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Agronomy, Volume 9, Issue 9 (September 2019) – 93 articles

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Cover Story (view full-size image) The chromosome 2Hch of Hordeum chilense. has the potential to improve seed carotenoid content in [...] Read more.
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Open AccessArticle
Back to the Future: Revisiting the Application of an Enzyme Kinetic Equation to Maize Development Nearly Four Decades Later
Agronomy 2019, 9(9), 566; https://doi.org/10.3390/agronomy9090566 - 19 Sep 2019
Viewed by 494
Abstract
With the recent resurgence in interest in models describing maize (Zea mays L.) development rate responses to temperature, this study uses published data to refit the Poikilotherm equation and compare it to broken stick “heat stress” equations. These data were for the [...] Read more.
With the recent resurgence in interest in models describing maize (Zea mays L.) development rate responses to temperature, this study uses published data to refit the Poikilotherm equation and compare it to broken stick “heat stress” equations. These data were for the development rate of eight open pollinated maize varieties at diverse sites in Africa. The Poikilotherm equation was applied with the original published parameters and after refitting with the data in this study. The heat stress equation was tested after fitting with just the first variety and after fitting with each variety. The Poikilotherm equation with the original parameter values had large errors in predicting development rates in much of the temperature range. The adjusted Poikilotherm equation did much better with the root-mean-square error (RMSE) decreasing from 0.034 to 0.003 (1/day) for a representative variety. The heat stress equation fit to the first variety did better than the Poikilotherm equation when applied to all the varieties. The heat stress equations fitted separately for each variety did not have an improved fit compared to the one heat stress equation. Thus, separate fitting of such an equation for different varieties may not be necessary. The one heat stress equation, the separate heat stress equation, and the Poikilotherm equation each had a better fit than nonlinear Briere et al. curves. The Poikilotherm equation showed promise, realistically capturing the high, low, and optimum rate values measured. All the equations showed promise to some degree for future applications in simulating the maize development rate. When fitting separate regressions for each variety for the heat stress equations, the base temperatures had a mean of 5.3 °C, similar to a previously published value of 6 °C. The last variety had noticeably different rates than the others. This study demonstrated that a simple approach (the heat stress equation) should be adequate in many cases. It also demonstrated that more detailed equations can be useful when a more mechanistic system is desired. Future research could investigate the reasons for the different development rate response of the last variety and investigate similar varieties. Full article
(This article belongs to the Section Agricultural Engineering)
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Open AccessArticle
Effects of Quantitative Ordinal Scale Design on the Accuracy of Estimates of Mean Disease Severity
Agronomy 2019, 9(9), 565; https://doi.org/10.3390/agronomy9090565 - 19 Sep 2019
Cited by 2 | Viewed by 706
Abstract
Estimates of plant disease severity are crucial to various practical and research-related needs in agriculture. Ordinal scales are used for categorizing severity into ordered classes. Certain characteristics of quantitative ordinal scale design may affect the accuracy of the specimen estimates and, consequently, affect [...] Read more.
Estimates of plant disease severity are crucial to various practical and research-related needs in agriculture. Ordinal scales are used for categorizing severity into ordered classes. Certain characteristics of quantitative ordinal scale design may affect the accuracy of the specimen estimates and, consequently, affect the accuracy of the resulting mean disease severity for the sample. The aim of this study was to compare mean estimates based on various quantitative ordinal scale designs to the nearest percent estimates, and to investigate the effect of the number of classes in an ordinal scale on the accuracy of that mean. A simulation method was employed. The criterion for comparison was the mean squared error of the mean disease severity for each of the different scale designs used. The results indicate that scales with seven or more classes are preferable when actual mean disease severities of 50% or less are involved. Moreover, use of an amended 10% quantitative ordinal scale with additional classes at low severities resulted in a more accurate mean severity compared to most other scale designs at most mean disease severities. To further verify the simulation results, estimates of mean severity of pear scab on samples of leaves from orchards in Taiwan demonstrated similar results. These observations contribute to the development of plant disease assessment scales to improve the accuracy of estimates of mean disease severities. Full article
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Open AccessArticle
Interaction of Preventive, Cultural, and Direct Methods for Integrated Weed Management in Winter Wheat
Agronomy 2019, 9(9), 564; https://doi.org/10.3390/agronomy9090564 - 19 Sep 2019
Cited by 1 | Viewed by 785
Abstract
Crop rotations dominated by winter annual crops and relying on the use of herbicides to control weeds have resulted in weed communities dominated by a few highly specialized species such as Alopecurus myosuroides. Integrated weed management (IWM) represents a sensible strategy to [...] Read more.
Crop rotations dominated by winter annual crops and relying on the use of herbicides to control weeds have resulted in weed communities dominated by a few highly specialized species such as Alopecurus myosuroides. Integrated weed management (IWM) represents a sensible strategy to target such difficult weeds, through a combination of preventive, cultural, and direct means. In six field trials over three years, we tested the effect of stale seedbed preparation, winter wheat seed rate, and chemical weed control strategy on Alopecurus myosuroides control efficacy and variability in efficacy. The field experiments were carried out under reduced tillage practice and without pre-sowing use of glyphosate. Stale seedbed preparation alone reduced A. myosuroides infestation level by 25% on average. No clear effect was found of increasing winter wheat seed rate from 300 to 400 seeds m−2. A combination of stale seedbed preparation and herbicide treatment in autumn and spring was found to be synergistic, improving weed control efficacy significantly and moreover reducing the variability in control efficacy and hence the risk for weed control failure. Full article
(This article belongs to the Special Issue Ecologically Sustainable Weed Management in Cropping Systems)
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Open AccessArticle
Genetical, Morphological and Physicochemical Characterization of the Autochthonous Cultivar ‘Uva Rey’ (Vitis vinifera L.)
Agronomy 2019, 9(9), 563; https://doi.org/10.3390/agronomy9090563 - 18 Sep 2019
Cited by 3 | Viewed by 690
Abstract
’Uva Rey’ is considered an Andalusian (Spain) ancient autochthonous cultivar with hard white grapes used for the production of wine and raisins and also for raw consumption. Currently, this cultivar is not included in the official register of Spanish grapevine varieties and there [...] Read more.
’Uva Rey’ is considered an Andalusian (Spain) ancient autochthonous cultivar with hard white grapes used for the production of wine and raisins and also for raw consumption. Currently, this cultivar is not included in the official register of Spanish grapevine varieties and there is neither a description nor a characterization that could facilitate its insertion in this register. In order to study this genetic resource, a genetic and morphological characterization of ’Uva Rey’ has been carried out in comparison with ’Palomino Fino’, the main cultivar in Andalusia (Spain). Additionally, grape must physicochemical characterization and grape berry texture profile analyses were performed. Genetically, ’Uva Rey’ was synonymous with the cultivar ’De Rey’. ’Uva Rey’ grape must physicochemical results showed a lower sugar concentration and a higher malic acid content compared to ’Palomino Fino’ must, while the analysis of the grape berry texture profile proved to be more consistent and cohesive. These results can be attributed to the longer phenological cycle presented by ’Uva Rey’. All these facts could lead to consideration of ’Uva Rey’ as a cultivar for the production of white wines in warm climate regions. Full article
Open AccessArticle
The Confirmation of a Ploidy Periclinal Chimera of the Meiwa Kumquat (Fortunella crassifolia Swingle) Induced by Colchicine Treatment to Nucellar Embryos and Its Morphological Characteristics
Agronomy 2019, 9(9), 562; https://doi.org/10.3390/agronomy9090562 - 18 Sep 2019
Viewed by 808
Abstract
A ploidy chimera of the Meiwa kumquat (Fortunella crassifolia Swingle), which had been induced by treating the nucellar embryos with colchicine, and had diploid (2n = 2x = 18) and tetraploid (2n = 4x = 36) cells, was examined for its ploidy [...] Read more.
