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Agronomy, Volume 9, Issue 12 (December 2019) – 120 articles

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Cover Story (view full-size image) The Super High Density (SHD) training system represents a new concept in almond tree cultivation. [...] Read more.
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Open AccessArticle
Water–Nitrogen Coupling and Multi-Objective Optimization of Cotton under Mulched Drip Irrigation in Arid Northwest China
Agronomy 2019, 9(12), 894; https://doi.org/10.3390/agronomy9120894 - 17 Dec 2019
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Abstract
Cotton is the most important cash crop in Xinjiang but low utilization rate of water and fertilizer is restricting healthy development of this industry. At present, there is a lack of water and nitrogen management optimization methods based on multi-objectives of cotton water [...] Read more.
Cotton is the most important cash crop in Xinjiang but low utilization rate of water and fertilizer is restricting healthy development of this industry. At present, there is a lack of water and nitrogen management optimization methods based on multi-objectives of cotton water use efficiency (WUE), nitrogen use efficiency (NUE), yield, and income. A continuous field experiment was conducted during 2017–2018 to study the effects of water–nitrogen coupling on cotton growth, WUE, NUE, nitrogen partial factor productivity, yield, quality, and economic benefits under drip irrigation in northern Xinjiang. Using multiple regression and spatial analyses, the water and nitrogen management strategy for multi-objective optimization was determined. Three irrigation levels were used—low (I1), medium (I2), and full (I3)—Representing 75%, 87.5%, and 100% of cotton water demand, respectively. The three nitrogen application levels were low (N1, 210 kg/ha), medium (N2, 280 kg/ha), and high (N3, 350 kg/ha), representing 75%, 100%, and 125% of the local nitrogen application, respectively. Among all treatments, the leaf area index, boll weight, dry matter quantity and yield reached respective maxima of 4.43 m2/m2, 4.73 g, 16,623 kg/ha, and 6333 kg/ha for the I3N2 treatment. Cotton fiber quality was the best for I3 irrigation, but too little or too much nitrogen reduced fiber quality. The economic benefit under I3 irrigation was 1.93–4.81 times that for I1. For a single optimization objective, WUE reached a maximum of 1.78 kg/ha·mm for irrigation of 415.80 mm and nitrogen application of 295.71 kg/ha; corresponding single maxima follow: NUE of 37.65% for 418.27 mm and 278.57 kg/ha; yield of 6416.42 kg/ha for 470.12 mm and 304.29 kg/ha; and economic benefit of 15,338.55 RMB/ha for 470.12 mm and 307.14 kg/ha. Multiple regression and spatial analysis showed that for irrigation of 430.71–440.12 mm and nitrogen application of 270.95–318.45 kg/ha, the WUE, NUE, yield, and economic benefits of cotton simultaneously exceeded 90% of their maxima, which was an efficient and reasonable water and nitrogen management mode in this location. The results provide a scientific basis for effective integrated management of water and fertilizer in drip irrigation cotton fields in northern Xinjiang. Full article
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Open AccessArticle
Genetic Transformation and siRNA-Mediated Gene Silencing for Aphid Resistance in Tomato
Agronomy 2019, 9(12), 893; https://doi.org/10.3390/agronomy9120893 - 17 Dec 2019
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Abstract
We explored the ability of RNA interference (RNAi) to silence the Acetylcholinesterase 1 (Ace 1) gene in aphid Myzus persicae and developed transgenic tomato plants resistant to aphid infestation. Three plasmid constructs, T-449: a single Ace 1 fragment (forward orientation), T-452: [...] Read more.
We explored the ability of RNA interference (RNAi) to silence the Acetylcholinesterase 1 (Ace 1) gene in aphid Myzus persicae and developed transgenic tomato plants resistant to aphid infestation. Three plasmid constructs, T-449: a single Ace 1 fragment (forward orientation), T-452: two Ace 1 fragments (reverse and forward orientations), and T455: a single inverted Ace 1 fragment, were developed and transformed into two tomato cultivars, Jamila and Tomaland. PCR, northern blotting, and small interfering RNAs (siRNA) analysis were performed to validate the success of Agrobacterium-mediated transformation. The efficiency of transformation was highest for the T-452 construct. In vivo effects of the transformed constructs were confirmed in feeding experiments, and there was significant downregulation of the Ace 1 gene. In addition, an aphid challenge assay was conducted to investigate the siRNA-mediated silencing of the target gene (Ace 1) in the inhibition of fecundity in M. persicae. We found that the plants that were transformed with the T-452 vector had 37.5% and 26.4% lower fecundity at 27 °C in the Jamila and Tomaland, respectively. Our results strongly indicated that the plant-mediated silencing of aphid-RNA might be a robust and effective approach for developing pest and disease resistant in plants. Full article
(This article belongs to the Section Horticultural and Floricultural Crops)
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Open AccessPerspective
Status of Wheat Rust Research and Progress in Rust Management-Indian Context
Agronomy 2019, 9(12), 892; https://doi.org/10.3390/agronomy9120892 - 16 Dec 2019
Viewed by 304
Abstract
The rusts of wheat, caused by three species of Puccinia, are very devastating diseases and are major biotic constraints in efforts to sustain wheat production worldwide. Their capacity to spread aerially over long distances, rapid production of infectious uredospores, and abilities to [...] Read more.
The rusts of wheat, caused by three species of Puccinia, are very devastating diseases and are major biotic constraints in efforts to sustain wheat production worldwide. Their capacity to spread aerially over long distances, rapid production of infectious uredospores, and abilities to evolve new pathotypes, makes the management of wheat pathogens a very challenging task. The development and deployment of resistant wheat varieties has proven to be the most economic, effective and efficient means of managing rust diseases. Rust resistance used in wheat improvement has included sources from the primary gene pool as well as from species distantly related to wheat. The 1BL/1RS translocation from cereal rye was used widely in wheat breeding, and for some time provided resistance to the wheat leaf rust, stripe rust, and stem rust pathogens conferred by genes Lr26, Yr9, and Sr31, respectively. However, the emergence of virulence for all three genes, and stripe rust resistance gene Yr27, has posed major threats to the cultivation of wheat globally. To overcome this threat, efforts are going on worldwide to monitor rust diseases, identify rust pathotypes, and to evaluate wheat germplasm for rust resistance. Anticipatory breeding and the responsible deployment of rust resistant cultivars have proven to be effective strategies to manage wheat rusts. Efforts are still however being made to decipher the recurrence of wheat rusts, their epidemiologies, and new genomic approaches are being used to break the yield barriers and manage biotic stresses such as the rusts. Efficient monitoring of pathotypes of Puccinia species on wheat, identification of resistance sources, pre-emptive breeding, and strategic deployment of rust resistant wheat cultivars have been the key factors to effective management of wheat rusts in India. The success in containing wheat rusts in India can be gauged by the fact that we had no wheat rust epiphytotic for nearly last five decades. This publication provides a comprehensive overview of the wheat rust research conducted in India. Full article
(This article belongs to the Special Issue Cereal Rust Management for Improving Global Food Security)
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Open AccessArticle
Assessment of Sustainability in Agriculture of the European Union Countries
Agronomy 2019, 9(12), 890; https://doi.org/10.3390/agronomy9120890 - 16 Dec 2019
Viewed by 367
Abstract
This paper aimed at evaluating the level of sustainability in agriculture in 28 member states of the European Union. The surveys were carried out based on a synthetic technique for order preference by similarity to an ideal solution (TOPSIS)-based measure. This method synthesizes [...] Read more.
