Special Issue "Sustainable Agro-Ecosystems: The Role of Innovative Amendments in Crop Production Under Polluted Environments"

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Sustainable Agriculture".

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Prof. Dr. Muhammad Naveed
E-Mail Website1 Website2
Guest Editor
Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan
Interests: recycling of organic wastes; formulation of bio-organo-fertilizer; biochar production and utilization; bacterial seed endophyte; impregnation of fertilizers with endophyte; microbial ecology/diversity; plant growth under stress conditions; micronutrient fertilization
Dr. Adnan Mustafa
E-Mail Website
Guest Editor
Biology Centre, SOWA RI, Czech Academy of Sciences, Na Sádkách 7, 370 05 České Budějovice Czech Republic
Interests: soil fertility and plant nutrition; biogeochemistry of C and N; soil organic matter (SOM); recycling of organic wastes; biochar production and utilization; plant growth under stress conditions; phytoremediation of emerging pollutants; bioremediation; biofertilizers; composting from organic wastes; soil microbial biomass

Special Issue Information

Dear Colleagues,

Global demand for food is expected to continue increasing markedly in the coming decades, mainly due to human population growth, but also to rising incomes in developing countries. In fact, an increase of 47% in the global food consumption has been estimated for the period 2010–2050. Consequently, sustaining crop production and food security has become an alarming and pressing issue for the scientific community. On the other hand, the increase in industrialization has caused the deterioration of soil, environment, and ultimately food quality. Agricultural crop production has been especially threatened by climatic extremes, including but not limited to droughts, salinity stress, heavy metal stress, water logging, heat waves, potentially toxic elements (PTEs), and attack by pathogens. Agricultural development in this regard has served to sustain crop production under stressed environments, but often with negative impacts on the environment. Therefore, more suitable strategies should be considered to produce more food on the existing land base, while simultaneously reducing environmental impacts. Pertinent to this, novel agricultural approaches to sustain agricultural production on marginal/degraded lands have been developed, our understanding of the effects of innovative (organic and inorganic) amendments on crop stress (biotic and abiotic) tolerance is limited. Recently, plant–microbe interactions have gained the attention of the scientific community to combat plant stresses. This Special Issue will also focus on such interactions, rhizospheric modifications/engineering, and the role of plant-growth-promoting rhizobacteria (PGPR) in sustainable crop production.

This Special Issue in the journal Sustainability will aim to gather a collection of high-quality works on sustainable agro-ecosystems through supporting crop production under polluted environments using advanced organic and inorganic amendments.

We are pleased to welcome original and technical articles, reviews, short communications, and meta-analyses pertaining to the following keywords.

Prof. Dr. Muhammad Naveed
Dr. Adnan Mustafa
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • sustainable agriculture
  • food security
  • environmental pollution
  • phytostimulants
  • heavy metal stress
  • salt stress
  • drought
  • plant pathogens
  • biochar
  • compost
  • zeolite
  • PGPR
  • nano-composites
  • crop physiology
  • agronomic practices
  • C sequestration
  • plant nutrition
  • phytoremediation
  • plant growth
  • stress tolerance mechanisms

Published Papers (12 papers)

