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Agronomy, Volume 9, Issue 7 (July 2019)

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Cover Story (view full-size image) Secondary salinization induced by brackish water irrigation has forced agricultural development to [...] Read more.
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Open AccessFeature PaperArticle
Application of Proximal Optical Sensors to Fine-Tune Nitrogen Fertilization: Opportunities for Woody Ornamentals
Agronomy 2019, 9(7), 408; https://doi.org/10.3390/agronomy9070408
Received: 17 June 2019 / Revised: 5 July 2019 / Accepted: 16 July 2019 / Published: 23 July 2019
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Abstract
Today, high amounts of residual nitrogen are regularly being reported in the open field production of hardy nursery stock. In some cases, excessive fertilizers or side-dressings are applied when circumstances are not favorable for uptake. Aquatic as well as terrestrial ecosystems are sensitive [...] Read more.
Today, high amounts of residual nitrogen are regularly being reported in the open field production of hardy nursery stock. In some cases, excessive fertilizers or side-dressings are applied when circumstances are not favorable for uptake. Aquatic as well as terrestrial ecosystems are sensitive to enrichment with nutrients, but growers also benefit when losses are avoided. In this study, the potential of proximal optical sensors to optimize nitrogen fertilization was investigated in four woody species: Acer pseudoplatanus L., Ligustrum ovalifolium Hassk., Prunus laurocerasus ‘Rotundifolia’ L. and Tilia cordata Mill. For three consecutive growing seasons, plants were grown under three different fertilization levels to generate different nitrogen contents. Plant growth and nitrogen uptake were monitored regularly and combined with sensor measurements including Soil Plant Analysis Development (SPAD), Dualex and GreenSeeker. Here, we show that optical sensors at the leaf level have good potential for assisting growers in the sustainable management of their nursery fields, especially if leaf mass per area is included. Nevertheless, care should be taken when plants with different leaf characteristics (e.g., wax-layer, color, and leaf thickness) are measured. When all measuring years were considered, high correlations (R2 ≥ 0.80) were found between area-based foliar nitrogen content and its non-destructive proxy (i.e., chlorophyll)measured by Dualex or SPAD. Based on our results, we recommend a relative rather than absolute approach at the nursery level, as the number of species and cultivars produced is very diverse. Hence, knowledge of absolute threshold values is scarce. In this relative approach, a saturation index was calculated based on the sensor measurements of plants grown in a reference plot with an ample nitrogen supply. Full article
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Open AccessArticle
Genetic Mapping Reveals Large-Effect QTL for Anther Extrusion in CIMMYT Spring Wheat
Agronomy 2019, 9(7), 407; https://doi.org/10.3390/agronomy9070407
Received: 5 June 2019 / Revised: 4 July 2019 / Accepted: 17 July 2019 / Published: 23 July 2019
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Abstract
Hybrid breeding facilitates the exploitation of heterosis and it can result in significant genetic gains and increased crop yields. Inefficient cross-pollination is a major limiting factor that hampers hybrid wheat seed production. In this study, we examined the genetic basis of anther extrusion [...] Read more.
Hybrid breeding facilitates the exploitation of heterosis and it can result in significant genetic gains and increased crop yields. Inefficient cross-pollination is a major limiting factor that hampers hybrid wheat seed production. In this study, we examined the genetic basis of anther extrusion (AE), which is an important trait in increasing cross-pollination, and thus improving seed set on the female lines and hybrid wheat seed production. We studied 300 segregating F2 plants and F2:3 families that result from a cross of two elite spring wheat lines. We observed that F2 and F2:3 populations hold significant and continuous genetic variation for AE, which suggests its reliable phenotypic selection. Composite interval mapping detected three quantitative trait loci (QTL) on chromosomes 3A, 5A, and 5D. The QTL on chromosome 5A (i.e., QAe.cimmyt-5A) was of large-effect, being consistently identified across generations, and spanned over 25 cM. Our study shows that (1) AE possesses strong genetic control (heritability), and (2) the QTL QAe.cimmyt-5A that imparted on an average of 20% of phenotypic variation can be used for marker-assisted selection (MAS) in breeding programs. In addition, pyramiding the large-effect QTL for MAS could efficiently complement the phenotypic selection since it is relatively easy and cheap to visually phenotype AE. This study reports the first large-effect QTL for AE in spring wheat, endorsing the use of this analysis in current hybrid wheat breeding and future Mendelization for the detection of underlying gene(s). Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessArticle
Influence of Pyrolyzed Grape-Seeds/Sewage Sludge Blends on the Availability of P, Fe, Cu, As and Cd to Maize
Agronomy 2019, 9(7), 406; https://doi.org/10.3390/agronomy9070406
Received: 24 May 2019 / Revised: 11 July 2019 / Accepted: 18 July 2019 / Published: 22 July 2019
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Abstract
Current intensive agricultural practices, although highly successful in terms of production, have been found to be environmentally unsustainable. One of the crucial approaches to increase agricultural sustainability is the recycling of organic wastes, since these materials often contain many beneficial nutrients for soil [...] Read more.
Current intensive agricultural practices, although highly successful in terms of production, have been found to be environmentally unsustainable. One of the crucial approaches to increase agricultural sustainability is the recycling of organic wastes, since these materials often contain many beneficial nutrients for soil and agriculture. Recently, pyrolytic conversion of biodegradable waste into charred material has gained global attention as an amendment to recycle nutrients while improving soil health. Increasing interest in the beneficial applications of pyrolyzed biomass has expanded multidisciplinary areas for science and engineering. The fertilizers used in this study were prepared by pyrolyzing mixtures of two abundant residues in Mediterranean areas: grape seeds and sewage sludge, in different proportions (100% GS, 75% GS-25% SS, 50% GS-50% SS, 25% GS-75% SS, 100% SS). In addition, fresh sludge was mixed with pyrolyzed grape seeds and included as an additional treatment. In this study, the positives and negatives of the application of biochars on agronomic potential and environmental risk have been addressed, taking into account P, Zn, Cu, Fe, As and Cd. In order to choose the best mixture, it is necessary to find a compromise between maximizing the beneficial elements that are translocated to the plant crop, as well as reducing the elements that are leached. Results of a 6-week greenhouse study indicated that the unpyrolyzed sludge mixture contained the largest amount of available nutrients Fe, Cu and P. In agreement, this treatment mixed with a Chromic Luvisol soil (40 ton/ha) increased the uptake of these elements in corn (Zea mays L.—LG ambitious). The yield also increased by 60% in this treatment. However, this mixture also contained more contaminants (As, Cd) which were extracted with Ammonium Bicarbonate-DTPA. According to our results, the treatments where grape seeds and sewage sludge were mixed at 50% and then pyrolyzed exhibited the optimal compromise between efficiency (nutrients uptake) and tolerable levels of potentially toxic elements in leachates. Full article
(This article belongs to the Special Issue Remediation of Contaminated Soil for Food Security)
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Open AccessArticle
Assessment of Stability and Adaptation Patterns of White Sugar Yield from Sugar Beet Cultivars in Temperate Climate Environments
Agronomy 2019, 9(7), 405; https://doi.org/10.3390/agronomy9070405
Received: 13 June 2019 / Revised: 7 July 2019 / Accepted: 19 July 2019 / Published: 21 July 2019
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Abstract
The yield and yield quality of sugar from the sugar beet (Beta vulgaris L.) and are determined by genotype, environment and crop management. This study was aimed at analyzing the stability of white sugar yield and the adaptation of cultivars based on [...] Read more.