This paper aimed at evaluating the level of sustainability in agriculture in 28 member states of the European Union. The surveys were carried out based on a synthetic technique for order preference by similarity to an ideal solution (TOPSIS)-based measure. This method synthesizes factors of various nature and assigns them a synthetic aggregate measure. The analysis made it possible to develop a ranking of EU member states according to a differentiated level of measures and assign them to one of four groups characterized by different levels of sustainability in agriculture. The group of member states representing the highest level of sustainability in agriculture included two countries from Central and Eastern Europe, i.e., Slovakia and the Czech Republic. The group of countries with a greater than average level of sustainability comprised 14 member states of the European Union, including seven countries admitted to the community after 2004. The group with a low level of sustainability consisted of eight EU member states, six of them from the group of old EU member states, i.e., Ireland, Portugal, Greece, Italy, Denmark and the United Kingdom, and two new members, i.e., Romania and Slovenia. On the other hand, the lowest level of sustainability was characteristic of two “old EU” member states, i.e., The Netherlands and Belgium, and two “new EU” member states, i.e., Cyprus and Malta. The differentiated synthetic measure values showed disparities in the level of sustainability in agriculture among the member states of the European Union. They are a result of the varied level of development of this sector, production intensity and the resulting environmental impact. Full article
(This article belongs to the Section Farming Sustainability)
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Open AccessArticle
Cladobotryum mycophilum as Potential Biocontrol Agent
Agronomy 2019, 9(12), 891; https://doi.org/10.3390/agronomy9120891 - 15 Dec 2019
Viewed by 359
Abstract
A study was conducted to explore the efficacy of potential biocontrol agent Cladobotryum mycophilum against different phytopathogenic fungi. The growth rates of 24 isolates of C. mycophilum were determined, and their antagonistic activity was analysed in vitro and in vivo against Botrytis cinerea [...] Read more.
A study was conducted to explore the efficacy of potential biocontrol agent Cladobotryum mycophilum against different phytopathogenic fungi. The growth rates of 24 isolates of C. mycophilum were determined, and their antagonistic activity was analysed in vitro and in vivo against Botrytis cinerea, Fusarium oxysporum f. sp. radicis-lycopersici, Fusarium oxysporum f.sp. cucumerinum, Fusarium solani, Phytophthora parasitica, Phytophthora capsici, Pythium aphanidermatum and Mycosphaerella melonis. Most isolates grow rapidly, reaching the opposite end of the Petri dish within 72–96 h. Under dual-culture assays, C. mycophilum showed antagonistic activity in vitro against all phytopathogenic fungi tested, with mycelial growth inhibition ranging from 30 to 90% against all the different phytopathogens tested. Similarly, of all the selected isolates, CL60A, CL17A and CL18A significantly (p < 0.05) reduced the disease incidence and severity in the plant assays compared to the controls for the different pathosystems studied. Based on these results, we conclude that C. mycophilum can be considered as a potential biological control agent in agriculture. This is the first study of Cladobotryum mycophilum as a biological control agent for different diseases caused by highly relevant phytopathogens in horticulture. Full article
(This article belongs to the Special Issue Integrating Pest Management into Agricultural Production Systems)
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Open AccessArticle
Improving the Conservation and Use of Traditional Germplasm through Breeding for Local Adaptation: The Case of the Castellfollit del Boix Common Bean (Phaseolus vulgaris L.) Landrace
Agronomy 2019, 9(12), 889; https://doi.org/10.3390/agronomy9120889 - 14 Dec 2019
Viewed by 368
Abstract
The dramatic reduction in the diversity of crops in the last century is often attributed to the consolidation of scientific breeding, probably because the two processes have occurred at the same time. We carried out a breeding program to enhance the Castellfollit del [...] Read more.
The dramatic reduction in the diversity of crops in the last century is often attributed to the consolidation of scientific breeding, probably because the two processes have occurred at the same time. We carried out a breeding program to enhance the Castellfollit del Boix landrace of common bean (Phaseolus vulgaris L.) in a low-input environment to determine the effects of breeding on a landrace at risk of disappearing. The program increased the number of accessions conserved ex situ and obtained more efficient genotypes that are less likely to be abandoned by farmer without altering the characteristics that consumers appreciate most. As a result, the availability of the product, its promotion, and its use have increased. We propose a Conservation Potential Index to measure the impact of changes in the crop’s epiphenotype, and also apply it to a set of landraces from several crops. We argue that scientific breeding and information gathered in the context of genetic improvement programs can help to conserve biodiversity when they aim to adapt materials to different local environments, rather than having a negative impact on the biodiversity of crops. This approach contrasts with the genetic erosion that results from efforts to homogenize environments by increasing inputs, so that a few improved varieties adapted to these environments can be grown. Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessArticle
Potential and Actual Water Savings through Improved Irrigation Scheduling in Small-Scale Vegetable Production
Agronomy 2019, 9(12), 888; https://doi.org/10.3390/agronomy9120888 - 14 Dec 2019
Viewed by 312
Abstract
Appropriate irrigation scheduling for efficient water use is often a challenge for small-scale farmers using drip irrigation. In a trial with 12 farmers in Sébaco, Nicaragua, two tools to facilitate irrigation scheduling were tested: the Water Chart (a table indicating required irrigation doses) [...] Read more.
Appropriate irrigation scheduling for efficient water use is often a challenge for small-scale farmers using drip irrigation. In a trial with 12 farmers in Sébaco, Nicaragua, two tools to facilitate irrigation scheduling were tested: the Water Chart (a table indicating required irrigation doses) and tensiometers. The study aimed at evaluating if and to what extent simple tools can reduce irrigation water use and improve water productivity in drip-irrigated vegetable (beetroot; Beta vulgaris L.) production compared with the farmers’ usual practice. Irrigation water use was substantially reduced (around 20%) when farmers irrigated according to the tools. However, farmers did not fully adhere to the tool guidance, probably because they feared that their crop would not get sufficient water. Thus they still over-irrigated their crop: between 38% and 88% more water than recommended was used during the treatment period, resulting in 91% to 139% higher water use than required over the entire growing cycle. Water productivity of beetroot production was, therefore, much lower (around 3 kg/m3) than what can be achieved under comparable conditions, although yields were decent. Differences in crop yield and water productivity among treatments were not significant. The simplified Water Chart was not sufficiently understandable to farmers (and technicians), whereas tensiometers were better perceived, although they do not provide any indication on how much water to apply. We conclude that innovations such as drip irrigation or improved irrigation scheduling have to be appropriately introduced, e.g., by taking sufficient time to co-produce a common understanding about the technologies and their possible usefulness, and by ensuring adequate follow-up support. Full article
(This article belongs to the Special Issue Increasing Agricultural Water Productivity in a Changing Environment)
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Open AccessArticle
Multi-Level Characterization of Eggplant Accessions from Greek Islands and the Mainland Contributes to the Enhancement and Conservation of this Germplasm and Reveals a Large Diversity and Signatures of Differentiation between both Origins
Agronomy 2019, 9(12), 887; https://doi.org/10.3390/agronomy9120887 - 13 Dec 2019
Viewed by 316
Abstract
Crop landraces are found in many inhabited islands of Greece. Due to the particularity of environment and isolation from the mainland, Greek islands represent a natural laboratory for comparing the diversity of landraces from the islands with those of the Greek mainland. A [...] Read more.
