Open AccessArticle
Combination of Lactic Acid-Based Deep Eutectic Solvents (DES) with β-Cyclodextrin: Performance Screening Using Ultrasound-Assisted Extraction of Polyphenols from Selected Native Greek Medicinal Plants
Agronomy 2017, 7(3), 54; doi:10.3390/agronomy7030054 -
Abstract
A series of novel l-lactic acid-based deep eutectic solvents (DES) were tested for polyphenol extraction performance, using organically grown, native Greek medicinal plants. The extractions were ultrasonically-assisted and the effect of the addition of β-cyclodextrin (β-CD) as extraction booster was also tested,
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A series of novel l-lactic acid-based deep eutectic solvents (DES) were tested for polyphenol extraction performance, using organically grown, native Greek medicinal plants. The extractions were ultrasonically-assisted and the effect of the addition of β-cyclodextrin (β-CD) as extraction booster was also tested, at a concentration of 1.5% (w/v). The estimation of total polyphenol yield (YTP) suggested that DES composed of l-lactic acid and nicotinamide and l-lactic acid and l-alanine, both at a molar ratio of 7:1, are promising solvents giving significantly higher yields compared with 60% (v/v) aqueous ethanol and water. However, when β-CD was combined with DES comprised of l-lactic acid and ammonium acetate (molar ratio 7:1), the extraction yields obtained in some instances were equal of even higher. The pattern was not consistent when the yield in total flavonoids (YTFn) was considered, indicating water, 60% (v/v) aqueous ethanol and l-lactic acid:sodium acetate (molar ratio 7:1) to be the most efficient solvents. In this case, the effect of β-CD was of rather lower magnitude. The examination of the antioxidant activity of the extracts generated showed that there is a close correlation mainly with their concentration in total polyphenols. Full article
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Open AccessArticle
Characterisation of Faba Bean (Vicia faba L.) Transcriptome Using RNA-Seq: Sequencing, De Novo Assembly, Annotation, and Expression Analysis
Agronomy 2017, 7(3), 53; doi:10.3390/agronomy7030053 -
Abstract
RNA sequencing (RNA-Seq) is a deep sequencing method used for transcriptome profiling. RNA-Seq assemblies have successfully been used for a broad variety of applications, such as gene characterisation, functional genomic studies, and gene expression analysis, particularly useful in the absence of a well-studied
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RNA sequencing (RNA-Seq) is a deep sequencing method used for transcriptome profiling. RNA-Seq assemblies have successfully been used for a broad variety of applications, such as gene characterisation, functional genomic studies, and gene expression analysis, particularly useful in the absence of a well-studied genome reference sequence. This study reports on the development of reference unigene sets from faba bean using RNA-Seq. Two Australian faba bean cultivars (Doza and Farah) that differ in terms of disease resistance, breeding habit, and adaptation characteristics, and have been extensively used in breeding programs, were utilised in this study. The de novo assembly resulted in a total of 58,962 and 53,275 transcripts with approximately 67 Mbp (1588 bp N50) and 61 Mbp (1629 bp N50) for Doza and Farah, respectively. The generated transcripts have been compared to the protein and nucleotide databases of NCBI, as well as to the gene complements of several related legume species such as Medicago truncatula, soybean, and chickpea. Both assemblies were compared to previously-published faba bean transcriptome reference sets for the degree of completeness and utility. Annotation of unigenes has been performed, and patterns of tissue-specific expression identified. The gene complement derived from this comprehensive transcriptome analysis shows that faba bean, despite its complex 13 Gbp genome, compares well to other legumes in expressed gene content. This study in faba bean represents the most comprehensive reference transcriptomes from two different Australian cultivars available to date and it provides a valuable resource for future genomics-assisted breeding activities in this species. Full article
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Open AccessArticle
Variability and Correlations among Groundnut Populations for Early Leaf Spot, Pod Yield, and Agronomic Traits
Agronomy 2017, 7(3), 52; doi:10.3390/agronomy7030052 -
Abstract
The present experiment was conducted in Mali to study the genetic variability and correlation of early leaf spot (ELS) resistance parameters and agro-morphological traits in groundnut using two F3 populations from crosses QH243C X NAMA and TS32-1 X NAMA. Estimates of genotypic coefficient
