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Agronomy, Volume 9, Issue 5 (May 2019) – 56 articles

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Cover Story (view full-size image) Plant factories are advanced indoor cultivation systems that can produce plants inside cities with [...] Read more.
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Open AccessCorrection
Correction: Responses of Canopy Growth and Yield of Potato Cultivars to Weather Dynamics in a Complex Topography: Belg Farming Seasons in the Gamo Highlands, Ethiopia: Agronomy 2019, 9, 163
Agronomy 2019, 9(5), 267; https://doi.org/10.3390/agronomy9050267 - 27 May 2019
Viewed by 766
Abstract
In Minda et al. [1], an error was introduced. We propose the following amendment: Figure 9, in
Section 3.2.4 (Days to Maturity and Yield), should be replaced by the following updated figure [...] Full article
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Open AccessArticle
Exogenous Application of Amino Acids Improves the Growth and Yield of Lettuce by Enhancing Photosynthetic Assimilation and Nutrient Availability
Agronomy 2019, 9(5), 266; https://doi.org/10.3390/agronomy9050266 - 26 May 2019
Viewed by 1231
Abstract
As natural plant growth stimulators, amino acids are widely used to improve the yield and quality of crops. Several studies have illustrated the effects of different amino acids on lettuce plant parts. However, the effects of applying single amino acids on root growth [...] Read more.
As natural plant growth stimulators, amino acids are widely used to improve the yield and quality of crops. Several studies have illustrated the effects of different amino acids on lettuce plant parts. However, the effects of applying single amino acids on root growth remain elusive. The objective of this study was to evaluate the effect of root application of L-methionine on the growth of lettuce. In this study, two successive experiments on butterhead lettuce were conducted under hydroponic conditions. Three amino acids, L-methionine (20 mg/L), L-glycine (210 mg/L), and L-tryptophan (220 mg/L), were applied separately. L-methionine significantly increased the growth performance by 23.60%, whereas growth using L-tryptophan and L-glycine decreased by 98.78% and 27.45%, respectively. Considering the results of the first experiment, a second experiment was established with different concentrations of L-methionine (2200 mg/L, 220 mg/L, 22 mg/L, 2.2 mg/L, 0.2 mg/L, and 0.02 mg/L). The plants were allowed to grow for four weeks. Leaf width, plant area, leaf area, chlorophyll contents, etc., were evaluated. The results show that plant growth significantly improved by applying L-methionine at the lowest concentrations of 0.2 mg/L and 0.02 mg/L, which can, therefore, improve hydroponic production of lettuce and, accordingly, human nutrition. Full article
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Open AccessArticle
Brassinosteroids Regulate Antioxidant System and Protect Chloroplast Ultrastructure of Autotoxicity-Stressed Cucumber (Cucumis sativus L.) Seedlings
Agronomy 2019, 9(5), 265; https://doi.org/10.3390/agronomy9050265 - 26 May 2019
Cited by 3 | Viewed by 1123
Abstract
Autotoxicity is a common problem being faced in protected vegetable cultivation system. Phytoremediation of plant autotoxicity is an emerging concept to minimize deterioration of soil environment and reduction of yield and quality of vegetable crops. Brassinosteroids (BRs) have been reported as a potential [...] Read more.
Autotoxicity is a common problem being faced in protected vegetable cultivation system. Phytoremediation of plant autotoxicity is an emerging concept to minimize deterioration of soil environment and reduction of yield and quality of vegetable crops. Brassinosteroids (BRs) have been reported as a potential phytohormone to assist phytoremediation. However, the effects of BRs-induced autotoxicity stress on plant growth, photosynthesis and antioxidant defense system are poorly understood. Hence, we focused on the changes in physiological characteristics and ultrastructure of cucumber leaves in response to the application of 24-epibrassinolide (EBR) under autotoxicity stress conditions. The results showed that leaf area, plant height, fresh weight and dry weight of cucumber were obviously decreased under autotoxicity stress conditions. EBR application obviously improved the phenotypic characteristics of cucumber seedlings. Chlorophyll content, net photosynthetic rate, stomatal conductance and transpiration rate of cucumber leaves were markedly reduced under autotoxicity stress conditions. Application of EBR improved the photosynthetic pigments (chlorophyll a by 15.80%, chlorophyll b by 18.70% and total chlorophyll content by 17.30%), net photosynthetic rate by 36.40% and stomatal opening of leaves under autotoxicity stress conditions. EBR application also maintained the integrity of chloroplast and thylakoid structures under autotoxicity stress conditions. The activity of catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) and antioxidative compounds ascorbate (AsA) and reduced glutathione (GSH) contents were markedly decreased, however, these were obviously increased after EBR application under autotoxicity stress. EBR application also increased the soluble sugar and protein, and proline concentration by 59.70%, 7.22% and 36.58%, respectively in the leaves of cucumber, decreased malondialdehyde by 24.13% and reactive oxygen species contents (H2O2 by 35.17%, O2 by 12.01% and OH by 16.59%), and reduced the relative permeability of the cell membrane by 14.31%. These findings suggest that EBR application enhanced the photosynthetic capacity of leaves, maintained the integrity of chloroplast and thylakoid structures, and effectively alleviated the damage of membrane caused by lipid peroxidation and root damage under autotoxicity stress conditions. The growth inhibition effect of autotoxicity stress on cucumber was reduced by EBR application. Full article
(This article belongs to the Special Issue Functional Metabolism in Crops/Agronomy)
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Open AccessArticle
Intersowing Cover Crops into Standing Soybean in the US Upper Midwest
Agronomy 2019, 9(5), 264; https://doi.org/10.3390/agronomy9050264 - 25 May 2019
Cited by 1 | Viewed by 767
Abstract
Nutrient losses and soil erosion after soybean (Glycine max (L.) Merr.) harvest are common in the US Upper Midwest. Cover crops need to provide adequate growth and cover to prevent soil degradation throughout the winter and early spring months. The objective of [...] Read more.
Nutrient losses and soil erosion after soybean (Glycine max (L.) Merr.) harvest are common in the US Upper Midwest. Cover crops need to provide adequate growth and cover to prevent soil degradation throughout the winter and early spring months. The objective of this study was to determine the establishment of intersown cover crops and their impacts on a soybean-wheat rotation. Four cover crops—winter camelina (Camelina sativa (L.) Crantz), winter pea (Pisum sativum ssp. arvense (L.) Poir), winter rye (Secale cereale L.), and radish (Raphanus sativus L.)—were directly sown at the R4 and R6 stages of soybean at two locations, Prosper and Fargo, ND in 2016–2017. Cover crops above ground biomass in the fall ranged from 0.4 to 3.0 Mg ha−1 and N accumulation ranged from 28.7 to 73.2 kg ha−1. Winter camelina and winter rye reduced subsequent spring wheat yield compared with the no cover crop treatment. Fall soil residual NO3-N levels were lowest where cover crops were sown compared with the check. Spring NO3-N levels were lowest in winter camelina and winter rye compared with all the other cover crops and the check. Results indicated intersowing cover crops have no impact on soybean yield, and show potential to mitigate soil nitrate losses in areas that grow soybean as a cash crop. Full article
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Open AccessArticle
Durum Wheat (Triticum durum Desf.): Origin, Cultivation and Potential Expansion in Sub-Saharan Africa
Agronomy 2019, 9(5), 263; https://doi.org/10.3390/agronomy9050263 - 24 May 2019
Cited by 8 | Viewed by 1741
Abstract
Durum wheat is an important food crop in the world and an endemic species of sub-Saharan Africa (SSA). In the highlands of Ethiopia and the oases of the Sahara this crop has been cultivated for thousands of years. Today, smallholder farmers still grow [...] Read more.