Crop landraces are found in many inhabited islands of Greece. Due to the particularity of environment and isolation from the mainland, Greek islands represent a natural laboratory for comparing the diversity of landraces from the islands with those of the Greek mainland. A collection of 36 Greek eggplant landraces and traditional cultivars from the mainland and the islands has been phenotypically and genetically characterized using 22 morphological descriptors and 5 SSR markers. The mineral composition (K, Mg, Cu, Fe, Mn, Zn) of fruits was also determined. The objectives of this study include the multi-level characterization of eggplant local landraces and the comparison of diversity among accessions from the Greek mainland and the islands. Characterization of eggplant landraces will contribute to the enhancement and prevention of genetic erosion in this local group and will provide a resource for future investigation and breeding. PCA analysis of morphological traits explained 45.4% of the total variance revealing the formation of two clusters, one with most of the island accessions, and another with most of the mainland ones. The SSR markers used exhibited high average values for the number of alleles/locus (4.6), expected heterozygosity (0.60) and PIC (0.55), while the observed heterozygosity was low (0.13). Both STRUCTURE and PCoA analyses based on SSR data revealed two genetic clusters, one made up mainly by the mainland accessions, while the other one was mainly made up by the island accessions. Although there was considerable variation among the landraces for the concentration of minerals studied, only average Mg concentration was significantly different between mainland and island accessions. Based on our data, the Greek eggplant landraces present considerable morphological and genetic diversity with some differentiation signatures between the island and the mainland accessions. Our results have implications for conservation of Greek landraces and suggest that Greece might be considered as part of a secondary center of diversity for eggplant in the Mediterranean basin. Full article
(This article belongs to the Special Issue Analysis of Crop Genetic and Germplasm Diversity)
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Open AccessArticle
A Technical-Economic Comparison between Conventional Tillage and Conservative Techniques in Paddy-Rice Production Practice in Northern Italy
Agronomy 2019, 9(12), 886; https://doi.org/10.3390/agronomy9120886 - 13 Dec 2019
Viewed by 283
Abstract
In this study a technical-economic comparison was conducted to compare three different agronomic practices applied to paddy rice cultivation areas in Italy: one based on conventional tillage (CT), and two adopting conservative agriculture approaches, namely minimum tillage (MT) and no-tillage (NT). Data about [...] Read more.
In this study a technical-economic comparison was conducted to compare three different agronomic practices applied to paddy rice cultivation areas in Italy: one based on conventional tillage (CT), and two adopting conservative agriculture approaches, namely minimum tillage (MT) and no-tillage (NT). Data about production inputs (seed, fertilizers, agrochemicals, fuel) and working time were measured for each technique during the whole production season in three experimental fields. The total production costs were computed by adding the mechanization costs, calculated through the ASABE (American Society of Agricultural and Biological Engineers) EP (Engineering Practice) 496.3 methodology, and the production input costs. The results of the study highlighted a significant reduction of total costs obtained with both minimum (−16%) and no-tillage (−19%) compared to conventional tillage. Full article
(This article belongs to the Special Issue Smart Management of Conservative, Organic and Integrated Agriculture)
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Open AccessArticle
In-Field Estimation of Orange Number and Size by 3D Laser Scanning
Agronomy 2019, 9(12), 885; https://doi.org/10.3390/agronomy9120885 - 13 Dec 2019
Viewed by 361
Abstract
The estimation of fruit load of an orchard prior to harvest is useful for planning harvest logistics and trading decisions. The manual fruit counting and the determination of the harvesting capacity of the field results are expensive and time-consuming. The automatic counting of [...] Read more.
The estimation of fruit load of an orchard prior to harvest is useful for planning harvest logistics and trading decisions. The manual fruit counting and the determination of the harvesting capacity of the field results are expensive and time-consuming. The automatic counting of fruits and their geometry characterization with 3D LiDAR models can be an interesting alternative. Field research has been conducted in the province of Cordoba (Southern Spain) on 24 ‘Salustiana’ variety orange trees—Citrus sinensis (L.) Osbeck—(12 were pruned and 12 unpruned). Harvest size and the number of each fruit were registered. Likewise, the unitary weight of the fruits and their diameter were determined (N = 160). The orange trees were also modelled with 3D LiDAR with colour capture for their subsequent segmentation and fruit detection by using a K-means algorithm. In the case of pruned trees, a significant regression was obtained between the real and modelled fruit number (R2 = 0.63, p = 0.01). The opposite case occurred in the unpruned ones (p = 0.18) due to a leaf occlusion problem. The mean diameters proportioned by the algorithm (72.15 ± 22.62 mm) did not present significant differences (p = 0.35) with the ones measured on fruits (72.68 ± 5.728 mm). Even though the use of 3D LiDAR scans is time-consuming, the harvest size estimation obtained in this research is very accurate. Full article
(This article belongs to the Special Issue In-Field Estimation of Fruit Quality and Quantity)
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Open AccessArticle
Moderation of Inulin and Polyphenolics Contents in Three Cultivars of Helianthus tuberosus L. by Potassium Fertilization
Agronomy 2019, 9(12), 884; https://doi.org/10.3390/agronomy9120884 - 13 Dec 2019
Viewed by 285
Abstract
Jerusalem artichoke, a widely consumed edible, is an excellent source of inulin and selected phytochemicals. However, the improvement of its chemical composition by potassium fertilization has not yet been studied. Thus, the aim of the study was to evaluate the effect of different [...] Read more.
Jerusalem artichoke, a widely consumed edible, is an excellent source of inulin and selected phytochemicals. However, the improvement of its chemical composition by potassium fertilization has not yet been studied. Thus, the aim of the study was to evaluate the effect of different potassium (K) fertilization levels (K2O 150 kg ha−1, 250 kg ha−1, 350 kg ha−1) on the content of inulin; profile and changes in polyphenolic compounds; and the antioxidant capacity, including on-line ABTS antioxidant profiles of freeze-dried tubers originated from Violette de Rennes, Topstar, and Waldspindel cultivars. Inulin content was highest in the early maturing cv. Topstar. The application of 350 kg ha−1 of K fertilizer rates during the growth of cv. Topstar increased the inulin content of tubers by 13.2% relative to the lowest K fertilizer rate of 150 kg ha−1. In cv. Violette de Rennes, inulin accumulation increased in response to the fertilizer rate of 250 kg ha−1. A further increase in K fertilizer rates had no effect on inulin content. The inulin content of cv. Waldspindel was not modified by any of the tested K fertilizer rates. Thus, the accumulation of the inulin was cultivar-dependent. In the cultivars analyzed, 11 polyphenolic compounds were identified and polyphenolic compound content was affected by the applied rate of potassium fertilizer, which was dependent on the cultivar. Chlorogenic acid was the predominant phenolic acid in all cultivars, and it accounted for around 66.4% of the identified polyphenolic compounds in cv. Violette de Rennes and for around 77% of polyphenolic compounds in cv. Waldspindel and Topstar. Full article
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Open AccessArticle
Soybean in No-Till Cover-Crop Systems
Agronomy 2019, 9(12), 883; https://doi.org/10.3390/agronomy9120883 - 13 Dec 2019
Viewed by 409
Abstract
Introducing agro-ecological techniques such as no-tillage systems with cover crops in rotations with soybean (Glycine max (L.) Merr.) could provide more resilience to changing climatic conditions and, at the same time, reduce soil erosion, nitrate leaching, and weed density in the main [...] Read more.