The yield and yield quality of sugar from the sugar beet (Beta vulgaris L.) and are determined by genotype, environment and crop management. This study was aimed at analyzing the stability of white sugar yield and the adaptation of cultivars based on 36 modern sugar beet cultivars under different environmental conditions. The compatibility of sugar beet cultivars’ rankings between the three growing seasons and between the 11 examined locations was assessed. In addition, an attempt was made to group environments to create mega-environments. From among the 11 examined locations, four mega-environments were distinguished on the basis of the compatibility of the white sugar yield rankings. The assessment of the adaptation of cultivars and the determination of mega-environments was carried out using GGE (genotype main effects plus genotype environment interaction effects) biplots and confirmed by the Spearman rank correlation test performed for cultivars between locations. The cultivars studied were characterized by a high stability of white sugar yield in the considered growing seasons. The high compliance of the sugar yield rankings between the years contributes to a more effective recommendation of cultivars. Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessArticle
Integrating Sentinel-2 Imagery with AquaCrop for Dynamic Assessment of Tomato Water Requirements in Southern Italy
Agronomy 2019, 9(7), 404; https://doi.org/10.3390/agronomy9070404
Received: 1 June 2019 / Revised: 17 July 2019 / Accepted: 18 July 2019 / Published: 21 July 2019
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Abstract
A research study was conducted in an open field tomato crop in order to: (i) Evaluate the capability of Sentinel-2 imagery to assess tomato canopy growth and its crop water requirements; and (ii) explore the possibility to predict crop water requirements by assimilating [...] Read more.
A research study was conducted in an open field tomato crop in order to: (i) Evaluate the capability of Sentinel-2 imagery to assess tomato canopy growth and its crop water requirements; and (ii) explore the possibility to predict crop water requirements by assimilating the canopy cover estimated by Sentinel-2 imagery into AquaCrop model. The pilot area was in Campania, a region in the south west of Italy, characterized by a typical Mediterranean climate, where field campaigns were conducted in seasons 2017 and 2018 on processing tomato. Crop water use and irrigation requirement were estimated by means of three different methods: (i) The AquaCrop model; (ii) an irrigation advisory service based on Sentinel-2 imagery known as IRRISAT and (iii) assimilating the canopy cover estimated by Sentinel-2 imagery into AquaCrop model Sentinel-2 imagery proved to be effective for monitoring canopy growth and for predicting irrigation water requirements during mid-season stage of the crop, when the canopy is fully developed. Conversely, the integration of the Sentinel-2 imagery with a crop growth model can contribute to improve the irrigation water requirement predictions in the early and development stage of the crop, when the soil evaporation is not negligible with respect to the total evapotranspiration. Full article
(This article belongs to the Special Issue Remote Sensing Applications for Agriculture and Crop Modelling)
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Open AccessArticle
AgROS: A Robot Operating System Based Emulation Tool for Agricultural Robotics
Agronomy 2019, 9(7), 403; https://doi.org/10.3390/agronomy9070403
Received: 2 May 2019 / Revised: 13 June 2019 / Accepted: 17 July 2019 / Published: 20 July 2019
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Abstract
This research aims to develop a farm management emulation tool that enables agrifood producers to effectively introduce advanced digital technologies, like intelligent and autonomous unmanned ground vehicles (UGVs), in real-world field operations. To that end, we first provide a critical taxonomy of studies [...] Read more.
This research aims to develop a farm management emulation tool that enables agrifood producers to effectively introduce advanced digital technologies, like intelligent and autonomous unmanned ground vehicles (UGVs), in real-world field operations. To that end, we first provide a critical taxonomy of studies investigating agricultural robotic systems with regard to: (i) the analysis approach, i.e., simulation, emulation, real-world implementation; (ii) farming operations; and (iii) the farming type. Our analysis demonstrates that simulation and emulation modelling have been extensively applied to study advanced agricultural machinery while the majority of the extant research efforts focuses on harvesting/picking/mowing and fertilizing/spraying activities; most studies consider a generic agricultural layout. Thereafter, we developed AgROS, an emulation tool based on the Robot Operating System, which could be used for assessing the efficiency of real-world robot systems in customized fields. The AgROS allows farmers to select their actual field from a map layout, import the landscape of the field, add characteristics of the actual agricultural layout (e.g., trees, static objects), select an agricultural robot from a predefined list of commercial systems, import the selected UGV into the emulation environment, and test the robot’s performance in a quasi-real-world environment. AgROS supports farmers in the ex-ante analysis and performance evaluation of robotized precision farming operations while lays the foundations for realizing “digital twins” in agriculture. Full article
(This article belongs to the Special Issue Agricultural Route Planning and Feasibility)
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Open AccessArticle
Genetic Diversity and Geographic Differentiation of Tung Tree, Vernicia Fordii (Euphorbiaceae), A Potential Biodiesel Plant Species with Low Invasion Risk
Agronomy 2019, 9(7), 402; https://doi.org/10.3390/agronomy9070402
Received: 4 June 2019 / Revised: 5 July 2019 / Accepted: 16 July 2019 / Published: 20 July 2019
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Abstract
The tung tree, Vernicia fordii (Herbert Kenneth Airy Shaw), is a woody species native to South-East Asia (from Central and Southwest China to North Vietnam), which is also cultivated in China for the production of industrial oil. It is listed as a Category [...] Read more.
The tung tree, Vernicia fordii (Herbert Kenneth Airy Shaw), is a woody species native to South-East Asia (from Central and Southwest China to North Vietnam), which is also cultivated in China for the production of industrial oil. It is listed as a Category II invasive plant species in Florida, USA. During the introduction period of the tung tree from China to other countries in the last century, its low invasion feature led to its successful establishment in only a few countries. However, the genetic consideration for the population in its widespread native environment remains lacking. In this study, a set of 95 accessions covering most of the tung tree distribution areas in China were collected. Fifty simple sequence repeat (SSR) primer pairs were selected for the genotyping of the germplasm. Population genetics analysis indicated a medium level of genetic variation within the collected samples. The genetic diversity of the tung tree from the main production region was obviously higher than those from the marginal regions. A significant genetic differentiation occurred between the two regions, as well as among the 12 regional groups of administration. The dendrogram based on Nei’s gene diversity showed that the clustering pattern for the germplasm collections basically coincided with their geographic distribution. In their native environment, human activities have had a significant impact on the gene flow via seed movement among the production areas of the tung tree in history. This study will be helpful for molecular breeding and germplasm preservation of the tung tree, and for understanding the tung tree as a biodiesel plant species with a low invasion risk when introduced into foreign countries. Full article
(This article belongs to the Special Issue Genetic Diversity and Invasion Risk of Cultivated Plants)
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Open AccessArticle
Effect of Fertilization on Yield and Quality of Sisymbrium officinale (L.) Scop. Grown as Leafy Vegetable Crop
Agronomy 2019, 9(7), 401; https://doi.org/10.3390/agronomy9070401
Received: 14 June 2019 / Revised: 16 July 2019 / Accepted: 17 July 2019 / Published: 19 July 2019
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Abstract
Sisymbrium officinale is a wild Brassicaceae species that is known for its use in the alleviation of vocal inflammatory states. Since this species is particularly rich in bioactive compounds, there is an interest for developing cultivation protocols to use this plant as a [...] Read more.