Durum wheat is an important food crop in the world and an endemic species of sub-Saharan Africa (SSA). In the highlands of Ethiopia and the oases of the Sahara this crop has been cultivated for thousands of years. Today, smallholder farmers still grow it on marginal lands to assure production for their own consumption. However, durum wheat is no longer just a staple crop for food security but has become a major cash crop. In fact, the pasta, burghul and couscous industry currently purchase durum grain at prices 10 to 20% higher than that of bread wheat. Africa as a whole imports over €4 billion per year of durum grain to provide the raw material for its food industry. Hence, African farmers could obtain a substantial share of this large market by turning their production to this crop. Here, the achievements of the durum breeding program of Ethiopia are revised to reveal a steep acceleration in variety release and adoption over the last decade. Furthermore, the variety release for Mauritania and Senegal is described to show how modern breeding methods could be used to deliver grain yields above 3 t ha−1 in seasons of just 92 days of length and in daytime temperatures always above 32 °C. This review describes the potential of releasing durum wheat varieties adapted to all growing conditions of SSA, from the oases of the Sahara to the highlands of Ethiopia. This indicates that the new breeding technologies offer great promise for expanding the area of durum wheat production in SSA but that this achievement remains primarily dependent on the market ability to purchase these grains at a higher price to stimulate farmer adoption. The critical importance of connecting all actors along the semolina value chain is presented in the example of Oromia, Ethiopia and that success story is then used to prompt a wider discussion on the potential of durum wheat as a crop for poverty reduction in Africa. Full article
(This article belongs to the Special Issue Durum Wheat Breeding and Genetics)
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Open AccessArticle
Urea Addition Promotes the Metabolism and Utilization of Nitrogen in Cucumber
Agronomy 2019, 9(5), 262; https://doi.org/10.3390/agronomy9050262 - 23 May 2019
Viewed by 839
Abstract
Nitrogen (N) forms include ammonium [NH4+-N], nitrate [NO3-N], and urea [CO(NH2)2]. Urea is the most common nitrogen fertilizer in agriculture due to its inexpensive price and high N content. Although the reciprocal influence [...] Read more.
Nitrogen (N) forms include ammonium [NH4+-N], nitrate [NO3-N], and urea [CO(NH2)2]. Urea is the most common nitrogen fertilizer in agriculture due to its inexpensive price and high N content. Although the reciprocal influence between NO3-N and NH4+-N is well known, CO(NH2)2 interactions with these inorganic N forms have been poorly studied. We studied the effects of different nitrogen forms with equal nitrogen on dry matter, yield, enzyme activity, and gene expression levels in cucumber. NO3-N treatment with equal CO(NH2)2 promoted nitrate reduction, urea utilization, and the GS/GOGAT cycle but reduced the nitrate content. UR-2, NR-2, NR-3, NiR, GOGAT-1-1, and GS-4 were upregulated in response to these changes. NH4+-N treatment with equal CO(NH2)2 promoted nitrogen metabolism and relieved the ammonia toxicity of pure NH4+-N treatment. UR-2, GOGAT-2-2, and GS-4 were upregulated, and GDH-3 was downregulated in response to these changes. Treatment with both NO3-N with added equal CO(NH2)2 and NH4+-N with added equal CO(NH2)2 enhanced the activities of GOGAT, GS, and UR and the amino acid pathway of urea metabolism; manifested higher glutamate, protein, chlorophyll, and nitrogen contents; and improved dry matter weight. A greater proportion of dry matter was distributed to the fruit, generating significantly higher yields. Therefore, the addition of urea to ammonium or nitrate promoted N metabolism and N utilization in cucumber plants, especially treatments with 50% NO3-N + 50% CO(NH2)2, as the recommended nitrogen form in this study. Full article
(This article belongs to the collection Nutrition Management of Hydroponic Vegetable Crops)
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Open AccessArticle
Wx Gene in Hordeum chilense: Chromosomal Location and Characterisation of the Allelic Variation in the Two Main Ecotypes of the Species
Agronomy 2019, 9(5), 261; https://doi.org/10.3390/agronomy9050261 - 22 May 2019
Viewed by 686
Abstract
Starch, as the main grain component, has great importance in wheat quality, with the ratio between the two formed polymers, amylose and amylopectin, determining the starch properties. Granule-bound starch synthase I (GBSSI), or waxy protein, encoded by the Wx gene is the sole [...] Read more.
Starch, as the main grain component, has great importance in wheat quality, with the ratio between the two formed polymers, amylose and amylopectin, determining the starch properties. Granule-bound starch synthase I (GBSSI), or waxy protein, encoded by the Wx gene is the sole enzyme responsible for amylose synthesis. The current study evaluated the variability in Wx genes in two representative lines of Hordeum chilense Roem. et Schult., a wild barley species that was used in the development of tritordeum (×Tritordeum Ascherson et Graebner). Two novel alleles, Wx-Hch1a and Wx-Hch1b, were detected in this material. Molecular characterizations of these alleles revealed that the gene is more similar to the Wx gene of barley than that of wheat, which was confirmed by phylogenetic studies. However, the enzymatic function should be similar in all species, and, consequently, the variation present in H. chilense could be utilized in wheat breeding by using tritordeum as a bridge species. Full article
(This article belongs to the Special Issue Chromosome Manipulation for Plant Breeding Purposes)
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Open AccessArticle
The Influence of Biochar and Solid Digestate on Rose-Scented Geranium (Pelargonium graveolens L’Hér.) Productivity and Essential Oil Quality
Agronomy 2019, 9(5), 260; https://doi.org/10.3390/agronomy9050260 - 22 May 2019
Cited by 2 | Viewed by 932
Abstract
In recent years, biochar has generated global interest in the areas of sustainable agriculture and climate adaptation. The main positive effects of biochar were observed to be the most remarkable when nutrient-rich feedstock was used as the initial pyrolysis material (i.e., anaerobic digestate). [...] Read more.
