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Agronomy, Volume 11, Issue 10 (October 2021) – 184 articles

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Article
Detection of Crop Hail Damage with a Machine Learning Algorithm Using Time Series of Remote Sensing Data
Agronomy 2021, 11(10), 2078; https://doi.org/10.3390/agronomy11102078 (registering DOI) - 18 Oct 2021
Abstract
Hailstorms usually result in total crop loss. After a hailstorm, the affected field is inspected by an insurance claims adjuster to assess yield loss. Assessment accuracy depends largely on in situ detection of homogeneous damage sectors within the field, using visual techniques. This [...] Read more.
Hailstorms usually result in total crop loss. After a hailstorm, the affected field is inspected by an insurance claims adjuster to assess yield loss. Assessment accuracy depends largely on in situ detection of homogeneous damage sectors within the field, using visual techniques. This paper presents an algorithm for the automatic detection of homogeneous hail damage through the application of unsupervised machine learning techniques to vegetation indices calculated from remote sensing data. Five microwave and five spectral indices were evaluated before and after a hailstorm in zones with different degrees of damage. Dual Polarization SAR Vegetation Index and Normalized Pigment Chlorophyll Ratio Index were the most sensitive to hail-induced changes. The time series and rates of change of these indices were used as input variables in the K-means method for clustering pixels into homogeneous damage zones. Validation of the algorithm with data from 91 soybean, wheat, and corn plots showed that in 87.01% of cases there was significant evidence of differences in average damage between zones determined by the algorithm within the plot. Thus, the algorithm presented in this paper allowed efficient detection of homogeneous hail damage zones, which is expected to improve accuracy and transparency in the characterization of hailstorm events. Full article
(This article belongs to the Special Issue Geoinformatics Application in Agriculture)
Article
Estimation of Daily Reference Evapotranspiration from NASA POWER Reanalysis Products in a Hot Summer Mediterranean Climate
Agronomy 2021, 11(10), 2077; https://doi.org/10.3390/agronomy11102077 (registering DOI) - 18 Oct 2021
Abstract
This study aims at assessing the accuracy of estimating daily reference evapotranspiration (ETo) computed with NASA POWER reanalysis products. Daily ETo estimated from local observations of weather variables in 14 weather stations distributed across Alentejo Region, Southern Portugal were compared with ETo derived [...] Read more.
This study aims at assessing the accuracy of estimating daily reference evapotranspiration (ETo) computed with NASA POWER reanalysis products. Daily ETo estimated from local observations of weather variables in 14 weather stations distributed across Alentejo Region, Southern Portugal were compared with ETo derived from NASA POWER weather data, using raw and bias-corrected datasets. Three different methods were used to compute ETo: (a) FAO Penman-Monteith (PM); (b) Hargreaves-Samani (HS); and (c) MaxTET. Results show that, when using raw NASA POWER datasets, a good accuracy between the observed ETo and reanalysis ETo was observed in most locations (R2 > 0.70). PM shows a tendency to over-estimating ETo with an RMSE as high as 1.41 mm d−1, while using a temperature-based ET estimation method, an RMSE lower than 0.92 mm d−1 is obtained. If a local bias correction is adopted, the temperature-based methods show a small over or underestimation of ETo (–0.40 mm d−1≤ MBE < 0.40 mm d−1). As for PM, ETo is still underestimated for 13 locations (MBE < 0 mm d−1) but with an RMSE never higher than 0.77 mm d−1. When NASA POWER raw data is used to estimate ETo, HS_Rs proved the most accurate method, providing the lowest RMSE for half the locations. However, if a data regional bias correction is used, PM leads to the most accurate ETo estimation for half the locations; also, when a local bias correction is performed, PM proved the be the most accurate ETo estimation method for most locations. Nonetheless, MaxTET proved to be an accurate method; its simplicity may prove to be successful not only when only maximum temperature data is available but also due to the low data required for ETo estimation. Full article
(This article belongs to the Special Issue Advances in Irrigation Technology and Adaptation to Climate Change)
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Article
Defensive Impact of Foliar Applied Potassium Nitrate on Growth Linked with Improved Physiological and Antioxidative Activities in Sunflower (Helianthus annuus L.) Hybrids Grown under Salinity Stress
Agronomy 2021, 11(10), 2076; https://doi.org/10.3390/agronomy11102076 (registering DOI) - 17 Oct 2021
Abstract
Salt stress is recognized to negatively influence the fundamental processes in plants regarding growth and yield. The sunflower (Helianthus annuus L.) is considered an important industrial crop because of the good quality of oil it produces that can be used for cooking [...] Read more.
Salt stress is recognized to negatively influence the fundamental processes in plants regarding growth and yield. The sunflower (Helianthus annuus L.) is considered an important industrial crop because of the good quality of oil it produces that can be used for cooking purposes. The exogenous application of potassium (K) has been reported to enhance abiotic resistance and increase yield in crops. Here, we explored the impact of foliar-applied K at 500 ppm on the physiological and biochemical traits, antioxidant activities, and growth attributes of sunflower grown under salt stress (140 mM NaCl). The findings indicated that salinity stress adversely affected photosynthesis and various gas exchange characteristics. Foliar applied K markedly improved the stomatal conductance, transpiration rate, water use efficiency, CO2 assimilation rate, total soluble proteins, chlorophyll pigments, and upregulated antioxidant system, which are responsible for the healthy growth of sunflower hybrids grown under salinity stress. The shoot and root lengths, plant fresh and dry weights, and achene weight were significantly increased by K application. Overall, foliar applied K significantly improved all of the aforementioned attributes and can attenuate the deleterious influences of salinity stress in sunflower. Full article
(This article belongs to the Special Issue Improving Mineral Nutrition to Obtain Stress Tolerant Crops)
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Article
Differential Interferometry over Sentinel-1 TopSAR Images as a Tool for Water and Tillage Soil Erosion Analysis
Agronomy 2021, 11(10), 2075; https://doi.org/10.3390/agronomy11102075 (registering DOI) - 17 Oct 2021
Abstract
Erosion is a major problem on agricultural lands in Europe. Erosion measurement tools have traditionally been focused on delocalized quantification but without mapping the real places inside the basin where the erosion took effect. In this article, we use new space missions, such [...] Read more.
Erosion is a major problem on agricultural lands in Europe. Erosion measurement tools have traditionally been focused on delocalized quantification but without mapping the real places inside the basin where the erosion took effect. In this article, we use new space missions, such as Sentinel-1, and the opportunity they offer to obtain SAR (Synthetic Aperture Radar) images with high frequency, resolution, range, and, above all, availability to enable the application of techniques, like differential interferometry, in new fields. We propose to measure ground deformation caused by water and tillage erosion in small agricultural basins using TopSAR (Terrain Observation with Progressive Scans SAR, Synthetic Aperture Radar) images acquired by the Sentinel-1 mission, after previously verifying the accuracy of these measurements through comparison with measurements from a LIDAR (Light Detection and Ranging) system. The results of this work confirm the potential of monitoring erosion in agricultural basins with differential interferometry over Sentinel-1 TopSAR images. Its capabilities have been successfully tested in different conditions related to agricultural tasks without precipitation or storm events. This technique makes it possible to study both water and tillage erosion and sedimentation processes and even to test the efficiency of anti-erosion measures in the field or to verify the results of different management practices over time. Full article
(This article belongs to the Section Agricultural Engineering)
Review
Recent Trends in the Foliar Spraying of Zinc Nutrient and Zinc Oxide Nanoparticles in Tomato Production
Agronomy 2021, 11(10), 2074; https://doi.org/10.3390/agronomy11102074 (registering DOI) - 16 Oct 2021
Abstract
Growing vegetables can be seen as a means of improving people’s livelihoods and nutritional status. Tomatoes are one of the world’s most commonly planted vegetable crops. The nutritional arrangement of the tomato depends on the quantity and type of nutrients taken from the [...] Read more.