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The present experiment was conducted in Mali to study the genetic variability and correlation of early leaf spot (ELS) resistance parameters and agro-morphological traits in groundnut using two F3 populations from crosses QH243C X NAMA and TS32-1 X NAMA. Estimates of genotypic coefficient of variation and phenotypic coefficient of variation revealed high value for pod yield, kernel yield, and ELS score at 60 and 80 days after sowing for the cross QH243C X NAMA. Low-to-moderate GCV and PCV were obtained for the remaining traits for both crosses. High heritability values coupled with high genetic advance as percentage of mean recorded for ELS_II, defoliation percent, pod yield in cross QH243C X NAMA; shelling percent for the cross TS32-1 X NAMA and ELS_III; and plant height, kernel yield in both crosses, indicate the significant role of additive gene action for inheritance of these traits. Correlation analysis indicated that pod and kernel yield were significant and positively correlated with 100 kernel weight and shelling percent. For cross QH243C X NAMA, kernel yield showed significant positive correlation with all ELS resistance components but the correlation was not significant for the cross TS32-1 X NAMA. Positive and significant correlation was observed between ELS resistance components themselves, suggesting that these components could be controlled by a similar polygenic system. The findings suggest that early generation selection should be effective for days to first flowering, days to 50% flowering, plant height, pod yield, kernel yield, 100 kernel weight and early leaf spot resistance which recorded the highest value of heritability in the two crosses. Full article
Open AccessArticle
Evaluation of Agronomic Traits and Drought Tolerance of Winter Wheat Accessions from the USDA-ARS National Small Grains Collection
Agronomy 2017, 7(3), 51; doi:10.3390/agronomy7030051 -
Abstract
Wheat accessions from the USDA-ARS National Small Grains Collection (NSGC) are a potential genetic resource for variety improvement. This study assessed the agronomic performance and drought tolerance in 198 winter wheat accessions under irrigated and terminal drought environments in the 2012–2013 season, and
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Wheat accessions from the USDA-ARS National Small Grains Collection (NSGC) are a potential genetic resource for variety improvement. This study assessed the agronomic performance and drought tolerance in 198 winter wheat accessions under irrigated and terminal drought environments in the 2012–2013 season, and repeated the test under terminal drought only during the 2013–2014 season. The 198 accessions were classified into three maturity groups, early, intermediate, and late based on heading data. In all three environments, the early accessions had the best agronomic performance, produced higher grain yield, thousand-kernel weight and grain volume weight, and had earlier heading date and shorter plant height. The intermediate accessions had similar grain yield and thousand-kernel weight as the early accessions in the irrigated environment, but had lower thousand-kernel weight in the terminal drought environments. Terminal drought had significant effects on grain yield, plant height, thousand-kernel weight, and grain volume weight. The positive correlation between GY and HD suggests that the ‘late early’ types in the early maturity were the most successful. Out of 198 accessions evaluated, twenty-three had high yield stability and drought tolerance according to the drought susceptibility index and membership function value of drought tolerance. The eight of twenty-three accessions identified (four early and four intermediate) had high grain yield in three environments. Some of these accessions have been further used in bi-parental mapping studies and by breeders for grain yield and drought tolerance improvement. Full article
Open AccessArticle
Detection and Response of Sugarcane against the Infection of Sugarcane Mosaic Virus (SCMV) in Indonesia
Agronomy 2017, 7(3), 50; doi:10.3390/agronomy7030050 -
Abstract
Sugarcane mosaic virus (SCMV) is one among many viruses that infect sugarcane, cause yield loss, and become serious disease agents on sugarcane plantations. Since the morphological symptoms of SCMV are similar to other symptoms caused by Sugarcane streak mosaic virus (SCSMV) or nitrogen
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Sugarcane mosaic virus (SCMV) is one among many viruses that infect sugarcane, cause yield loss, and become serious disease agents on sugarcane plantations. Since the morphological symptoms of SCMV are similar to other symptoms caused by Sugarcane streak mosaic virus (SCSMV) or nitrogen deficiency, the detection of SCMV is important through accurate diagnostic-like ELISA or RT-PCR. This research aimed to study the causative mosaic pathogen of SCMV in East Java, Indonesia, including mosaic development. The results showed that the mosaic symptom is present in all sugarcane plantations with 78% and 65% disease incidence and severity, respectively. Moreover, the detection procedure based on an amplification of cDNA of the coat protein gene sequence confirmed that SCMV was the causative agent of mosaic disease on sugarcane. Re-inoculation of healthy sugarcane plants with plant sap from a symptomatic leaf from the field showed similar mosaic or yellowish chlorotic areas on the leaf blade, and appeared on the fourth leaves upward from the inoculation leaf, in addition to showing different levels of peroxidase but not total phenol. Mosaic also correlated with the amount of total chlorophyll. Although Sucrose phosphate synthase (SPS) protein accumulation and activity were at a lower level in infected leaves, sucrose accumulation was at a higher level in the same leaves. Full article
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Open AccessArticle
Impact of Different Agricultural Waste Biochars on Maize Biomass and Soil Water Content in a Brazilian Cerrado Arenosol
Agronomy 2017, 7(3), 49; doi:10.3390/agronomy7030049 -
Abstract
Arenosols in the Brazilian Cerrado are increasingly being used for agricultural production, particularly maize. These sandy soils are characterized by low soil organic matter, low available nutrients, and poor water-holding capacity. For this reason, adding biochar as a soil amendment could lead to