In recent years, biochar has generated global interest in the areas of sustainable agriculture and climate adaptation. The main positive effects of biochar were observed to be the most remarkable when nutrient-rich feedstock was used as the initial pyrolysis material (i.e., anaerobic digestate). In this study, the influence of solid anaerobic digestate and biochar that was produced by the slow pyrolysis of solid digestate was evaluated by comparing the differences in the crop growth performances of Pelargonium graveolens. The experiment was conducted in a greenhouse while using three different growth media (i.e., solid digestate, biochar, and vermiculite). The results indicated that: (i) the pyrolysis of solid digestate caused a reduction in the bulk density (−52%) and an increase in the pH (+16%) and electrical conductivity (+9.5%) in the derived biochar; (ii) the best crop performances (number of leaves, number of total branches, and plant dry weight) were found using biochar, particularly for plant dry weight (+11.4%) and essential oil content (+9.4%); (iii) the essential oil quality was slightly affected by the growth media; however, the main chemical components were found within the acceptable range that was set by international standard trade; and, iv) biochar induced the presence of leaf chlorosis in Pelargonium graveolens. Full article
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Open AccessArticle
Integrated Rice-Duck Farming Decreases Soil Seed Bank and Weed Density in a Paddy Field
Agronomy 2019, 9(5), 259; https://doi.org/10.3390/agronomy9050259 - 22 May 2019
Viewed by 882
Abstract
Coupled cropping-breeding modes have been highly recommended due to their ecological and sustainable nature. Integrated rice-duck farming is a typical ecological planting system in rice paddy fields and has been widely popularized in Asia where a considerable area of cropland has been planting [...] Read more.
Coupled cropping-breeding modes have been highly recommended due to their ecological and sustainable nature. Integrated rice-duck farming is a typical ecological planting system in rice paddy fields and has been widely popularized in Asia where a considerable area of cropland has been planting rice. In this study, two experimental treatments of turbid water or rice-duck treatment were established to compare with the control and a conventional treatment in absence of ducks. The turbid water treatment imitated the muddying effect by duck activities with the trampling and foraging effects excluded, while the rice-duck treatment included all of the mentioned effects by raising ducks in rice paddy field. Results showed that the rice-duck treatment significantly reduced soil seed bank density by more than 40% and the figures under the turbid water treatment were 18.2% and 30.5%, accordingly, in the early and late rice growing seasons. Moreover, the rice-duck treatment significantly altered the vertical distribution of soil seed bank by substantially declining the seed density in the topsoil (0–5 cm). Changes in soil seed bank density considerably contributed to the declines in above-ground weed density because a significant correlation was detected between the soil seed bank density in the early season and the weed density in the late season. Our results of declined soil seed bank and weed density in integrated rice-duck farming imply that this system is highly efficient as a biological pathway for controlling weeds. Full article
(This article belongs to the Special Issue Ecologically Sustainable Weed Management in Cropping Systems)
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Open AccessReview
High-Throughput Field-Phenotyping Tools for Plant Breeding and Precision Agriculture
Agronomy 2019, 9(5), 258; https://doi.org/10.3390/agronomy9050258 - 22 May 2019
Cited by 4 | Viewed by 1744
Abstract
High-throughput field phenotyping has garnered major attention in recent years leading to the development of several new protocols for recording various plant traits of interest. Phenotyping of plants for breeding and for precision agriculture have different requirements due to different sizes of the [...] Read more.
High-throughput field phenotyping has garnered major attention in recent years leading to the development of several new protocols for recording various plant traits of interest. Phenotyping of plants for breeding and for precision agriculture have different requirements due to different sizes of the plots and fields, differing purposes and the urgency of the action required after phenotyping. While in plant breeding phenotyping is done on several thousand small plots mainly to evaluate them for various traits, in plant cultivation, phenotyping is done in large fields to detect the occurrence of plant stresses and weeds at an early stage. The aim of this review is to highlight how various high-throughput phenotyping methods are used for plant breeding and farming and the key differences in the applications of such methods. Thus, various techniques for plant phenotyping are presented together with applications of these techniques for breeding and cultivation. Several examples from the literature using these techniques are summarized and the key technical aspects are highlighted. Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessArticle
The Effect of Shallow Tillage on Soil Erosion in a Semi-Arid Vineyard
Agronomy 2019, 9(5), 257; https://doi.org/10.3390/agronomy9050257 - 22 May 2019
Cited by 8 | Viewed by 810
Abstract
Soil erosion has been considered a threat for semi-arid lands due to the removal of solid materials by water and wind. Although water erosion is currently considered the most important process of soil degradation, a growing interest has been drawn to the impact [...] Read more.
Soil erosion has been considered a threat for semi-arid lands due to the removal of solid materials by water and wind. Although water erosion is currently considered the most important process of soil degradation, a growing interest has been drawn to the impact of soil tillage. Although numerous studies on tillage erosion have been carried out on arable land using a moldboard plow, a chisel, and a tandem disc for different crops, there are no studies on the effect of shallow tillage on soil redistribution in vineyards. The aim of this work was to evaluate the soil tillage erosion rate in a vineyard using a 13C natural abundance tracer. A strip of soil (C3-C soil) was removed, mixed with C4-C tracer, and replaced. After the installation of the strip, tillage (upslope in one inter-row and downslope in the other inter-row) was performed with a cultivator and soil was collected along the slope with an interval of 0.2 m from the C4-C strip. Soil organic carbon and δ13C were measured and the total mass of translocated soil (T) soil was calculated. The net effect of tillage after two consecutive operations (downslope and upslope tillage) was a T of 49.3 ± 4.2 kg m−1. The estimated annual erosion rate due to tillage in the studied vineyard was 9.5 ± 1.2 Mg ha−1year−1. The contribution of the soil tillage erosion rate was compared with that of water erosion in the same vineyard, and we conclude that tillage is a threat to soil degradation. Full article
(This article belongs to the Special Issue Surface Runoff and Soil Erosion under Various Climate Conditions)
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Open AccessFeature PaperReview
Low Lignin Mutants and Reduction of Lignin Content in Grasses for Increased Utilisation of Lignocellulose
Agronomy 2019, 9(5), 256; https://doi.org/10.3390/agronomy9050256 - 21 May 2019
Cited by 2 | Viewed by 847
Abstract
Biomass rich in lignocellulose from grasses is a major source for biofuel production and animal feed. However, the presence of lignin in cell walls limits its efficient utilisation such as in its bioconversion to biofuel. Reduction of the lignin content or alteration of [...] Read more.