Growing vegetables can be seen as a means of improving people’s livelihoods and nutritional status. Tomatoes are one of the world’s most commonly planted vegetable crops. The nutritional arrangement of the tomato depends on the quantity and type of nutrients taken from the growing medium, such assoil and foliar application; therefore, an adequate amount of macro- and micro-nutrients, including zinc (Zn) and zinc oxide nanoparticles (ZnO-NPs), are crucial for tomato production. Zinc foliar spraying is one of the effective procedures that may improve crop quality and yield. Zinc oxide nanoparticles (ZnO-NPs) are represented as a biosafety concern for biological materials. Foliar application of Zn showed better results in increasing soluble solids(TSS), firmness, titratable acidity, chlorophyll-a, chlorophyll-b, ascorbic acid, amount of lycopene. Researchers have observed the effect of nanoparticles of zinc oxide on various crops, including tomatoes. Foliar spraying of ZnO-NPs gave the most influential results in terms of best planting parameters, namely plant height, early flowering, fruit yields as well as lycopene content. Therefore, more attention should be given to improving quantity and quality as well as nutrient use efficiency of Zn and ZnO-NPs in tomato production. Recent information on the effect of zinc nutrient foliar spraying and ZnO-NPs as a nano fertilizer on tomato productivity is reviewed in this article. Full article
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Article
Agronomic and Environmental Performances of On-Farm Compost Production and Application in an Organic Vegetable Rotation
Agronomy 2021, 11(10), 2073; https://doi.org/10.3390/agronomy11102073 (registering DOI) - 16 Oct 2021
Abstract
Horticultural crops produce huge amounts of wastes due to the large difference between total and marketable yields, and plant residues. The biological stabilization and sanitization of these organic materials directly on-farm through a simple technique such as composting may be a feasible and [...] Read more.
Horticultural crops produce huge amounts of wastes due to the large difference between total and marketable yields, and plant residues. The biological stabilization and sanitization of these organic materials directly on-farm through a simple technique such as composting may be a feasible and sustainable management strategy. The objectives of this research were to (i) estimate the sustainability and the energy impact of the on-farm composting process; (ii) to evaluate the agronomic performance and sustainability of the compost application, compared to a commercial organic fertilizer; and (iii) to identify the management and environmental hotspots. To accomplish these aims, a composting process was set up and monitored using the organic wastes and residues produced in the experimental farm. The compost produced was compared to a commercial organic fertilizer in combination with the use of cover crops in the rotation, in a two-year pepper cultivation. All processes were assessed using an energy analysis and a carbon stocks and emissions evaluation. Our findings point out that the composting process on-farm was environmentally sustainable in terms of energy consumption and carbon emissions and produced a good quality fertilizer. The use of this compost determined the best agronomic performance, especially when it was combined with other agro-ecological techniques. The yield values were slightly higher and statistically comparable with the commercial fertilizer ones. Moreover, the treatments that included the compost were most energy efficient and showed the best compromise between C emissions and C stocks. Full article
Article
Predicting the Emergence of Echinochloa crus-galli (L.) P. Beauv. in Maize Crop in Croatia with Hydrothermal Model
Agronomy 2021, 11(10), 2072; https://doi.org/10.3390/agronomy11102072 - 15 Oct 2021
Abstract
Echinochloa crus-galli (L.) P. Beauv. is the most common monocotyledonous weed in maize crops in Croatia. Crop–weed interference is influenced by weed emergence patterns, and knowledge of the timing of weed emergence is crucial for the development of an efficient integrated weed-management program. [...] Read more.
Echinochloa crus-galli (L.) P. Beauv. is the most common monocotyledonous weed in maize crops in Croatia. Crop–weed interference is influenced by weed emergence patterns, and knowledge of the timing of weed emergence is crucial for the development of an efficient integrated weed-management program. Therefore, two-year field experiments were conducted in a maize crop sown in early May in continental Croatia to determine the emergence pattern of E. crus-galli from natural seedbank. In laboratory studies, the estimated base temperature and base water potential for the Croatian ecotype of E. crus-galli were 10.8 °C and −0.97 MPa, respectively. Then, the estimated germination parameters were compared with the values embedded in the AlertInf model from Italy (Veneto) to calibrate this hydrothermal model. The estimated hydrothermal units were around 28 for the onset (10%) and 93 for the middle (50%) emergence of E. crus-galli. Our findings showed that the AlertInf model satisfactorily simulated the emergence of E. crus-galli in maize crop in Croatia (EF = 0.97 in 2019 and 0.98 in 2020), indicating its potential use in other geographical areas Full article
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Article
Assessing and Modeling Ecosystem Carbon Exchange and Water Vapor Flux of a Pasture Ecosystem in the Temperate Climate-Transition Zone
Agronomy 2021, 11(10), 2071; https://doi.org/10.3390/agronomy11102071 - 15 Oct 2021
Abstract
The rising frequency of extreme weather events and global warming are greatly challenging pastoral ecosystem productivity, particularly in the temperate climate-transition regions. While this could cause greater gross primary production (GPP) mainly contributed by the warm-season vegetation, the consequences for the dynamics of [...] Read more.
The rising frequency of extreme weather events and global warming are greatly challenging pastoral ecosystem productivity, particularly in the temperate climate-transition regions. While this could cause greater gross primary production (GPP) mainly contributed by the warm-season vegetation, the consequences for the dynamics of net ecosystem exchange (NEE) and hydrological responses (e.g., evapotranspiration, ET) on an ecosystem level are poorly known. Here, we investigated the evolution of plant phenology, nutritive value, energy balance, and carbon/water budgets of a cool-season dominated pastoral ecosystem in the temperate zone; integrating both eddy covariance (EC) flux measurement and simulation modeling-based uncertainty analysis. Throughout the two-year duration (2017–2018) of this study, the entire pasture ecosystem remained a strong carbon sink (NEE = −1.23 and −1.95 kg C m−2, respectively) with 74% and 62% of available energy loss explained by EC fluxes, respectively. The cumulative ET was 735.8 and 796.8 mm, respectively; and the overall ecosystem water use efficiency (EWUE) were calculated as 6.5 g C kg−1 water across both growing seasons. The above-ground biomass yield agreed with the cumulative GPP and was inversely correlated with grass nutritive value. The uncertainty analysis indicated that accurate EC flux gap-filling models could be constructed using support vector machine trained time-series models (NEE, R2 = 0.77, RMSE = 11.8; ET, R2 = 0.90, RMSE = 73.8). The performance benchmarking tests indicated that REddyProc-based gap-filling performance was very limiting and highly variable (NEE, R2 = 0.21–0.64; ET, R2 = 0.79–0.87), particularly for estimating NEE. Overall, the warm-season vegetation encroachment greatly filled the production gap of cool-season grasses, leading to greater cumulative NEE and EWUE on a system level, compared with those from many other reported field-crop or grassland studies using EC approaches. The complex and dynamic nature of grassland ecosystems greatly challenged the conventional REddyProc-based EC flux gap-filling performance. However, accurate machine learning models could be constructed for error/uncertainty control purposes and, thus, should be encouraged in future studies. Full article
(This article belongs to the Section Grassland and Pasture Science)
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Article
Combined Use of Calciprill and Sodium Silicate Improves Chemical Properties of Low-pH Soil
Agronomy 2021, 11(10), 2070; https://doi.org/10.3390/agronomy11102070 - 15 Oct 2021
Abstract
The highly weathered, acidic tropical soils are generally less fertile because of their low pH, high exchangeable acidity, and Al, Fe, and Mn saturations. Using soil amendments to solve the aforementioned problems is essential. To this end, Calciprill and sodium silicate are worth [...] Read more.