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Research

Jump to: Review

Article
Risk Assessment of Heavy Metals in Basmati Rice: Implications for Public Health
Sustainability 2021, 13(15), 8513; https://doi.org/10.3390/su13158513 - 30 Jul 2021
Viewed by 434
Abstract
Basmati rice is increasingly recognized and consumed in different parts of the world due to its different tastes and nutritional properties. This research focused on determining the cadmium (Cd), cobalt (Co), Copper (Cu), iron (Fe), manganese (Mn), nickel (Ni) and zinc (Zn) content [...] Read more.
Basmati rice is increasingly recognized and consumed in different parts of the world due to its different tastes and nutritional properties. This research focused on determining the cadmium (Cd), cobalt (Co), Copper (Cu), iron (Fe), manganese (Mn), nickel (Ni) and zinc (Zn) content in locally grown basmati rice in Pakistan and assessing the risks of these values to human health. Root, shoot and grain samples of basmati rice were taken, along with soil samples from the five regions studied. Metal mean concentrations (mg/kg) in grains fluctuated from 2.70 to 9.80 for Cd, 4.80 to 9.85 for Zn, 1.16 to 1.46 for Cu, 1.84 to 10.86 for Co, 2.05 to 13.07 for Fe, 5.03 to 11.11 for Mn and 3.24 to 13.28 for Ni, respectively. All metal values were within permissible limits except for Cd. The enrichment factor for Cd was highest among all sites. Cobalt and zinc had the highest bioaccumulation factor and translocation factor. The highest enrichment factor was noticed for Cd and the lowest for Cu. The health risk index at all examined sites was less than one. Consistent examination is recommended to limit health hazards instigated by the use of rice polluted with a greater concentration of Cd. Full article
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Article
Determining the Optimum Level of Soil Olsen Phosphorus and Phosphorus Fertilizer Application for High Phosphorus-Use Efficiency in Zea mays L. in Black Soil
Sustainability 2021, 13(11), 5983; https://doi.org/10.3390/su13115983 - 26 May 2021
Viewed by 511
Abstract
Phosphorus is an essential macronutrient, both as a component of several important plant structural compounds and as a catalyst in the conversion of numerous important biochemical reactions in plants. The soil Olsen P (OP) level is an important factor affecting crop production and [...] Read more.
Phosphorus is an essential macronutrient, both as a component of several important plant structural compounds and as a catalyst in the conversion of numerous important biochemical reactions in plants. The soil Olsen P (OP) level is an important factor affecting crop production and P-use efficiency (PUE). We tested the effect of six OP levels and P doses on maize yield, where the P doses were 0, 22, 44, 59, 73, and 117 kg P2O5 ha−1, with three replications, from 2017 to 2019. The response of crop yield to the OP level can be divided into two parts, below 28 mg kg−1 and above 28 mg kg−1. The change point between the two parts was determined as the agronomic critical level for maize crops in the study area. The PUE (%) increased with soil OP levels and decreased with P fertilizer application rates. In addition, results for the low P application rate (P2), 22 kg P2O5 ha−1, showed that PUE significantly increased with an increase in the soil OP level compared with PUE at a low OP level (OP1), 0 kg P2O5 ha−1. The PUE value increased by 49.5%, 40.1%, and 32.4% at a high OP level (OP6) in 2017, 2018, and 2019, respectively, compared to that at a low OP level (OP1). At the same OP levels, in all three years, the PUE at a high P application rate (P6) decreased significantly, in the range of 62.8% to 78.7%, compared to that at a low P application rate (P2). Under an average deficit of 100 kg ha−1 P, the OP level of the soil in all three years decreased by 3.9 mg kg−1 in the treatment without P addition (P1) and increased by 2.4–3.5 mg kg−1 in the P treatments for each 100 kg ha−1 P surplus. A phosphorus application rate of 44 kg P2O5 ha−1 and an OP level of 28 mg kg−1 are sufficient to obtain an optimum yield, increase the PUE, and reduce environmental hazards in the study area in northeastern China. Full article
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Article
Assessing Yield Response and Relationship of Soil Boron Fractions with Its Accumulation in Sorghum and Cowpea under Boron Fertilization in Different Soil Series
Sustainability 2021, 13(8), 4192; https://doi.org/10.3390/su13084192 - 09 Apr 2021
Viewed by 469
Abstract
Boron (B) is an essential micronutrient in the growth of reproductive plant parts. Its deficiency and/or toxicity are widespread in arid and semi-arid soils with low clay contents. This study was planned to determine the response of sorghum (Sorghum bicolor L., non-leguminous [...] Read more.