Biomass rich in lignocellulose from grasses is a major source for biofuel production and animal feed. However, the presence of lignin in cell walls limits its efficient utilisation such as in its bioconversion to biofuel. Reduction of the lignin content or alteration of its structure in crop plants have been pursued, either by regulating genes encoding enzymes in the lignin biosynthetic pathway using biotechnological techniques or by breeding naturally-occurring low lignin mutant lines. The aim of this review is to provide a summary of these studies, focusing on lignin (monolignol) biosynthesis and composition in grasses and, where possible, the impact on recalcitrance to bioconversion. An overview of transgenic crops of the grass family with regulated gene expression in lignin biosynthesis is presented, including the effect on lignin content and changes in the ratio of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units. Furthermore, a survey is provided of low-lignin mutants in grasses, including cereals in particular, summarising their origin and phenotypic traits together with genetics and the molecular function of the various genes identified. Full article
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Open AccessArticle
Assimilation of Sentinel-2 Leaf Area Index Data into a Physically-Based Crop Growth Model for Yield Estimation
Agronomy 2019, 9(5), 255; https://doi.org/10.3390/agronomy9050255 - 21 May 2019
Cited by 8 | Viewed by 1723
Abstract
Remote sensing data, crop growth models, and optimization routines constitute a toolset that can be used together to map crop yield over large areas when access to field data is limited. In this study, Leaf Area Index (LAI) data from the Copernicus Sentinel-2 [...] Read more.
Remote sensing data, crop growth models, and optimization routines constitute a toolset that can be used together to map crop yield over large areas when access to field data is limited. In this study, Leaf Area Index (LAI) data from the Copernicus Sentinel-2 satellite were combined with the Environmental Policy Integrated Climate (EPIC) model to estimate crop yield using a re-calibration data assimilation approach. The experiment was implemented for a winter wheat crop during two growing seasons (2016 and 2017) under four different fertilization management strategies. A number of field measurements were conducted spanning from LAI to biomass and crop yields. LAI showed a good correlation between the Sentinel-2 estimates and the ground measurements using non-destructive method. A correlating fit between satellite LAI curves and EPIC modelled LAI curves was also observed. The assimilation of LAI in EPIC provided an improvement in yield estimation in both years even though in 2017 strong underestimations were observed. The diverging results obtained in the two years indicated that the assimilation framework has to be tested under different environmental conditions before being applied on a larger scale with limited field data. Full article
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Open AccessCase Report
Comparative Assessment of Biochar Stability Using Multiple Indicators
Agronomy 2019, 9(5), 254; https://doi.org/10.3390/agronomy9050254 - 21 May 2019
Cited by 3 | Viewed by 1010
Abstract
Biochar application is one strategy proposed to improve carbon sequestration in soil. Maintaining high carbon content in soil for a long period requires stable biochar. In this work, we assessed biochar stability by two methodologies, i.e., laboratory incubation and chemical oxidation. Biochar was [...] Read more.
Biochar application is one strategy proposed to improve carbon sequestration in soil. Maintaining high carbon content in soil for a long period requires stable biochar. In this work, we assessed biochar stability by two methodologies, i.e., laboratory incubation and chemical oxidation. Biochar was produced at four different temperatures (400 °C, 500 °C, 600 °C, and 800 °C) from rice (Oryza sativa L.) straw and husk, applewood branch (Malus pumila), and oak (Quercus serrata Murray) residues. Results showed that the high-temperature biochars were more stable in both abiotic and biotic incubations, whereas the low-temperature biochars had reduced longevity. In addition, we showed biochars originated from woody material have higher stable carbon than those produced from rice residues. Finally, the oxidative assessment method provided a more reliable estimation of stability than the biotic incubation method and showed a strong correlation with other stability indicators. Full article
(This article belongs to the Special Issue Interaction of Biochar on Organic Waste Composting)
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Open AccessArticle
Forced Postures in Courgette Greenhouse Workers
Agronomy 2019, 9(5), 253; https://doi.org/10.3390/agronomy9050253 - 21 May 2019
Cited by 4 | Viewed by 592
Abstract
Occupational health and safety allows the prevention of occupational diseases and accidents. Agriculture is one of the sectors in which it is important to prevent the musculoskeletal disorders that workers usually develop. The objective of this study is the evaluation of postures adopted [...] Read more.
Occupational health and safety allows the prevention of occupational diseases and accidents. Agriculture is one of the sectors in which it is important to prevent the musculoskeletal disorders that workers usually develop. The objective of this study is the evaluation of postures adopted by courgette farmers in greenhouses of the Almeria-type. OWAS (Ovako Working Posture Assessment System), an ergonomic evaluation method, is used and applied after making observations to the postures adopted by the workers who were previously video recorded. The results concluded that the four risk levels established by OWAS appeared, with 37.14% being the highest rate and belonging to risk level 2, 33.33% to risk level 1, 28.57% to risk level 3, and 0.95% to risk level 4. Therefore, depending on the severity of the postures adopted in each task, the need for changes in a short, medium, or long period of time was concluded. Full article
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Open AccessArticle
Nematode Management in the Strawberry Fields of Southern Spain
Agronomy 2019, 9(5), 252; https://doi.org/10.3390/agronomy9050252 - 21 May 2019
Viewed by 839
Abstract
(1) Background: Spain is the sixth strawberry producer in the world, with about 6500 ha producing more than 350,000 tons, and an annual commercial value about 390 million €. Stunted and dead strawberry plants are frequently associated with plant-parasitic nematodes, but nematode diseases [...] Read more.
(1) Background: Spain is the sixth strawberry producer in the world, with about 6500 ha producing more than 350,000 tons, and an annual commercial value about 390 million €. Stunted and dead strawberry plants are frequently associated with plant-parasitic nematodes, but nematode diseases have not been characterized to date in the country. (2) Methods: A poll on the perception of the impact of nematodes on strawberry production was carried out by face-to-face interviews with farm advisors. In addition, nematological field surveys were carried out at the end of the growing season in 2017 and 2018 to determine prevalence and abundance of plant-parasitic nematodes in strawberry crops. The host suitability to Meloidogyne hapla of seventeen strawberry cultivars and the tolerance limit to M. hapla at progressively higher initial population densities (Pi) were assessed in pot experiments in a growth chamber. Comparison of the relative efficacies of several soil disinfestation methods in controlling nematode populations (M. hapla and Pratylenchus penetrans) was carried out in experimental field trials for twelve consecutive years. (3) Results: Meloidogyne spp., Pratylenchus penetrans, and Hemicycliophora spp. were the main plant-parasitic nematodes in the strawberry fields in South Spain. Root-knot nematodes were found in 90% of the fields, being M. hapla the most prevalent species (71% of the fields). A tolerance limit of 0.2 M. hapla juveniles per g of soil was estimated for strawberry, and currently cropped strawberry cultivars did not show resistance to M. hapla. Nematode population densities were reduced by more than 70% by soil fumigation with 1,3-dichloropropene, dazomet, dimethyl-disulfide, and methyl iodide. The efficacy of metam-sodium in reducing nematode populations was about 50% and that of chloropicrin, furfural, and sodium-azide, less than 40%. Combination of solarization with organic manures (biosolarization) reduced soil nematode populations by 68–73%. (4) Conclusions: Plant-parasitic nematodes (Meloidogyne, Pratylenchus, and Hemicycliophora) are widely distributed in the strawberry fields of Southern Spain. Strawberry is a poor host for M. hapla with a tolerance limit of 0.2 J2 per g of soil, and low population increases in cropping cycles of 7–8 months. Strawberry cultivars show a range of susceptibility and tolerance to M. hapla, but no resistance is found. Nematodes are effectively controlled by chemical fumigation of soils, but soil biosolarization is equally effective, and therefore, can be proposed as a sustainable alternative for pathogen control in strawberry cultivation. Full article
(This article belongs to the Special Issue Etiology and Control of Crop Diseases)
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Open AccessArticle
Mapping the Depth-to-Soil pH Constraint, and the Relationship with Cotton and Grain Yield at the Within-Field Scale
Agronomy 2019, 9(5), 251; https://doi.org/10.3390/agronomy9050251 - 21 May 2019
Cited by 2 | Viewed by 823
Abstract
Subsoil alkalinity is a common issue in the alluvial cotton-growing valleys of northern New South Wales (NSW), Australia. Soil alkalinity can cause nutrient deficiencies and toxic effects, and inhibit rooting depth, which can have a detrimental impact on crop production. The depth at [...] Read more.