A ploidy chimera of the Meiwa kumquat (Fortunella crassifolia Swingle), which had been induced by treating the nucellar embryos with colchicine, and had diploid (2n = 2x = 18) and tetraploid (2n = 4x = 36) cells, was examined for its ploidy level, morphological characteristics, and sizes of its cells in its leaves, flowers, and fruits to reveal the ploidy level of each histogenic layer. Furthermore, the chimera was crossed with the diploid kumquat to evaluate the ploidy level of its reproductive organs. The morphological characteristics and the sizes of the cells in the leaves, flowers, and fruits of the chimera were similar to those of the tetraploid Meiwa kumquat and the ploidy periclinal chimera known as “Yubeni,” with diploids in the histogenic layer I (L1) and tetraploids in the histogenic layer II (L2) and III (L3). However, the epidermis derived from the L1 of the chimera showed the same result as the diploid Meiwa kumquat in all organs and cells. The sexual organs derived from the L2 of the chimera were significantly larger than those of the diploid. Moreover, the ploidy level of the seedlings obtained from the chimera was mostly tetraploid. In the midrib derived from the L3, the chimera displayed the fluorescence intensity of a tetraploid by flow cytometric analysis and had the same size of the cells as the tetraploid and the Yubeni. According to these results, the chimera is thought to be a ploidy periclinal chimera with diploid cells in the outermost layer (L1) and tetraploid cells in the inner layers (L2 and L3) of the shoot apical meristem. The chimera had desirable fruit traits for a kumquat such as a thick pericarp, a high sugar content, and a small number of developed seeds. Furthermore, triploid progenies were obtained from reciprocal crosses between the chimera and diploid kumquat. Full article
(This article belongs to the Special Issue Chromosome Manipulation for Plant Breeding Purposes)
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Open AccessArticle
Water–Nitrogen Coupling Effect on Drip-Irrigated Dense Planting of Dwarf Jujube in an Extremely Arid Area
Agronomy 2019, 9(9), 561; https://doi.org/10.3390/agronomy9090561 - 18 Sep 2019
Cited by 1 | Viewed by 554
Abstract
Hami, Xinjiang, is located in an extremely arid region and jujube is the main economic crop. It is important to adopt dwarf and close-planting technology under drip irrigation and to optimize water and fertilizer management to improve jujube yield and quality. Local 12-year-old [...] Read more.
Hami, Xinjiang, is located in an extremely arid region and jujube is the main economic crop. It is important to adopt dwarf and close-planting technology under drip irrigation and to optimize water and fertilizer management to improve jujube yield and quality. Local 12-year-old jujube trees were treated using two factors of irrigation and fertilization. Three irrigation amounts (520, 700, and 880 mm) and three fertilization levels (248, 318, and 388 kg/hm2) were set up in plot experiments. The root system, yield, and quality of jujube were monitored under different irrigation and nitrogen application combinations. The effects on water use efficiency (WUE), nitrogen partial factor productivity (PNP), and economic benefit were analyzed. The water and fertilizer coupling effect of dwarf closely planted jujube was studied by combining multiple regression and spatial analyses. The yield, quality, economic benefits, WUE, and PNP of jujube were significantly affected by irrigation and fertilization. Multiple regression and spatial analyses showed that the highest yield was for irrigation of 700 mm and a nitrogen rate of 340 kg/hm2. For the maximum net benefit, irrigation was 806 mm and nitrogen was 388 kg/hm2; correspondingly, for the highest total sugar, values were 688 mm and 362 kg/hm2; for vitamin C, they were 622 mm and 376 kg/hm2; for PNP, they were 880 mm and 256.57 kg/hm2; and for WUE, they were 520 mm and 388 kg/hm2. A comprehensive evaluation of each index showed that the acceptable irrigation amount for yield, quality, WUE, and net benefit of ≥85% of the maximum value was 600–628 mm, and the nitrogen application rate was 360–372 kg/hm2. This study provides guidance for the scientific management of water and fertilizer in the drip irrigation and fertilization process of local jujube trees. Full article
(This article belongs to the Section Water Use and Irrigation)
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Open AccessArticle
Genome-Wide Mining and Identification of Protein Kinase Gene Family Impacts Salinity Stress Tolerance in Highly Dense Genetic Map Developed from Interspecific Cross between G. hirsutum L. and G. darwinii G. Watt
Agronomy 2019, 9(9), 560; https://doi.org/10.3390/agronomy9090560 - 18 Sep 2019
Cited by 1 | Viewed by 790
Abstract
Abiotic stress is an important limiting factor in crop growth and yield around the world. Owing to the continued genetic erosion of the upland cotton germplasm due to intense selection and inbreeding, attention has shifted towards wild cotton progenitors which offer unique traits [...] Read more.
Abiotic stress is an important limiting factor in crop growth and yield around the world. Owing to the continued genetic erosion of the upland cotton germplasm due to intense selection and inbreeding, attention has shifted towards wild cotton progenitors which offer unique traits that can be introgressed into the cultivated cotton to improve their genetic performance. The purpose of this study was to characterize the Pkinase gene family in a previously developed genetic map of the F2 population derived from a cross between two cotton species: Gossypium hirsutum (CCRI 12-4) and Gossypium darwinii (5-7). Based on phylogenetic analysis, Pkinase (PF00069) was found to be the dominant domain with 151 genes in three cotton species, categorized into 13 subfamilies. Structure analysis of G. hirsutum genes showed that a greater percentage of genes and their exons were highly conserved within the group. Syntenic analysis of gene blocks revealed 99 duplicated genes among G. hirsutum, Gossypium arboreum and Gossypium raimondii. Most of the genes were duplicated in segmental pattern. Expression pattern analysis showed that the Pkinase gene family possessed species-level variation in induction to salinity and G. darwinii had higher expression levels as compared to G. hirsutum. Based on RNA sequence analysis and preliminary RT-qPCR verification, we hypothesized that the Pkinase gene family, regulated by transcription factors (TFs) and miRNAs, might play key roles in salt stress tolerance. These findings inferred comprehensive information on possible structure and function of Pkinase gene family in cotton under salt stress. Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessArticle
Biostimulation of Maize (Zea mays) and Irrigation Management Improved Crop Growth and Water Use under Controlled Environment
Agronomy 2019, 9(9), 559; https://doi.org/10.3390/agronomy9090559 - 17 Sep 2019
Cited by 1 | Viewed by 730
Abstract
Water deficits during the growing season are a major factor limiting crop production. Therefore, reducing water use during crop production by the application of regulated deficit irrigation (RDI) is crucially important in water resources. There are few reports on the biostimulants used for [...] Read more.