Boron (B) is an essential micronutrient in the growth of reproductive plant parts. Its deficiency and/or toxicity are widespread in arid and semi-arid soils with low clay contents. This study was planned to determine the response of sorghum (Sorghum bicolor L., non-leguminous crop) and cowpea (Vigna sinensis L., leguminous crop) to boron (0, 2, 4, and 16 µg g−1) on four distinct soil series from Punjab, Pakistan i.e., Udic Haplustalf (Pindorian region), Typic Torrifluvent (Shahdra region), Halic Camborthid (Khurianwala region), and Udic Haplustalf (Gujranwala region). Overall, there was a significant difference (p < 0.05) in yield between the sorghum (3.8 to 5.5 g pot−1 of 5 kg dry soil) and cowpea (0.2 to 3.2 g pot−1 of 5 kg dry soil) in response to B application. The highest yield was observed in both sorghum and cowpea either in control or at 2 µg g−1 B application in all four soils. Cowpea showed the same yield trend in all four soils (i.e., an increase in yield at 2 µg g−1 B application, followed by a significant decrease at the higher B levels). In contrast, sorghum exhibited greater variability of response on different soils; Udic Haplustalf (Pindorian region) produced the greatest yield at low levels of B application. However, Halic Camborthid produced its lowest yield at that level. Boron concentration in shoots increased with the levels of B application, particularly in sorghum. In cowpea, the plant growth was extremely retarded—and most of the plants died at higher levels of B application even if a lower concentration of B was measured within the shoot. Hot water-extractable B was the most available fraction for cowpea (R2 = 0.96), whereas the easily exchangeable B was most available for sorghum (R2 = 0.90). Overall, these results have implications for micronutrient uptake for both leguminous and non-leguminous crops. Full article
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Article
Combined Citric Acid and Glutathione Augments Lead (Pb) Stress Tolerance and Phytoremediation of Castorbean through Antioxidant Machinery and Pb Uptake
Sustainability 2021, 13(7), 4073; https://doi.org/10.3390/su13074073 - 06 Apr 2021
Viewed by 530
Abstract
Lead (Pb) is one of the most toxic elements on earth. The main origins of Pb pollution are automobiles, paint and electroplating industries. Pb-induced stress has very toxic effects on plant growth and biomass. The concentration of reactive oxygen species (ROS) in plant [...] Read more.
Lead (Pb) is one of the most toxic elements on earth. The main origins of Pb pollution are automobiles, paint and electroplating industries. Pb-induced stress has very toxic effects on plant growth and biomass. The concentration of reactive oxygen species (ROS) in plant cells significantly increases under Pb stress, which interrupts the biochemical cycles in cells and leads to cell death. Therefore, it is essential to clean up the Pb-polluted soils. Among all techniques that are used to clean soil that is metal-contaminated, the best technique is phytoremediation. The present study intends to determine the role of citric acid (CA) and glutathione (GSH) in the phytoremediation of Pb by using castor bean plants. Plant biomass was significantly reduced due to Pb stress. Lead toxicity was also harmful to the photosynthetic pigments and antioxidant enzymes activities. In reverse, the content of malondialdehyde (MDA), H2O2 concentration and electrolyte leakage (EL) were increased under Pb stress. The combined application of GSH and CA enhanced photosynthetic pigments, antioxidant enzyme activities and plant biomass and minimized MDA, H2O2 and EL under Pb stress. The amount of Pb in roots and leaves remarkably increased by the joint application of CA and GSH. The combined application of CA and GSH (5 mM + 25 mM, respectively) was proven to be beneficial compared to the control. From the present results, we can conclude that the combined application of CA and GSH promoted the phytoremediation of Pb and helped the host plant to combat Pb toxicity. Full article
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Article
The Recovery of Phosphate and Ammonium from Biogas Slurry as Value-Added Fertilizer by Biochar and Struvite Co-Precipitation
Sustainability 2021, 13(7), 3827; https://doi.org/10.3390/su13073827 - 31 Mar 2021
Viewed by 564
Abstract
Biowaste materials could be considered a renewable source of fertilizer if methods for recovering P from waste can be developed. Over the last few decades, there has been a high level of interest in using biochar to remove contaminants from aqueous solutions. This [...] Read more.
