. El presente estudio evaluó el efecto de la fertilización foliar con magnesio y manganeso sobre el contenido de compuestos fenólicos, antocianinas y carotenoides, y la actividad antioxidante en tubérculos cocidos de cuatro cultivares de papa del Grupo Phureja. Se determinó la actividad antioxidante y el contenido de fenolestotales, antocianinas totales, ácidos fenólicos y carotenoides. El cultivar Violeta presentó los mayores contenidos de fenoles totales y la mayor actividad antioxidante. Se observó un efecto significativo de la fertilización con magnesio, que aumentó el contenido de fenoles totales en el cultivar Criolla Colombia y lo redujo en los cultivares Violeta y Milagros. Estos resultados sugieren alta influencia del genotipo sobre la respuesta de las variables evaluadas. Como consecuencia, el cultivar Violeta es recomendado para el estudio de actividad antioxidante in vivo, teniendo en cuenta que mostró los mayores valores, comparado con los demás cultivares.

Sowing date and maize response to the splitting of nitrogen side-dressing fertilization

The splitting of nitrogen side-dressing fertilization with the application of a nitrogen dose at maize tasseling may increase grain yield, mainly when the crop is sown at the most favorable date to achieve high productivity. This research was carried out to evaluate the effect of sowing date on the response of maize to the splitting of nitrogen side-dressing fertilization at different growth stages. Two sowing dates were tested: preferential (10/15/2015 and 09/20/2016) and late (12/5/2015 and 12/5/2016). Six nitrogen side-dressing management treatments were evaluated at each sowing date: control without N; complete nitrogen rate applied at phenological stages V5, V10 and VT; ½ N rate at V5 + ½ N rate at V10; and ⅓ N rate at V5 + ⅓ N rate at V10 + ⅓ N rate at VT. The N rate was equivalent to 300 kg ha-1. Grain yield ranged from 8.9 to 15.3 t ha-1 in Lages and from 7.4 to 16.4 t ha-1 in Atalanta. There were no significant differences in grain yield and agronomic efficiency of nitrogen use (AE) among the treatments with the entire N side-dressing fertilization at V5 and V10 and those when the nutrient was split into two or three times, regardless of sowing date. AE was higher when the crop was sown at the preferential sowing date than in the late sowing date, regardless of N side-dressing application. The splitting of nitrogen fertilization up to the crop tasseling did not increase maize grain yield or AE.

Efficacy of imazapic/imazapyr and other herbicides in mixtures for the control of Digitaria insularis prior to soybean sowing

Herbicide mixtures, use of multiple sites of action, and other weed management practices are necessary to avoid cases of biotype resistance. The aim of this study was to evaluate the efficiency of imazapic/imazapyr and other herbicides in mixtures to control Digitaria insularis at burndown before soybean sowing. This field research was conducted in Umuarama, State of Parana (PR), Brazil, in the 2018/19 soybean season. The experiment was conducted in a randomized block experimental design with four replications and 11 treatments composed of the application of glyphosate, clethodim, haloxyfop, imazapic/imazapyr, glufosinate, 2,4-dichlorophenoxyacetic acid (2,4-D), dicamba, triclopyr, and saflufenacil, in mixtures. Weed control was evaluated as well as soybean injury and yield. An analysis of variance and F-test were performed, and the treatment means were compared by the Scott-Knott test. All treatments showed great control over the weed and low crop injury rate while maintaining soybean yield. The application of imazapic/imazapyr in mixtures with other herbicides was effective in controlling glyphosate-resistant D. insularis in burndown before soybean sowing and with sequential application of haloxyfop + glyphosate at V3 stage of soybean. This chemical management was also selective for soybean.

Narrow and twin-row plantings do not increase maize yield

Reducing row space and sowing in twin rows of maize (Zea mays L.) allow more equidistant plant distribution at the same density. The objective of this research was to evaluate the effect of these two management practices on the nitrogen content of the index leaf, the leaf area index at silking, and the grain yield of maize at different plant densities. The experiment was carried out in Lages, Santa Catarina State University, in southern Brazil during the growing seasons 2016-2017 and 2017-2018. A split-plot arrangement of a randomized complete block design was used. Two plant densities (7 and 9 plants m-2) were distributed in the main plot, and five row spaces (0.4, 0.6, 0.8, 1.0 m and twin rows 0.6 m apart with 0.18 m between rows) were evaluated in split-plots. Physiological traits and grain yield were determined on the maize hybrid P30R50YH. The experiments were sown on 10/20/2016 and 10/21/2017. Kernel yields were higher at the plant density of 9 plants m-2 than at 7 plants m-2. The row space did not affect the nitrogen content of the index leaf, the crop leaf area index at silking, and the maize grain yield. The increment of plant density was more effective than the use of narrow and twin rows to enhance P30R50YH hybrid grain yield.