Sisymbrium officinale is a wild Brassicaceae species that is known for its use in the alleviation of vocal inflammatory states. Since this species is particularly rich in bioactive compounds, there is an interest for developing cultivation protocols to use this plant as a leafy vegetable harvested at the 13th BBCH growth stage. Two wild populations of S. officinale (L.) Scop., denominate MI (Milan) and BG (Bergamo), have been used, and three different levels of nutrients (g/m2) have been provided such as 13 N, 7 P2O5, 8 K2O (100%); 9 N, 5 P2O5, 5.5 K2O (70%); and 6.5 N, 3.5 P2O5, 4.0 K2O (50%). The effects of different fertilization levels were evaluated on the yield, leaf pigments (chlorophylls, carotenoids), nitrate concentration, sugars content, and on the antioxidant compounds such as anthocyanins, total phenols and glucosinolates (GLS). Plant stress monitoring was performed by measuring the chlorophyll a fluorescence. Results indicated that yield was not affected and ranged from 0.18 to 0.47 kg/m2, and differences were not statistically significant for chlorophylls, carotenoids, and total sugars content. Nitrate concentrations were higher in the BG wild population (4388.65 mg/kg FW) during the second cultivation cycle and lower (1947.21 mg/kg FW) in the same wild population during the first cultivation cycle, both at the 100% fertilization level. Total phenols and anthocyanins were higher in the highest fertilization rate in the MI wild population during the second cycle. The GLS were higher in the lowest fertilization rate in the BG wild population (19 µmol/g FW) grown at the fertilization level of the 50%, and significant differences were observed in the second cycle. In conclusion, the 50% fertilization level can be considered the most suitable for our experimental conditions. Full article
(This article belongs to the Special Issue Nitrogen Fertilization in Vegetable Crops)
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Open AccessArticle
The Management Strategies of Pearl Millet Farmers to Cope with Seasonal Rainfall Variability in a Semi-Arid Agroclimate
Agronomy 2019, 9(7), 400; https://doi.org/10.3390/agronomy9070400
Received: 19 May 2019 / Revised: 11 July 2019 / Accepted: 17 July 2019 / Published: 19 July 2019
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Abstract
Rainfed agriculture constitutes around 80% of the world’s agricultural land, achieving the lowest on-farm crop yields and greatest on-farm water losses. Much of this land is in developing countries, including sub-Saharan Africa (SSA), where hunger is chronic. The primary constraint of rainfed agriculture—frequently [...] Read more.
Rainfed agriculture constitutes around 80% of the world’s agricultural land, achieving the lowest on-farm crop yields and greatest on-farm water losses. Much of this land is in developing countries, including sub-Saharan Africa (SSA), where hunger is chronic. The primary constraint of rainfed agriculture—frequently experienced in SSA—is water scarcity, heightened by the unpredictability of season onset, erratic rainfall, as well as the inability of farmers to provide adequate soil and crop management. Farmers react differently to constraints, making a variety of choices—including the timing of planting, type of land cultivation, fertilization, and scattered fields, among many others. Limited information is available on the combined effects of these strategies for improving crop yield and water use efficiency (WUE). An experiment was co-conducted with farmers over four consecutive rainy seasons (2014–2018) in Tanzania, to evaluate these strategies for single and joint effects in improving yield and WUE on rainfed pearl millet (Pennisetum glaucum (L.) R.Br.). The treatments used were flat cultivation both without and with microdosing, as well as tied ridging without and with microdose interaction, with different planting dates depending on farmers’ decisions. Results show that farmers react differently to the early, normal, or late onset of the rainy season, and cumulative rainfall during its onset, which affects their decisions regarding planting dates, yield, and WUE. Microdose fertilization increases both the yield and WUE of pearl millet significantly, with greater effects obtained using tied ridging compared to flat cultivation. For low-income smallholder farmers in a semi-arid agroclimate, using tied ridging with microdosing during early planting is an effective response to spatiotemporal rainfall variability and poor soils. Full article
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Open AccessArticle
Morphological Description and Classification of Wheat Kernels Based on Geometric Models
Agronomy 2019, 9(7), 399; https://doi.org/10.3390/agronomy9070399
Received: 25 June 2019 / Revised: 2 July 2019 / Accepted: 16 July 2019 / Published: 18 July 2019
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Abstract
Modern automated and semi-automated methods of shape analysis depart from the coordinates of the points in the outline of a figure and obtain, based on artificial vision algorithms, descriptive parameters (i.e., the length, width, area, and circularity index). These methods omit an important [...] Read more.
Modern automated and semi-automated methods of shape analysis depart from the coordinates of the points in the outline of a figure and obtain, based on artificial vision algorithms, descriptive parameters (i.e., the length, width, area, and circularity index). These methods omit an important factor: the resemblance of the examined images to a geometric figure. We have described a method based on the comparison of the outline of seed images with geometric figures. The J index is the percentage of similarity between a seed image and a geometric figure used as a model. This allows the description and classification of wheat kernels based on their similarity to geometric models. The figures used are the ellipse and the lens of different major/minor axis ratios. Kernels of different species, subspecies and varieties of wheat adjust to different figures. A relationship is found between their ploidy levels and morphological type. Kernels of diploid einkorn and ancient tetraploid emmer varieties adjust to the lens and have curvature values in their poles superior to modern “bread” varieties. Kernels of modern varieties (hexaploid common wheat) adjust to an ellipse of aspect ratio = 1.6, while varieties of tetraploid durum and Polish wheat and hexaploid spelt adjust to an ellipse of aspect ratio = 2.4. Full article
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Open AccessErratum
Erratum: Novelli, F., et al. Assimilation of Sentinel-2 Leaf Area Index Data into a Physically-Based Crop Growth Model for Yield Estimation. Agronomy 2019, 9, 255
Agronomy 2019, 9(7), 398; https://doi.org/10.3390/agronomy9070398
Received: 12 July 2019 / Accepted: 17 July 2019 / Published: 18 July 2019
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Abstract
The authors wish to correct the following erratum in this paper [...] Full article
(This article belongs to the Special Issue Remote Sensing Applications for Agriculture and Crop Modelling)
Open AccessArticle
The Impact of Possible Decadal-Scale Cold Waves on Viticulture over Europe in a Context of Global Warming
Agronomy 2019, 9(7), 397; https://doi.org/10.3390/agronomy9070397
Received: 12 June 2019 / Revised: 14 July 2019 / Accepted: 16 July 2019 / Published: 18 July 2019
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Abstract
A comprehensive analysis of all the possible impacts of future climate change is crucial for strategic plans of adaptation for viticulture. Assessments of future climate are generally based on the ensemble mean of state-of-the-art climate model projections, which prefigures a gradual warming over [...] Read more.