Biowaste materials could be considered a renewable source of fertilizer if methods for recovering P from waste can be developed. Over the last few decades, there has been a high level of interest in using biochar to remove contaminants from aqueous solutions. This study was conducted using a range of salts that are commonly found in biogas slurry (ZnCl2, FeCl3, FeCl2, CuCl2, Na2CO3, and NaHCO3). Experiments with a biogas digester and aqueous solution were conducted at pH nine integration with NH4+, Mg2+, and PO43− molar ratios of 1.0, 1.2, and 1.8, respectively. The chemical analysis was measured to find out the composition of the precipitate, and struvite was employed to remove the aqueous solutions. The study found that the most efficient removal of phosphate and ammonium occurred at pH nine in Tongan sludge urban biochar and rice biochar, respectively. Increasing the concentration of phosphate and ammonium increased the phosphate and ammonium content. Moreover, increasing the biochar temperature and increasing the concentration of phosphate and ammonium increased the efficiency of the removal of ammonium and phosphate. The removal efficiency of ammonium and phosphate increased from 15.0% to 71.0% and 18.0% to 99.0%, respectively, by increasing the dose of respective ions K+, Zn2+, Fe3+, Fe2+, Cu2+, and CO32.The elements were increased from 58.0 to 71.0 for HCO3 with the increasing concentration from 30 mg L−1 to 240 mg L−1.This study concluded that phosphate and ammonium can be recovered from mushroom soil biochar and rice biochar, and phosphate can be effectively recovered via the struvite precipitation method. Full article
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Article
Deciphering the Effects of Waste Amendments on Particulate Organic Carbon and Soil C-Mineralization Dynamics
Sustainability 2021, 13(7), 3790; https://doi.org/10.3390/su13073790 - 29 Mar 2021
Viewed by 410
Abstract
It is important to understand the dynamics of soil carbon to study the effects of waste amendment inputs on soil organic carbon decomposition. The aim of this study was to evaluate the effect of waste amendment carbon input on the soil organic carbon [...] Read more.
It is important to understand the dynamics of soil carbon to study the effects of waste amendment inputs on soil organic carbon decomposition. The aim of this study was to evaluate the effect of waste amendment carbon input on the soil organic carbon (SOC) content, soil particulate organic carbon (POC) content and soil organic carbon mineralization rate dynamics. A 60-day experiment was carried out in the laboratory. The following treatments were compared: (1) CK: soil without amendments; (2) FW1: soil with food waste compost (soil/food waste compost = 100:1); (3) FW2: soil with food waste compost (soil/food waste compost = 100:2); (4) GW1: soil with garden waste compost (soil/garden waste compost = 100:0.84); (5) GW2: soil with garden waste compost (soil/garden waste compost = 100:1.67); (6) FGW1: soil amendments mixture (soil/food waste compost/garden waste compost = 100:0.5:0.42); (7) FGW2: soil amendments mixture (soil/food waste compost/garden waste compost = 100:1:0.84); the inputs of amendment carbon to FW1, GW1 and FGW1 were 2.92 g kg−1, the inputs of amendment carbon to FW2, GW2 and FGW2 were 5.84 g kg−1. The results showed that the addition of waste amendments increased the amount of cumulative mineralization from 95% to 262% and accelerated the rate of soil mineralization. After adding organic materials, the change in the soil organic carbon mineralization rate could be divided into two stages: the fast stage and the slow stage. The dividing point of the two stages was approximately 10 days. When equal amounts of waste amendment carbon were input to the soil, there was no significant difference in SOC between food waste and garden waste. However, SOC increased with the amount of amendment addition. However, for POC, there was no significant difference between the different amounts of carbon input to the garden waste compost treatments. SOC and POC were significantly correlated with the cumulative emissions of CO2. Full article
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Article
Contribution of Rhizobium–Legume Symbiosis in Salt Stress Tolerance in Medicago truncatula Evaluated through Photosynthesis, Antioxidant Enzymes, and Compatible Solutes Accumulation
Sustainability 2021, 13(6), 3369; https://doi.org/10.3390/su13063369 - 18 Mar 2021
Cited by 1 | Viewed by 599
Abstract
The effects of salt stress on the growth, nodulation, and nitrogen (N) fixation of legumes are well known, but the relationship between symbiotic nitrogen fixation (SNF) driven by rhizobium–legume symbiosis and salt tolerance in Medicago truncatula is not well studied. The effects of [...] Read more.