Introducing agro-ecological techniques such as no-tillage systems with cover crops in rotations with soybean (Glycine max (L.) Merr.) could provide more resilience to changing climatic conditions and, at the same time, reduce soil erosion, nitrate leaching, and weed density in the main crop. However, there are challenges in introducing no-tillage techniques in crop systems in Europe as there is little quantitative knowledge about the agro-economic impact. The objectives of this study were to evaluate the agronomic and economic impacts of three soybean cropping systems involving a rye (Secale cereal L.) cover crop prior to soybean, i.e., two no-tillage systems; either herbicide-free with crimping the rye or herbicide-based without rye crimping and one plough-based in which rye was cut as green silage. The impacts of these cropping strategies were compared in a three-year cropping system experiment at a research station in north-eastern Germany with and without irrigation. The following parameters were measured: (1) cover crop biomass; (2) weed biomass; (3) soybean plant density; (4) soybean grain yield; and (5) gross margin of the cropping system. The results showed that all three soybean cropping systems can effectively suppress weeds. System (C), the no-tillage herbicide-based system, produced the lowest rye biomass and highest soybean yield; system (B), the no-tillage herbicide-free/crimped rye system, produced the highest rye biomass and lowest soybean yield compared to system (A), the standard cutting/plough-based system. The differences in rye biomass and soybean yield observed between the three systems could be mainly attributed to the timing of the cover crop termination and the soybean sowing date. The gross margin was highest in system (C), due to the high soybean grain yield. The low soybean grain yield in system (B) resulted in lower revenues and gross margins compared to systems (A) and (C), although system (B) could be economically attractive in organic farming with higher prices for organic soybean. In the particularly dry year 2016, gross margins were higher when soybean was irrigated compared to the rainfed cultivation, due to significantly higher grain yields. Before recommending the application of the no-tillage with cover crop technique for the conditions tested in north-eastern Germany, more investigations on the benefits and risks of this technique are needed. Further research needs to focus on maintaining a high rye biomass as well as on ensuring an early soybean planting date. Optimizing the crimping and drilling equipment is still required in order to develop good management practices for no-tillage herbicide-free systems in European conditions. Full article
(This article belongs to the Special Issue Sustainable Cropping Systems)
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Open AccessArticle
Experimental Evaluation of a New Giant Reed (Arundo Donax L.) Composite Using Citric Acid as a Natural Binder
Agronomy 2019, 9(12), 882; https://doi.org/10.3390/agronomy9120882 - 12 Dec 2019
Viewed by 273
Abstract
The raw materials used to manufacture thermal insulation in buildings consume a large amount of energy and are not generally biodegradable, which means it is necessary to increase the use of renewable, eco-friendly resources such as plant fibers in order to reduce the [...] Read more.
The raw materials used to manufacture thermal insulation in buildings consume a large amount of energy and are not generally biodegradable, which means it is necessary to increase the use of renewable, eco-friendly resources such as plant fibers in order to reduce the environmental problems this generates. The wood adhesives developed by the petrochemical industry offer excellent performance and are affordable. However, their use has an expiry date and in the future they will be rejected due to the environmental and health problems they can cause. The objective of this work was to develop a new eco-friendly biocomposite that could be used for thermal insulation in buildings. Boards were manufactured from giant reed particles with a particle size of 2 to 4 mm, using 5 and 10% by weight of citric acid as a natural binder. Experiments were then carried out to investigate the effect of board density on mechanical, physical, and thermal properties. A new type of composite was obtained with a thermal conductivity of 0.081–0.093 W/m K, which makes it suitable as an insulating material. The boards with a density of 850 kg/m3 had a modulus of rupture (MOR) of 12.5 N/mm2, a modulus of elasticity (MOE) of 2440 N/mm2, and an internal bonding strength (IB) of 0.61 N/mm2, and they could be used as insulation panels for divisions and enclosures in buildings. Full article
(This article belongs to the Special Issue Selected Papers from 10th Iberian Agroengineering Congress)
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Open AccessReview
DNA-Based Assessment of Genetic Diversity in Grassland Plant Species: Challenges, Approaches, and Applications
Agronomy 2019, 9(12), 881; https://doi.org/10.3390/agronomy9120881 - 12 Dec 2019
Viewed by 494
Abstract
Grasslands are wide-spread, multi-species ecosystems that provide many valuable services. Plant genetic diversity (i.e., the diversity within species) is closely linked to ecosystem functioning in grasslands and constitutes an important reservoir of genetic resources that can be used to breed improved cultivars of [...] Read more.
Grasslands are wide-spread, multi-species ecosystems that provide many valuable services. Plant genetic diversity (i.e., the diversity within species) is closely linked to ecosystem functioning in grasslands and constitutes an important reservoir of genetic resources that can be used to breed improved cultivars of forage grass and legume species. Assessing genetic diversity in grassland plant species is demanding due to the large number of different species and the level of resolution needed. However, recent methodological advances could help in tackling this challenge at a larger scale. In this review, we outline the methods that can be used to measure genetic diversity in plants, highlighting their strengths and limitations for genetic diversity assessments of grassland plant species, with a special focus on forage plants. Such methods can be categorized into DNA fragment, hybridization array, and high-throughput sequencing (HTS) methods, and they differ in terms of resolution, throughput, and multiplexing potential. Special attention is given to HTS approaches (i.e., plastid genome skimming, whole genome re-sequencing, reduced representation libraries, sequence capture, and amplicon sequencing), because they enable unprecedented large-scale assessments of genetic diversity in non-model organisms with complex genomes, such as forage grasses and legumes. As no single method may be suited for all kinds of purposes, we also provide practical perspectives for genetic diversity analyses in forage breeding and genetic resource conservation efforts. Full article
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Open AccessArticle
Conventional Industrial Robotics Applied to the Process of Tomato Grafting Using the Splicing Technique
Agronomy 2019, 9(12), 880; https://doi.org/10.3390/agronomy9120880 - 12 Dec 2019
Viewed by 561
Abstract
Horticultural grafting is routinely performed manually, demanding a high degree of concentration and requiring operators to withstand extreme humidity and temperature conditions. This article presents the results derived from adapting the splicing technique for tomato grafting, characterized by the coordinated work of two [...] Read more.