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Arenosols in the Brazilian Cerrado are increasingly being used for agricultural production, particularly maize. These sandy soils are characterized by low soil organic matter, low available nutrients, and poor water-holding capacity. For this reason, adding biochar as a soil amendment could lead to improved water and nutrient retention. A greenhouse experiment was carried out using twelve biochars derived from four feedstocks (cotton husks, swine manure, eucalyptus sawmill residue, sugarcane filtercake) pyrolized at 400, 500 and 600 °C and applied at 5% w/w. The biochars’ effect on maize biomass was examined, along with their contribution to soil physical properties including water retention, electrical conductivity (EC), and grain size distribution. After six weeks, maize plants in soils with eucalyptus and particularly filtercake biochar had higher biomass compared to those in soils with cotton and swine manure biochars. The latter’s low biomass was likely related to excessive salinity. In general, our biochars showed potential for increasing θ in sandy soils compared to the soil alone. Filtercake and eucalyptus biochars may improve soil aeration and water infiltration, while applying cotton and swine manure biochars at levels <5% to avoid high salinity could contribute to improved soil water retention in Cerrado Arenosols. Full article
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Open AccessArticle
Effect of Constitutive miR164 Expression on Plant Morphology and Fruit Development in Arabidopsis and Tomato
Agronomy 2017, 7(3), 48; doi:10.3390/agronomy7030048 -
Abstract
Several miRNAs are conserved in different plant families, but their abundance and target genes vary between species, organs, and stages of development. Target genes of miRNAs are mostly transcription factors, involved in the control of many plant developmental processes, including fruit development. MiR164
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Several miRNAs are conserved in different plant families, but their abundance and target genes vary between species, organs, and stages of development. Target genes of miRNAs are mostly transcription factors, involved in the control of many plant developmental processes, including fruit development. MiR164 is a conserved miRNA, highly expressed in fruits, and is validated to target a subset of genes of the NAC-domain transcription factor gene family. The objective of this work was to analyze the phenotypic effects of the constitutive expression of miR164 during the life cycle of Arabidopsis and tomato. MiR164 overexpression (164-OE) lines for Arabidopsis and tomato were generated and analyzed during plant development. The constitutive miR164 expression showed that miR164 affected the morphology of Arabidopsis and tomato, and it affected the transition from the vegetative to the reproductive phase in Arabidopsis. Moreover, the miR164 overexpression affected the time required for each developmental stage of tomato fruit. These results suggest that miR164 plays general and specific roles during development in Arabidopsis and tomato, including fruit development, which could be exploited for the improvement of traits of agronomic interest in important species. Full article
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Open AccessReview
Ultrasound Assisted Extraction for the Recovery of Phenolic Compounds from Vegetable Sources
Agronomy 2017, 7(3), 47; doi:10.3390/agronomy7030047 -
Abstract
Vegetable sources and agro-industrial residues represent an important source of phenolic compounds that are useful in a wide range of applications, especially those with biological activities. Conventional techniques of phytochemical extraction have been associated with a high consumption of organic solvents that limits
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Vegetable sources and agro-industrial residues represent an important source of phenolic compounds that are useful in a wide range of applications, especially those with biological activities. Conventional techniques of phytochemical extraction have been associated with a high consumption of organic solvents that limits the application of bioactive extracts, leading to the implementation of novel extraction technologies using mechanisms such as Ultrasound Assisted Extraction (UAE). In the present review, an analysis of the involved variables in the extraction yield of phenolic compounds through UAE is presented, highlighting the advantages of this technology based on the results obtained in various optimized studies. A comparison with other technologies and a proposal of its possible application for agro industrial residues as raw material of phenolic compounds is also indicated. Finally, it is concluded that UAE is a technology that is placed within the area of Sustainable Chemistry since it promotes the use of renewable raw materials through the extraction of phenolic compounds, implementing the substitution of organic solvents with solvents that do not present toxic effects, lowering the energy consumption when compared to conventional methods and minimizing process times and temperatures, which is useful for the extraction of thermo-labile compounds. Full article
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Open AccessArticle
Assessment of Conservation Agriculture Practices by Smallholder Farmers in the Eastern Cape Province of South Africa