Water deficits during the growing season are a major factor limiting crop production. Therefore, reducing water use during crop production by the application of regulated deficit irrigation (RDI) is crucially important in water resources. There are few reports on the biostimulants used for growth and water use efficiency (WUE) in maize (Zea mays Linn.) under RDI. Therefore, the influence of betaine and chitin treatments, alone and in combination, on maize cultivar ‘White Pearl’ was assessed by observing changes in the physiology and morphology of plants exposed to RDI. Plants were grown in plastic pots in greenhouses and maintained under full irrigation (FI) for 1 week until imposing RDI and biostimulants. Plants were then subjected to FI (no water deficiency treatment, field capacity >70%) and RDI (field capacity <50%) conditions until the end of each experiment. Plant agronomic performance, photosynthesis parameters, and WUE values were recorded weekly for 8 weeks and three individual experiments were carried out to assess the efficacy of biostimulants and irrigation treatments. Betaine (0, 50, and 100 mM/plant) was foliage-treated every 2 weeks during Experiment 1, but chitin (0, 2, and 4 g/kg) was applied to the soil at the beginning of Experiment 2. The optimal concentration of each chemical alone or in combination was then applied to the plants as Experiment 3. A factorial experiment design of two factors with different levels under a completely randomized arrangement was used in this investigation. Betaine (50 mM) or chitin (2 g/kg) treatments alone significantly elevated total fresh weight (63.03 or 124.07 g/plant), dry weight (18.00 or 22.34 g/plant), and cob weight (3.15 or 6.04 g/plant) and boosted the water-stress tolerance of the maize under RDI compared to controls. However, a combination treatment of 50 mM betaine and 2 g/kg chitin did not increase plant height, fresh shoot and root weights, dry cob weight, and total dry weight under RDI compared to controls. Soil-plant analysis development (SPAD) values (>30) were effective in detecting plant growth performance and WUE values under RDI. These findings may have greater significance for farming in dry lands and offer information for further physiological studies on maize WUE and water stress tolerance. Full article
(This article belongs to the Section Water Use and Irrigation)
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Open AccessArticle
Pre-Anthesis Nutritional Status of Spelt Wheat as a Tool for Predicting the Attainable Grain Yield
Agronomy 2019, 9(9), 558; https://doi.org/10.3390/agronomy9090558 - 17 Sep 2019
Cited by 2 | Viewed by 532
Abstract
The nutrient content in leaves of spelt wheat at late heading is crucial for the development of its yield components, and in consequence, grain yield. This hypothesis was verified based on data from long-term field experiments with four potassium (K) treatments based on [...] Read more.
The nutrient content in leaves of spelt wheat at late heading is crucial for the development of its yield components, and in consequence, grain yield. This hypothesis was verified based on data from long-term field experiments with four potassium (K) treatments based on the progressive K supply potential to plants from soil and fertilizer and two magnesium treatments (−Mg, +Mg). The number of ears (NE) and the number of grains per ear (NGE) responded significantly to the increased K and Mg supply. The grain yield was positively correlated with NGE. A shortage of N and Mg resulted in a lower NGE, whereas a shortage of N and Zn, concomitant with an excess of Ca, resulted in a significant decrease in NGE and thousand-grain weight. This effect can be diminished by the increased content of Mg. It has been revealed that the content of Zn in leaves of spelt wheat at heading is an important nutritional factor effectively controlling N, P and Fe contents in grain, and consequently, grain yield. This study showed that the content of nutrients in spelt leaves measured just before anthesis can be used for reliable prediction of the grain yield. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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Open AccessArticle
Oxadiazon Dissipation in Water and Topsoil in Flooded and Dry-Seeded Rice Fields
Agronomy 2019, 9(9), 557; https://doi.org/10.3390/agronomy9090557 - 17 Sep 2019
Cited by 1 | Viewed by 606
Abstract
The aim of the present study was to assess the behavior of oxadiazon in topsoil and waters of paddy fields cultivated according to the two rice seeding systems: conventional water seeding (CON) and dry seeding (DRY). The study was carried out from 2012 [...] Read more.
The aim of the present study was to assess the behavior of oxadiazon in topsoil and waters of paddy fields cultivated according to the two rice seeding systems: conventional water seeding (CON) and dry seeding (DRY). The study was carried out from 2012 to 2013 in Vercelli, north-west of Italy, the most important rice growing area of Europe. Variations in oxadiazon concentrations were studied over time in topsoil, paddy water, inlet water and outlet water. Over the two years, the estimated oxadiazon topsoil half-life was 3.27 days, without significant differences between systems and years. Oxadiazon dissipation in the paddy water was rapid during the first week, but less pronounced late in the season. Residues of oxadiazon were frequently detected in inlet waters. Transfer of oxadiazon residues in outlet waters occurred over all the growing seasons, with important peaks in the first weeks after the treatment. A possible way to reduce the transfer of oxadiazon to water bodies could be increasing the residence time of the herbicide in the paddy fields during the first 7–10 days after spraying, avoiding the release of water from them. Full article
(This article belongs to the Section Weed Science and Weed Management)
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Open AccessArticle
A Copernicus Sentinel-1 and Sentinel-2 Classification Framework for the 2020+ European Common Agricultural Policy: A Case Study in València (Spain)
Agronomy 2019, 9(9), 556; https://doi.org/10.3390/agronomy9090556 - 16 Sep 2019
Cited by 1 | Viewed by 1078
Abstract
This paper proposes a methodology for deriving an agreement map between the Spanish Land Parcel Information System (LPIS), also known as SIGPAC, and a classification map obtained from multitemporal Sentinel-1 and Sentinel-2 data. The study area comprises the province of València (Spain). The [...] Read more.
This paper proposes a methodology for deriving an agreement map between the Spanish Land Parcel Information System (LPIS), also known as SIGPAC, and a classification map obtained from multitemporal Sentinel-1 and Sentinel-2 data. The study area comprises the province of València (Spain). The approach exploits predictions and class probabilities obtained from an ensemble method of decision trees (boosting trees). The overall accuracy reaches 91.18% when using only Sentinel-2 data and increases up to 93.96% when Sentinel-1 data are added in the training process. Blending both Setninel-1 and Sentinel-2 data causes a remarkable classification improvement ranging from 3.6 to 8.7 percentage points over shrubs, forest, and pasture with trees, which are the most confusing classes in the optical domain as demonstrated by a spectral separability analysis. The derived agreement map is built upon combining per pixel classifications, their probabilities, and the Spanish LPIS. This map can be exploited into the decision-making chain for subsidies payment to cope with the 2020+ European Common Agricultural Policy (CAP). Full article
(This article belongs to the Special Issue Remote Sensing of Agricultural Monitoring)
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Open AccessArticle
Optimization of Nitrogen Rate and Planting Density for Improving the Grain Yield of Different Rice Genotypes in Northeast China
Agronomy 2019, 9(9), 555; https://doi.org/10.3390/agronomy9090555 - 16 Sep 2019
Cited by 1 | Viewed by 718
Abstract
Nitrogen fertilization and planting density are two key factors that can interactively affect the grain yield of rice. Three different types of rice cultivars—inbred Shendao 47, inbred Shendao 505, and hybrid Jingyou 586—were applied to investigate the effects of the nitrogen (N) rate [...] Read more.