The highly weathered, acidic tropical soils are generally less fertile because of their low pH, high exchangeable acidity, and Al, Fe, and Mn saturations. Using soil amendments to solve the aforementioned problems is essential. To this end, Calciprill and sodium silicate are worth considering because of their high neutralizing value and dissolution to suppress exchangeable acidity and Al, Fe, and Mn hydrolysis, while at the same time increasing soil pH to improve the availability of inorganic N, available P, exchangeable base cations, and Effective Cation Exchange Capacity (ECEC). An incubation study was conducted to determine the right combination of Calciprill and sodium silicate to reduce exchangeable acidity and Al and Fe hydrolysis to improve inorganic N, available P, exchangeable base cations availability, and ECEC. Bekenu series (Typic Paleudults) was incubated with a combined use of Calciprill at 80%, 90%, and 100% Ca saturations and sodium silicate at 90, 105, 120, 135, and 150 kg ha−1 for 40, 80, and 120 days, respectively. The laboratory incubation study was carried out using a Completely Randomized Design (CRD) with triplicates to determine the aforementioned treatment effects of the combined use of Calciprill and sodium silicate on soil pH, exchangeable, Al, inorganic N, available P, electrical conductivity, exchangeable cations (K, Ca, Mg, Na, Fe, and Mn), and ECEC using standard procedures. Soils with both amendments significantly increased soil inorganic N, available P, electrical conductivity, exchangeable base cations (K, Ca, Mg, and Na), and ECEC. This was because the amendments increased soil pH by suppressing exchangeable acidity. Moreover, they transformed Al, Fe, and Mn ions into insoluble compounds such as Al and Fe hydroxides and Mn oxides because of their high inherent exchangeable cations, especially Ca and Na. This suggests that the combined use of Calciprill and sodium silicate can enhance soil productivity. The most suitable combination is 7.80 g Calciprill and 9.26 g sodium silicate (C3S5) per one kilogram soil. Additionally, the findings provide fundamental information for future greenhouse and field trials to determine the effects of the suitable combination of the amendments uncovered by this present study on soil health and crop productivity. Full article
(This article belongs to the Section Soil and Plant Nutrition)
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Article
Long-Term Fertilization and Lime-Induced Soil pH Changes Affect Nitrogen Use Efficiency and Grain Yields in Acidic Soil under Wheat-Maize Rotation
Agronomy 2021, 11(10), 2069; https://doi.org/10.3390/agronomy11102069 (registering DOI) - 15 Oct 2021
Abstract
Liming (L) is a common practice to mitigate soil acidification and enhance soil quality and crop productivity. However, in acidic soil, it is not clear how long-term application of lime and nitrogen (N)-based fertilizer affects soil chemical properties, the wheat and maize grain [...] Read more.
Liming (L) is a common practice to mitigate soil acidification and enhance soil quality and crop productivity. However, in acidic soil, it is not clear how long-term application of lime and nitrogen (N)-based fertilizer affects soil chemical properties, the wheat and maize grain yields (GY), and N-use efficiency (NUE). Thus, to investigate the effects of N-based fertilizations without L (−L) and with L (+L) on wheat and maize GY and NUE through their effects on soil chemical properties, we analyzed a 28-year field experiment in acidic soil under a wheat-maize system in South China. The analysis was carried out between 1991 and 2010 (before L) and between 2011 and 2018 (after L). We categorized the treatments into (1) no fertilizer (C); nitrogen (N); N and phosphorus (NP); N and potassium (NK); N, P and K (NPK); and NPKCR, NPK and crops residue (CR) applications (NPKCR), before L; and (2) C; N−L; N+L; NP−L; NP+L; NK−L; NK+L; NPK−L; NPK+L; NPKCR−L and NPKCR+L, after L. The effects of long-term fertilization resulted in lower soil pH by 15%, soil available K (AK) by 19%, POlsen by 6%, NO3-N by 15%, soil organic matter (SOM) by 16%, total N by 16%, and C:N ratio by 13% in −L soil than in +L soil. However, the accumulation of NH4+-N was higher by 40% in −L soil than in +L soil. Wheat and maize GY, N recovery efficiency (REN), and N partial factor productivity (PEPN) were more adversely affected by 8-year fertilizations in −L compared with fertilizations before L and in +L primarily because of the significantly decreased soil pH. Conversely, improvements in wheat and maize yields, REN, and PFPN by 8-year fertilizations in +L were related to increasing soil pH, exchangeable base cations such as Ca2+, Mg2+, and the alleviated toxicity of Al3+. Overall, improvement of GY and NUE from the acidified soil in South China requires the long-term integrated use of fertilizer (NPK), retention of CR, and the +L (i.e., NPKCR+L). Full article
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Article
Exploration of Machine Learning Approaches for Paddy Yield Prediction in Eastern Part of Tamilnadu
Agronomy 2021, 11(10), 2068; https://doi.org/10.3390/agronomy11102068 - 15 Oct 2021
Viewed by 68
Abstract
Agriculture is the principal basis of livelihood that acts as a mainstay of any country. There are several changes faced by the farmers due to various factors such as water shortage, undefined price owing to demand–supply, weather uncertainties, and inaccurate crop prediction. The [...] Read more.
Agriculture is the principal basis of livelihood that acts as a mainstay of any country. There are several changes faced by the farmers due to various factors such as water shortage, undefined price owing to demand–supply, weather uncertainties, and inaccurate crop prediction. The prediction of crop yield, notably paddy yield, is an intricate assignment owing to its dependency on several factors such as crop genotype, environmental factors, management practices, and their interactions. Researchers are used to predicting the paddy yield using statistical approaches, but they failed to attain higher accuracy due to several factors. Therefore, machine learning methods such as support vector regression (SVR), general regression neural networks (GRNNs), radial basis functional neural networks (RBFNNs), and back-propagation neural networks (BPNNs) are demonstrated to predict the paddy yield accurately for the Cauvery Delta Zone (CDZ), which lies in the eastern part of Tamil Nadu, South India. The performance of each developed model is examined using assessment metrics such as coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), mean squared error (MSE), mean absolute percentage error (MAPE), coefficient of variance (CV), and normalized mean squared error (NMSE). The observed results show that the GRNN algorithm delivers superior evaluation metrics such as R2, RMSE, MAE, MSE, MAPE, CV, and NSME values about 0.9863, 0.2295 and 0.1290, 0.0526, 1.3439, 0.0255, and 0.0136, respectively, which ensures accurate crop yield prediction compared with other methods. Finally, the performance of the GRNN model is compared with other available models from several studies in the literature, and it is found to be high while comparing the prediction accuracy using evaluation metrics. Full article
Article
Assessing a Removable Mini-Lysimeter for Monitoring Crop Evapotranspiration Using a Well-Established Large Weighing Lysimeter: A Case Study for Barley and Potato
Agronomy 2021, 11(10), 2067; https://doi.org/10.3390/agronomy11102067 - 15 Oct 2021
Viewed by 151
Abstract
Further research is required on the measurement of crop evapotranspiration (ETc) to produce new or updated crop coefficients for a large number of crops using accurate weighing lysimeters. However, large weighing lysimeters are sometimes expensive and are not portable, and different [...] Read more.