Subsoil alkalinity is a common issue in the alluvial cotton-growing valleys of northern New South Wales (NSW), Australia. Soil alkalinity can cause nutrient deficiencies and toxic effects, and inhibit rooting depth, which can have a detrimental impact on crop production. The depth at which a soil constraint is reached is important information for land managers, but it is difficult to measure or predict spatially. This study predicted the depth in which a pH (H2O) constraint (>9) was reached to a 1-cm vertical resolution to a 100-cm depth, on a 1070-hectare dryland cropping farm. Equal-area quadratic smoothing splines were used to resample vertical soil profile data, and a random forest (RF) model was used to produce the depth-to-soil pH constraint map. The RF model was accurate, with a Lin’s Concordance Correlation Coefficient (LCCC) of 0.63–0.66, and a Root Mean Square Error (RMSE) of 0.47–0.51 when testing with leave-one-site-out cross-validation. Approximately 77% of the farm was found to be constrained by a strongly alkaline pH greater than 9 (H2O) somewhere within the top 100 cm of the soil profile. The relationship between the predicted depth-to-soil pH constraint map and cotton and grain (wheat, canola, and chickpea) yield monitor data was analyzed for individual fields. Results showed that yield increased when a soil pH constraint was deeper in the profile, with a good relationship for wheat, canola, and chickpea, and a weaker relationship for cotton. The overall results from this study suggest that the modelling approach is valuable in identifying the depth-to-soil pH constraint, and could be adopted for other important subsoil constraints, such as sodicity. The outputs are also a promising opportunity to understand crop yield variability, which could lead to improvements in management practices. Full article
(This article belongs to the Special Issue Precision Agriculture)
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Open AccessArticle
Winter Wheat Grain Quality, Zinc and Iron Concentration Affected by a Combined Foliar Spray of Zinc and Iron Fertilizers
Agronomy 2019, 9(5), 250; https://doi.org/10.3390/agronomy9050250 - 20 May 2019
Cited by 7 | Viewed by 1092
Abstract
Wheat (Triticum aestivum L.) is one of the main foods globally. Nutrition problems associated with Zinc and Iron deficiency affect more than two billion individuals. Biofortification is a strategy believed to be sustainable, economical and easily implemented. This study evaluated the effect [...] Read more.
Wheat (Triticum aestivum L.) is one of the main foods globally. Nutrition problems associated with Zinc and Iron deficiency affect more than two billion individuals. Biofortification is a strategy believed to be sustainable, economical and easily implemented. This study evaluated the effect of combined Zn and Fe applied as foliar fertilizer to winter wheat on grain yield, quality, Zn and Fe concentration in the grains. Results showed that treatments containing high Fe increased the yield. Grain crude fat content remained unaffected. Crude fiber was enhanced up to three-fold by 60% Zn + 40% Fe5.5 (5.5 kg ha−1 of 60% Zn + 40% Fe). Moreover, 80% Zn + 20% Fe5.5 (5.5 kg ha−1 of 80% Zn + 20% Fe) was the best combination for increasing crude protein. Zinc applied alone enhanced Zn concentration in grain. In addition, Fe was slightly improved by an application of Zn and Fe in the first year, but a greater increase was observed in the second year, where 100% Fe13 (13 kg ha−1 of 100% Fe) was the best in improving Fe in grain. Foliar application of Zn and Fe is a practical approach to increase Zn and Fe concentration, and to improve the quality of wheat grains. Full article
(This article belongs to the Special Issue Biofortification of Crops)
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Open AccessArticle
Biostimulant Application with a Tropical Plant Extract Enhances Corchorus olitorius Adaptation to Sub-Optimal Nutrient Regimens by Improving Physiological Parameters
Agronomy 2019, 9(5), 249; https://doi.org/10.3390/agronomy9050249 - 19 May 2019
Cited by 12 | Viewed by 1026
Abstract
The emerging role of plant biostimulants in enhancing nutrient efficiency is important for maintaining soil fertility under sub-optimal nutrient regimens. We aimed to elucidate the morpho-physiological and biochemical effects as well as mineral composition changes of greenhouse jute (Corchorus olitorius L.) treated [...] Read more.
The emerging role of plant biostimulants in enhancing nutrient efficiency is important for maintaining soil fertility under sub-optimal nutrient regimens. We aimed to elucidate the morpho-physiological and biochemical effects as well as mineral composition changes of greenhouse jute (Corchorus olitorius L.) treated with a commercial vegetal-derived biostimulant from a tropical plant extract (PE; Auxym®, Italpollina, Rivoli Veronese, Italy). Plants were sprayed in weekly intervals with a solution containing 2 mL·L−1 PE. Jute plants were supplied with three nutrient solution concentrations: full-, half-, and quarter-strength. Decreasing macronutrient concentrations in the nutrient solution (NS), especially at quarter-strength, triggered a decrease in several morphological (plant height, leaf number, and dry biomass) and physiological (net CO2 assimilation rate (ACO2) and SPAD (Soil Plant Analysis Development) index) parameters. PE application triggered specific ameliorative effects in terms of fresh yield at both half- and quarter-strength nutrient solution (15.5% and 29.5%, respectively). This was associated with an enhancement in ACO2, SPAD index, and especially the nutritional status (high nitrate, K, and Mg contents, and low Na content). The foliar application of PE, strongly increased chlorophyll b content, enhancing jute plant adaptation to fluctuating light and therefore the efficiency of photosynthesis, positively affecting starch, soluble proteins, and total amino acids content but only when jute plants were irrigated with full-strength NS, compared to the respective control treatment. At lower nutrient strength, PE reprogrammed the nitrogen distribution, allowing its remobilization from glutamate, which was quantitatively the major amino acid under lower nutrient strength, but not from chlorophylls, thus maintaining efficient photosynthesis. We confirmed that PE Auxym® acts in a balanced manner on the main metabolic pathways of the plant, regulating the uptake and transport of mineral nutrients and protein synthesis, increasing the accumulation of essential amino acids under full nutritive solutions, and re-distributing nitrogen from amino acids to allow leaf growth and expansion even under sub-optimal nutrient conditions. Overall, the use of natural plant biostimulants may be a potential solution in low-input conditions, where environmental constraints and restricted use of fertilizers may affect potential crop productivity. Full article
(This article belongs to the collection Nutrition Management of Hydroponic Vegetable Crops)
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Open AccessFeature PaperArticle
The Efficiency of a Low Dose of Biochar in Enhancing the Aromaticity of Humic-Like Substance Extracted from Poultry Manure Compost
Agronomy 2019, 9(5), 248; https://doi.org/10.3390/agronomy9050248 - 18 May 2019
Cited by 2 | Viewed by 1276
Abstract
Using biochar as a bulking agent in composting is gradually becoming popular for the minimization of nitrogen losses during the process and the improvement in compost quality. While a wide range of different biochar doses is applied, not much clear information was available [...] Read more.