Nitrogen fertilization and planting density are two key factors that can interactively affect the grain yield of rice. Three different types of rice cultivars—inbred Shendao 47, inbred Shendao 505, and hybrid Jingyou 586—were applied to investigate the effects of the nitrogen (N) rate and planting density (D) on the aboveground biomass, harvest index, leaf photosynthetic features, grain yield, and yield components using a split-split-plot design at two sites over two continuous years. The main plots were assigned to four nitrogen fertilizer rates: 0 (N0), 140 (N1), 180 (N2), and 220 (N3) kg ha−1 N; the subplots were assigned to three planting densities: 25 × 104 (D1), 16.7 × 104 (D2), and 12.5 × 104 (D3) hills ha-1, and the sub-subplots were assigned to three rice cultivars. The results showed that the grain yield had a significantly positive correlation with the stomatal conductance (Gs), net photosynthesis rate (Pn), transpiration rate (Tr), chlorophyll content (SPAD value), leaf area index (LAI), panicles per unit area, and spikelets per panicle. The N rate and planting density had significant interaction effects on grain yield, and the maximum values of Shendao 47, Shendao 505, and Jingyou 586 appeared in N3D2, N2D1, and N3D3, respectively. The higher grain yield of midsized panicle Shendao 47 was mostly ascribed to both panicles per unit area and spikelets per panicle. More panicles per unit area and spikelets per panicle primarily contributed to a larger sink capacity of small-sized panicle rice Shendao 505 and large-sized panicle rice Jingyou 586. We found that the treatments N3D2, N2D1, and N3D3 could optimize the contradiction between yield formation factors for Shendao 47, Shendao 505, and Jingyou 586, respectively. Across years and sites, the regression analysis indicated that the combinations of nitrogen fertilization of 195.6 kg ha−1 with a planting density of 22 × 104 hills ha−1, 182.5 kg ha−1 with 25 × 104 hills ha−1, and 220 kg ha−1 with 13.1 × 104 hills ha−1 are recommended for medium-, small-, and large-sized panicle rice cultivars, respectively. Full article
(This article belongs to the Section Innovative Cropping Systems)
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Open AccessArticle
Leguminous Cover Crop Astragalus sinicus Enhances Grain Yields and Nitrogen Use Efficiency through Increased Tillering in an Intensive Double-Cropping Rice System in Southern China
Agronomy 2019, 9(9), 554; https://doi.org/10.3390/agronomy9090554 - 16 Sep 2019
Cited by 1 | Viewed by 697
Abstract
Chinese milk vetch (Astragalus sinicus L., vetch), a leguminous winter cover crop, has been widely adopted by farmers in southern China to boost yield of the succeeding rice crop. However, the effects of vetch on rice grain yield and nitrogen (N) use [...] Read more.
Chinese milk vetch (Astragalus sinicus L., vetch), a leguminous winter cover crop, has been widely adopted by farmers in southern China to boost yield of the succeeding rice crop. However, the effects of vetch on rice grain yield and nitrogen (N) use efficiency have not yet been well studied in the intensive double-cropped rice cropping systems. To fill this gap, we conducted a three-year field experiment to evaluate the impacts of the vetch crop on yields and N use efficiency in the subsequent early and late rice seasons. With moderate N input (100 kg N ha−1 for each rice crop), vetch cover significantly increased grain yields by 7.3–13.4% for early rice, by 8.2–10.4% for late rice, and by 8.6–11.5% for total annual rice production when compared with winter fallow. When rice crops received an N input of 200 kg N ha−1, vetch cover increased grain yields by 5.9–18.4% for early rice, by 3.8–10.1% for late rice, and by 6.2–11.3% for annual rice production. Moreover, comparable grain yields (11.9 vs. 12.0 Mg ha−1 for annual rice production) were observed between vetch cover with moderate N and fallow with added N fertilizer. Yield components analysis indicated that the increased tillering number was the main factor for the enhanced grain yields by vetch cover. Vetch cover with moderate and higher N input resulted in higher agronomic N use efficiency and applied N recovery efficiency compared with the fallow treatments. Here, our results showed that vetch as a winter cover crop can be combined with reduced N fertilizer input while maintaining high grain yields, thus gaining a more sustainable rice production system. Full article
(This article belongs to the Special Issue Sustainable Cropping Systems) Printed Edition available
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Open AccessArticle
A Novel Compost for Rice Cultivation Developed by Rice Industrial By-Products to Serve Circular Economy
Agronomy 2019, 9(9), 553; https://doi.org/10.3390/agronomy9090553 - 15 Sep 2019
Cited by 1 | Viewed by 717
Abstract
Rice is the major staple crop worldwide, whereas fertilization practices include mainly the application of synthetic fertilizers. A novel compost was developed using 74% of rice industrial by-products (rice bran and husks) and tested in rice cultivation in Greece’s main rice producing area. [...] Read more.
Rice is the major staple crop worldwide, whereas fertilization practices include mainly the application of synthetic fertilizers. A novel compost was developed using 74% of rice industrial by-products (rice bran and husks) and tested in rice cultivation in Greece’s main rice producing area. Field experimentation was conducted in two consecutive growing seasons (2017 and 2018) and comprised six fertilization treatments, including four compost rates (C1: 80, C2: 160, C3: 320 kg ha−1 of nitrogen all in split application, C4: 160 kg ha−1 of nitrogen in single application), a conventional treatment, as well as an untreated control. A total of 21 morpho-physiological and quality traits were evaluated during the experimentation. The results indicated that rice plants in all compost treatments had greater height (8%–64%) and biomass (32%–113%) compared to the untreated control. In most cases, chlorophyll content index (CCI) and quantum yield (QY) were similar or higher in C3 compared to the conventional treatment. C2 and C3 exhibited similar or greater yields, 7.5–8.7 Mg ha−1 in 2017 and 6.3–6.9 Mg ha−1 in 2018, whereas the conventional treatment resulted in 7.3 Mg ha−1 and 6.8 Mg ha−1 in the two years, respectively. No differences were observed in most quality traits that affect the rice commodity. The current study reveals that in sustainable farming systems based on circular economy, such as organic ones, the application of the proposed compost at the rate of 6 Mg ha−1 can be considered sufficient for the rice crop nutrient requirements. Full article
(This article belongs to the Special Issue Transfer of Waste to Resource in Agriculture)
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Open AccessFeature PaperReview
The Effect of Chromosome Structure upon Meiotic Homologous and Homoeologous Recombinations in Triticeae
Agronomy 2019, 9(9), 552; https://doi.org/10.3390/agronomy9090552 - 14 Sep 2019
Cited by 2 | Viewed by 623
Abstract
The tribe Triticeae contains about 500 diploid and polyploid taxa, among which are important crops, such as wheat, barley and rye. The phylogenetic relationships, genome compo-sition and chromosomal architecture, were already reported in the pioneer genetic studies on these species, given their implications [...] Read more.