The effects of salt stress on the growth, nodulation, and nitrogen (N) fixation of legumes are well known, but the relationship between symbiotic nitrogen fixation (SNF) driven by rhizobium–legume symbiosis and salt tolerance in Medicago truncatula is not well studied. The effects of the active nodulation process on salt stress tolerance of Medicago truncatula were evaluated by quantifying the compatible solutes, soluble sugars, and antioxidants enzymes, as well as growth and survival rate of plants. Eight weeks old plants, divided in three groups: (i) no nodules (NN), (ii) inactive nodules (IN), and (iii) active nodules (AN), were exposed to 150 mM of NaCl salt stress for 0, 8, 16, 24, 32, 40, and 48 h in hydroponic system. AN plants showed a higher survival rate (30.83% and 38.35%), chlorophyll contents (37.18% and 44.51%), and photosynthesis compared to IN and NN plants, respectively. Improved salt tolerance in AN plants was linked with higher activities of enzymatic and nonenzymatic antioxidants and higher K+ (20.45% and 39.21%) and lower Na+ accumulations (17.54% and 24.51%) when compared with IN and NN plants, respectively. Additionally, higher generation of reactive oxygen species (ROS) was indicative of salt stress, causing membrane damage as revealed by higher electrolyte leakage and lipid peroxidation. All such effects were significantly ameliorated in AN plants, showing higher compatible solutes (proline, free amino acids, glycine betaine, soluble sugars, and proteins) and maintaining higher relative water contents (61.34%). This study advocates positive role of Rhizobium meliloti inoculation against salt stress through upregulation of antioxidant system and a higher concentration of compatible solutes. Full article
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Article
The Coupled Effects of Irrigation Scheduling and Nitrogen Fertilization Mode on Growth, Yield and Water Use Efficiency in Drip-Irrigated Winter Wheat
Sustainability 2021, 13(5), 2742; https://doi.org/10.3390/su13052742 - 03 Mar 2021
Viewed by 549
Abstract
Sound irrigation and nitrogen management strategies are necessary to achieve sustainable yield and water use efficiency of winter wheat in the North China Plain (NCP). The coupled effects of irrigation scheduling and the nitrogen application mode (NAM) on winter wheat growth, yield and [...] Read more.
Sound irrigation and nitrogen management strategies are necessary to achieve sustainable yield and water use efficiency of winter wheat in the North China Plain (NCP). The coupled effects of irrigation scheduling and the nitrogen application mode (NAM) on winter wheat growth, yield and water use efficiency under drip irrigation were evaluated with a two-year field experiment, which consisted of three irrigation scheduling levels (ISLs) (irrigating when soil water consumption (SWC) reached 20, 35 and 50 mm, referred as I20, I35 and I50, respectively) and three nitrogen application modes (NAMs) (ratio of basal application and topdressing as 50:50, 25:75 and 0:100, referred as N50:50, N25:75 and N0:100, respectively). The experimental results showed that irrigating winter wheat at ISL I35 substantially (p < 0.05) improved the grain yield by 15.89%, 3.32% and 14.82%, 4.31% and water use efficiency (WUE) by 5.23%, 16.03% and 5.26%, 12.36%, compared with those at ISL I20 and I50 in 2017–2018 and 2018–2019 growing seasons, respectively. NAM N25:75 appeared very beneficial in terms of grain yield, yield components and WUE as compared to other NAM levels. The maximum grain yield (8.62 and 9.40 t ha−1) and water use efficiency (1.88 and 2.09 kg m−3) were achieved in treatment I35N25:75 in two growing seasons over those in other treatments. The results in this study may deliver a scientific basis for irrigation and nitrogen fertilization management of the drip-irrigated winter wheat production in the NCP. Full article
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Article
A Field Evidence of Cd, Zn and Cu Accumulation in Soil and Rice Grains after Long-Term (27 Years) Application of Swine and Green Manures in a Paddy Soil
Sustainability 2021, 13(4), 2404; https://doi.org/10.3390/su13042404 - 23 Feb 2021
Viewed by 541
Abstract
Although inorganic and organic manures with high concentrations of heavy metals can lead to accumulation or contamination of heavy metals in soils, there are few reports on the effects of long-term application of swine and green manures on the accumulation of heavy metals [...] Read more.
Although inorganic and organic manures with high concentrations of heavy metals can lead to accumulation or contamination of heavy metals in soils, there are few reports on the effects of long-term application of swine and green manures on the accumulation of heavy metals in rice grains in paddy soils. A long-term field experiment, which was established in 1990 in paddy soil in Hangzhou, China, was used to investigate the effects of inorganic and organic manures on the availability and accumulation of heavy metals in soil and uptake by rice plant. The results showed that long-term application of nitrogen, phosphorus and potash (NPK) plus green manure or swine manure, and swine manure only increased 202%, 146%, and 100% for total Cd, and 5.5%, 7.6%, and 6.6% for total Cu in rice grains, respectively compared to the control without fertilization. Total Zn in rice grain was significantly increased by 13.9% for the treatment of NPK plus green manure. The accumulation of Cd, Zn, and Cu in rice grains after long-term application of swine and green manures is due to the combined effects of the increased concentrations of total and EDTA extractable Cd, Zn, and Cu in soil and the changes of soil properties. Furthermore, the highest bioconcentration factor for Cd was found in the treatment of NPK plus green manure while for Zn and Cu it was observed in NPK treatment. Thus, it may be concluded that green manure and manure with increased Cd, Zn, and Cu in rice grain results in a potential risk of metal accumulation in paddy soils. Full article