Using biochar as a bulking agent in composting is gradually becoming popular for the minimization of nitrogen losses during the process and the improvement in compost quality. While a wide range of different biochar doses is applied, not much clear information was available about the optimum ratio. This study presents the impact of adding a low dose (2% v/v) of slow-pyrolysis oak biochar (Quercus serrate Murray), into poultry manure on the recalcitrant characteristic of humified organic matter. The influence in the chemical composition of humic-like substance was evaluated in poultry manure compost prepared with (PM+B) and without biochar (PM). The shift to slightly more stable chemical composition was shown in humic acid-like (HA) and fulvic acid-like (FA) extracted from PM+B compost, by increasing the proportion of aromatic carbon groups and thermal stability measured by thermogravimetry. We conclude that the addition of 2% biochar moderately enhances the recalcitrance of humified organic carbon and this could be feasible for the implementation of the biochar use in composting since only a small amount is required. Full article
(This article belongs to the Special Issue Interaction of Biochar on Organic Waste Composting)
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Open AccessArticle
Effect of Row Cleaner Operational Settings on Crop Residue Translocation in Strip-Tillage
Agronomy 2019, 9(5), 247; https://doi.org/10.3390/agronomy9050247 - 18 May 2019
Cited by 2 | Viewed by 555
Abstract
Through field experiments and empirical analysis methods, this study determined the dependence of plant residue removal on the row cleaner’s settings in strip-tillage. The main research object of this study is row cleaners. By changing the slip angles (10, 15, and 22.5°), the [...] Read more.
Through field experiments and empirical analysis methods, this study determined the dependence of plant residue removal on the row cleaner’s settings in strip-tillage. The main research object of this study is row cleaners. By changing the slip angles (10, 15, and 22.5°), the gap between row cleaner discs in parallel (165, 180, and 195 mm), and the driving speed (1.3, 1.9, 2.5, and 3.1 m s−1), we determined what percentage of wheat residue was removed from the strip on the surface of the soil and what distance it was moved. The percentage of removed plant residue was determined by evaluating the differences between the masses of the plant residue taken from non-removed and removed strips. Empirical analysis of the results of the field experiments showed that both the amount of the removed plant residue and the distance it is moved to were the best when the slip angle was 15°, the gap between the discs of row cleaner was 180 mm, and the driving speed was 2.5 m s−1. With these parameters, up to three-quarters of the plant residue was removed from the soil surface of the strip, which was relocated 308 mm from the middle of the strip. If the slip angle and the driving speed are increased further, even more plant residue can be removed; however, if the plant residue is relocated too far away, it may fall into the zone of the adjacent strip. Full article
(This article belongs to the Section Agricultural Engineering)
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Open AccessArticle
Application of Nano-Silicon Dioxide Improves Salt Stress Tolerance in Strawberry Plants
Agronomy 2019, 9(5), 246; https://doi.org/10.3390/agronomy9050246 - 17 May 2019
Cited by 4 | Viewed by 969
Abstract
Silicon application can improve productivity outcomes for salt stressed plants. Here, we describe how strawberry plants respond to treatments including various combinations of salt stress and nano-silicon dioxide, and assess whether nano-silicon dioxide improves strawberry plant tolerance to salt stress. Strawberry plants were [...] Read more.
Silicon application can improve productivity outcomes for salt stressed plants. Here, we describe how strawberry plants respond to treatments including various combinations of salt stress and nano-silicon dioxide, and assess whether nano-silicon dioxide improves strawberry plant tolerance to salt stress. Strawberry plants were treated with salt (0, 25 or 50 mM NaCl), and the nano-silicon dioxide treatments were applied to the strawberry plants before (0, 50 and 100 mg L−1) or after (0 and 50 mg L−1) flowering. The salt stress treatments reduced plant biomass, chlorophyll content, and leaf relative water content (RWC) as expected. Relative to control (no NaCl) plants the salt treated plants had 10% lower membrane stability index (MSI), 81% greater proline content, and 54% greater cuticular transpiration; as well as increased canopy temperature and changes in the structure of the epicuticular wax layer. The plants treated with nano-silicon dioxide were better able to maintain epicuticular wax structure, chlorophyll content, and carotenoid content and accumulated less proline relative to plants treated only with salt and no nano-silicon dioxide. Analysis of scanning electron microscopic (SEM) images revealed that the salt treatments resulted in changes in epicuticular wax type and thickness, and that the application of nano-silicon dioxide suppressed the adverse effects of salinity on the epicuticular wax layer. Nano-silicon dioxide treated salt stressed plants had increased irregular (smoother) crystal wax deposits in their epicuticular layer. Together these observations indicate that application of nano-silicon dioxide can limit the adverse anatomical and biochemical changes related to salt stress impacts on strawberry plants and that this is, in part, associated with epicuticular wax deposition. Full article
(This article belongs to the Special Issue Berry Crop Production and Protection) Printed Edition available
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Open AccessArticle
Consistency of Yield Ranking and Adaptability Patterns of Winter Wheat Cultivars between Multi-Environmental Trials and Farmer Surveys
Agronomy 2019, 9(5), 245; https://doi.org/10.3390/agronomy9050245 - 15 May 2019
Cited by 2 | Viewed by 722
Abstract
Cultivar recommendation based on mean performance determined by multi-environment trials (METs) conducted on research stations could be unreliable and ineffective for assessing performance in farmers’ fields. It is important to improve the efficiency of cultivar recommendation based on METs. For this purpose, it [...] Read more.