Horticultural grafting is routinely performed manually, demanding a high degree of concentration and requiring operators to withstand extreme humidity and temperature conditions. This article presents the results derived from adapting the splicing technique for tomato grafting, characterized by the coordinated work of two conventional anthropomorphic industrial robots with the support of low-cost passive auxiliary units for the transportation, handling, and conditioning of the seedlings. This work provides a new approach to improve the efficiency of tomato grafting. Six test rates were analyzed, which allowed the system to be evaluated across 900 grafted units, with gradual increases in the speed of robots work, operating from 80 grafts/hour to over 300 grafts/hour. The results obtained show that a higher number of grafts per hour than the number manually performed by skilled workers could be reached easily, with success rates of approximately 90% for working speeds around 210–240 grafts/hour. Full article
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Open AccessArticle
Influence of Different Photoperiod and Temperature Regimes on Growth and Bulb Quality of Garlic (Allium sativum L.) Cultivars
Agronomy 2019, 9(12), 879; https://doi.org/10.3390/agronomy9120879 - 11 Dec 2019
Viewed by 349
Abstract
Growth and bulb development in garlic is affected considerably by variations in photoperiod and temperature thereby influencing its morphology, physiology, and nutritive quality. Varied combinations of photoperiods and temperatures may influence the bulb development and quality, and can determine the suitability of a [...] Read more.
Growth and bulb development in garlic is affected considerably by variations in photoperiod and temperature thereby influencing its morphology, physiology, and nutritive quality. Varied combinations of photoperiods and temperatures may influence the bulb development and quality, and can determine the suitability of a cultivar for a particular region. Experiments were conducted to study the impact of different photoperiod and temperature combinations on the growth, morpho-physiology, and nutritive quality of garlic bulb. Three garlic cultivars viz; G103, G024, and G2011-5 were exposed to different combinations of photoperiod (8 h/16 h, 10 h/14 h, 12 h/12 h, 14 h/10 h, 16 h/8 h (light/dark)) and temperature (20 °C/15 °C, 25 °C/18 °C, and 30 °C/20 °C). Results revealed that longer photoperiod (14 h or 16 h) and higher temperature (25 °C or 30 °C) treatments significantly improved the garlic bulbing imparting maximum bulb diameter, height, bulbing index, and the shortest growth period. Whereas, 12-h photoperiod had maximum bulb weight. In addition, total soluble solid (TSS), content of soluble protein, soluble sugar, total sugar, glucose, sucrose, fructose, starch, total phenols, and total flavonoids increased significantly because of 14-h photoperiod and 30 °C temperature condition, however exhibited decline with 8 h photoperiod and lowest temperature (20 °C). These alterations were related to bulb characteristics and bulbing index. Maximum plant standing height and pseudostem diameter of the garlic plant were observed at 20 °C. Additionally, plants under the combination of 14 h–30 °C had maximum fresh weight, bulb diameter, shortest growth period, maximum physiological and nutritive quality traits of the bulb, while as 12 h–30 °C combinations resulted in maximum bulb weight and 16 h–30 °C had maximum bulb height. Among cultivars cv. G103 showed best response to tested photoperiod and temperature combinations in terms of morpho-physiological and biochemical attributes studied, except for bulbing index which was maximum in cv. G024. Present study concludes the influence of photoperiod and temperature combinations on garlic growth and bulbing characteristics through the modulations induced in soluble protein, sugars, and phenolic compounds. Full article
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Open AccessArticle
Effect of Long-Term Cropping Systems on the Diversity of the Soil Bacterial Communities
Agronomy 2019, 9(12), 878; https://doi.org/10.3390/agronomy9120878 - 11 Dec 2019
Viewed by 340
Abstract
Soil microbial communities are involved in the maintenance of productivity and health of agricultural systems; therefore an adequate understanding of soil biodiversity plays a key role in ensuring sustainable use of soil. In the present study, we evaluated the influence of different cropping [...] Read more.
Soil microbial communities are involved in the maintenance of productivity and health of agricultural systems; therefore an adequate understanding of soil biodiversity plays a key role in ensuring sustainable use of soil. In the present study, we evaluated the influence of different cropping systems on the biodiversity of the soil bacterial communities, based on a 54-year field experiment established in Martonvásár, Hungary. Terminal restriction fragment length polymorphism (T-RFLP) fingerprinting technique was used to assess soil bacterial diversity and community structure in maize monoculture and three different crop rotations (maize–alfalfa, maize–wheat and the maize–barley–peas–wheat Norfolk type). No differences in richness and diversity were detected between maize monoculture and crop rotations except for the most intense rotation system (Norfolk-type). Although the principal component analysis did not reveal a clear separation between maize monoculture and the other rotation systems, the pairwise tests of analysis of similarity (ANOSIM) revealed that there are significant differences in the composition of bacterial communities between the maize monoculture and maize–alfalfa rotation as well as between wheat–maize and Norfolk-type rotation. Full article
(This article belongs to the Section Innovative Cropping Systems)
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Open AccessArticle
Fire Risks Associated with Combine Harvesters: Analysis of Machinery Critical Points
Agronomy 2019, 9(12), 877; https://doi.org/10.3390/agronomy9120877 - 11 Dec 2019
Viewed by 335
Abstract
Combine harvesters are an important cause of fires worldwide. The purpose of this work has been to investigate the critical points associated with the risk of fire, identified through a survey distributed to combine owners in Aragon (Spain). Information was collected on the [...] Read more.
Combine harvesters are an important cause of fires worldwide. The purpose of this work has been to investigate the critical points associated with the risk of fire, identified through a survey distributed to combine owners in Aragon (Spain). Information was collected on the technical characteristics of the machines and, when appropriate, on the characteristics of the generated fires (crop, use of straw chopper, point in which the fire was originated, etc.). Based on the survey data, relationships between the characteristics of the machine and the ignition of a fire were analyzed, and the points of the harvester in which the fire originated were investigated. A statistically significant relationship of fire risk was only found with the number of hectares harvested, in such a way that the risk would be especially high for machines with more than 6000 accumulated ha. 32% of the fires were originated in the engine zone, compared with 31% in the cutting bar and 18% in the bearings and belts. The study was completed with on-site temperature measurements carried out on nine machines in 2018 and 2019, in which temperatures above 250 °C were recorded in the exhaust manifold and in the cutting bar. These temperatures exceeded the ignition thresholds obtained in the flammability studies conducted for wheat residues collected from the harvesters. Full article
(This article belongs to the Special Issue Selected Papers from 10th Iberian Agroengineering Congress)
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Open AccessArticle
Glyphosate as a Tool for the Incorporation of New Herbicide Options in Integrated Weed Management in Maize: A Weed Dynamics Evaluation
Agronomy 2019, 9(12), 876; https://doi.org/10.3390/agronomy9120876 - 11 Dec 2019
Viewed by 334
Abstract
A farm-scale investigation was conducted to evaluate the potential impact of integrating glyphosate into different weed management programs when cultivating herbicide-tolerant maize in central Spain from 2012 to 2014. The weed management programs were (1) a conventional weed management with pre- and post-emergent [...] Read more.
A farm-scale investigation was conducted to evaluate the potential impact of integrating glyphosate into different weed management programs when cultivating herbicide-tolerant maize in central Spain from 2012 to 2014. The weed management programs were (1) a conventional weed management with pre- and post-emergent herbicide applications, (2) a weed management program in which the number and total amount of conventional herbicides applied were reduced, and (3) three weed management programs that comprised either two post-emergent applications of the herbicide glyphosate, or only one glyphosate application combined with pre- and/or post-emergent herbicides. Weed density throughout each cropping season was greater in those weed management programs that did not include a pre-emergence application of herbicides than those that did. Moreover, none of the weed management programs affected the richness and species diversity of the weeds or reduced yields. Although the impact of the different programs was similar in terms of weed species diversity, the composition of the weed community differed and this effect must be considered when providing agroecosystem services. Our results indicate that glyphosate-tolerant maize provides an additional tool that allows integrated weed control of the weed populations without reducing yields. Full article
(This article belongs to the Special Issue Herbicide Resistance in Weed Management)
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Open AccessArticle
Effect of Light Intensity on Rooting and Growth of Hydroponic Strawberry Runner Plants in a LED Plant Factory
Agronomy 2019, 9(12), 875; https://doi.org/10.3390/agronomy9120875 - 11 Dec 2019
Viewed by 567
Abstract
To rapidly produce strawberry (Fragaria × ananassa Duch. cv. Benihoppe) transplants from cuttings, suitable light intensities for unrooted runner plants at the rooting stage and rooted runner plants at the seedling stage were determined in a plant factory under LED lighting. At [...] Read more.