Further research is required on the measurement of crop evapotranspiration (ETc) to produce new or updated crop coefficients for a large number of crops using accurate weighing lysimeters. However, large weighing lysimeters are sometimes expensive and are not portable, and different prototypes of small-sized lysimeters may be a feasible alternative. This study evaluated the performance of a removable mini-lysimeter model to measure ETc and derive crop coefficients using a long-established large precision weighing lysimeter over a two-year period. The study was conducted during the 2017 and 2018 barley and potato growing seasons, respectively, at a lysimeter facility located in Albacete (southeast Spain). ETc values were determined using daily mass change in the lysimeters. Irrigation was managed to avoid any water stress. In the barley season, the mini-lysimeter underestimated the seasonal ETc by 2%, the resulting errors in barley ETc estimation were an MBE of −0.070 mm d−1 and an RMSE of ±0.289 mm d−1. In the potato season, the mini-lysimeter overestimated the cumulative ETc by 5%, the resulting errors in potato ETc measurement were an MBE of 0.222 mm d−1 and an RMSE of ±0.497 mm d−1. The goodness of fit indicators showed a good agreement between the large and mini-lysimeter barley and potato ETc measurements at daily time step. Single (Kc) and dual crop coefficients (Kcb, crop transpiration + Ke, soil evaporation) were derived from the lysimeter measurements, the grass reference evapotranspiration (ETo) and the FAO56 dual Kc approach; after temperate standard climate adjustment, mid-season values were Kc mid (std) = 1.05 and Kcb mid (std) = 1.00 for barley; and Kc mid (std) = 1.06 and Kcb mid (std) = 1.02 for potato. The good agreement found between Kcb values and fc will allow barley and potato water requirements to be accurately estimated. Full article
(This article belongs to the Special Issue Modernization and Optimization of Irrigation Systems)
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Article
Gliding Arc Plasma Treatment of Maize (Zea mays L.) Grains Promotes Seed Germination and Early Growth, Affecting Hormone Pools, but Not Significantly Photosynthetic Parameters
Agronomy 2021, 11(10), 2066; https://doi.org/10.3390/agronomy11102066 (registering DOI) - 14 Oct 2021
Viewed by 120
Abstract
Maize grains (Zea mays convar. Indentata Sturt.) were treated with non-thermal plasma, where Gliding Arc plasma discharge at an atmospheric pressure was used (working gas: Air; time duration: 0 s, 180 s, 300 s, 600 s). The experiment was conducted at a [...] Read more.
Maize grains (Zea mays convar. Indentata Sturt.) were treated with non-thermal plasma, where Gliding Arc plasma discharge at an atmospheric pressure was used (working gas: Air; time duration: 0 s, 180 s, 300 s, 600 s). The experiment was conducted at a temperature of 18 °C, light/dark 12/12 h, and a light intensity of 100 µmol/m2s. Seed germination, seedling growth, photosynthetic parameters, and hormone (abscisic acid, jasmonic acid, salicylic acid, indole-3-acetic acid, and cytokinin) contents were measured. The highest stimulation of seed germination (to 141%), root length (to 221%), shoot length (to 298%), and root weight (to 122%) in comparison with the control was recorded after Gliding Arc plasma treatment for 600 s. The photochemical and non-photochemical Chl fluorescence parameters were not significantly affected by Gliding Arc plasma treatment. In contrast, hormonal pools in maize were significantly affected. The short-term plasma treatment (180 s) was associated with a decrease in the stress hormones abscisic acid, salicylic acid, jasmonic acid, and jasmonate isoleucine, while indole-3-acetic acid and cytokinin precursors were elevated. Longer-term treatment (300 s, 600 s) had an opposite effect—an elevation of abscisic acid, jasmonic acid, and jasmonate isoleucine as well as active cytokinins. The content of auxin decreased. Gliding plasma treatment may significantly affect maize physiology, dependent on the treatment duration. Full article
(This article belongs to the Special Issue Applied High-Voltage Plasma Technologies in Agricultural Industry)
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Article
Comparative Effects of Bio-Wastes in Combination with Plant Growth-Promoting Bacteria on Growth and Productivity of Okra
Agronomy 2021, 11(10), 2065; https://doi.org/10.3390/agronomy11102065 - 14 Oct 2021
Viewed by 147
Abstract
Plant growth-promoting rhizobacteria with multiple growth-promoting traits play a significant role in soil to improve soil health, crop growth and yield. Recent research studies have focused on the integration of organic amendments with plant growth-promoting rhizobacteria (PGPR) to enhance soil fertility and reduce [...] Read more.
Plant growth-promoting rhizobacteria with multiple growth-promoting traits play a significant role in soil to improve soil health, crop growth and yield. Recent research studies have focused on the integration of organic amendments with plant growth-promoting rhizobacteria (PGPR) to enhance soil fertility and reduce the hazardous effects of chemical fertilizers. This study aims to evaluate the integrated application of biochar, compost, fruit and vegetable waste, and Bacillus subtilis (SMBL 1) to soil in sole application and in combined form. The study comprises eight treatments—four treatments without inoculation and four treatments with SMBL 1 inoculation in a completely randomized design (CRD), under factorial settings with four replications. The results indicate that the integrated treatments significantly improved okra growth and yield compared with sole applications. The integration of SMBL 1 with biochar showed significant improvements in plant height, root length, leaf chlorophyll a and b, leaf relative water content, fruit weight, diameter and length by 29, 29, 50, 53.3, 4.3, 44.7 and 40.4%, respectively, compared with control. Similarly, fruit N, P and K contents were improved by 33, 52.7 and 25.6% and Fe and Zn in shoot were 37.1 and 35.6%, respectively, compared with control. The results of this study reveal that the integration of SMBL 1 with organic amendments is an effective approach to the sustainable production of okra. Full article
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Article
Testing Combined Effect of Amendments and Inoculation with Bacteria for Improving Phytostabilisation of Smelter Waste Extremely Contaminated with Trace Elements
Agronomy 2021, 11(10), 2064; https://doi.org/10.3390/agronomy11102064 - 14 Oct 2021
Viewed by 127
Abstract
Smelter waste deposits pose environmental and health threats and require remediation actions. Phytostabilisation techniques, based on soil amendments, help to establish plant cover and limit the secondary emission of potentially toxic trace elements. However, methods to optimize their effectiveness are needed. The application [...] Read more.