A comprehensive analysis of all the possible impacts of future climate change is crucial for strategic plans of adaptation for viticulture. Assessments of future climate are generally based on the ensemble mean of state-of-the-art climate model projections, which prefigures a gradual warming over Europe for the 21st century. However, a few models project single or multiple O(10) year temperature drops over the North Atlantic due to a collapsing subpolar gyre (SPG) oceanic convection. The occurrence of these decadal-scale “cold waves” may have strong repercussions over the continent, yet their actual impact is ruled out in a multi-model ensemble mean analysis. Here, we investigate these potential implications for viticulture over Europe by coupling dynamical downscaled EUR-CORDEX temperature projections for the representative concentration pathways (RCP)4.5 scenario from seven different climate models—including CSIRO-Mk3-6-0 exhibiting a SPG convection collapse—with three different phenological models simulating the main developmental stages of the grapevine. The 21st century temperature increase projected by all the models leads to an anticipation of all the developmental stages of the grapevine, shifting the optimal region for a given grapevine variety northward, and making climatic conditions suitable for high-quality wine production in some European regions that are currently not. However, in the CSIRO-Mk3-6-0 model, this long-term warming trend is suddenly interrupted by decadal-scale cold waves, abruptly pushing the suitability pattern back to conditions that are very similar to the present. These findings are crucial for winemakers in the evaluation of proper strategies to face climate change, and, overall, provide additional information for long-term plans of adaptation, which, so far, are mainly oriented towards the possibility of continuous warming conditions. Full article
(This article belongs to the Special Issue Viticulture and Winemaking under Climate Change)
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Open AccessArticle
Caffeine: The Allelochemical Responsible for the Plant Growth Inhibitory Activity of Vietnamese Tea (Camellia sinensis L. Kuntze)
Agronomy 2019, 9(7), 396; https://doi.org/10.3390/agronomy9070396
Received: 26 April 2019 / Revised: 13 July 2019 / Accepted: 15 July 2019 / Published: 18 July 2019
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Abstract
The present study aimed to examine the phytotoxic potential of seven Vietnamese tea samples based on the specific and total activity of caffeine and tea extracts on test plants. The sandwich method results indicated that the inhibitory effect of tea samples on the [...] Read more.
The present study aimed to examine the phytotoxic potential of seven Vietnamese tea samples based on the specific and total activity of caffeine and tea extracts on test plants. The sandwich method results indicated that the inhibitory effect of tea samples on the radicle and hypocotyl growth of lettuce seedlings was dependent on the concentration and type of tea samples, and also the presence of agar soluble allelochemicals. Among the seven tea samples, the leachates from Vinatea-green tea showed the highest inhibition on the radicle growth of lettuce seedlings with 50% suppression at 0.12 mg dry leaves/mL of agar. Caffeine concentration in tea samples analyzed by high-performance liquid chromatography (HPLC) varied from 20.7 to 38.2 µg/mL of dry leaves. The specific activity (EC50 value) of pure caffeine was 75 µg/mL, and the highest total activity of caffeine estimated in Vinatea-green tea was 0.51 [no unit]. Caffeine from green and oolong tea may be considered as one of the contributors to the inhibitory activity of the crude extract. Moreover, the phytotoxicity of pure caffeine and aqueous tea extracts was highly selective on the growth of different plant species. The concentration of caffeine detected from tea farm soil ranged from 0.137 to 0.145 µg/g soil. The results indicated that caffeine might be considered as a promising allelochemical from Vietnamese tea and can be a good candidate for weed management. Full article
(This article belongs to the Special Issue Weed Management & New Approaches)
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Open AccessArticle
Exogenous ABA Induces Osmotic Adjustment, Improves Leaf Water Relations and Water Use Efficiency, But Not Yield in Soybean under Water Stress
Agronomy 2019, 9(7), 395; https://doi.org/10.3390/agronomy9070395
Received: 8 June 2019 / Revised: 16 July 2019 / Accepted: 17 July 2019 / Published: 18 July 2019
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Abstract
Abscisic acid (ABA) plays a central role in the plant response to water deficit by inducing stomatal closure to conserve water when the soil dries. Exogenous ABA was applied at 45 days after sowing (DAS) as a soil drench, the physiological and seed [...] Read more.
Abscisic acid (ABA) plays a central role in the plant response to water deficit by inducing stomatal closure to conserve water when the soil dries. Exogenous ABA was applied at 45 days after sowing (DAS) as a soil drench, the physiological and seed yield response of soybean to exogenous ABA were examined as the soil was drying. Three experiments were conducted using the drought-tolerant soybean cultivar Jindou 19, grown in pots at the Yuzhong Experimental Station of Lanzhou University, China. In experiment 1, plants were exposed to progressive soil drying and leaf ABA concentration, leaf photosynthesis rate, leaf relative water content (RWC) and osmotic adjustment (OA) were measured. In experiment 2, plants were under progressive soil drying and lethal leaf water potential was measured. In experiment 3, flower production and abortion, and grain yield were measured in plants under well-watered (WW), moderate (MWD) and severe water deficits (SWD). Exogenous ABA application increased ABA accumulation in leaves and reduced the rate of soil drying. It also increased leaf photosynthetic rate, stomatal conductance and transpiration rate at 7–10 days after withholding water. The intrinsic and instantaneous water use efficiency (WUE) was consistently higher with exogenous ABA than without ABA as the soil dried. Exogenous ABA increased OA when the leaf relative water content (RWC) decreased at eight days after withholding water, lowering the lethal leaf water potential by 0.4 MPa. Exogenous ABA reduced water use, increased WUE for grain yield under WW and MWD, and had no effect on flower number, flower abortion or grain yield in any water treatment. We concluded that (1) exogenous ABA induced OA, improved leaf photosynthetic rate, leaf water relations and desiccant tolerance, but did not benefit grain yield in soybean under water deficits; (2) exogenous ABA improved the WUE at the leaf level as soil drying and WUE for grain yield under moderate water deficit. Full article
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Open AccessArticle
Paramylon Treatment Improves Quality Profile and Drought Resistance in Solanum lycopersicum L. cv. Micro-Tom
Agronomy 2019, 9(7), 394; https://doi.org/10.3390/agronomy9070394
Received: 15 May 2019 / Revised: 9 July 2019 / Accepted: 14 July 2019 / Published: 17 July 2019
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Abstract
Tomatoes, the most cultivated vegetables worldwide, require large amounts of water and are adversely affected by water stress. Solanum lycopersicum L., cv. Micro-Tom was used to assess the effects of β-(1,3)-glucan (paramylon) purified from the microalga Euglena gracilis on drought resistance and fruit [...] Read more.
Tomatoes, the most cultivated vegetables worldwide, require large amounts of water and are adversely affected by water stress. Solanum lycopersicum L., cv. Micro-Tom was used to assess the effects of β-(1,3)-glucan (paramylon) purified from the microalga Euglena gracilis on drought resistance and fruit quality profile. Plants were grown in an aeroponic system under three cultivation conditions: optimal water regimen, water scarcity regimen, and water scarcity regimen coupled with a root treatment with paramylon. Eco–physiological, physicochemical and quality parameters were monitored and compared throughout the lifecycle of the plants. Drought stress caused only a transient effect on the eco–physiological parameters of paramylon-treated plants, whereas physicochemical and biochemical parameters underwent significant variations. In particular, the fruits of paramylon-treated plants reached the first ripening stage two weeks before untreated plants grown under the optimal water regime, while the fruits of stressed untreated plants did not ripe beyond category II. Moreover, antioxidant compounds (carotenoids, phenolic acid, and vitamins) of fruits from treated plants underwent a two-fold increase with respect to untreated plants, as well as soluble carbohydrates (glucose, fructose, and sucrose). These results show that paramylon increases plant resistance to drought and highly improves the quality profile of the fruits with respect to untreated plants grown under drought stress. Full article
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Open AccessArticle
Assessing the Potential of Cereal Production Systems to Adapt to Contrasting Weather Conditions in the Mediterranean Region
Agronomy 2019, 9(7), 393; https://doi.org/10.3390/agronomy9070393
Received: 10 June 2019 / Revised: 20 June 2019 / Accepted: 20 June 2019 / Published: 17 July 2019
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Abstract
Variable rainfall, water stress, and spring frost are the main challenges for cereal growers in the Mediterranean region. The potential of wheat and barley to adapt to contrasting weather conditions was investigated through the adoption of no-till, supplemental irrigation and drought tolerant cultivars [...] Read more.