The tribe Triticeae contains about 500 diploid and polyploid taxa, among which are important crops, such as wheat, barley and rye. The phylogenetic relationships, genome compo-sition and chromosomal architecture, were already reported in the pioneer genetic studies on these species, given their implications in breeding-related programs. Hexaploid wheat, driven by its high capacity to develop cytogenetic stocks, has always been at the forefront of these studies. Cytogenetic stocks have been widely used in the identification of homoeologous relationships between the chromosomes of wheat and related species, which has provided valuable information on genome evolution with implications in the transfer of useful agronomical traits into crops. Meiotic recombination is non-randomly distributed in the Triticeae species, and crossovers are formed in the distal half of the chromosomes. Also of interest for crops improvement is the possibility of being able to modulate the intraspecific and interspecific recombination landscape to increase its frequency in crossover-poor regions. Structural changes may help in this task. In fact, chromosome truncation increases the recombination frequency in the adjacent intercalary region. However, structural changes also have a negative effect upon recombination. Gross chromosome rearrangements produced in the evolution usually suppress meiotic recombination between non-syntenic homoeologs. Thus, the chromosome structural organization of related genomes is of great interest in designing strategies of the introgression of useful genes into crops. Full article
(This article belongs to the Special Issue Chromosome Manipulation for Plant Breeding Purposes)
Open AccessArticle
A New Approach to Farm Biodiversity Assessment
Agronomy 2019, 9(9), 551; https://doi.org/10.3390/agronomy9090551 - 14 Sep 2019
Viewed by 567
Abstract
A reduction in biodiversity due to farming operations has been broadly reported. As a solution, policy makers in the European Union have introduced several programs in recent years to enhance biodiversity on farms but these have met with only limited success. One of [...] Read more.
A reduction in biodiversity due to farming operations has been broadly reported. As a solution, policy makers in the European Union have introduced several programs in recent years to enhance biodiversity on farms but these have met with only limited success. One of the main reasons for this lack of success is that the experience, knowledge and attitudes of farmers are not taken into account when biodiversity conservation programs are formulated. Farmers’ opinions must be taken into consideration in the creation of future programs, which should also include an assessment by the farmers of the value of the nature of their farms. In this study, farmers were asked to express their opinion on the attractiveness of their farm in relation to pollinators, game, birds, amphibians, reptiles, rodents and non-crop (wild) plants. Data were then analysed using a novel method in which each farm was assigned to one of four categories. High nature-value farms contained more natural features in the landscape, such as individual trees or ponds. Socio-economic factors, such as gender, also influenced the farm assessments; female farmers were more critical compared to their male counterparts. The establishment of field margins or watercourse by the farmers significantly increased the possibility that the farm would be classified as attractive. Full article
(This article belongs to the Section Farming Sustainability)
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Open AccessArticle
Physiological and Molecular Osmotic Stress Responses in Three Durum Wheat (Triticum Turgidum ssp Durum) Genotypes
Agronomy 2019, 9(9), 550; https://doi.org/10.3390/agronomy9090550 - 13 Sep 2019
Cited by 2 | Viewed by 643
Abstract
This study aims to investigate the activities and expression of enzymes of primary metabolism and relate these data with the growth performance of three different durum wheat genotypes (Maali; YT13; and ON66) under osmotic stress. Growth traits—including plant height, dry weight (DW) and [...] Read more.
This study aims to investigate the activities and expression of enzymes of primary metabolism and relate these data with the growth performance of three different durum wheat genotypes (Maali; YT13; and ON66) under osmotic stress. Growth traits—including plant height, dry weight (DW) and relative water content (RWC)—were measured to classify genotypes depending on their tolerance to stress. Several enzymes were investigated: Ascorbate peroxidase (APX), Glutamine Synthetase (GS), Glutamine dehydrogenase (GDH), Glutamate synthase (GOGAT), Glucose 6-phosphate dehydrogenase (G6PDH), and Phosphoenolpyruvate Carboxylase (PEPC). The expression of the cytosolic and plastidic glutamine synthetase (TaGS1 and TaGS2), high affinity nitrate transporters (TaNRT2.3) and Glutamate dehydrogenase (TaGDH) were also detected by qRT-PCR. The results indicated different growth performances among genotypes, indicating Maali and YT13 as tolerant genotypes and ON66 as a drought-susceptible variety. Data showed a decrease in PEPC and increase in APX activities under osmotic stress; a slight decrease in GS activity was observed, together with an increase in G6PDH in all genotypes; GS and NRT2 expressions changed in a similar pattern in the different genotypes. Interestingly, Maali and YT13 showed higher transcript abundance for GDH under stress compared to ON66, suggesting the implication of GDH in protective phenomena upon osmotic stress. Full article
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Open AccessArticle
Freeze-Thaw Induced Gully Erosion: A Long-Term High-Resolution Analysis
Agronomy 2019, 9(9), 549; https://doi.org/10.3390/agronomy9090549 - 13 Sep 2019
Cited by 1 | Viewed by 449
Abstract
Gullies are significant contributors of sediment to streams in the southeastern USA. This study investigated gully erosion in the clay-rich soils of east Tennessee under a humid subtropical climate. The aims of this study were to (1) estimate long-term erosion rates for different [...] Read more.
Gullies are significant contributors of sediment to streams in the southeastern USA. This study investigated gully erosion in the clay-rich soils of east Tennessee under a humid subtropical climate. The aims of this study were to (1) estimate long-term erosion rates for different gully geomorphic settings, (2) compare patterns of erosion for the different settings, and (3) model the response of gully erosion to freeze-thaw events. Erosion was measured weekly from June 2012 to August 2018 using 105 erosion pins distributed in gully channels, interfluves, and sidewalls. Erosion rates were estimated from average slopes of lines of best fit of pin lengths versus time. Maximum and minimum temperature was calculated daily using an on-site weather station and freeze-thaw events were identified. Gully erosion was modeled using antecedent freeze-thaw activity for the three geomorphic settings. Long-term erosion rates in channels, interfluves, and sidewalls were 2.5 mm/year, 20 mm/year, and 21 mm/year, respectively; however, week-by-week erosion was statistically different between the three settings, indicating different erosive drivers. Models of erosion with lagged freeze-thaw variables explained up to 34.8% of the variability in erosion variables; sidewall erosion was most highly related to freeze-thaw activity. Freeze-thaw in prior weeks was an important variable in all erosion models. Full article
(This article belongs to the Special Issue Surface Runoff and Soil Erosion under Various Climate Conditions)
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Open AccessCommunication
Effects of Sewage Sludge Amendments on the Growth and Physiology of Sweet Basil
Agronomy 2019, 9(9), 548; https://doi.org/10.3390/agronomy9090548 - 13 Sep 2019
Cited by 2 | Viewed by 698
Abstract
Currently, wastewater treatment plants produce large amounts of sewage sludge. Due to the rich content of organic matter and minerals, sewage sludge can be used as soil amendments for eroded soils. The aim of this work was to assess sewage sludge (SS) in [...] Read more.