Smelter waste deposits pose environmental and health threats and require remediation actions. Phytostabilisation techniques, based on soil amendments, help to establish plant cover and limit the secondary emission of potentially toxic trace elements. However, methods to optimize their effectiveness are needed. The application of bacterial inoculants in combination with soil amendments in the remediation of soils and wastes contaminated with metals still has not been extensively tested. Therefore, the aim of this study was to determine the effectiveness of indigenous (Streptomyces sp., Pseudomonas sp.) and foreign (Streptomyces costaricanus) strains of bacteria in supporting grass growth on extremely contaminated waste slag. They were applied alone and in combination with compost mixed with phosphate fertilizer or iron oxide. The tested strains improved plant growth and increased plant availability of phosphorus. The interaction of the soil amendments and some bacterial strains also stimulated a decrease in the extractability of metals, likely through the phosphate-induced precipitation of lead. Our data show that the effectiveness of soil amendments in the phytostabilisation of heavily polluted smelter deposits can be enhanced by plant growth-promoting bacteria (PGPB). Full article
(This article belongs to the Special Issue New Phytoremediation in Trace Elements Contaminated Soils)
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Article
The Role of Water Content in the Casing Layer for Mushroom Crop Production and the Occurrence of Fungal Diseases
Agronomy 2021, 11(10), 2063; https://doi.org/10.3390/agronomy11102063 - 14 Oct 2021
Viewed by 121
Abstract
Mushroom cultivation requires effective control of environmental cues to obtain the best yield and high quality. The impact of water content in the casing layer on mushroom yield and the incidence of two of the most important diseases in the mushroom growing farms, [...] Read more.
Mushroom cultivation requires effective control of environmental cues to obtain the best yield and high quality. The impact of water content in the casing layer on mushroom yield and the incidence of two of the most important diseases in the mushroom growing farms, dry bubble and cobweb diseases, was evaluated. Different initial water content in the casing and two alternative irrigation programs applied (light or moderate irrigation) were the agronomic parameters under study during five separate button mushroom crop trials. Higher initial humidity content in the casing layer reported a larger yield, with a fewer number of basidiomes but heavier, while no correlation to the dry matter content or the colour of the basidiomes was noted. The incidence of dry bubble disease was not conditioned by the water content of the casing layer, at the high moisture levels established in the study. In the case of Cladobotryum mycophilum, the lower moisture level of the casing layer reported more incidence of cobweb disease, and subsequently harmful yield losses. According to the results obtained, the right management of the moisture level in the casing materials could promote crop yield and preclude the significant impact of dry bubble and cobweb diseases. Full article
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Article
Dual Crop Coefficient Approach in Vitis vinifera L. cv. Loureiro
Agronomy 2021, 11(10), 2062; https://doi.org/10.3390/agronomy11102062 (registering DOI) - 14 Oct 2021
Viewed by 207
Abstract
Vineyard irrigation management in temperate zones requires knowledge of the crop water requirements, especially in the context of climate change. The main objective of this work was to estimate the crop evapotranspiration (ETc) of Vitis vinifera cv. Loureiro for local conditions, [...] Read more.
Vineyard irrigation management in temperate zones requires knowledge of the crop water requirements, especially in the context of climate change. The main objective of this work was to estimate the crop evapotranspiration (ETc) of Vitis vinifera cv. Loureiro for local conditions, applying the dual crop coefficient approach. The study was carried out in a vineyard during two growing seasons (2019–2020). Three irrigation treatments, full irrigation (FI), deficit irrigation (DI), and rainfed (R), were considered. The ETc was estimated using the SIMDualKc model, which performs the soil water balance with the dual Kc approach. This balance was performed by calculating the basal coefficients for the grapevine (Kcb crop) and the active soil ground cover (Kcb gcover), which represent the transpiration component of ETc and the soil evaporation coefficient (Ke). The model was calibrated and validated by comparing the simulated soil water content (SWC) with the soil water content data measured with frequency domain reflectometry (FDR). A suitable adjustment between the simulated and observed SWC was obtained for the 2019 R strategy when the model was calibrated. As for the vine crop, the best fit was obtained for Kcb full ini = 0.33, Kcb full mid = 0.684, and Kcb full end = 0.54. In this sense, the irrigation schedule must adjust these coefficients to local conditions to achieve economically and environmentally sustainable production. Full article
(This article belongs to the Special Issue Papers from AgEng2021)
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Article
Evaluation of Metabolomic Profile and Growth of Moringa oleifera L. Cultivated with Vermicompost under Different Soil Types
Agronomy 2021, 11(10), 2061; https://doi.org/10.3390/agronomy11102061 - 14 Oct 2021
Viewed by 119
Abstract
Moringa oleifera is a highly versatile plant with potential use in the agro-food and biochemical industry. The goals of this study were to evaluate the effect of chemical fertilization and vermicompost on plant growth, and to analyze the metabolomic profile of M. oleifera [...] Read more.
Moringa oleifera is a highly versatile plant with potential use in the agro-food and biochemical industry. The goals of this study were to evaluate the effect of chemical fertilization and vermicompost on plant growth, and to analyze the metabolomic profile of M. oleifera crops cultivated over agricultural and native soils. The extracts were obtained from 90-day-old leaves via extraction with a hydroalcoholic mixture. Multivariate data analyses, such as principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA), were used to differentiate the distribution of leaf metabolites according to the soils or types of fertilizers used for the cultivation of Moringa oleifera. The results indicated that there was no significant effect on parameters such as plant height, root length and dry weight of leaves (p < 0.05). UPLC-ESI-MS/MS analysis of leaf extracts revealed a wide range of flavonoids, alkaloids and organic acids. The results of PCA and PLS-DA confirmed that the type of fertilizer had an effect on the metabolomic profile of M. oleifera leaves. The application of vermicompost induced changes in the metabolomic profile, but not in the morphometric variables of Moringa oleifera. These results are important for metabolite production via organic cultures and over different soil types in the industrialization of Moringa. Full article
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Article
Lignocellulosic Biomass Production and Persistence of Perennial Grass Species Grown in Mediterranean Marginal Lands
Agronomy 2021, 11(10), 2060; https://doi.org/10.3390/agronomy11102060 - 14 Oct 2021
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Abstract
Biomass production in marginal lands represents one of the most challenging and promising alternatives to sustainably produce biofuels. Native species seem to be the most adequate option to obtain a profitable output when low-input techniques are applied, and biomass is grown in depleted [...] Read more.
Biomass production in marginal lands represents one of the most challenging and promising alternatives to sustainably produce biofuels. Native species seem to be the most adequate option to obtain a profitable output when low-input techniques are applied, and biomass is grown in depleted soils and harsh climatic conditions. In this study, a 5-year field trial in the island of Majorca served to investigate different autochthonous and naturalized Mediterranean perennial grasses as novel candidate lignocellulosic bioenergy crops for the semi-arid Mediterranean area and compare them with commercial ones (both Mediterranean and non-Mediterranean). Species and growing season had a significant effect on biomass production, perennialism and biomass quality. Arundo donax (winter crops) and Piptatherum miliaceum (autumn crops) performed better than the commercial species tested (Panicum virgatum for winter crops and Festuca arundinacea for autumn crops) in biomass production and perennialism. In terms of biomass quality, Panicum virgatum was the best species, having high structural content (mainly cellulose and hemicellulose), low non-structural content and the lowest ash. However, Ampelodesmos mauritanicus and Arundo donax rendered similar results, with no significant difference in terms of cellulose production for this latter but with higher lignin content. For the autumn species, Festuca arundinacea was the species with the best biomass quality but with the highest ash production for all the species considered. Hence, both for winter or autumn regimes, native or naturalized plants seem to be better suited than the commercial commonly used for biomass production with energy-producing purposes. Further research must be conducted in terms of seed biology and physiology, seedbed preparation methods, sowing time, seedling density and weed control before they can firmly be proposed as adequate alternatives for energy purposes. Full article
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Article
Cold Stress during Flowering Alters Plant Structure, Yield and Seed Quality of Different Soybean Genotypes
Agronomy 2021, 11(10), 2059; https://doi.org/10.3390/agronomy11102059 - 13 Oct 2021
Viewed by 157
Abstract
The objective of the study was to evaluate the effect of cold stress at flowering stage on plant structure, yield and chemical composition of seeds of 15 soybean cultivars. The study was conducted in 2019–2020, using the complete randomization method, in three replications. [...] Read more.