Agronomy 2017, 7(3), 46; doi:10.3390/agronomy7030046 -
Abstract
Conservation agriculture (CA) can sustainably address soil degradation and improve crop yields. However, the success of CA amongst South African smallholder farmers is not known. The aims of the study were to find out: (1) the extent of CA practice by the Eastern
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Conservation agriculture (CA) can sustainably address soil degradation and improve crop yields. However, the success of CA amongst South African smallholder farmers is not known. The aims of the study were to find out: (1) the extent of CA practice by the Eastern Cape smallholder farmers; (2) perceptions towards CA amongst smallholder farmers with some history of practising the technology; and (3) the impact of practised CA components on soil quality indicators. Diagnostic survey techniques and soil sampling in farmers’ fields were employed to gather data from five districts of the Eastern Cape, South Africa. The most common CA principle adopted by surveyed farmers was no-till (34.81%), whilst crop rotation and residue retention were practised by only 25.93% and 22.22% of the farmers, respectively. Education level and CA training influenced the likelihood of a farmer to practise no-till farming, whilst the likelihood of farmers to retain residues was influenced by education level and access to grazing lands. Lack of appropriate equipment and costly herbicides were the major constraining factors to practising CA. Crop residue retention conflicted with the common practice of free-range livestock grazing. Cabbage, maize and beans were the most common crops of choice for the few farmers that practised crop rotations. No significant (p > 0.05) improvement on soil quality indicators was observed with CA compared to the conventional farming method. The noted high dependency on government grants by the smallholder farmers could be a disincentive towards the adoption of agricultural innovations such as CA. Identification of practical key CA entry points is recommended, bearing in mind the noted impediments to CA adoption. Full article
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Open AccessArticle
Yield Stability in Winter Wheat Production: A Survey on German Farmers’ and Advisors’ Views
Agronomy 2017, 7(3), 45; doi:10.3390/agronomy7030045 -
Abstract
Most of the available research studies have focused on the production of high grain yields of wheat and have neglected yield stability. However, yield stability is a relevant factor in agronomic practice and, therefore, is the focus of this comprehensive survey. The aim
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Most of the available research studies have focused on the production of high grain yields of wheat and have neglected yield stability. However, yield stability is a relevant factor in agronomic practice and, therefore, is the focus of this comprehensive survey. The aim was to first describe the importance of yield stability as well as currently used practical management strategies that ensure yield stability in wheat production and secondly, to obtain potential research areas supporting yield stability in the complex system of agronomy. The target groups were German farmers with experience in wheat production and advisors with expertise in the field of wheat cultivation or research. A sample size of 615 completed questionnaires formed the data basis of this study. The study itself provides evidence that the yield stability of winter wheat is even more important than the amount of yield for a large proportion of farmers (48%) and advisors (47%). Furthermore, in the view of the majority of the surveyed farmers and advisors, yield stability is gaining importance in climate change. Data analysis showed that site adapted cultivar choice, favorable crop rotations and integrated plant protection are ranked as three of the most important agronomic management practices to achieve high yield stability of wheat. Soil tillage and fertilization occupied a middle position, whereas sowing date and sowing density were estimated with lower importance. However, yield stability is affected by many environmental, genetic and agronomic factors, which subsequently makes it a complex matter. Hence, yield stability in farming practice must be analyzed and improved in a systems approach. Full article
Open AccessArticle
Rhizoctonia solani and Bacterial Inoculants Stimulate Root Exudation of Antifungal Compounds in Lettuce in a Soil-Type Specific Manner
Agronomy 2017, 7(2), 44; doi:10.3390/agronomy7020044 -
Abstract
Previous studies conducted on a unique field site comprising three contrasting soils (diluvial sand DS, alluvial loam AL, loess loam LL) under identical cropping history, demonstrated soil type-dependent differences in biocontrol efficiency against Rhizoctonia solani-induced bottom rot disease in lettuce by two