Currently, wastewater treatment plants produce large amounts of sewage sludge. Due to the rich content of organic matter and minerals, sewage sludge can be used as soil amendments for eroded soils. The aim of this work was to assess sewage sludge (SS) in combination with an eroded soil (ES) collected from the North Eastern Romania as growth substrate for sweet basil, and their effect on basil growth and physiology. The experiment was conducted in a greenhouse under controlled environment conditions. The tested substrates were: (1) eroded soil, ES; (2) mixture of eroded soil (15%) + sewage sludge, ES + SS (85%); and (3) sewage sludge, SS (100%). Three types of parameters were studied: morphological traits, physiological, and biochemical parameters. The maximum quantum yield of Photosystem II Fv/Fm was reduced in basil leaves grown on eroded soil (0.80) and was close to the normal value in ES + SS (0.83). Chlorophyll a and the carotenoids content were higher for plants grown on SS and significantly higher for those grown in ES + SS compared with the one of plants grown on ES. The fresh biomass yield and height of basil increased with 44% and 34.5% under ES + SS over ES. Total phenolic content was higher in plants grown on ES (7.34 mg/g dry weight Gallic acid equivalent), which also led to an increased antioxidant activity (44.4%) evaluated by the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. Fourier-Transform Infrared (FT-IR) (4000–400 cm−1) spectra of basil did not show significant qualitative differences among the plants from different treatments. The results of this study demonstrated that SS application led to the improvement of the basil morpho-physiological parameters, allowing the growth of basil on ES + SS. Full article
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Open AccessArticle
Optimization of Herbicide Use: Study on Spreading and Evaporation Characteristics of Glyphosate-Organic Silicone Mixture Droplets on Weed Leaves
Agronomy 2019, 9(9), 547; https://doi.org/10.3390/agronomy9090547 - 12 Sep 2019
Cited by 2 | Viewed by 674
Abstract
Herbicide deposition rate can be affected by the leaf surface features of weeds and have a significant impact on the overall efficacy. In this paper, an orthogonal experiment was conducted to investigate the differences of droplet evaporation and spreading characteristics corresponding to weed [...] Read more.
Herbicide deposition rate can be affected by the leaf surface features of weeds and have a significant impact on the overall efficacy. In this paper, an orthogonal experiment was conducted to investigate the differences of droplet evaporation and spreading characteristics corresponding to weed leaf surface with hairy, waxy and rough (ridged) structures. Three weed species—Descurainia sophia, Lepidium lotifolium, and Lolium temulentum—were included in the study, representing these three leaf structures respectively. Glyphosate sprays with organic silicone surfactant in different concentrations were composed for the test. Single droplets with two diameters of 0.05 μL and 0.1 μL were deposited on the leaves to evaluate the evaporation and spreading characteristics. A digital camera was used and the evaporation duration and the maximum droplet coverage images could be captured and extracted from the recorded videos. The Image Processing Toolbox in Matlab was applied to segment the images for droplet and leaf background and the binary images’ pixel numbers were counted for coverage area calculation. The results revealed that the evaporation duration was reduced with the increase of the organic silicone concentration, while the spread area was expanded. The droplet spread more widely and evaporated faster on D. sophia leaves than on the leaves with L. lotifolium and L. temulentum surfaces. The spreading area and evaporation duration varied much faster on L. lotifolium leaves than on the leaves of other weed species. The droplet sizes affected spreading more significantly on L. temulentum leaf surface, as the spreading procedure of small size droplets was restrained by the groove structure. The results of this study would benefit the consideration of the farmers when selecting the proper nozzle code and the determining of the surfactant mixture in order to optimize the use of herbicides like glyphosate. Full article
(This article belongs to the Special Issue Weed Management & New Approaches)
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Open AccessArticle
Regulation of Spraying 6-BA in the Late Jointing Stage on the Fertile Floret Development and Grain Setting in Winter Wheat
Agronomy 2019, 9(9), 546; https://doi.org/10.3390/agronomy9090546 - 12 Sep 2019
Viewed by 523
Abstract
Wheat yield is largely determined by the grains per spike, which in turn is related to the fertile floret development prior to anthesis. The aim of this study was to assess the physiological mechanism of exogenous 6-benzylaminopurine (6-BA) on fertile floret development and [...] Read more.
Wheat yield is largely determined by the grains per spike, which in turn is related to the fertile floret development prior to anthesis. The aim of this study was to assess the physiological mechanism of exogenous 6-benzylaminopurine (6-BA) on fertile floret development and grain setting characteristics by foliar application in winter wheat. Field experiments were conducted during the 2016–2017 and 2017–2018 growing seasons in China. Two foliar spraying applications with water (S0) and 6-BA (S1) were applied to a large-spike variety (V1) and a multiple-spike variety (V2) 25 days after jointing. At anthesis, spike dry weight and soluble sugar, sucrose, auxin, and cytokinin were all positively correlated with the number of fertile florets and grains per spike. During the abortion stage of fertile florets, 6-BA application compared to the control reduced the auxin content, increased the cytokinin content and spike dry matter and transported more soluble sugar and sucrose from the non-spike organs to the spike. Exogenous 6-BA application increased the number of fertile florets (~1.84 to ~2.50) and number of grains (~2.83 to ~3.51) by primarily suppressing the number of degenerated and aborted florets. The results provide important evidence that 6-BA application has a positive effect on floret fertility and grain setting, which lead to a further increase in grain yield. Full article
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Open AccessArticle
Effect of Salinity Stress and Microbial Inoculations on Glomalin Production and Plant Growth Parameters of Snap Bean (Phaseolus vulgaris)
Agronomy 2019, 9(9), 545; https://doi.org/10.3390/agronomy9090545 - 12 Sep 2019
Cited by 4 | Viewed by 1550
Abstract
Salinity is a major abiotic stress that can adversely affect plant growth, yield, other physiological parameters, and soil health. Salinity stress on biomass production of salt-sensitive crops, like snap bean (Phaseolus vulgaris), is a serious problem, and specifically in South Florida, [...] Read more.
Salinity is a major abiotic stress that can adversely affect plant growth, yield, other physiological parameters, and soil health. Salinity stress on biomass production of salt-sensitive crops, like snap bean (Phaseolus vulgaris), is a serious problem, and specifically in South Florida, USA, where saline soils can be found in major agricultural lands. Research studies focused on the ‘snap bean–Rhizobium–arbuscular mycorrhizal fungi (AMF)’ relationship under salinity stress are limited, and fewer studies have evaluated how this tripartite symbiosis affects glomalin production (GRSP), a glycoprotein released by AMF. A shade house experiment was conducted to elucidate the effects of three microbial inoculations (IC = inoculation control; IT1 = AMF and IT2 = AMF + Rhizobium) on three salinity treatments (SC = salinity control 0.6 dS m−1, S1 = 1.0 dS m−1, and S2 = 2.0 dS m−1) on snap bean growth and yield. Our results indicate that S2 reduced 20% bean biomass production, 11% plant height, 13% root weight, and 23% AMF root colonization. However, microbial inoculations increased 26% bean yield over different salinity treatments. Maximum salinity stress (S2) increased 6% and 18% GRSP production than S1 and SC, respectively, indicating the relative advantage of abiotic stress on AMF’s role in soil. Dual inoculation (IT2) demonstrated a beneficial role on all physiological parameters, biomass production, and GRSP synthesis compared to single inoculation (IT1) treatment with all three salinity levels. Full article
(This article belongs to the Special Issue Rhizobium–Legume Symbiosis)
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Open AccessArticle
Killing Weed Seeds with Exhaust Gas from a Combine Harvester
Agronomy 2019, 9(9), 544; https://doi.org/10.3390/agronomy9090544 - 12 Sep 2019
Cited by 4 | Viewed by 765
Abstract
We investigated if hot exhaust gas from a combine harvester could be used to reduce germination or kill weed seeds during the harvesting process. During the threshing and cleaning process in the combine, weed seeds and chaff are separated from the crop grains. [...] Read more.