The objective of the study was to evaluate the effect of cold stress at flowering stage on plant structure, yield and chemical composition of seeds of 15 soybean cultivars. The study was conducted in 2019–2020, using the complete randomization method, in three replications. Fifteen soybean cultivars belonging to three maturity groups: early (EC), middle-early (MC) and late (LC) cultivars were included. Weekly cold stress (17/13 °C day/night) was applied at plant flowering stage. In the control treatment, plants were kept under natural conditions (24/17 °C day/night). Our research showed that cold stress negatively influenced the elements of plant structure: height, number of nodes, stem dry mass, number and weight of pods, number and weight of seeds per plant, as well as yield of soybean seeds, reducing it on average by 24%, as compared to the control treatment. The highest yield decrease was found in LC cultivars (31.2%), while a smaller and similar one in EC and MC cultivars (by 19.7 and 20.1%, respectively). Significant varietal differences were found for plant biometric traits and seed yield. EC cultivars had the lowest set first pod, as well as the lowest number of nodes, number of pods and seeds, pod and seed weight per plant, and seed yield. MC cultivars had the highest set first pod, and the smallest stem DM and seed yield average by 29.2% higher compared to EC cultivars. LC cultivars had the highest stem DM, number of pods and seeds, and pod and seed weight per plant compared to the other cultivar groups, and yield by 22.8% higher compared to EC cultivars. The experimental factors significantly affected crude protein, crude fat, and crude ash content, while they did not differentiate water-soluble carbohydrate and crude fiber content. Cold stress at the flowering stage caused a significant increase in protein content (by 4.1% on average) and ash content (by 3.8%) and a decrease in fat concentration (by 6.9%) in soybean seeds. Differences in nutrient content among cultivars were a genetic trait not related to cultivar maturity. Full article
Article
Response of Bromus valdivianus (Pasture Brome) Growth and Physiology to Defoliation Frequency Based on Leaf Stage Development
Agronomy 2021, 11(10), 2058; https://doi.org/10.3390/agronomy11102058 - 13 Oct 2021
Viewed by 140
Abstract
The increase in drought events due to climate change have enhanced the relevance of species with greater tolerance or avoidance traits to water restriction periods, such as Bromus valdivianus Phil. (B. valdivianus). In southern Chile, B. valdivianus and Lolium perenne L. [...] Read more.
The increase in drought events due to climate change have enhanced the relevance of species with greater tolerance or avoidance traits to water restriction periods, such as Bromus valdivianus Phil. (B. valdivianus). In southern Chile, B. valdivianus and Lolium perenne L. (L. perenne) coexist; however, the pasture defoliation criterion is based on the physiological growth and development of L. perenne. It is hypothesised that B. valdivianus needs a lower defoliation frequency than L. perenne to enhance its regrowth and energy reserves. Defoliation frequencies tested were based on B. valdivianus leaf stage 2 (LS-2), leaf stage 3 (LS-3), leaf stage 4 (LS-4) and leaf stage 5 (LS-5). The leaf stage development of Lolium perenne was monitored and contrasted with that of B. valdivianus. The study was conducted in a glasshouse and used a randomised complete block design. For Bromus valdivianus, the lamina length, photosynthetic rate, stomatal conductance, tiller number per plant, leaf area, leaf weights, root growth rate, water-soluble carbohydrates (WSCs) and starch were evaluated. Bromus valdivianus maintained six live leaves with three leaves growing simultaneously. When an individual tiller started developing its seventh leaf, senescence began for the second leaf (the first relevant leaf for photosynthesis). Plant herbage mass, the root growth rate and tiller growth were maximised at LS-4 onwards. The highest leaf elongation rate, evaluated through the slope of the lamina elongation curve of a fully expanded leaf, was verified at LS-4. The water-soluble carbohydrates (WSCs) increased at LS-5; however, no statistical differences were found in LS-4. The LS-3 and LS-2 treatments showed a detrimental effect on WSCs and regrowth. The leaf photosynthetic rate and stomatal conductance diminished while the leaf age increased. In conclusion, B. valdivianus is a ‘six-leaf’ species with leaf senescence beginning at LS-4.25. Defoliation at LS-4 and LS-5 was optimum for plant regrowth, maximising the aboveground plant parameters and total WSC accumulation. The LS-4 for B. valdivianus was equivalent to LS-3.5 for L. perenne. No differences related to tiller population in B. valdivianus were found in the different defoliation frequencies. Full article
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Article
Nitrogen Mineralization, Soil Microbial Biomass and Extracellular Enzyme Activities Regulated by Long-Term N Fertilizer Inputs: A Comparison Study from Upland and Paddy Soils in a Red Soil Region of China
Agronomy 2021, 11(10), 2057; https://doi.org/10.3390/agronomy11102057 - 13 Oct 2021
Viewed by 199
Abstract
A long-term experiment (38 years) was conducted to elucidate the effects of long-term N addition on the net N mineralization in both paddy and upland soils, based on their initial soil N status, with and in connection with soil microbial biomass and N [...] Read more.
A long-term experiment (38 years) was conducted to elucidate the effects of long-term N addition on the net N mineralization in both paddy and upland soils, based on their initial soil N status, with and in connection with soil microbial biomass and N cycling extracellular enzyme activities. Two treatments without N addition CK (No fertilizer) and K (inorganic potassium fertilizer) and two treatments with N addition (inorganic nitrogen fertilizer) and NK (inorganic nitrogen and potassium fertilizer) were placed in incubation for 90 days. Results showed that the total N and soil organic carbon (SOC) contents were higher in the treatments with N application compared to the treatments without N in both paddy and upland soils. The SOC content of paddy soil was increased relative to upland soil by 56.2%, 45.7%, 61.1% and 62.2% without N (CK, K) and with N (N and NK) treatments, respectively. Site-wise, total N concentration in paddy soil was higher by 0.06, 0.10, 0.57 and 0.60 times under the CK, K, N and NK treatments, respectively, compared with upland soil. In paddy soil, soil microbial biomass nitrogen (SMBN) was higher by 39.6%, 2.77%, 29.5% and 31.4%, and microbial biomass carbon (SMBC) was higher by 11.8%, 11.9%, 10.1% and 12.3%, respectively, in CK, K, N and NK treatment, compared with upland soil. Overall, compared to upland soil, the activities of leucine-aminopeptidase (LAP) were increased by 31%, 18%, 20% and 11%, and those of N-acetyl-b-D-glucosaminidase (NAG) were increased by 70%, 21%, 13% and 18% by CK, K, N and NK treatments, respectively, in paddy soil. A significantly linear increase was found in the NO3-N and NH4+-N concentrations during the 90 days of the incubation period in both soils. NK treatment showed the highest N mineralization potential (No) along with mineralization rate constant, k (NMR) at the end of the incubation. SMBC, SMBN, enzyme activities, NO3-N and NH4+-N concentrations and the No showed a highly significant (p ≤ 0.05) positive correlation. We concluded that long-term N addition accelerated the net mineralization by increasing soil microbial activities under both soils. Full article
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Article
Changes in Photosynthetic Pigments Content in Non-Transformed and AtCKX Transgenic Centaury (Centaurium erythraea Rafn) Shoots Grown under Salt Stress In Vitro
Agronomy 2021, 11(10), 2056; https://doi.org/10.3390/agronomy11102056 - 13 Oct 2021
Viewed by 139
Abstract
The effects of graded sodium chloride (NaCl) concentrations (0-, 50-, 100-, 150-, and 200-mM) on photosynthetic pigment contents in in vitro grown shoots of important medicinal plant species (Centaurium erythraea Rafn) were investigated. Non-transformed, one AtCKX1 and two AtCKX2 transgenic centaury lines, [...] Read more.