To rapidly produce strawberry (Fragaria × ananassa Duch. cv. Benihoppe) transplants from cuttings, suitable light intensities for unrooted runner plants at the rooting stage and rooted runner plants at the seedling stage were determined in a plant factory under LED lighting. At the rooting stage, unrooted runner plants at the 3-leaf stage were hydroponically rooted for 6 days under light intensity of 30, 90, 150, and 210 μmol m−2 s−1, respectively. At the seedling stage, rooted runner plants were hydroponically grown for 18 days under light intensity of 90, 180, 270, and 360 μmol m−2 s−1, respectively. The tube LED lights consisting of white and red LED chips were used as sole light source, and photoperiod was controlled as 16 h d−1. The results showed that the maximum root number (7.7) and longest root length (14.8 cm) of the runner plants were found under 90 μmol m−2 s−1 at the rooting stage. Photosynthetic activity in runner plant leaves under 90 μmol m−2 s−1 were higher than that under 30, 150, and 210 μmol m−2 s−1. Higher light intensity at the range of 90–270 μmol m−2 s−1 increased the stomatal conductance of newly formed leaves of rooted runner plants, thus improving the net photosynthetic rate and growth of rooted runner plants at the seedling stage. The crown diameter, shoot and root dry weights, and root to shoot ratio of rooted runner plants increased by 9.7%, 38.8%, 106.1%, and 48.7%, respectively, when the light intensity increased from 90 to 270 μmol m−2 s−1. However, there was no further improvement of runner plant growth under 360 μmol m−2 s−1. Furthermore, no significant difference of increased dry biomass per mole of photons delivered was found between 180 and 270 μmol m−2 s−1. In consideration of transplant quality and economic balance, light intensity of 90 μmol m−2 s−1 at the rooting stage and 270 μmol m−2 s−1 at the seedling stage were suggested for rapidly producing hydroponic strawberry transplants based on unrooted runner plants in the LED plant factory. Full article
(This article belongs to the Special Issue Control of LED Lighting Based on Plant Physiological Principles)
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Open AccessArticle
Comparison of SHD and Open-Center Training Systems in Almond Tree Orchards cv. ‘Soleta’
Agronomy 2019, 9(12), 874; https://doi.org/10.3390/agronomy9120874 - 11 Dec 2019
Viewed by 387
Abstract
The increase in the demand for almonds, the development of novel self-fertile and late-flowering varieties, and the establishment of plantations in new irrigated areas have led to significant progress in the productive techniques of almond tree cultivation. One of the most important has [...] Read more.
The increase in the demand for almonds, the development of novel self-fertile and late-flowering varieties, and the establishment of plantations in new irrigated areas have led to significant progress in the productive techniques of almond tree cultivation. One of the most important has been the increase in planting density, due to the development of dwarfing rootstocks. This paper presents a comparison between two training systems with ‘Soleta’ almond cultivar: a super high density (SHD) system using Rootpac-20 dwarfing rootstock versus an open-center training system using GF-677 rootstock. To this end, several parameters related to chlorophyll content (fluorescence and SPAD) and light interception (from photosynthetically active radiation (PAR) measurements) were monitored throughout two vegetative cycles, and other productive conditions (flowering, fruit set and production) were tracked at specific times of the cycle. The open-center system resulted in higher PAR interception than the SHD system, but also in the presence of poorly illuminated fractions of the canopy. Differences were observed between both systems in terms of average fruit weight and yield per canopy volume. Lower yields were obtained in SHD system than in open-center, which may be significantly increased by adapting the inter-row spacing. However, the degree of efficiency in the use of resources or productive inputs, such as irrigation, was favorable to the new SHD training system, so its potential to become a reference system in modern plantations (using over-the-row harvesters similar to those used for vine and olive trees) seems promising. Full article
(This article belongs to the Special Issue Selected Papers from 10th Iberian Agroengineering Congress)
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Open AccessArticle
An Integrated Yield Prediction Model for Greenhouse Tomato
Agronomy 2019, 9(12), 873; https://doi.org/10.3390/agronomy9120873 - 11 Dec 2019
Viewed by 474
Abstract
The commonly used greenhouse crop yield prediction models today have their specific application scenarios, which may not ensure the accuracy of the results if the greenhouse environment changes. This greatly restricts their use in the greenhouse environment. To solve this problem, two widely [...] Read more.
The commonly used greenhouse crop yield prediction models today have their specific application scenarios, which may not ensure the accuracy of the results if the greenhouse environment changes. This greatly restricts their use in the greenhouse environment. To solve this problem, two widely used tomato growth models were compared in the study: TOMGRO and Vanthoor, and then an integrated model was obtained. Through the extended Fourier amplitude sensitivity test (EFAST), the model parameters were divided into three categories: optimized, fixed and ignored. In addition, Bayesian optimization was used as an optimization algorithm, through which the parameters applicable to the greenhouse can be optimized based on the greenhouse data. Compared with TOMGRO and Vanthoor, the output of the integrated model was more reasonable and universal, and the RMSE in the integrated model was 2.5974 while that in TOMGRO and Vanthoor both were over 17, reflecting the fact that the model output was closer to the actual value. According to the verification results of four-year greenhouse data, the model had high performance in predicting yield. Full article
(This article belongs to the Special Issue Greenhouse Technology)
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Open AccessArticle
The CYP74 Gene Family in Watermelon: Genome-Wide Identification and Expression Profiling Under Hormonal Stress and Root-Knot Nematode Infection
Agronomy 2019, 9(12), 872; https://doi.org/10.3390/agronomy9120872 - 11 Dec 2019
Viewed by 283
Abstract
Allene oxide synthase (AOS) and hydroperoxide lyase (HPL), members of the CYP74 gene family, are branches of the oxylipin pathway and play vital roles in plant responses to a number of stresses. In this study, four HPL genes and one AOS gene were [...] Read more.