We investigated if hot exhaust gas from a combine harvester could be used to reduce germination or kill weed seeds during the harvesting process. During the threshing and cleaning process in the combine, weed seeds and chaff are separated from the crop grains. After this separation, weed and crop seeds not collected can be exposed to exhaust gas before seeds are returned to the field. Seeds of some common weed species (Alopecurus myosuroides, Centaurea cyanus, Geranium pusillum, Lapsana communis, Lolium perenne, Rumex crispus, Spergula arvensis, and Tripleurospermum inodorum) were treated with exhaust gas at temperatures of 75 °C or 85 °C, 110 °C, and 140 °C for 2, 4, and 6 s, respectively. Afterwards, the seeds were germinated for 16 days. We found that 75 °C and 85 °C were insufficient to significantly reduce germination of the seeds after three durations. Some seeds were still able to germinate after 4 s exposure of 110 °C. An exposure of 140 °C for 4 and 6 s repressed germination of all species. We conclude that there is potential to develop combine harvesters that exploit the exhaust gas to either kill or reduce the ability of weed seeds to germinate before seeds are returned to the field. Full article
(This article belongs to the Special Issue Weed Management & New Approaches)
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Open AccessArticle
Applications of Fungal Strains with Keratin-Degrading and Plant Growth Promoting Characteristics
Agronomy 2019, 9(9), 543; https://doi.org/10.3390/agronomy9090543 - 12 Sep 2019
Cited by 2 | Viewed by 762
Abstract
Protein hydrolysates (PHs) are organic non-microbial biostimulants having beneficial effects on plants. The study was designed to assess the effects on plants by the applications of PHs obtained from Trichoderma isolates grown on keratin wastes. Trichoderma isolates were characterized for indole-3-acetic acid and [...] Read more.
Protein hydrolysates (PHs) are organic non-microbial biostimulants having beneficial effects on plants. The study was designed to assess the effects on plants by the applications of PHs obtained from Trichoderma isolates grown on keratin wastes. Trichoderma isolates were characterized for indole-3-acetic acid and siderophores production, activity of lytic enzymes, phosphorous solubilization and inhibition of pathogens growth, using qualitative specific tests. Fungal isolates were cultured on a medium with keratin wastes (wool and feathers) to obtain PHs. Fungal PHs were tested in vivo for plant biostimulant action, as follows: (i) seeds germination test; (ii) activation of plant proton pump; (iii) evaluation of effect on tomato seedling growth. PHs from T. asperellum cultured on feathers medium reached the highest values for all parameters recorded (plant height and diameter, number of leaves and branches), with the exception of those for plant biomass, which were maximum for the wool medium. The metabolites released by keratin degradation under the activity of selected T. asperellum isolate improved crop health and productivity. The use of PHs can be a reasonable solution for the environmental pollution of by-products from the food chain, as well as for the replacement of chemical fertilizers with microbial formulations to stimulate plant growth. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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Open AccessReview
Potential Benefits and Risks for Soil Health Derived From the Use of Organic Amendments in Agriculture
Agronomy 2019, 9(9), 542; https://doi.org/10.3390/agronomy9090542 - 12 Sep 2019
Cited by 8 | Viewed by 1096
Abstract
The use of organic amendments in agriculture is a common practice due to their potential to increase crop productivity and enhance soil health. Indeed, organic amendments of different origin and composition (e.g., animal slurry, manure, compost, sewage sludge, etc.) can supply valuable nutrients [...] Read more.
The use of organic amendments in agriculture is a common practice due to their potential to increase crop productivity and enhance soil health. Indeed, organic amendments of different origin and composition (e.g., animal slurry, manure, compost, sewage sludge, etc.) can supply valuable nutrients to the soil, as well as increase its organic matter content, with concomitant benefits for soil health. However, the application of organic amendments to agricultural soil entails a variety of risks for environmental and human health. Organic amendments often contain a range of pollutants, including heavy metals, persistent organic pollutants, potential human pathogens, and emerging pollutants. Regarding emerging pollutants, the presence of antibiotic residues, antibiotic-resistant bacteria, and antibiotic-resistance genes in agricultural amendments is currently a matter of much concern, due to the concomitant risks for human health. Similarly, currently, the introduction of microplastics to agricultural soil, via the application of organic amendments (mainly, sewage sludge), is a topic of much relevance, owing to its magnitude and potential adverse effects for environmental health. There is, currently, much interest in the development of efficient strategies to mitigate the risks associated to the application of organic amendments to agricultural soil, while benefiting from their numerous advantages. Full article
(This article belongs to the Special Issue Soil Health in Agroecosystems)
Open AccessArticle
The Current Stage of Greening Vegetation in Selected Wine-Regions of South Moravian Region (Czech Republic)
Agronomy 2019, 9(9), 541; https://doi.org/10.3390/agronomy9090541 - 12 Sep 2019
Cited by 2 | Viewed by 694
Abstract
Viticulture, as a large part of the agriculture sector of the South Moravian Region, represents significant erosion-prone land use in which soils face various agronomic issues, such as poor organic carbon levels, erosion, and fertility loss. Service crops providing a so-called ecosystem service [...] Read more.
Viticulture, as a large part of the agriculture sector of the South Moravian Region, represents significant erosion-prone land use in which soils face various agronomic issues, such as poor organic carbon levels, erosion, and fertility loss. Service crops providing a so-called ecosystem service can reduce erosion and runoff, regulate pests and weeds and increase soil organic matter and fertility. However, these crops may generate some disservices, such as water and nutrient competition; and thus, it is important for winegrowers to find applicable options for service crops depending on local soil, climate conditions, and the expected service. Inter-row management in the South Moravian Region varies from bare soils to grass cover to different types of cover with herbaceous (flowering) species. A total of 113 vineyard sites were evaluated during the years 2016 and 2017. This study presents the actual state of inter-row management in vineyards and comparison within six wine-growing regions. A two-year evaluation shows significant differences in prevalent greening management between regions. Bare soil in vineyards, the most erosion-prone vineyard floor management, appear from 10% (e.g., Bzenec, Valtice) to 19% (e.g., Mikulov, V. Bílovice) of vineyard area within evaluated regions. Bare soil management is mostly used in new plantations to reduce water and nutrient competition; however, the erosion and the runoff rates are generally higher on this variant compared to other types of cover crop management, especially on slopes. Although, alternate greening is the most used type occurring from 50% to 74% of vineyards area in five of the six selected regions, the type of inter-row vegetation differs considerably. While in Bzenec and Mikulov there is a higher appearance of herbaceous cover with native species in later succession stages, in Velké Bílovice and Valtice grass cover and commercial plant mixtures are more frequent. Knowledge current stage can be useful for planning new plantation or anti-erosion measures. Full article
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Open AccessArticle
Evaluation of Mobile Heat Treatment System for Treating In-Field HLB-Affected Trees by Analyzing Survival Rate of Surrogate Bacteria
Agronomy 2019, 9(9), 540; https://doi.org/10.3390/agronomy9090540 - 12 Sep 2019
Cited by 1 | Viewed by 935
Abstract
Huanglongbing (HLB or citrus greening) is a disease caused by an insect-transmitted bacterial pathogen Candidatus Liberibacter asiaticus (CLas). Thermotherapy has been successfully used by others to reduce the population of CLas bacteria in HLB-affected citrus trees under greenhouse studies. Thermotherapy is [...] Read more.