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Previous studies conducted on a unique field site comprising three contrasting soils (diluvial sand DS, alluvial loam AL, loess loam LL) under identical cropping history, demonstrated soil type-dependent differences in biocontrol efficiency against Rhizoctonia solani-induced bottom rot disease in lettuce by two bacterial inoculants (Pseudomonas jessenii RU47 and Serratia plymuthica 3Re-4-18). Disease severity declined in the order DS > AL > LL. These differences were confirmed under controlled conditions, using the same soils in minirhizotron experiments. Gas chromatography-mass spectrometry (GC-MS) profiling of rhizosphere soil solutions revealed benzoic and lauric acids as antifungal compounds; previously identified in root exudates of lettuce. Pathogen inoculation and pre-inoculation with bacterial inoculants significantly increased the release of antifungal root exudates in a soil type-specific manner; with the highest absolute levels detected on the least-affected LL soil. Soil type-dependent differences were also recorded for the biocontrol effects of the two bacterial inoculants; showing the highest efficiency after double-inoculation on the AL soil. However, this was associated with a reduction of shoot growth and root hair development and a limited micronutrient status of the host plants. Obviously, disease severity and the expression of biocontrol effects are influenced by soil properties with potential impact on reproducibility of practical applications. Full article
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Open AccessArticle
Drought Stress-Related Physiological Changes and Histone Modifications in Barley Primary Leaves at HSP17 Gene
Agronomy 2017, 7(2), 43; doi:10.3390/agronomy7020043 -
Abstract
Stress-inducible genes undergo epigenetic modifications under stress conditions. To investigate if HSP17, of which transcripts accumulate in plant cells under stress, is regulated through epigenetic mechanisms under drought stress, 5-day-old barley (Hordeumvulgare cv. Carina) plants were subjected to progressive drought
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Stress-inducible genes undergo epigenetic modifications under stress conditions. To investigate if HSP17, of which transcripts accumulate in plant cells under stress, is regulated through epigenetic mechanisms under drought stress, 5-day-old barley (Hordeumvulgare cv. Carina) plants were subjected to progressive drought through water withholding for 22 days. Changes in physiological status and expression of HSP17 gene were monitored in primary leaves of control and drought-treated plants every two days. Twelve days after drought started, control and drought-treated plants were analyzed by chromatin-immunoprecipitation using antibodies against three histone modifications (H3K4me3, H3K9ac, and H3K9me2) and H3 itself. Already after four days of drought treatment, stomatal conductance was severely decreased. Thereafter, maximum and quantum yield of photosystem II (PSII), regulated and non-regulated energy dissipation in PSII, and later also chlorophyll content, were affected by drought, indicating the stress-induced onset of senescence. At the 12th day of drought, before leaf water content declined, expression of HSP17 gene was increased two-fold in drought-treated plants compared to the controls. Twelve days of drought caused an increase in H3 and a loss in H3K9me2 not only at HSP17, but also at constitutively transcribed reference genes ACTIN, PROTEIN PHOSPHATASE 2A (pp2A), and at silent regions BM9, CEREBA. In contrast, H3K4me3 showed a specific increase at HSP17 gene at the beginning and the middle part of the coding region, indicating that this mark is critical for the drought-responsive transcription status of a gene. Full article
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Open AccessArticle
The Effect of Organic and Inorganic Fertilizers on the Yield of Two Contrasting Soybean Varieties and Residual Nutrient Effects on a Subsequent Finger Millet Crop
Agronomy 2017, 7(2), 42; doi:10.3390/agronomy7020042 -
Abstract
The problems of low soil fertility resulting from continuous monocropping, crop residue removal and limited fertilizer use represent key challenges to produce surplus food for the ever increasing population of Ethiopia. However, the practices of crop rotation and integrated sources of fertilizer uses
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The problems of low soil fertility resulting from continuous monocropping, crop residue removal and limited fertilizer use represent key challenges to produce surplus food for the ever increasing population of Ethiopia. However, the practices of crop rotation and integrated sources of fertilizer uses could potentially improve soil fertility and productivity. In 2012 and 2014, soybean with different trials consisting of two soybean varieties (Boshe and Ethio-ugozilavia), three levels of farm yard manure (FYM) (3, 6 and 9 t/ha) and three phosphorus levels (8, 16 and 24 kg P ha−1) were combinedin2×3×3factorialarrangements. Twosoybeanvarietiesreceivingnofertilizerapplication followed by finger millet receiving a recommended rate (20 kg P/ha) were included. The experiment was laid out in a randomized complete block design with three replications. In 2013 and 2015, finger millet was planted on each soybean plot as per previous treatment arrangements to evaluate the effect of the precursor crop (soybean) and integrated fertilizer application on yield performance of the subsequent finger millet. Soil pH, organic carbon, total nitrogen and available phosphorus before planting and after crop harvest of soybean in each year showed treatment differences. Both precursor crop and fertilizer application had a positive effect on soil fertility status and, hence, improved the performance of the subsequent finger millet. On the other hand, since the rainfall amount and distribution were different in the 2012 and 2014 seasons, the response of soybean varieties to applied fertilizers was significantly affected, and the correlation between soybean yield and annual rainfall was strongly positive. Use of an early maturing soybean variety (Boshe) with the lowest rates of organicandinorganicfertilizersgavesignificantlyhigheryieldin2012(shortrainyseason)compared with other treatment combinations. In the 2014 cropping season, however, ‘Ethio-ugozilavia’ showed greateryield performancewith the combinedapplication of3 t FYM/haand 1616kg PP/ha followed by 3 t FYM and 88 kg P/ha. Hence, it is recommended to use the ‘Boshe’ variety under a short rainy season and under a low soil fertility status, while variety the ‘Ethio-ugozilavia’ can be used under goodrainyandsoilfertilitymanagementconditions. Consideringresidualeffects,theuseoftheearly maturing soybean variety as a precursor with 3 t FYM/ha and 8–16,816 kg P/ha during the short rainy season could enhance the yield of the subsequent finger millet. On the other hand, the use of the late maturing soybean variety as a precursor with higher organic fertilizer rates (6–9 t FYM/ha) resulted in a significant yield increase of the subsequent finger millet. The use of a late maturing variety of soybean with lower rates of organic manure resulted in a finger millet yield comparable to farmers’ practice, indicating that this option can be adopted by smallholder farmers who cannot produce sufficient organic manure. This study showed that planting of finger millet after a soybean precursor crop even without fertilizer application could give better yield and economic benefits as it saves 70–85% of chemical fertilizer costs compared to the farmers’ practice. Full article
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Open AccessArticle
Water Infiltration and Moisture in Soils under Conservation and Conventional Agriculture in Agro-Ecological Zone IIa, Zambia
Agronomy 2017, 7(2), 40; doi:10.3390/agronomy7020040 -
Abstract
Conservation agriculture is often presented as being ‘climate smart’ due to anticipated increases in soil moisture. The extent of enhanced water availability in farmers’ fields is, however, poorly documented. This paper presents five data sets describing soil moisture in fields of small-scale conservation
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Conservation agriculture is often presented as being ‘climate smart’ due to anticipated increases in soil moisture. The extent of enhanced water availability in farmers’ fields is, however, poorly documented. This paper presents five data sets describing soil moisture in fields of small-scale conservation and conventional farmers in the Agro-ecological Zone IIa, Zambia. The data include (1) soil cover; (2) time required for visible soil surface saturation, ponding and initial runoff under artificial rainfall; (3) saturated water infiltration rates; (4) weekly soil moisture at six soil depths for two entire rain seasons; and (5) weekly rainfall in each field. Measurements were done for 15 pairs of comparable fields under conservation and conventional agriculture. Pairwise analysis showed significantly shorter time for surface saturation, ponding, and runoff in conservation fields compared to conventional fields. Saturated infiltration rates in riplines and basins of conservation fields were similar to rates in ploughed/hoed fields. Infiltration rates between riplines and between basins were 31–37% lower than those in ploughed/hoed fields. Soil moisture in riplines and basins of conservation fields was higher by an average factor of 1.08 down to 40 cm soil depth, whereas it was lower by an average factor of 0.89 between plant rows compared to fields under conventional tillage. Based on 34,000 soil moisture measurements from 0 to 60 cm depth over two seasons, soils in conservation fields contained a weighted average of 18.2% (vol.) water compared to 19.9% (vol.) in conventional fields (p < 0.05). The results indicate that small-scale adopters of conservation agriculture are less ‘climate smart’ than conventional farmers in terms of water infiltration and soil moisture. Full article
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Open AccessArticle
Mid-Season Leaf Glutamine Predicts End-Season Maize Grain Yield and Nitrogen Content in Response to Nitrogen Fertilization under Field Conditions
Agronomy 2017, 7(2), 41; doi:10.3390/agronomy7020041 -
Abstract
After uptake in cereal crops, nitrogen (N) is rapidly assimilated into glutamine (Gln) and other amino acids for transport to sinks. Therefore Gln has potential as an improved indicator of soil N availability compared to plant N demand. Gln has primarily been assayed
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After uptake in cereal crops, nitrogen (N) is rapidly assimilated into glutamine (Gln) and other amino acids for transport to sinks. Therefore Gln has potential as an improved indicator of soil N availability compared to plant N demand. Gln has primarily been assayed to understand basic plant physiology, rather than to measure plant/soil-N under field conditions. It was hypothesized that leaf Gln at early-to-mid season could report the N application rate and predict end-season grain yield in field-grown maize. A three-year maize field experiment was conducted with N application rates ranging from 30 to 218 kg ha−1. Relative leaf Gln was assayed from leaf disk tissue using a whole-cell biosensor for Gln (GlnLux) at the V3-V14 growth stages. SPAD (Soil Plant Analysis Development) and NDVI (Normalized Difference Vegetation Index) measurements were also performed. When sampled at V6 or later, GlnLux glutamine output consistently correlated with the N application rate, end-season yield, and grain N content. Yield correlation outperformed GreenSeekerTM NDVI, and was equivalent to SPAD chlorophyll, indicating the potential for yield prediction. Additionally, depleting soil N via overplanting increased GlnLux resolution to the earlier V5 stage. The results of the study are discussed in the context of luxury N consumption, leaf N remobilization, senescence, and grain fill. The potential and challenges of leaf Gln and GlnLux for the study of crop N physiology, and future N management are also discussed. Full article