Cultivar recommendation based on mean performance determined by multi-environment trials (METs) conducted on research stations could be unreliable and ineffective for assessing performance in farmers’ fields. It is important to improve the efficiency of cultivar recommendation based on METs. For this purpose, it would be useful to validate recommendations based on yield data obtained directly from farmers, i.e., through surveys. The aim of this study was to discuss the possibility and statistical methodology of assessing cultivar performance patterns based on yield data obtained through farmer surveys. We suggest that this might be accomplished by assessing the conformity of yield ranking and yield performance patterns between MET and survey datasets in the same growing regions. As an example, we compare winter wheat (Triticum aestivum L.) yield data obtained from Polish farmers via surveys with data obtained via METs. In the METs, cultivars were evaluated at two levels of crop-management, a moderate-input management (MIM) system and a high-input management (HIM) system. Based on the yield evaluations in the current study, half of the agro-ecological regions had relatively high levels of consistency in yield rankings between the MET MIM system and survey yield dataset. This indicated a relatively high efficiency of cultivar recommendations based on METs in these regions, especially for the MIM system. For the HIM system, however, with the exception of one region, we observed a poor degree of consistency in cultivar ranking. Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessArticle
Anti-Transpirant Effects on Vine Physiology, Berry and Wine Composition of cv. Aglianico (Vitis vinifera L.) Grown in South Italy
Agronomy 2019, 9(5), 244; https://doi.org/10.3390/agronomy9050244 - 14 May 2019
Cited by 3 | Viewed by 966
Abstract
In viticulture, global warming requires reconsideration of current production models. At the base of this need there are some emerging phenomena: modification of phenological phases; acceleration of the maturation process of grapes, with significant increases in the concentration of sugar musts; decoupling between [...] Read more.
In viticulture, global warming requires reconsideration of current production models. At the base of this need there are some emerging phenomena: modification of phenological phases; acceleration of the maturation process of grapes, with significant increases in the concentration of sugar musts; decoupling between technological grape maturity and phenolic maturity. The aim of our study was to evaluate the effect of a natural anti-transpirant on grapevine physiology, berry, and wine composition of Aglianico cultivar. For two years, Aglianico vines were treated at veraison with the anti-transpirant Vapor Gard and compared with a control sprayed with only water. A bunch thinning was also applied to both treatments. The effectiveness of Vapor Gard were assessed through measurements of net photosynthesis and transpiration and analyzing the vegetative, productive and qualitative parameters. The results demonstrate that the application of anti-transpirant reduced assimilation and transpiration rate, stomatal conductance, berry sugar accumulation, and wine alcohol content. No significant differences between treatments were observed for other berry and wine compositional parameters. This method may be a useful tool to reduce berry sugar content and to produce wines with a lower alcohol content. Full article
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Open AccessArticle
Effects of Elevated CO2 on Wheat Yield: Non-Linear Response and Relation to Site Productivity
Agronomy 2019, 9(5), 243; https://doi.org/10.3390/agronomy9050243 - 14 May 2019
Cited by 5 | Viewed by 1399
Abstract
Elevated carbon dioxide (eCO2) is well known to stimulate plant photosynthesis and growth. Elevated carbon dioxide’s effects on crop yields are of particular interest due to concerns for future food security. We compiled experimental data where field-grown wheat (Triticum aestivum [...] Read more.
Elevated carbon dioxide (eCO2) is well known to stimulate plant photosynthesis and growth. Elevated carbon dioxide’s effects on crop yields are of particular interest due to concerns for future food security. We compiled experimental data where field-grown wheat (Triticum aestivum Linnaeus) was exposed to different CO2 concentrations. Yield and yield components were analyzed by meta-analysis to estimate average effects, and response functions derived to assess effect size in relation to CO2 concentration. Grain yield increased by 26% under eCO2 (average ambient concentration of 372 ppm and elevated 605 ppm), mainly due to the increase in grain number. The response function for grain yield with CO2 concentration strongly suggests a non-linear response, where yield stimulation levels off at ~600 ppm. This was supported by the meta-analysis, which did not indicate any significant difference in yield stimulation in wheat grown at 456–600 ppm compared to 601–750 ppm. Yield response to eCO2 was independent of fumigation technique and rooting environment, but clearly related to site productivity, where relative CO2 yield stimulation was stronger in low productive systems. The non-linear yield response, saturating at a relatively modest elevation of CO2, was of large importance for crop modelling and assessments of future food production under rising CO2. Full article
(This article belongs to the Special Issue Effects of CO2 on Crop Growth and Quality)
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Open AccessArticle
Sensitivity Analysis of Plant- and Cultivar-Specific Parameters of APSIM-Sugar Model: Variation between Climates and Management Conditions
Agronomy 2019, 9(5), 242; https://doi.org/10.3390/agronomy9050242 - 14 May 2019
Cited by 2 | Viewed by 848
Abstract
With increasing demand for food and energy, there is a great need for improving sugarcane productivity. New cultivars and management strategies can be assessed using process-based crop models. Information on cultivars needs to be updated frequently, but it is still limited in most [...] Read more.
With increasing demand for food and energy, there is a great need for improving sugarcane productivity. New cultivars and management strategies can be assessed using process-based crop models. Information on cultivars needs to be updated frequently, but it is still limited in most crop models. Therefore, it is important to identify possible candidates for varietal parameterization and calibration. Because sensitivity analysis is computationally expensive, we used a less expensive emulator-based approach to conduct a global sensitivity analysis using the apsimr package and GEM-SA software. We studied the sensitivity of four yield outputs of the APSIM-Sugar model to 13 parameters in rainfed and irrigated conditions in Japan and Sri Lanka. Unlike previous studies, our aim was to give comprehensive insights into the variation in sensitivity due to variation in climate. The results confirmed distinct variation of parameter influence between climates and between management conditions. We identify possible candidates for parameterization and calibration of new cultivars for APSIM-Sugar under different environments, and show the effect of variation in climate on variation in parameter influence under different management conditions. It was confirmed that both radiation use efficiency and transpiration efficiency were sensitive and have to be examined to use new cultivars, though these are not listed as cultivar parameters. Full article
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Open AccessArticle
Uncertainty of CERES-Maize Calibration under Different Irrigation Strategies Using PEST Optimization Algorithm
Agronomy 2019, 9(5), 241; https://doi.org/10.3390/agronomy9050241 - 10 May 2019
Cited by 2 | Viewed by 956
Abstract
An important but rarely studied aspect of crop modeling is the uncertainty associated with model calibration and its effect on model prediction. Biomass and grain yield data from a four-year maize experiment (2008–2011) with six irrigation treatments were divided into subsets by either [...] Read more.