Allene oxide synthase (AOS) and hydroperoxide lyase (HPL), members of the CYP74 gene family, are branches of the oxylipin pathway and play vital roles in plant responses to a number of stresses. In this study, four HPL genes and one AOS gene were identified in the watermelon genome, which were clustered into three subfamilies (CYP74A, CYP74B and CYP74C). Sequence analysis revealed that most HPL and AOS proteins from various plants contain representative domains, including Helix-I region, Helix-K region (ExxR) and Heme-binding domain. A number of development-, stress-, and hormone-related cis-elements were found in the promoter regions of the ClAOS and ClHPL genes, and the detected ClAOS and ClHPL genes were differentially expressed in different tissues and fruit development stages, as well as in response to various hormones. In addition, red light could enhance the expression of ClAOS in root-knot nematode-infected leaves and roots of watermelon, implying that ClAOS might play a primary role in red light-induced resistance against root-knot nematodes. These findings lay a foundation for understanding the specific function of CYP74 genes in watermelon. Full article
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Open AccessArticle
Hydrangea DNA Methylation Caused by pH Substrate Changes to Modify Sepal Colour is Detected by MSAP and ISSR Markers
Agronomy 2019, 9(12), 871; https://doi.org/10.3390/agronomy9120871 - 11 Dec 2019
Viewed by 281
Abstract
The hydrangea (Hydrangea macrophylla (Thunb). Ser.) is an ornamental species with great market potential. It is known for its ability to change the colour of its inflorescence, according to the pH of the culture substrate. The molecular mechanisms that underlie these changes [...] Read more.
The hydrangea (Hydrangea macrophylla (Thunb). Ser.) is an ornamental species with great market potential. It is known for its ability to change the colour of its inflorescence, according to the pH of the culture substrate. The molecular mechanisms that underlie these changes are still unclear. It is known that epigenetic mechanisms, such as DNA methylation, play an important role in genetic expression, so they could be responsible for this phenomenon in hydrangea. In the present study, the molecular markers ISSR (Inter Simple Sequence Repeat) and MSAP (Methyl-Sensitive Amplification Polymorphism) were used to detect molecular changes in the genome of hydrangea plants that were cultivated under different pH levels to modify the colour of the sepals. The results showed a correspondence between the methylation signal measured with MSAP and amplification ISSR patterns when compared before and after the modification of pH culture substrates. These results suggest that DNA methylation might be involved as a molecular mechanism underlying the colour change of hydrangea sepals in response to a differential pH in the substrate. In addition, the results pave the way to study the relationship between DNA methylation and ISSR marker profiles. Full article
(This article belongs to the Section Horticultural and Floricultural Crops)
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Open AccessArticle
Optimal LED Wavelength Composition for the Production of High-Quality Watermelon and Interspecific Squash Seedlings Used for Grafting
Agronomy 2019, 9(12), 870; https://doi.org/10.3390/agronomy9120870 - 10 Dec 2019
Viewed by 435
Abstract
Watermelon is cultivated worldwide and is mainly grafted onto interspecific squash rootstocks. Light-emitting diodes (LEDs) can be implemented as light sources during indoor production of both species and their spectral quality is of great importance. The objective of the present study was to [...] Read more.
Watermelon is cultivated worldwide and is mainly grafted onto interspecific squash rootstocks. Light-emitting diodes (LEDs) can be implemented as light sources during indoor production of both species and their spectral quality is of great importance. The objective of the present study was to determine the optimal emission of LEDs with wide wavelength for the production of watermelon and interspecific squash seedlings in a growth chamber. Conditions were set at 22/20 °C temperature (day/night), 16 h photoperiod, and 85 ± 5 μmol m−2 s−1 photosynthetic photon flux density. Illumination was provided by fluorescent (FL, T0) lamps or four LEDs (T1, T2, T3, and T4) emitting varying wide spectra. Watermelon seedlings had greater shoot length, stem diameter, cotyledon area, shoot dry weight-to-length (DW/L) ratio, and Dickson’s quality index (DQI) under T1 and T3, while leaf area and shoot dry weight (DW) had higher values under T1. Interspecific squash seedlings had greater stem diameter, and shoot and root DW under T1 and T3, while leaf and cotyledon areas were favored under T1. In both species, T0 showed inferior development. It could be concluded that a light source with high red emission, relatively low blue emission, and a red:far-red ratio of about 3 units seems ideal for the production of high-quality watermelon (scion) and interspecific squash (rootstock) seedlings. Full article
(This article belongs to the Special Issue Control of LED Lighting Based on Plant Physiological Principles)
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Open AccessArticle
An Assessment of the Spatial and Temporal Distribution of Soil Salinity in Combination with Field and Satellite Data: A Case Study in Sujawal District
Agronomy 2019, 9(12), 869; https://doi.org/10.3390/agronomy9120869 - 10 Dec 2019
Viewed by 325
Abstract
Soil salinization is a serious environmental issue that significantly influences crop yield and soil fertility, especially in coastal areas. Numerous studies have been conducted on the salinity status in Pakistan. Information about the geospatial and temporal distribution of salinity in the Sujawal district [...] Read more.
Soil salinization is a serious environmental issue that significantly influences crop yield and soil fertility, especially in coastal areas. Numerous studies have been conducted on the salinity status in Pakistan. Information about the geospatial and temporal distribution of salinity in the Sujawal district is still lacking. The present study examines the soil salinity status and the impact of seawater intrusion in the entire district from 1990 to 2017 using field and remote sensing (RS) data. In addition, 210 soil samples at different depths (0–20, 20–40, and 40–60 cm) were collected from randomly selected locations for lab measurements of physiochemical properties. The results showed that the soil texture classes were mainly fine to medium particles. The samples collected at the 0–20 cm depth were mostly dominated by three textural classes of soil: clay at 19.5%, clay loam at 25.6%, and loam at 32.9%. The electrical conductivity (EC) of 65.7% soil samples collected from the top layer exceeded the normal range. The quantitative results indicated that the exchangeable sodium percentage (ESP) ranged between 1.38 and 64.58, and 72.2% of the top layer soil samples had ESP >15, while 81.5% of soil samples were in the normal range of soil pH. Furthermore, the results indicated that the vegetation decreased by 8.6% from 1990 to 2017, while barren land and water bodies increased significantly, by approximately 4.4% and 4.2%, respectively. The extreme and high salinity classes were characterized by high contents of soluble salt on the surface in the Jati and Shah Bandar subdistricts. In addition, the soil EC values at the 0–20 cm depth were significantly correlated with the salinity index (S1). Therefore, it was concluded that more than 50% of the top layer of soil was affected by salinity due to seawater intrusion, low rainfall, climate change, and erratic river flow. It is suggested that remote sensing (RS) data are more suitable for the detection of the soil salinity status of a region and impose a lower cost compared to other conventional approaches. However, this study could provide significant knowledge to land managers, policymakers, and government officials to allow them to take action to implement salinity control measures in the study area. Full article
(This article belongs to the Special Issue Remote Sensing of Agricultural Monitoring)
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Open AccessArticle
Effects of Postponing Topdressing-N on the Yield of Different Types of japonica Rice and Its Relationship with Soil Fertility
Agronomy 2019, 9(12), 868; https://doi.org/10.3390/agronomy9120868 - 10 Dec 2019
Viewed by 263
Abstract
N fertilizer is usually supplied via multiple applications in rice production in China. Due to the high N-recovery efficiency (NRE) of panicle fertilizer, applying large amounts of fertilizer at the booting stage is considered to be an effective measure of increasing yields, although [...] Read more.