The effects of graded sodium chloride (NaCl) concentrations (0-, 50-, 100-, 150-, and 200-mM) on photosynthetic pigment contents in in vitro grown shoots of important medicinal plant species (Centaurium erythraea Rafn) were investigated. Non-transformed, one AtCKX1 and two AtCKX2 transgenic centaury lines, with altered cytokinin profiles, were used in this study. The chlorophyll (Chl) and carotenoid contents differed in the non-transformed and transgenic lines. In general, salinity significantly reduced the Chl a and Chl b contents in comparison to the NaCl-free medium. The lowest Chl content was observed in AtCKX2 transgenic shoots grown on all the culture media. The total carotenoid content was increased in shoots of non-transformed and both AtCKX2 transgenic lines grown in 50-mM NaCl. On the other hand, in concentrations >50-mM NaCl, the total carotenoid content was decreased in all analysed centaury shoots. The Chl a/Chl b ratio in all the shoots increased progressively in the graded NaCl concentrations. Contrarily, the addition of NaCl in the culture medium reduced the Chl/carotenoid ratio in centaury shoots. Taken together, the results of this study partly explained the mode of centaury plant adaptations to salt stress in vitro. Thus, the results on centaury shoots confirmed that the determination of the photosynthetic pigment contents can be a very useful non-destructive screening method in order to discriminate susceptible and resistant plant species/lines to salt stress conditions. Full article
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Article
Potato Yield Response and Seasonal Nitrate Leaching as Influenced by Nitrogen Management
Agronomy 2021, 11(10), 2055; https://doi.org/10.3390/agronomy11102055 - 13 Oct 2021
Viewed by 204
Abstract
Nitrate leaching is of great environmental concern, particularly with potatoes grown on sandy soils. This 3-year study evaluated the effect of three N rates (100, 150, and 200 kg ha−1) of single applications of polymer-coated urea (PCU) and a 75% PCU [...] Read more.
Nitrate leaching is of great environmental concern, particularly with potatoes grown on sandy soils. This 3-year study evaluated the effect of three N rates (100, 150, and 200 kg ha−1) of single applications of polymer-coated urea (PCU) and a 75% PCU + 25% urea mixture, plus a conventional split application of 200 kg N ha−1 of a 50% ammonium sulfate + 50% calcium ammonium nitrate mixture (CONV) on NO3-N leaching, potato yield, and N uptake under irrigated and non-irrigated conditions on a sandy soil in Quebec (Canada). Fertilizer N application increased growing season NO3-N leaching only under irrigation. On average, irrigation increased seasonal NO3-N leaching by 52%. Under irrigated conditions, PCU reduced NO3-N leaching compared to PCU + urea. However, both PCU and PCU + urea significantly increased NO3-N leaching compared to the CONV at the equivalent N rate of 200 kg N ha−1. This was attributed to the timing of soil N availability and deep-water percolation. Total (TY) and marketable (MY) yields in the CONV were similar to those in the PCU applied at the equivalent N rate of 200 kg N ha−1. Despite lower plant N uptake, PCU resulted in greater TY and MY compared to PCU + urea. Residual soil inorganic N was greater for PCU and PCU + urea compared to the CONV, providing evidence that PCU products have the potential to increase NO3-N leaching after the growing season. In this study, PCU was an agronomically and environmentally better choice than PCU + urea. The results also showed that the efficiency of PCU to reduce seasonal NO3-N leaching may vary according to the timing of precipitation and irrigation. Full article
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Article
Genetic Diversity and Molecular Characterization of Worldwide Prairie Grass (Bromus catharticus Vahl) Accessions Using SRAP Markers
Agronomy 2021, 11(10), 2054; https://doi.org/10.3390/agronomy11102054 - 13 Oct 2021
Viewed by 216
Abstract
Prairie grass (Bromus catharticus Vahl) is an important grass species that could be used in the production systems of certified seed and high-quality forage for grazing ruminants. In the present research, a sequence-related amplified polymorphism (SRAP) marker was employed to detect the [...] Read more.
Prairie grass (Bromus catharticus Vahl) is an important grass species that could be used in the production systems of certified seed and high-quality forage for grazing ruminants. In the present research, a sequence-related amplified polymorphism (SRAP) marker was employed to detect the genetic variability and structure of 80 prairie grass accessions from all over the world. Altogether, 460 reliable bands were amplified from 47 SRAP primer pairs with 345 (75%) polymorphic bands. The average values of discrimination power (DP) and polymorphic information content (PIC) were 0.753 and 0.317, respectively. Both the UPGMA clustering and PCoA analyses grouped the 80 accessions into five clusters, whereas the STRUCTURE analysis showed that 80 prairie grass accessions possessed three genetic memberships (K = 3). The results of the Mantel test showed that the distance matrix has a moderately positive correlation between the morphological and molecular data sets (r = 0.524). A poor genetic differentiation (Fst = 0.045) was discovered among the six geo-groups of accessions. Besides, the highest intragroup genetic diversity was found in the North America group (He = 0.335). This study provides a genetic structure and diversity case for prairie grass, and supplies new clues for the study and utilization of prairie grass. Full article
(This article belongs to the Section Grassland and Pasture Science)
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Article
Effect of Pesticide and Humic Preparation on the Soil Structure during Pea and Chickpea Cultivation
Agronomy 2021, 11(10), 2053; https://doi.org/10.3390/agronomy11102053 - 13 Oct 2021
Viewed by 222
Abstract
The article presents the results of a 3-year experiment to study the soil structure with the combined use of insecticides and a humic preparation. Crops were peas (Pisum sativum) and chickpeas (Cicer arietinum). The experiment was carried out in [...] Read more.
The article presents the results of a 3-year experiment to study the soil structure with the combined use of insecticides and a humic preparation. Crops were peas (Pisum sativum) and chickpeas (Cicer arietinum). The experiment was carried out in 2019–2021 at the experimental fields of the Federal Rostov Agrarian Scientific Center, located in the Rostov region in the south of the European part of Russia (47°21′ N, 39°52′ E). Soil was Calcic Chernozem Loamic. The studies were carried out both without fertilization and with the use of mineral fertilizers (N40P40K40). Sowings of leguminous crops were treated with a mixture of insecticides and a humic preparation in the phase of bean formation. The humic preparation BIO-Don10 was obtained according to the authors’ technology by alkaline extraction from vermicompost—a product of manure processing by compost worms of the Eisenia foetida species. The preparation contains salts of humic acids and fulvic acids in the amount of 1.9 g/L; the concentration in the mixture with the insecticide was 0.002%. An increase in the structure and water resistance coefficients was observed. A decrease in the block fraction and an increase in the total number of agronomically valuable aggregates were substantiated. It was found that in the cultivation of legumes, the application of mineral fertilizers had a negative effect on the structure of the soil, while, when using pesticides, the structure was preserved better by the end of the growing season. The revealed patterns can be associated with the activity of microorganisms participating in the hydrolysis of organic compounds that stabilize soil aggregates. Full article
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Article
Physicochemical Changes in Loam Soils Amended with Bamboo Biochar and Their Influence in Tomato Production Yield
Agronomy 2021, 11(10), 2052; https://doi.org/10.3390/agronomy11102052 - 13 Oct 2021
Viewed by 245
Abstract
Soil degradation and water stress in Costa Rica challenge the production of highly sensitive crops. This work is aimed at evaluating the physical and chemical changes in sandy loam (SL) and a silt loam (SiL) soil when amended with bamboo biochar while estimating [...] Read more.