Huanglongbing (HLB or citrus greening) is a disease caused by an insect-transmitted bacterial pathogen Candidatus Liberibacter asiaticus (CLas). Thermotherapy has been successfully used by others to reduce the population of CLas bacteria in HLB-affected citrus trees under greenhouse studies. Thermotherapy is the application of heat as a strategy to reduce the adverse economic impact of certain pests and diseases. CLas is a fastidious, non-cultivable organism. The high variance in CLas titers in canopy samples together with this lack of cultivability makes it impossible to use classical bacteriological techniques to measure the viability either before or after treatments. Therefore, we used the survival rates of a surrogate bacterium, Klebsiella oxytoca, in order to evaluate the effectiveness of a mobile thermotherapy delivery system developed for in-field treatment of HLB-affected trees. K. oxytoca is a Gram-negative, rod-shaped bacterium that was originally isolated from soil and has been used in the development of industrial applications related to ethanol fuel production. It served as a biologically-based sensor of temperature stress (biosensor) in this study. Thermocouples and biosensor packets (plastic cups with suspended small snap-top tubes) containing the K. oxytoca were attached to an HLB-affected citrus tree and their canopy locations mapped. The mobile thermotherapy treatment hood covered the canopy of the HLB-affected tree. Then, steam and hot water were injected through nozzles inside of the hood to increase the temperature of the tree canopy. A standard temperature–time combination of 54 °C for 90 s was chosen based on preliminary studies where heat treatment parameters caused a significant reduction in CLas populations without inflicting permanent damage to the tree. The survival ratio of the K. oxytoca in the biosensor packets was found to range from complete elimination to 5% with treatments of 250 s and a maximum temperature of 54 °C. Full article
(This article belongs to the Special Issue Precision Agriculture)
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Open AccessArticle
Stacking Agricultural Management Tactics to Promote Improvements in Soil Structure and Microbial Activities
Agronomy 2019, 9(9), 539; https://doi.org/10.3390/agronomy9090539 - 12 Sep 2019
Cited by 2 | Viewed by 571
Abstract
Linking agricultural management tactics to quantifiable changes in soil health-related properties is a key objective for increasing adoption of the most favorable management practices. We used two long-term, no-till cropping studies to illustrate the variable patterns of response of soil structure indices and [...] Read more.
Linking agricultural management tactics to quantifiable changes in soil health-related properties is a key objective for increasing adoption of the most favorable management practices. We used two long-term, no-till cropping studies to illustrate the variable patterns of response of soil structure indices and microbial activity to additional management tactics, including crop rotational diversity, residue management and cover cropping. We found that observable effects of management tactics on soil properties were often dependent on the current crop phase sampled, even though the treatments were well-established. In some cases, a single additional management tactic produced a response, two tactics each produced a response and sometimes there were interactions between tactics. However, importantly, we never observed a negative effect for any of the response variables when stacking soil health building practices in no-till cropping systems. The collective results from the two field studies illustrate that soil health improvements with stacking management tactics are not always simply additive and are affected by temporal relationships inherent to the treatments. We conclude that the implementation of multiple positive management tactics increases the likelihood that improvements in soil properties can be documented with one or more of the proxy measures for soil health. Full article
(This article belongs to the Special Issue Soil Health in Agroecosystems)
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Open AccessArticle
Planting Locations with Higher Temperature Produce More Bioactive Compounds and Antioxidant Capacities of Wheat
Agronomy 2019, 9(9), 538; https://doi.org/10.3390/agronomy9090538 - 11 Sep 2019
Viewed by 572
Abstract
Bioactive compounds such as phenols and phytic acid in wheat contribute to antioxidant capacities. (1) Background: Prior studies drew a general conclusion that the environment affected bioactive compounds greatly, but how the single environmental factor affects these characteristics remains unclear. (2) Methods: We [...] Read more.
Bioactive compounds such as phenols and phytic acid in wheat contribute to antioxidant capacities. (1) Background: Prior studies drew a general conclusion that the environment affected bioactive compounds greatly, but how the single environmental factor affects these characteristics remains unclear. (2) Methods: We conducted that twenty-eight winter wheat genotypes were grown in replicated trials at seven locations in China for two consecutive years and subdivided the environmental factor into five soil factors and six meteorological factors to evaluate the impact on the antioxidant capabilities and bioactive compounds contents of wheat grains by using principal component analysis (PCA). RT-PCR was used to identify gene expression of bioactive compounds under different conditions. (3) Results: Temperature affects bioactive compounds contents and antioxidant capacities greatly in wheat grains. Accumulation time, daylight length, and daily maximum temperature showed a high correlation with bioactive compounds contents and antioxidant capacities, especially in the vegetative growth phase. The gene TaMIPs related to phytic acid and TaPAL1, TaC3H1, TaC4H, Ta4CL1, and TaCOMT1 related to total phenolics had higher gene expression level with larger temperature differences in wheat grains. (4) Conclusions: The planting locations with higher temperatures and longer daylight length could produce higher contents of bioactive compounds and antioxidant capacities and the cooler temperatures of a planting location might produce wheat grains with lower phytic acid contents in wheat grains. Full article
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Open AccessArticle
Influence of Zeolite and Phosphorus Applications on Water Use, P Uptake and Yield in Rice under Different Irrigation Managements
Agronomy 2019, 9(9), 537; https://doi.org/10.3390/agronomy9090537 - 11 Sep 2019
Cited by 2 | Viewed by 875
Abstract
Phosphorus (P) deficiency often occurs in paddy fields due to its high fixation, and low solubility and mobility in soils, especially under water stress. Available soil P and plant P uptake could be improved through the application of zeolite. However, little is known [...] Read more.
Phosphorus (P) deficiency often occurs in paddy fields due to its high fixation, and low solubility and mobility in soils, especially under water stress. Available soil P and plant P uptake could be improved through the application of zeolite. However, little is known about the impact of zeolite on P uptake in rice under water stress. A two-year lysimetric experiment using a split-split plot design investigated the effects of zeolite (0 or 15 t ha−1) and P (0 or 60 kg ha−1) applications on water use, P uptake, and grain yield in rice under two irrigation management systems (continuous flooding irrigation (CF) and improved alternate wetting and drying irrigation (IAWD)). Both irrigation systems produced equivalent effective panicles and grain yield. Compared with CF, IAWD reduced water use and aboveground P uptake and improved water-use efficiency (WUE) in rice. The applications of zeolite or P alone increased grain yield, WUE, soil available P, and stem, leaf, and panicle P concentration, and aboveground P uptake, but had no significant effect on water use. The enhanced grain yield induced by zeolite was related to the increase in aboveground P uptake. The zeolite application enhanced NH4+–N retention in the topsoil and prevented NO3–N from leaching into deeper soil layers. Moreover, Zeolite made lower rates of P fertilizer possible in paddy fields, with benefits for remaining P supplies and mitigating pollution due to excessive P. These results suggest that the combined application of zeolite and P under improved AWD regime reduced water use, improved P uptake and grain yield in rice, and alleviated environment risk. Full article
(This article belongs to the Special Issue Increasing Agricultural Water Productivity in a Changing Environment)
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