An important but rarely studied aspect of crop modeling is the uncertainty associated with model calibration and its effect on model prediction. Biomass and grain yield data from a four-year maize experiment (2008–2011) with six irrigation treatments were divided into subsets by either treatments (Calibration-by-Treatment) or years (Calibration-by-Year). These subsets were then used to calibrate crop cultivar parameters in CERES (Crop Environment Resource Synthesis)-Maize implemented within RZWQM2 (Root Zone Water Quality Model 2) using the automatic Parameter ESTimation (PEST) algorithm to explore model calibration uncertainties. After calibration for each subset, PEST also generated 300 cultivar parameter sets by assuming a normal distribution of each parameter within their reported values in the literature, using the Latin hypercube sampling (LHS) method. The parameter sets that produced similar goodness of fit (11–164 depending on subset used for calibration) were then used to predict all the treatments and years of the entire dataset. Our results showed that the selection of calibration datasets greatly affected the calibrated crop parameters and their uncertainty, as well as prediction uncertainty of grain yield and biomass. The high variability in model prediction of grain yield and biomass among the six (Calibration-by-Treatment) or the four (Calibration-by-Year) scenarios indicated that parameter uncertainty should be considered in calibrating CERES-Maize with grain yield and biomass data from different irrigation treatments, and model predictions should be provided with confidence intervals. Full article
(This article belongs to the Special Issue Model Application for Sustainable Agricultural Water)
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Open AccessArticle
Evaluation of Yield-Based Low Nitrogen Tolerance Indices for Screening Maize (Zea mays L.) Inbred Lines
Agronomy 2019, 9(5), 240; https://doi.org/10.3390/agronomy9050240 - 10 May 2019
Viewed by 926
Abstract
To screen the desired criterion to identify desirable genotypes and select genotypes best suited to limited nitrogen availability in order to facilitate the practice of low-nitrogen-tolerant breeding in maize, the response of 31 maize inbred lines, containing four control inbred lines (PH6WC, PH4CV, [...] Read more.
To screen the desired criterion to identify desirable genotypes and select genotypes best suited to limited nitrogen availability in order to facilitate the practice of low-nitrogen-tolerant breeding in maize, the response of 31 maize inbred lines, containing four control inbred lines (PH6WC, PH4CV, Zheng58, and Chang7-2) and others selected from the Shaan A and Shaan B heterotic groups cultivated at Northwest A&F University (Yangling, Shaanxi, China), were evaluated. The experiment was conducted following a split plot design with two replications during three growing seasons (2015, 2016, and 2017) under both high nitrogen (HN) and low nitrogen (LN) conditions at the Yulin and Yangling in Shaanxi Province, China. Seven screening indices, based on grain yield under two contrasting nitrogen (N) conditions, the stress susceptibility index (SSI), yield stability index (YSI), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), harmonic mean (HM), and low nitrogen tolerance index (LNTI), were computed to assess the overall index that accurately screened the desirable genotypes. The results of the correlation analyses and principal component analysis showed that MP, GMP, HM and STI were correlated with grain yield significantly and positively under contrasting N conditions, and were able to accurately discriminate the desirable genotypes. Compared with the control inbred lines, many inbred lines selected from the Shaan A and Shaan B groups showed a higher LN tolerance. This shows that we can effectively improve the LN tolerance of maize inbred lines through LN screening. Based on the screening indices, the three-dimensional diagram and genotype and genotype × environment (GGE) biplots are agreed with this results, and we identified KA105, KB081, KA225, 91227, and 2013KB-47 as the desired genotypes that have the potential to be used to breed a high yield and stable hybrid. Full article
(This article belongs to the Section Crop Breeding and Genetics)
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Open AccessReview
Drivers, Process, and Consequences of Native Grassland Degradation: Insights from a Literature Review and a Survey in Río de la Plata Grasslands
Agronomy 2019, 9(5), 239; https://doi.org/10.3390/agronomy9050239 - 10 May 2019
Cited by 2 | Viewed by 1160
Abstract
Natural grasslands are being progressively degraded around the world due to human-induced action (e.g., overgrazing), but there is neither a widely accepted conceptual framework to approach degradation studies nor a clear definition of what “grassland degradation” is. Most of the drivers, processes, and [...] Read more.
Natural grasslands are being progressively degraded around the world due to human-induced action (e.g., overgrazing), but there is neither a widely accepted conceptual framework to approach degradation studies nor a clear definition of what “grassland degradation” is. Most of the drivers, processes, and consequences related to grassland degradation are widespread and are usually separately quoted in the literature. In this paper, we propose a comprehensive framework with different conceptual categories, for monitoring grassland degradation, and a new definition based on current ones. We provide a conceptual update of grassland degradation based on a literature review and an expert survey, focused on the Río de la Plata grasslands (RPG). We identified “drivers” as external forces or changes that cause degradation; “processes” as measurable changes in grasslands conditions that can be evaluated using indicators; and “consequences” as the impacts or results of the process of grassland degradation. We expect that this conceptual framework will contribute to monitoring programs, to support management decisions, to design conservation measures, and to communicate the importance of grasslands conservation and the different concepts involved. Particularly for RPG, we expect that this paper will contribute to promote sustainable management practices in this important and often neglected ecosystem. Full article
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Open AccessArticle
Evaluating the Impacts of Continuous and Rotational Grazing on Tallgrass Prairie Landscape Using High-Spatial-Resolution Imagery
Agronomy 2019, 9(5), 238; https://doi.org/10.3390/agronomy9050238 - 09 May 2019
Cited by 3 | Viewed by 723
Abstract
This study evaluated the impacts of different grazing treatments (continuous (C) and rotational (R) grazing) on tallgrass prairie landscape, using high-spatial-resolution aerial imagery (1-m at RGB and near-infrared bands) of experimental C and R pastures within two replicates (Rep A and Rep B) [...] Read more.
This study evaluated the impacts of different grazing treatments (continuous (C) and rotational (R) grazing) on tallgrass prairie landscape, using high-spatial-resolution aerial imagery (1-m at RGB and near-infrared bands) of experimental C and R pastures within two replicates (Rep A and Rep B) in the southern Great Plains (SGP) of the United States. The imagery was acquired by the National Agriculture Imagery Program (NAIP) during the agricultural growing season of selected years (2010, 2013, 2015, and 2017) in the continental United States. Land cover maps were generated by combining visual interpolation, a support vector machine, and a decision tree classifier. Landscape metrics (class area, patch number, percentage of landscape, and fragmentation indices) were calculated from the FRAGSTATS (a computer software program designed to compute a wide variety of landscape metrics for categorical map patterns) based on land cover results. Both the metrics and land cover results were used to analyze landscape dynamics in the experiment pastures. Results showed that both grass and shrubs of different pastures differed largely in the same year and had significant annual dynamics controlled by climate. High stocking intensity delayed grass growth. A large proportion of bare soil occurred in sub-paddocks of rotational grazing that were just grazed or under grazing. Rep A experienced rapid shrub encroachment, with a large proportion of shrub at the beginning of the experiment. Shrub may occupy 41% of C and 15% of R in Rep A by 2030, as revealed by the linear regression analysis of shrub encroachment. In contrast, shrub encroachment was not significant in Rep B, which only had a small number of shrub patches at the beginning of the experiment. This result indicates that the shrub encroachment is mainly controlled by the initial status of the pastures instead of grazing management. However, the low temporal resolution of the NAIP imagery (one snapshot in two or three years) limits our comparison of the continuous and rotational grazing at the annual scale. Future studies need to combine NAIP imagery with other higher temporal resolution imagery (e.g., WorldView), in order to better evaluate the interannual variabilities of grass productivity and shrub encroachment. Full article
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