Variable rainfall, water stress, and spring frost are the main challenges for cereal growers in the Mediterranean region. The potential of wheat and barley to adapt to contrasting weather conditions was investigated through the adoption of no-till, supplemental irrigation and drought tolerant cultivars over a period of three years. Seasonal precipitation was 732, 336 and 685 mm in the first, second and third seasons, respectively. The second and third seasons were characterized by the occurrence of spring frost. No tillage did not affect productivity in either crop, while supplemental irrigation increased yield only in barley. For wheat, the grain yield was 60 and 43% respectively lower in the second and third seasons than in the first season. For barley, grain yield was 43% higher in the first season than the other two. The negative effect of frost on wheat yield was indirectly assessed by crop growth simulation. Principal component analysis shows that freezing temperatures associated with spring frost and rainfall both dictated crop growth and productivity. Full article
(This article belongs to the Special Issue Agricultural Water Management)
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Open AccessReview
Modelling Crop Transpiration in Greenhouses: Different Models for Different Applications
Agronomy 2019, 9(7), 392; https://doi.org/10.3390/agronomy9070392
Received: 9 June 2019 / Revised: 12 July 2019 / Accepted: 13 July 2019 / Published: 17 July 2019
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Abstract
Models for the evapotranspiration of greenhouse crops are needed both for accurate irrigation and for the simulation or management of the greenhouse climate. For this purpose, several evapotranspiration models have been developed and presented, all based on the Penman–Monteith approach, the “big-leaf” model. [...] Read more.
Models for the evapotranspiration of greenhouse crops are needed both for accurate irrigation and for the simulation or management of the greenhouse climate. For this purpose, several evapotranspiration models have been developed and presented, all based on the Penman–Monteith approach, the “big-leaf” model. So, on the one hand, relatively simple models have been developed for irrigation scheduling purposes, and on the other, “knowledge–mechanistic” models have been developed for climate control purposes. These models differ in the amount of detail about variables, such as stomatal and aerodynamic conductance. The aim of this review paper is to present the variables and parameters affecting greenhouse crop transpiration, and to analyze and discuss the existing models for its simulation. The common sub-models used for the simulation of crop transpiration in greenhouses (aerodynamic and stomatal conductances, and intercepted radiation) are evaluated. The worth of the multilayer models for the simulation of the mass and energy exchanges between crops and air are also analyzed and discussed. Following the presentation of the different models and approaches, it is obvious that the different applications for which these models have been developed entail varying requirements to the models, so that they cannot always be compared. Models developed in different locations (high–low latitudes or for closed or highly ventilated greenhouses) are discussed, and their sensitivity to different parameters is presented. Full article
(This article belongs to the Special Issue Crop Evapotranspiration)
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Open AccessArticle
Pollution, Source, and Relationship of Trace Metal(loid)s in Soil-Wheat System in Hebei Plain, Northern China
Agronomy 2019, 9(7), 391; https://doi.org/10.3390/agronomy9070391
Received: 10 June 2019 / Revised: 12 July 2019 / Accepted: 12 July 2019 / Published: 17 July 2019
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Abstract
To study the complex migration and transformation of trace metal(loid)s in a soil–wheat system, 225 pairs of surface soil and wheat samples were collected from the Taihang Mountains front plain, Hebei Province, northern China. The concentrations and pools (F1, water-soluble; F2, exchangeable; F3, [...] Read more.
To study the complex migration and transformation of trace metal(loid)s in a soil–wheat system, 225 pairs of surface soil and wheat samples were collected from the Taihang Mountains front plain, Hebei Province, northern China. The concentrations and pools (F1, water-soluble; F2, exchangeable; F3, carbonate-bound; F4, humic acid-bound; F5, Fe–Mn oxide-bound; F6, organic matter-bound; and F7, residual) of Cu, Pb, Zn, Cr, Ni, Cd, and Hg, and the soil properties of the samples were analyzed. The sum of the F1, F2, F3, and F4 proportions of Cd was higher than that of the other trace metal(loid)s, implying that Cd has greater mobility. We found a significant correlation (p < 0.01) between pools of trace metal(loid)s and the corresponding elements in wheat and a significant correlation (p < 0.01) between pools of trace metal(loid)s and pH, cation exchange capacity, clay, and total organic carbon. The results of principle component analysis (PCA)indicated that Cr, Ni and As mainly come from natural sources and Cu, Pb, Zn, and Cd from mixed groups related to farming and industry, Hg come from the coal burning. In addition, the total target hazard quotients showed the presence of harmful levels of trace metal(loid)s in wheat. Full article
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Open AccessArticle
Morphometry of the Wheat Spike by Analyzing 2D Images
Agronomy 2019, 9(7), 390; https://doi.org/10.3390/agronomy9070390
Received: 27 May 2019 / Revised: 8 July 2019 / Accepted: 12 July 2019 / Published: 17 July 2019
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Abstract
Spike shape and morphometric characteristics are among the key characteristics of cultivated cereals associated with their productivity. Identification of the genes controlling these traits requires morphometric data at harvesting and analysis of numerous plants, which could be automatically done using technologies of digital [...] Read more.
Spike shape and morphometric characteristics are among the key characteristics of cultivated cereals associated with their productivity. Identification of the genes controlling these traits requires morphometric data at harvesting and analysis of numerous plants, which could be automatically done using technologies of digital image analysis. A method for wheat spike morphometry utilizing 2D image analysis is proposed. Digital images are acquired in two variants: a spike on a table (one projection) or fixed with a clip (four projections). The method identifies spike and awns in the image and estimates their quantitative characteristics (area in image, length, width, circularity, etc.). Section model, quadrilaterals, and radial model are proposed for describing spike shape. Parameters of these models are used to predict spike shape type (spelt, normal, or compact) by machine learning. The mean error in spike density prediction for the images in one projection is 4.61 (~18%) versus 3.33 (~13%) for the parameters obtained using four projections. Full article
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Open AccessArticle
Nutrient Solution Strength Does Not Interact with the Daily Light Integral to Affect Hydroponic Cilantro, Dill, and Parsley Growth and Tissue Mineral Nutrient Concentrations
Agronomy 2019, 9(7), 389; https://doi.org/10.3390/agronomy9070389
Received: 24 May 2019 / Revised: 4 July 2019 / Accepted: 5 July 2019 / Published: 17 July 2019
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Abstract
Our objectives were to quantify the growth and tissue mineral nutrient concentrations of cilantro (Coriandrum sativum ‘Santo’), dill (Anethum graveolens ‘Fernleaf’), and parsley (Petroselinum crispum ‘Giant of Italy’) in response to nutrient solution electrical conductivity (EC) under low and high [...] Read more.