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Open AccessArticle
N2 Fixation of Common and Hairy Vetches when Intercropped into Switchgrass
Agronomy 2017, 7(2), 39; doi:10.3390/agronomy7020039 -
Abstract
Interest in sustainable alternatives to synthetic nitrogen (N) for switchgrass (Panicum virgatum L.) forage and bioenergy production, such as biological N2 fixation (BNF) via legume-intercropping, continues to increase. The objectives were to: (i) test physical and chemical scarification techniques (10 total)
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Interest in sustainable alternatives to synthetic nitrogen (N) for switchgrass (Panicum virgatum L.) forage and bioenergy production, such as biological N2 fixation (BNF) via legume-intercropping, continues to increase. The objectives were to: (i) test physical and chemical scarification techniques (10 total) for common vetch (Vicia sativa L.); (ii) assess whether switchgrass yield is increased by BNF under optimum seed dormancy suppression methods; and (iii) determine BNF rates of common and hairy vetch (Vicia villosa L.) via the N-difference method. Results indicate that chemical scarification (sulfuric acid) and mechanical pretreatment (0.7 kg of pressure for one minute) improve common vetch germination by 60% and 50%, respectively, relative to controls. Under optimum scarification methods, BNF was 59.3 and 43.3 kg·N·ha−1 when seeded at 7 kg pure live seed ha−1 for common and hairy vetch, respectively. However, at this seeding rate, switchgrass yields were not affected by BNF (p > 0.05). Based on BNF rates and plant density estimates, seeding rates of 8 and 10 kg pure live seed (PLS) ha−1 for common and hairy vetch, respectively, would be required to obtain plant densities sufficient for BNF at the current recommended rate of 67 kg·N·ha−1 for switchgrass biomass production in the Southeastern U.S. Full article
Open AccessArticle
Spore Density of Arbuscular Mycorrhizal Fungi is Fostered by Six Years of a No-Till System and is Correlated with Environmental Parameters in a Silty Loam Soil
Agronomy 2017, 7(2), 38; doi:10.3390/agronomy7020038 -
Abstract
Arbuscular mycorrhizal fungi (AMF) play major roles in nutrient acquisition by crops and are key actors of agroecosystems productivity. However, agricultural practices can have deleterious effects on plant–fungi symbiosis establishment in soils, thus inhibiting its potential benefits on plant growth and development. Therefore,
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Arbuscular mycorrhizal fungi (AMF) play major roles in nutrient acquisition by crops and are key actors of agroecosystems productivity. However, agricultural practices can have deleterious effects on plant–fungi symbiosis establishment in soils, thus inhibiting its potential benefits on plant growth and development. Therefore, we have studied the impact of different soil management techniques, including conventional moldboard ploughing and no-till under an optimal nitrogen (N) fertilization regime and in the absence of N fertilization, on AMF spore density and soil chemical, physical, and biological indicators in the top 20 cm of the soil horizon. A field experiment conducted over six years revealed that AMF spore density was significantly lower under conventional tillage (CT) combined with intensive synthetic N fertilization. Under no-till (NT) conditions, the density of AMF spore was at least two-fold higher, even under intensive N fertilization conditions. We also observed that there were positive correlations between spore density, soil dehydrogenase enzyme activity, and soil penetration resistance and negative correlations with soil phosphorus and mineral N contents. Therefore, soil dehydrogenase activity and soil penetration resistance can be considered as good indicators of soil quality in agrosystems. Furthermore, the high nitrate content of ploughed soils appears to be detrimental both for the dehydrogenase enzyme activity and the production of AMF spores. It can be concluded that no-till, by preventing soil from structural and chemical disturbances, is a farming system that preserves the entire fungal life cycle and as such the production of viable spores of AMF, even under intensive N fertilization. Full article
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Open AccessArticle
Re-Programming Photosynthetic Cells of Perennial Ryegrass (Lolium perenne L) for Fructan Biosynthesis through Transgenic Expression of Fructan Biosynthetic Genes under the Control of Photosynthetic Promoters
Agronomy 2017, 7(2), 36; doi:10.3390/agronomy7020036 -
Abstract
High molecular weight fructans are the main class of water-soluble carbohydrate used for energy storage in many temperate grass species including perennial ryegrass (Lolium perenne L.). As well as being important readily mobilisable energy reserves for the plant, fructans are also involved