N fertilizer is usually supplied via multiple applications in rice production in China. Due to the high N-recovery efficiency (NRE) of panicle fertilizer, applying large amounts of fertilizer at the booting stage is considered to be an effective measure of increasing yields, although it has adverse effects on eating quality. In this study, using six inbred and four hybrid japonica varieties, we postponed topdressing-N to increase the ratio of panicle N from 20% to 40% by correspondingly reducing the N amount applied only at the tillering stage. We also analyzed the effects of postponing the topdressing-N on grain yield and dry matter accumulation in both high- and low-fertility blue clayey paddy fields in 2016 and 2017. The effects of postponing topdressing-N applications on japonica rice were related to variety, meteorological conditions, and soil fertility. With respect to the inbred varieties, regardless of whether panicle N was applied as a single or split application, increasing the ratio of panicle N had no effect on the yield components or dry matter accumulation of plants grown in either high- and low-fertility soils. Regarding the hybrid varieties grown in the high-fertility soil, although postponing the topdressing-N application had no effect on yield under good weather conditions (no low-temperature stress during grain-filling), a single application of 40% of the total N at the panicle initiation stage significantly decreased both the dry matter accumulation after heading and the seed-setting rate of varieties that presented long growth periods under low-temperature conditions. With respect to hybrid varieties grown in low-fertility soil, postponing the application of topdressing-N had an adverse effect on the number of effective panicles. Our results suggested that the proportion of panicle N applied to japonica rice should not exceed 30% in clayey paddy fields and that fertilizer management with respect to rice production should be adjusted according to soil type, soil fertility, and variety. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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Open AccessArticle
Genotype-Environment Interaction: Trade-Offs between the Agronomic Performance and Stability of Dual-Purpose Sorghum (Sorghum bicolor L. Moench) Genotypes in Senegal
Agronomy 2019, 9(12), 867; https://doi.org/10.3390/agronomy9120867 - 10 Dec 2019
Viewed by 304
Abstract
Introducing sorghum (Sorghum bicolor L. Moench) genotypes into new environments is necessary for expanding the production of food and fuel, but these efforts are complicated by significant genotype × environment interactions that can reduce their effectiveness. This study set out to thoroughly [...] Read more.
Introducing sorghum (Sorghum bicolor L. Moench) genotypes into new environments is necessary for expanding the production of food and fuel, but these efforts are complicated by significant genotype × environment interactions that can reduce their effectiveness. This study set out to thoroughly analyze genotype × environment interactions and assess trade-offs between the agronomic performance and the stability of grain and biomass yields of ten contrasting genotypes under Sudano-Sahelian conditions. Experiments were carried out in a randomized complete block design with four replicates. They were conducted from 2013 to 2016 in Bambey, Sinthiou Malem and Nioro du Rip in Senegal. The joint analysis of variance revealed a highly significant effect (p < 0.0001) of genotypes (G), environments (E) and G × E interaction. Most genotypes showed specific adaptations. The best grain yields were obtained by the Nieleni and Fadda hybrids, while the improved varieties IS15401 and SK5912 were best for biomass production. An Additive Main effect and Multiplicative Interaction (AMMI) analysis showed that good grain yields were associated with environments having good soil fertility and good rainfall, while biomass yields were more influenced by the sowing date and rainfall. Similarly, we were able to confirm for our 10 sorghum genotypes that yield stability was generally associated with low performance, except for the Nieleni and Fadda hybrids, which performed well for grain and biomass production regardless of the environment. The Senegalese control genotype, 621B, showed particular susceptibility to growing conditions (soil), but remained very productive (more than 3 tons per hectare) under good agro-pedological conditions. These results lead us to recommend the Fadda and Nieleni hybrids for the entire study region, while 621B can also be recommended, but only for highly specific environments with good soils. Full article
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Open AccessArticle
Adjusting Ceptometer Data to Improve Leaf Area Index Measurements
Agronomy 2019, 9(12), 866; https://doi.org/10.3390/agronomy9120866 - 10 Dec 2019
Viewed by 319
Abstract
Leaf Area Index (LAI) is an important plant parameter for both farmers and plant scientists to monitor and/or model the growth and the well-being of plants. Since direct LAI measurement techniques are relatively laborious and time-consuming, various indirect methods have been developed and [...] Read more.
Leaf Area Index (LAI) is an important plant parameter for both farmers and plant scientists to monitor and/or model the growth and the well-being of plants. Since direct LAI measurement techniques are relatively laborious and time-consuming, various indirect methods have been developed and widely used since the early 1990s. The LP-80 ceptometer uses a linear array of PAR (photosynthetically active radiation) sensors for non-destructive LAI measurements that is backed by 15 years of research. Despite this, considerable discrepancy can be found between the expert opinions regarding the optimal illumination conditions recommended for the measurement. The sensitivity of ceptometer-based LAI values to PAR was investigated, and a simple method was devised to correct raw ceptometer data collected under non-ideal light conditions. Inadequate light conditions (PAR < 1700 µmol m−2 s−1) could cause an underestimation of LAI. Using the corrected LAI values, the ceptometer data showed a significantly better fit (higher R2, smaller mean average error and closer to zero mean signed error values) to the destructive LAI data for both wheat and maize. With the help of the correction equations, the use of the LP-80 ceptometer could be extended to days when light conditions are not ideal. Full article
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Open AccessArticle
Incorporation of Manure into Ridge and Furrow Planting System Boosts Yields of Maize by Optimizing Soil Moisture and Improving Photosynthesis
Agronomy 2019, 9(12), 865; https://doi.org/10.3390/agronomy9120865 - 10 Dec 2019
Viewed by 281
Abstract
A sustainable management strategy of soil fertility and cropping system is critical to guaranteeing food security. However, little is known about the effects of soil amendment strategies on crop growth via regulating soil moisture and photosynthesis in a ridge and furrow cropping system. [...] Read more.
A sustainable management strategy of soil fertility and cropping system is critical to guaranteeing food security. However, little is known about the effects of soil amendment strategies on crop growth via regulating soil moisture and photosynthesis in a ridge and furrow cropping system. Here, field experiments were carried out in 2017 and 2018 in semi-arid areas of Loess Plateau, northwest China to investigate the effects of integrated use of ridge and furrow planting and manure amendment on grain yields of maize. Four treatments were designed: CK (flat planting with 100% chemical fertilizer), RFC (ridge and furrow planting with 100% chemical fertilizer), RFR (ridge and furrow planting with 100% control-released fertilizer), and RFM (ridge and furrow planting with 50% manure fertilizer + 50% N fertilizer). On average, RFM increased photosynthetic rates (Pn) by 74%, followed by RFR by 47%, and RFC by 26%, compared to CK. Also, stomatal conductance (Cd), transpiration rates (Tr), and intercellular CO2 concentration (Ci) were highest with RFM, followed by RFR and RFC. Averaged across the two years, RFM conserved 10% more soil water storage (SWS) than CK did at harvest, followed by RFR with an increment by 8%. However, RFC consumed more soil water than CK did, with its ETc 8% higher than CK. Consequently, spring maize treated with RFM suffered less drought stress, especially in 2017 when precipitation was insufficient. On average, grain yields and water use efficiency of RFM were increased by 18% and 27%, compared to CK. Structural equation modeling analysis showed that there existed significant positive correlation between SWS in top layers and grain yields, while SWS in deep layers had negative effects on grain yields. In conclusion, the incorporation of manure into ridge and furrow planting system can be an efficient agronomic practice to improve plant photosynthesis, optimize soil moisture, and boost grain yields in semi-arid areas of Loess Plateau, northwest China. Full article
(This article belongs to the Section Innovative Cropping Systems)
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