Our objectives were to quantify the growth and tissue mineral nutrient concentrations of cilantro (Coriandrum sativum ‘Santo’), dill (Anethum graveolens ‘Fernleaf’), and parsley (Petroselinum crispum ‘Giant of Italy’) in response to nutrient solution electrical conductivity (EC) under low and high photosynthetic daily light integrals (DLI). Three-week old seedlings of cilantro, dill, and parsley were transplanted into nutrient-film technique hydroponic systems with one of five nutrient solution EC treatments (0.5, 1.0, 2.0, 3.0, or 4.0 dS·m−1) in greenhouses under a low (~7.0 mol·m−2·d−1) or high (~18.0 mol·m−2·d−1) DLI. The DLI, but not nutrient solution EC, affected culinary herb growth. For example, fresh mass increased by 21.0 (154%), 17.1 (241%), or 13.3 g (120%) for cilantro, dill, and parsley, respectively, for plants grown under high DLI compared to those grown under a low DLI; dry mass followed a similar trend. Tissue nutrient concentrations were generally affected by either DLI or EC. For those nutrients affected by DLI, concentrations increased with increasing DLI, except for potassium (K; all species) and manganese (Mn; dill). For those nutrients affected by EC, Ca and Mg decreased with increasing EC, while the remaining increased with increasing EC. When our tissue nutrient data are compared to recommended tissue concentrations, the vast majority of elements were either within or above recommended tissue ranges for cilantro, dill, and parsley. Our results demonstrate cilantro, dill, and parsley can be successfully grown across a range of EC, regardless of the light intensity of the growing environment. Full article
(This article belongs to the Special Issue Nutrition Management of Hydroponic Vegetable Crops)
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Open AccessArticle
Silicon Improves the Production of High Antioxidant or Structural Phenolic Compounds in Barley Cultivars under Aluminum Stress
Agronomy 2019, 9(7), 388; https://doi.org/10.3390/agronomy9070388
Received: 9 May 2019 / Revised: 2 July 2019 / Accepted: 10 July 2019 / Published: 17 July 2019
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Abstract
Aluminum (Al) toxicity is one of the main growth and yield limiting factors for barley grown on acid soils. Silicon (Si) ameliorates Al toxicity as well as it promotes the phenolic compounds production that have antioxidant or structural role. We evaluated the time-dependent [...] Read more.
Aluminum (Al) toxicity is one of the main growth and yield limiting factors for barley grown on acid soils. Silicon (Si) ameliorates Al toxicity as well as it promotes the phenolic compounds production that have antioxidant or structural role. We evaluated the time-dependent kinetics of Al and Si uptake and the impact of Si on the production of antioxidant- or structural- phenols in barley cultivars at the short-term. Two barley cultivars with contrasting Al tolerance (Hordeum vulgare ‘Sebastian’, Al tolerant; and H. vulgare ‘Scarlett’, Al sensitive), exposed to either −Al (0 mM) or +Al (0.2 mM) nutrient solutions without Si (−Si) or with 2 mM (+Si) were cultured for 48 h. Aluminum and Si concentration decreased in plants at all harvest times when Al and Si were simultaneously supplied; this effect was more noticeable in ‘Scarlett’. Nevertheless, Si influenced the antioxidant system of barley irrespective of the Al tolerance of the cultivar, decreasing oxidative damage and enhancing radical scavenging activity, the production of phenolic compounds, and lignin accumulation in barley with short-term exposure to Al. Full article
(This article belongs to the Special Issue Nutrition Management of Hydroponic Vegetable Crops)
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Open AccessArticle
Effects of Nitrogen Fertilization and Seed Piece Applied Fungicides on Establishment, Tiller Dynamics, and Sucrose Yields in Successively Planted Sugarcane
Agronomy 2019, 9(7), 387; https://doi.org/10.3390/agronomy9070387
Received: 8 June 2019 / Revised: 4 July 2019 / Accepted: 8 July 2019 / Published: 16 July 2019
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Abstract
Sugarcane (Saccharum spp.) successive planting causes 25–30% yield reduction in comparison to fallow or rice rotation planting in a three-year production cycle on Florida Histosols. Field experiments were established to manage the yield losses associated with successive planting through nitrogen fertilization and [...] Read more.
Sugarcane (Saccharum spp.) successive planting causes 25–30% yield reduction in comparison to fallow or rice rotation planting in a three-year production cycle on Florida Histosols. Field experiments were established to manage the yield losses associated with successive planting through nitrogen fertilization and seed piece application of fungicides in plant and first ratoon crops each at two sites. Nitrogen fertilization treatments included 0 (N0), 50 (N50), and 100 (N100) kg ha−1 applied in furrows at the time of planting, and one split application (N50+50) with 50 kg ha−1 applied at planting and 50 kg ha−1 applied at 90 days after planting as side-dress. Fungicides treatments were mancozeb at 2.5 kg a.i. (active ingredient) ha−1, mefenoxam at 0.57 kg a.i. ha−1, and azoxystrobin at 0.30 kg a.i. ha−1 applied to seed cane pieces laid in the furrows at planting. Nitrogen fertilization showed increasing trends of the tiller and millable stalks production in plant and ratoon crops. N response varied with the time of ratooning. Overall, N50+50 produced greater tons of cane per hectare (TCH) and tons of sucrose per hectare (TSH) compared to other N treatments in plant crop and late season ratoon crop (ratooned in March). N100 treatment enhanced tillering and TCH in December ratooned crop. In 2016 plant crop, mefenoxam produced higher TCH than others, but no carryover effects were observed in ratoon crops. Both nitrogen fertilization and fungicides seem to be promising cultural practices to minimize yield losses in successive sugarcane planting in Histosols. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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Open AccessArticle
Foliar Zn Spraying Simultaneously Improved Concentrations and Bioavailability of Zn and Fe in Maize Grains Irrespective of Foliar Sucrose Supply
Agronomy 2019, 9(7), 386; https://doi.org/10.3390/agronomy9070386
Received: 8 June 2019 / Revised: 14 July 2019 / Accepted: 15 July 2019 / Published: 16 July 2019
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Abstract
Zinc (Zn) deficiency is a global nutritional problem that is reduced through agronomic biofortification. In the current study, the effects of foliar spraying of exogenous ZnSO4·7H2O (0.2% in Quzhou and 0.3% in Licheng, w/v) and/or sucrose [...] Read more.