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Article
Multi-Scale Evaluation of Dominant Factors (MSDF) on Forage: An Ecosystemic Method to Understand the Function of Forage
Sustainability 2021, 13(4), 2163; https://doi.org/10.3390/su13042163 - 18 Feb 2021
Viewed by 502
Abstract
Grassland agroecosystem plays a key role on resource cycling and sustainability of global ecosystem. Forage is the basic factor and core of the grassland agroecosystem. At a single scale, the most of forage evaluation remain in a state of qualitative or quantitative evaluation, [...] Read more.
Grassland agroecosystem plays a key role on resource cycling and sustainability of global ecosystem. Forage is the basic factor and core of the grassland agroecosystem. At a single scale, the most of forage evaluation remain in a state of qualitative or quantitative evaluation, and lack a series of quantitative evaluation at multi spatial scales and influence of society, environment and economy. This study collected dominant indicators at micro, plot, farm, ecoregional and macro scales to compile a systemic evaluation of forage in agroecosystems. A case study is presented for forage evaluation by using plot, farm, and regional data from an arid region of Gansu, China. Multi-scale evaluation of dominant factors (MSDF) was used to aggregate forage evaluation indicators. Results showed that the scale of evaluation had significant effects on the results of the evaluation. The evaluation results of the single index for the same forage species among plot, farm and ecoregional scales were different. Results implied that forage MSDF are needed to guide the evaluation of forage and then production of forage and herbivore in the future. An appropriate scale of evaluation could be selected in term of the forage production objectives and moreover, MSDF evaluation of forage should be used to improve the environmental, social and productive evaluation of forage in a grassland agroecosystems. Full article
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Article
Isolation and Characterization of Phosphate Solubilizing Microbes from Rock Phosphate Mines and Their Potential Effect for Sustainable Agriculture
Sustainability 2021, 13(4), 2151; https://doi.org/10.3390/su13042151 - 17 Feb 2021
Cited by 3 | Viewed by 1143
Abstract
Continuous application of phosphate (P) mineral to soil renders apatite addition during each crop growing season which is of great concern from a sustainable agriculture viewpoint. Use of efficient phosphate solubilizing microbes (PSB) is one of the most effective ways to solubilize this [...] Read more.
Continuous application of phosphate (P) mineral to soil renders apatite addition during each crop growing season which is of great concern from a sustainable agriculture viewpoint. Use of efficient phosphate solubilizing microbes (PSB) is one of the most effective ways to solubilize this apatite mineral in the soil. The current study targeted hydroxyapatite mines to explore, isolate and characterize efficient P solubilizers to solubilize apatite in the soil. Efficiency of isolated microbes to solubilize rock phosphate (hydroxyapatite) and tri-calcium phosphate (TCP) as well as indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate deaminase (ACC) activity were tested. Identification and phylogenetic analysis of bacterial and fungal isolates were carried out by 16S rRNA and internal transcribed spacer (ITS) rDNA sequence analyses, respectively. The isolated bacterial strains were identified as Staphylococcus sp., Bacillus firmus, Bacillus safensis, and Bacillus licheniformis whereas fungal isolates were identified as Penicillium sp. and Penicillium oxalicum. Results showed that the impact of identified strains in combination with three phosphate fertilizers sources (compost, rock phosphate and diammonium phosphate (DAP)) was conspicuous on maize crop grown in pot. Both bacterial and fungal strains increased the P uptake by plants as well as recorded with higher available P in post-harvested soil. Penicillium sp. in combination with compost resulted in maximum P-uptake by plants and post-harvest soil P contents, compared to other combinations of P sources and bio-inoculants. Screening and application of efficient P solubilizers can be a better option to utilize the indigenous phosphate reserves of soil as well as organic amendments for sustainable agriculture. Full article
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Review