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High molecular weight fructans are the main class of water-soluble carbohydrate used for energy storage in many temperate grass species including perennial ryegrass (Lolium perenne L.). As well as being important readily mobilisable energy reserves for the plant, fructans are also involved in stress tolerance. Fructans are also readily digested by grazing ruminants and hence are a valuable source of energy for sheep, beef and dairy production systems in temperate regions. This paper describes the re-programming of the expression of fructan biosynthesis genes through the transgenic manipulation of 6-glucose fructosyltransferase (6G-FFT) and sucrose:sucrose 1-fructosyl-transferase (1-SST) in perennial ryegrass. Transgenic events were developed with altered fructan accumulation patterns with increases in fructan accumulation and greatly increased accumulation of fructan in leaf blades as opposed to the traditional site of fructan accumulation in the pseudostem. This altered site of fructan accumulation has potential benefits for animal production as leaf blades form the major part of the diet of grazing ruminants. Some of the transgenic events also exhibited enhanced biomass production. This combination of high quality and enhanced yield is of great interest to forage plant breeders and whilst the expression of these phenotypes needs to be confirmed under field conditions, the identification and characterisation of the transgenic events described in this paper validate the potential for the manipulation of fructan biosynthesis in perennial ryegrass. Full article
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Open AccessArticle
Effect of Long-Term Continuous Fumigation on Soil Microbial Communities
Agronomy 2017, 7(2), 37; doi:10.3390/agronomy7020037 -
Abstract
High value crop producers in California rely heavily on soil fumigation to control a wide array of soil borne pests including nematodes, pathogens and weeds. Fumigants with broad biocidal activity can affect soil microbial communities that contribute to nutrient cycling and plant nutrient
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High value crop producers in California rely heavily on soil fumigation to control a wide array of soil borne pests including nematodes, pathogens and weeds. Fumigants with broad biocidal activity can affect soil microbial communities that contribute to nutrient cycling and plant nutrient uptake which can impact soil health. It is often thought that soil microbial communities make a relatively rapid recovery following fumigation. However, recently it has been found that repeated application of fumigants over time can have greater and longer lasting impacts on soil microorganisms than single fumigation events. Therefore, the main objective of this study was to determine the effect of long-term repeated application of fumigants on soil microbial communities and compare them with non-fumigated and organic sites. Soil samples were collected from fields in Watsonville, CA. Chronosequence sites were defined by number of years of annual fumigation (yaf) with methyl bromide (15, 26, 33, 39 yaf) at the time of sampling, and representative non-fumigated sites were also included for comparison. Phospholipid fatty acid (PLFA) analysis was used to analyze the samples. The canonical variate analysis showed that microbial communities in sites with a longer history of fumigation (33 and 39 yaf) were similar to one another; however, they differed significantly from 15 yaf site and further analysis concluded that non-fumigated sites were significantly different than fumigated sites. This study showed that the proportion of arbuscular mycorrhizal fungi (AMF) was lower in all fumigated (15, 33 and 39 yaf) sites as compared to their non-fumigated counterparts, which could be a threat to sustainability since AMF plays a major role in soil health and quality. Full article
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Open AccessArticle
Agro-Ecology for Potential Adaptation of Horticultural Systems to Climate Change: Agronomic and Energetic Performance Evaluation
Agronomy 2017, 7(2), 35; doi:10.3390/agronomy7020035 -
Abstract
Adaptation can be a key factor that will shape the future severity of climate change impacts on food production. The objective of this study was to assess the suitability of an agro-ecological approach based on various techniques as potential adaptation strategy in organic
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Adaptation can be a key factor that will shape the future severity of climate change impacts on food production. The objective of this study was to assess the suitability of an agro-ecological approach based on various techniques as potential adaptation strategy in organic horticultural systems. A long-term field experiment was set up in Southern Italy, combining: (i) appropriate soil surface shaping; (ii) cash crop rotation; (iii) agro-ecological service crops (ASC) introduction as living mulch and complementary crops; (iv) tailored organic fertilization; and (v) alternative tillage strategies. In this paper, the first two-year results on cauliflower (Brassica oleracea L.) and tomato (Solanum lycopersicum L.) crops, as well as energy consumptions through the Energy Analysis (EA) method are reported. Due to the climatic conditions that occurred, which were characterized by the absence of extreme climatic events (particularly rainfall), it was not possible to verify if the designed experimental device was able to mitigate the impact of climate change, whereas the EA indicated that total energy inputs were lower when ASC are introduced in cropping systems. Full article
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