Zinc (Zn) deficiency is a global nutritional problem that is reduced through agronomic biofortification. In the current study, the effects of foliar spraying of exogenous ZnSO4·7H2O (0.2% in Quzhou and 0.3% in Licheng, w/v) and/or sucrose (10.0%, w/v) on maize (Zea mays L.) agronomic traits; concentrations of Zn, iron (Fe), calcium (Ca), total phosphorus (P), phytic acid (PA) P, carbon (C), and nitrogen (N); C/N ratios; and Zn and Fe bioavailability (as evaluated by molar ratios of PA/Zn, PA × Ca/Zn, PA/Fe and PA × Ca/Fe) in maize grains were studied under field conditions for two years at two experimental locations. The results confirmed that there were no significant differences in maize agronomic traits following the various foliar treatments. Compared with the control treatment of foliar spraying with deionized water, foliar applications of Zn alone or combined with sucrose significantly increased maize grain Zn concentrations by 29.2–58.3% in Quzhou (from 18.4–19.9 to 25.2–29.6 mg/kg) and by 39.8–47.8% in Licheng (from 24.9 to 34.8–36.8 mg/kg), as well as its bioavailability. No significant differences were found between the foliar spraying of deionized water and sucrose, and between Zn-only and “sucrose + Zn” at each N application rate and across different N application rates and experimental sites. Similar results were observed for maize grain Fe concentrations and bioavailability, but the Fe concentration increased to a smaller extent than Zn. Foliar Zn spraying alone or with sucrose increased maize grain Fe concentrations by 4.7–28.4% in Quzhou (from 13.4–17.1 to 15.2–18.5 mg/kg) and by 15.4–25.0% in Licheng (from 24.0 to 27.7–30.0 mg/kg). Iron concentrations were significantly and positively correlated with Zn at each N application rate and across different N application rates and experimental locations, indicating that foliar Zn spraying facilitated the transport of endogenous Fe to maize grains. Therefore, foliar Zn spraying increased the Zn concentration and bioavailability in maize grains irrespective of foliar sucrose supply while also improving Fe concentrations and bioavailability to some extent. This is a promising agricultural practice for simultaneous Zn and Fe biofortification in maize grains, i.e., “killing two birds with one stone”. Full article
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Open AccessArticle
Toward a New Use for Carbon Isotope Discrimination in Wheat Breeding
Agronomy 2019, 9(7), 385; https://doi.org/10.3390/agronomy9070385
Received: 5 June 2019 / Revised: 11 July 2019 / Accepted: 12 July 2019 / Published: 16 July 2019
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Abstract
A major obstacle in the effort to develop drought tolerant varieties of wheat (Triticum aestivum L.) is phenotyping. Traits known to contribute to improved drought tolerance, such as water-use behavior, reliance on stem reserve carbohydrates, and the ability to develop deep roots, [...] Read more.
A major obstacle in the effort to develop drought tolerant varieties of wheat (Triticum aestivum L.) is phenotyping. Traits known to contribute to improved drought tolerance, such as water-use behavior, reliance on stem reserve carbohydrates, and the ability to develop deep roots, require time and resource-intensive screening techniques. Plant breeding programs often have many thousands of experimental genotypes, which makes testing for each of these traits impractical. This work proposes that carbon isotope discrimination (∆) analysis of mature grains may serve as a relatively high-throughput approach to identify genotypes exhibiting traits associated with drought tolerance. Using ∆ as a proxy for stomatal conductance and photosynthetic capacity, assumptions can be made regarding fundamental plant physiological responses. When combined with knowledge of the terminal drought severity experienced in a particular environment, genotypes exhibiting conservative and rapid water use, deep roots, and reliance on stem reserve carbohydrates may be identified. Preliminary data in support of this idea are presented. Further verification of this use for grain ∆ will better equip wheat breeding programs to develop more drought tolerant varieties. Full article
(This article belongs to the Special Issue Wheat Breeding: Procedures and Strategies)
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Open AccessArticle
Charcoal Fine Residues Effects on Soil Organic Matter Humic Substances, Composition, and Biodegradability
Agronomy 2019, 9(7), 384; https://doi.org/10.3390/agronomy9070384
Received: 16 June 2019 / Revised: 11 July 2019 / Accepted: 12 July 2019 / Published: 16 July 2019
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Abstract
Biochar has been shown as a potential mean to enhance carbon sequestration in the soil. In Brazil, approximately 15% of the produced charcoal is discarded as charcoal fines, which are chemically similar to biochar. Therefore, we aimed to test charcoal fines as a [...] Read more.
Biochar has been shown as a potential mean to enhance carbon sequestration in the soil. In Brazil, approximately 15% of the produced charcoal is discarded as charcoal fines, which are chemically similar to biochar. Therefore, we aimed to test charcoal fines as a strategy to increase soil carbon sequestration. Charcoal fines of hardwood Mimosa scabrella were incorporated into a Cambisol down to 10 cm (T1 = 0 and T4 = 40 Mg ha−1) in Southern Brazil. Soil samples were collected (0–30 cm) 20 months after charcoal amendment. Soil organic matter (SOM) acid extract, humic acid, fulvic acid, and humin fractions were separated. Solid-state 13C nuclear magnetic resonance (NMR) spectra from charcoal and SOM in T1 and T4 were obtained before and after 165 days of incubation under controlled conditions. Charcoal increased soil carbon as fulvic (10–20 cm) and humic acids (10–30 cm) and, especially, as humin (0–5 cm), which probably occurred due to the hydrophobic character of the charcoal. The 13C NMR spectra and mean residence times (MRT) measured from incubation essays indicated that the charred material decomposed relatively fast and MRT of T1 and T4 samples were similar. It follows that the charcoal fines underwent similar decomposition as SOM, despite the high charcoal dose applied to the soil and the high aryl C contribution (78%) to the total 13C intensity of the charcoal NMR spectra. Full article
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Open AccessCommunication
The Effect of Drying Methods on Water-Soluble Carbohydrates and Crude Protein Concentrations and Their Ratio in Two Perennial Ryegrass Cultivars
Agronomy 2019, 9(7), 383; https://doi.org/10.3390/agronomy9070383
Received: 5 June 2019 / Revised: 12 July 2019 / Accepted: 14 July 2019 / Published: 16 July 2019
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Abstract
The objective of this study was to assess the joint effect of perennial ryegrass cultivars and drying methods on concentrations of water-soluble carbohydrates (WSC) and crude protein (CP) and WSC/CP ratio. AberMagic AR1 and Expo AR1 forage were collected in December 2016, March, [...] Read more.
The objective of this study was to assess the joint effect of perennial ryegrass cultivars and drying methods on concentrations of water-soluble carbohydrates (WSC) and crude protein (CP) and WSC/CP ratio. AberMagic AR1 and Expo AR1 forage were collected in December 2016, March, June, September and November 2017 and either oven-dried at 60 °C for 48 h (OD_60), at 80 °C for 16 h (OD_80), frozen at −80 °C for 48 h then freeze-dried (−80_FD), or flash-frozen with liquid N then freeze-dried (LN_FD). Data were analyzed by ANOVA in a factorial design with cultivar and drying method as factors. AberMagic AR1 had between 9.0 to 31.5% higher WSC concentration than Expo AR1 in the four samplings. Freeze-drying preserved more WSC than oven-drying treatments (+22.7%), particularly in June. The CP concentration of Expo AR1 was higher only in December (+6.8%), and was 22.9 and 10.9% higher in OD_60 samples compared to LN_FD samples in December and November, respectively. The WSC/CP ratio varied in June, being greater in AberMagic AR1 (+36.1%). Drying method affected WSC/CP ratio in December, June and November where freeze-drying produced greater ratios. Drying techniques generated differences in WSC, CP and WSC/CP ratio, which may affect the accuracy of the estimated impacts of forages on productivity and N use efficiency. Full article
(This article belongs to the Section Grassland and Pasture Science)
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Open AccessArticle
Effect of Gibberellic Acid on Growth, Yield, and Quality of Leaf Lettuce and Rocket Grown in a Floating System
Agronomy 2019, 9(7), 382; https://doi.org/10.3390/agronomy9070382
Received: 9 June 2019 / Revised: 12 July 2019 / Accepted: 12 July 2019 / Published: 16 July 2019
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Abstract
Gibberellins (GAs) are growth hormones strongly involved in a wide variety of physiological activities. Currently, gibberellins are commercially used to enhance phenotypic characteristics, earliness, and productivity of many vegetable and ornamental crops. In this work, the efficacy of supplementation of low levels of [...] Read more.