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Review
Potentials, Utilization, and Bioengineering of Plant Growth-Promoting Methylobacterium for Sustainable Agriculture
Sustainability 2021, 13(7), 3941; https://doi.org/10.3390/su13073941 - 02 Apr 2021
Viewed by 614
Abstract
Plant growth-promoting bacteria (PGPB) have great potential to provide economical and sustainable solutions to current agricultural challenges. The Methylobacteria which are frequently present in the phyllosphere can promote plant growth and development. The Methylobacterium genus is composed mostly of pink-pigmented facultative methylotrophic bacteria, [...] Read more.
Plant growth-promoting bacteria (PGPB) have great potential to provide economical and sustainable solutions to current agricultural challenges. The Methylobacteria which are frequently present in the phyllosphere can promote plant growth and development. The Methylobacterium genus is composed mostly of pink-pigmented facultative methylotrophic bacteria, utilizing organic one-carbon compounds as the sole carbon and energy source for growth. Methylobacterium spp. have been isolated from diverse environments, especially from the surface of plants, because they can oxidize and assimilate methanol released by plant leaves as a byproduct of pectin formation during cell wall synthesis. Members of the Methylobacterium genus are good candidates as PGPB due to their positive impact on plant health and growth; they provide nutrients to plants, modulate phytohormone levels, and protect plants against pathogens. In this paper, interactions between Methylobacterium spp. and plants and how the bacteria promote crop growth is reviewed. Moreover, the following examples of how to engineer microbiomes of plants using plant-growth-promoting Methylobacterium are discussed in the present review: introducing external Methylobacterium spp. to plants, introducing functional genes or clusters to resident Methylobacterium spp. of crops, and enhancing the abilities of Methylobacterium spp. to promote plant growth by random mutation, acclimation, and engineering. Full article
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