Soil degradation and water stress in Costa Rica challenge the production of highly sensitive crops. This work is aimed at evaluating the physical and chemical changes in sandy loam (SL) and a silt loam (SiL) soil when amended with bamboo biochar while estimating the enhancement of tomato productivity. Biochar, obtained from Guadua Angustifolia bamboo feedstock, was mixed into sieved bulk soil substrate from the topsoil, from Andosol and Umbrisol groups, at application rates of 1, 2.5, and 5% (dry mass). Physicochemical and morphological properties of biochar such as pH, hydrophobicity, scanning electron microscopy images, helium picnometry, specific surface area by the Brunauer–Emmett–Teller (BET) method, CHNS, and ash content were determined. Soil hydrophobicity, acidity, electrical conductivity, cation exchange capacity and water retention, available water content, and air capacity were analyzed for the amended soils. Tomato yield was quantified after a harvest period of two months. The admixture of biochar did not significantly increase soil cation exchange capacity but increased water retention in the range of available water content. Class A (>200 g) tomato yield increased 350% in the SL and 151% in the SiL. Class B (100–200 g) tomato yields increased 27% in the SL but decreased about 30% in the SiL. Tomato yield response seems attributable to variation of water retention capacity, available water content, and air capacity. These results support the use of adapted water management strategies for tomato production based on soil physical changes of biochar. Full article
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Article
Management of Iron and Manganese Toxicities of Lentil Crops Grown in Central Chile
Agronomy 2021, 11(10), 2051; https://doi.org/10.3390/agronomy11102051 - 13 Oct 2021
Viewed by 231
Abstract
Iron (Fe) and manganese (Mn) toxicity is a widespread problem in lentil production in the coastal dryland of Chile. Increasing the soil pH by liming with CaCO3 or incrementing grain yields through nitrogen fertilization can help the plants to reduce metal concentration. [...] Read more.
Iron (Fe) and manganese (Mn) toxicity is a widespread problem in lentil production in the coastal dryland of Chile. Increasing the soil pH by liming with CaCO3 or incrementing grain yields through nitrogen fertilization can help the plants to reduce metal concentration. Thus, the main objective of this work was to evaluate two different fertilization strategies (lime (CaCO3) and nitrogen (N) additions) to reduce Fe and Mn toxicities in lentils. Lentils grown under field conditions with the highest Fe and Mn concentrations showed toxicity symptoms, but without grain yield reductions. In a pot experiment using the same soil as in the field with toxicity symptoms, the dry matter (DM) produced at the end of the trial was higher in the plants that received N while the lowest DM production was recorded in those plants treated with lime. In particular, higher root DM sustained the growth of the N-fertilized shoots, which also positively affected the grain yields being 33% higher than the control treatment (no fertilization addition). In the plants fertilized with N, the Fe and Mn levels in the shoots were lower than the control plants and those grown in soils treated with lime, but showed higher concentrations of Fe and Mn in roots. In parallel, roots exhibited high concentrations of Fe and Mn that were 13- and 9-fold higher than in the shoots. Additionally, a significant decrease of 29% in Mn concentration in the grains of plants treated with N was reported. Overall, our results suggest that an increase in DM of lentils by the addition of N can reduce the Mn concentration on leaves to a level that is likely under the threshold that causes toxicity in plant tissues. Finally, we conclude that the increase of Fe and Mn in the roots may be connected to the reduction of these metals on leaves. Full article
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Article
Effect of Substrate Flow Rate on Nutrient Uptake and Use Efficiency in Hydroponically Grown Swiss Chard (Beta vulgaris L. ssp. cicla ‘Seiyou Shirokuki’)
Agronomy 2021, 11(10), 2050; https://doi.org/10.3390/agronomy11102050 - 13 Oct 2021
Viewed by 294
Abstract
Unlike in soil culture, a substrate (nutrient solution) in a hydroponics system can flow, and this can affect both nutrient uptake and plant growth. In this study, we hydroponically cultivated Swiss chard (Beta vulgaris L. ssp. cicla) under different flow rates [...] Read more.
Unlike in soil culture, a substrate (nutrient solution) in a hydroponics system can flow, and this can affect both nutrient uptake and plant growth. In this study, we hydroponically cultivated Swiss chard (Beta vulgaris L. ssp. cicla) under different flow rates to analyze changes in the growth, nutrient uptake, and nutrient use efficiency. When the flow rate was intensified from 2 to 4 L/min, leaf area, the fresh weight, dry weight, and root length increased. However, when the flow rate was increased from 4 to 8 L/min, values of these growth parameters decreased. The nutrient uptake had a similar trend relative to the growth parameters and nutrient use efficiency of macronutrient elements, increased as the flow rate increased. This indicates that the flow rate affects plant growth by influencing the nutrient uptake, and an increase in the flow rate can aid in improving nutrient use efficiency. In hydroponics, regulating the flow rate at a reasonable volume is recommended to increase yield by enhancing nutrient use efficiency, but too intensive a flow rate may cause excessive physical stimulation to plants and inhibit their growth. Therefore, it is important to choose an appropriate substrate flow rate for optimal hydroponics production. Full article
(This article belongs to the Collection Nutrition Management of Hydroponic Vegetable Crops)
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Article
The Promotion of Festuca sinensis under Heavy Metal Treatment Mediated by Epichloë Endophyte
Agronomy 2021, 11(10), 2049; https://doi.org/10.3390/agronomy11102049 - 12 Oct 2021
Viewed by 213
Abstract
To more clearly clarify the relationship between the Epichloë endophyte and its host, F. sinensis, the effects of Epichloë endophyte on F. sinensis performance under heavy metal treatment was investigated. The growth performance and physiology variations of F. sinensis with (E+) and [...] Read more.
To more clearly clarify the relationship between the Epichloë endophyte and its host, F. sinensis, the effects of Epichloë endophyte on F. sinensis performance under heavy metal treatment was investigated. The growth performance and physiology variations of F. sinensis with (E+) and without the endophyte (E−) were evaluated after they were subjected to Zn2+ and Cd2+ treatments. The results showed that heavy metal treatments had significant effects on plants, as the performance of plants under Zn2+ and Cd2+ treatments was significantly different with plants under control treatment (p < 0.05). Cd2+ treatments showed a hormesis effect, whereas Zn2+ did not. The endophyte increased host heavy metal stress tolerance by promoting host growth as the E+ plants had significantly higher plant height, tiller number, root length (p < 0.05). The endophyte also promoted ion uptake by the host and induced endogenous hormone production (p < 0.05). These results suggested that the Epichloë endophyte regulated host growth and physiology to improve association tolerance to environmental conditions. This study provides another example that the Epichloë endophyte can increase plant tolerance to metal stress. Full article
(This article belongs to the Special Issue Plant-Soil-Microbe Interactions in Natural Soils)
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