Gibberellins (GAs) are growth hormones strongly involved in a wide variety of physiological activities. Currently, gibberellins are commercially used to enhance phenotypic characteristics, earliness, and productivity of many vegetable and ornamental crops. In this work, the efficacy of supplementation of low levels of gibberellic acid (0, 10−8, 10−6, and 10−4 M GA3) through the mineral nutrient solution of a floating system on yield and quality of leaf lettuce and rocket plants was tested. The marketability of plants was lost when 10−4 M GA3 was added to the mineral nutrient solution. This study demonstrated that the addition of 10−4 M GA3 exceeded the acceptable threshold for use in hydroponics production systems. Below the concentration of 10−4 M, the presence of GA3 in the mineral nutrient solutions (MNS), especially at 10−6 M GA3, stimulated plant growth and enhanced the yield. Various morphological and physiological traits were enhanced by GA3 treatments (biomass accumulation, leaf expansion, stomatal conductance, water use efficiency (WUE), Nitrogen use efficiency (NUE), etc.), with superimposable trends in both lettuce and rocket. The addition of 10−6 M GA3 to the nutrient solution of a hydroponic floating system can promote growth and quality of lettuce and rocket plants. Full article
(This article belongs to the Special Issue Nutrition Management of Hydroponic Vegetable Crops)
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Open AccessArticle
Effects of Water Stress on Gas Exchange, Water Relations and Leaf Structure in Two Ornamental Shrubs in the Mediterranean Area
Agronomy 2019, 9(7), 381; https://doi.org/10.3390/agronomy9070381
Received: 29 May 2019 / Revised: 8 July 2019 / Accepted: 14 July 2019 / Published: 16 July 2019
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Abstract
One of the main problems in the Mediterranean area is the long dry season, and hence there is a need to individuate plants that are tolerant to low water availability. The mechanisms adopted by different plant species to overcome drought stress conditions and [...] Read more.
One of the main problems in the Mediterranean area is the long dry season, and hence there is a need to individuate plants that are tolerant to low water availability. The mechanisms adopted by different plant species to overcome drought stress conditions and reduce water loss could allow the identification of tolerant species to drought stress, thereby increasing the sustainability of ornamental plant utilization in green areas. In this regard, the aim of this study was to investigate the morphological, physiological, and anatomical responses of Polygala myrtifolia L. and Viburnum tinus L. ‘Lucidum’ irrigated under different irrigation deficits. In pot plants, four water regimes were adopted (10%, 20%, 30% and 40% of water container capacity (WC)). Drought stress significantly reduced the biomass accumulation in both shrubs. In Viburnum, total dry biomass reduction was observed only in 10% WC with a reduction by 33%, while in Polygala, this was observed both in 20% WC and 10% WC (~48%). The higher deficit irrigation conditions improve the root-to-shoot ratio, which was increased in Polygala 20% WC (by 20%) but not in Viburnum ones. The latter species shows higher drought tolerance, as demonstrated by the gas exchange values, chlorophyll fluorescence, leaf structure, and water relationship. Full article
(This article belongs to the Section Horticultural and Floricultural Crops)
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Open AccessArticle
Organic Compared with Conventional Wheat Had Competitive Yields during the Early Years of Organic Production in the Northeast USA
Agronomy 2019, 9(7), 380; https://doi.org/10.3390/agronomy9070380
Received: 25 June 2019 / Revised: 11 July 2019 / Accepted: 14 July 2019 / Published: 16 July 2019
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Abstract
Organic wheat production has increased significantly because of increased demand by consumers. We used the same variety to evaluate organic (seed treatment) and conventional wheat (no seed treatment) under no-till conditions in 2016 and 2018 with recommended (296 kernels/m2 and 80 kg [...] Read more.
Organic wheat production has increased significantly because of increased demand by consumers. We used the same variety to evaluate organic (seed treatment) and conventional wheat (no seed treatment) under no-till conditions in 2016 and 2018 with recommended (296 kernels/m2 and 80 kg N/ha) and high inputs (420 kernels/m2 and 56 + 56 kg N/ha) to identify the best organic management practices. Organic compared with conventional wheat with recommended inputs had ~13% lower yields in 2016 but ~7.5% higher yields with high inputs in 2018. Organic wheat emerged 1 to 1.5 days earlier, had 10 to 38% higher plant establishment rates, and had similar weed densities (<0.25 weeds/m2) to high input conventional wheat, which received a fall herbicide. Organic compared with conventional wheat had lower grain N% (0.3 to 0.45% in 2016 and 0.17 to 0.27% in 2018). Organic compared with conventional wheat had mostly higher spike densities, especially with high inputs (~60 more spikes/m2 in 2016 and ~130 more in 2018), probably because of better plant establishment, but mostly lower kernels/spike and kernel weight. Organic compared with conventional wheat had comparable yields, probably because of its competitiveness with weeds. We recommend that growers use recommended seeding and N rates on organic wheat because high seeding rates did not improve weed control, and high N rates were not economical. Full article
(This article belongs to the Section Innovative Cropping Systems)
Open AccessArticle
Yield, Quality and Physiological Traits of Red Beet Under Different Magnesium Nutrition and Light Intensity Levels
Agronomy 2019, 9(7), 379; https://doi.org/10.3390/agronomy9070379
Received: 30 June 2019 / Revised: 9 July 2019 / Accepted: 12 July 2019 / Published: 15 July 2019
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Abstract
The effects of light intensity and Magnesium (Mg) supply on quality traits, yield and macronutrient assimilation of red beet plants were studied in two greenhouse experiments (in 2017 and 2018). According to a split-plot design, we compared two photosynthetically active radiation (PAR) levels [...] Read more.
The effects of light intensity and Magnesium (Mg) supply on quality traits, yield and macronutrient assimilation of red beet plants were studied in two greenhouse experiments (in 2017 and 2018). According to a split-plot design, we compared two photosynthetically active radiation (PAR) levels (100% PAR, Full Light, FL and 50% PAR, Light Reduction, LR) as the main factor and three Mg application rates (0, 30, and 60 kg Mg ha−1: MG_0, MG_30 and MG_60, respectively) as the secondary factor. Yield and dry matter accumulations were principally affected by Mg. In both growing seasons, storage root dry weight (DW) increased about 5-fold in MG_60 with respect to MG_0; the highest leaves DW was achieved with the “LR × MG_60” treatment. Nitrogen and Mg contents in leaves and storage roots increased as Mg availability increased; also, the highest chlorophyll content was obtained combining LR and a high Mg rate. Moreover, the reflectance-derivative Normalized Difference Vegetation Index (NDVI670) and Chlorophyll Index (CI) allowed for discriminating the Mg sub-optimal supply in red beet plants. Sucrose was found to be the most abundant sugar in both the leaves and storage organs and was affected by Mg supply. Total phenolic content and betalains in storage roots at harvest were affected by both PAR and Mg application rates. Our results highlight the potential of Mg nutrition in ensuring good yield and quality of red beet crops. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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