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Background Tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire) is a popular perennial grass species for livestock production and amenities in the United States. Tall fescue often forms a symbiotic relationship with fungal endophytes (Epichloë coenophiala) which provides increased plant tolerance to environmental stress compared to endophyte-free plants. However, whether this improved plant performance is the sole result of the unique relationship between the grass and the shoot-dwelling fungal endophyte of rhizosphere origin remains a question. This symbiosis possibly regulates the recruitment of beneficial soil microbial communities in endophyte-infected tall fescue rhizosphere and may offer enhanced nutrients and water acquisition, thereby, providing the plant with an increased tolerance level against environmental stresses. We compared the soil bacterial and fungal community composition and investigated possible community shifts in soil microbial populations based on endophyte infection in tall fescue by analyzing the 16s rRNA gene and ITS specific region. Results Our data revealed that bacterial community richness and the evenness indicated by Shannon Diversity Index (SDI) was greater than 4 in both endophyte-infected and endophyte-free tall fescue soil. In both types tall fescue soil, the prominent bacterial families were Planctomycetaceae, Balstocatellaceae_(subgroup_4), Chitinophagaceae, and Bacillaceae. In the case of soil fungal diversity, the SDI was overall low and ranged between 1.21 for endophyte-free and 1.27 for endophyte-infected tall fescue soil. The prominent fungal phyla were Basidiomycota and Ascomycota, and we observed a clear fungal community difference between endophyte-infected and endophyte-free soil at the phylum level. Moreover, endophyte-infected tall fescue soil showed a greater diversity at the genus level compared to endophyte-free tall fescue soil. In addition, plant-available soil phosphorus (P) is also influenced by the presence of endophytes in tall fescue. Conclusion Our results indicate that there is a tripartite relationship between tall fescue, the presence of fungal endophyte in the tall fescue, and the below-ground soil fungal communities. The dynamic of this three-way interaction perhaps contributes to the nutrient acquisition and stress tolerance by tall fescue possibly by recruiting a diverse array of potentially beneficial soil microbes.
Kishan Mahmud; Kendall Lee; Nicholas Hill; Ali Missaoui. Influence of Tall Fescue Epichloë endophytes on Rhizosphere Soil Microbiome. 2021, 1 .
AMA StyleKishan Mahmud, Kendall Lee, Nicholas Hill, Ali Missaoui. Influence of Tall Fescue Epichloë endophytes on Rhizosphere Soil Microbiome. . 2021; ():1.
Chicago/Turabian StyleKishan Mahmud; Kendall Lee; Nicholas Hill; Ali Missaoui. 2021. "Influence of Tall Fescue Epichloë endophytes on Rhizosphere Soil Microbiome." , no. : 1.
The major forces driving farm-level production for the ever-growing global population have relied upon mechanized farming techniques, synthetic inputs, and developing high-yielding crop varieties. Recently, however, there has been a gradual shift toward developing sustainable approaches addressing the potential use of beneficial traits of the soil-plant microbiome to establish a sustainable food supply as well as to maintain soil and plant health. The intricate relationship of the soil-plant microbiome complex often faces difficulty in the efficient translation for the broad spectrum of audiences across society. In recent years, there has been a growing need to formulate strategies and streamline the global sharing of the generated information on plant microbiome interactions. In this review, we discuss novel and emerging strategies to use indigenous microbial consortia and engineered exogenous microbial inoculants for rhizosphere engineering. In addition, this review also details the use of these microbial consortia to improve crop yields and environmental protection that are currently in practice.
Kishan Mahmud; Ali Missaoui; Kendall C. Lee; Bhawana Ghimire; Holly W. Presley; Shiva Makaju. Rhizosphere Microbiome Manipulation for Sustainable Crop Production. Current Plant Biology 2021, 27, 100210 .
AMA StyleKishan Mahmud, Ali Missaoui, Kendall C. Lee, Bhawana Ghimire, Holly W. Presley, Shiva Makaju. Rhizosphere Microbiome Manipulation for Sustainable Crop Production. Current Plant Biology. 2021; 27 ():100210.
Chicago/Turabian StyleKishan Mahmud; Ali Missaoui; Kendall C. Lee; Bhawana Ghimire; Holly W. Presley; Shiva Makaju. 2021. "Rhizosphere Microbiome Manipulation for Sustainable Crop Production." Current Plant Biology 27, no. : 100210.
The study of interrelationships among soil health indicators is important for (i) achieving better understanding of nutrient cycling, (ii) making soil health assessment cost-effective by eliminating redundant indicators, and (iii) improving nitrogen (N) fertilizer recommendation models. The objectives of this study were to (i) decipher complex interrelationships of selected chemical, physical, and biological soil health indicators in pastures with history of inorganic or broiler litter fertilization, and (ii) establish associations among inorganic N, potentially mineralizable N (PMN), and soil microbial biomass (SMBC), and other soil health indicators. In situ soil respiration was measured and soil samples were collected from six beef farms in 2017 and 2018 to measure selected soil health indicators. We were able to establish associations between easy-to-measure active carbon (POXC) vs. PMN (R2 = 0.52), and N (R2 = 0.43). POXC had a noteworthy quadratic relationship with N and nitrate, where we found dramatic increase of N and nitrate beyond an inflection point of 500 mg kg−1 POXC. This point may serve as threshold for soil health assessment. The relationships of loss-on-ignition (LOI) carbon with other soil health indicators were discernable between inorganic- and broiler litter-fertilized pastures. We were able to establish association of SMBC with other soil variables (R2 = 0.76) and there was detectable difference in SMBC between inorganic-fertilized and broiler litter-fertilized pastures. These results could be useful for cost-effective soil health assessment and optimization of N fertilizer recommendation models to improve N use efficiency and grazing system sustainability.
Subash Dahal; Dorcas Franklin; Anish Subedi; Miguel Cabrera; Laura Ney; Brendan Fatzinger; Kishan Mahmud. Interrelationships of Chemical, Physical and Biological Soil Health Indicators in Beef-Pastures of Southern Piedmont, Georgia. Sustainability 2021, 13, 4844 .
AMA StyleSubash Dahal, Dorcas Franklin, Anish Subedi, Miguel Cabrera, Laura Ney, Brendan Fatzinger, Kishan Mahmud. Interrelationships of Chemical, Physical and Biological Soil Health Indicators in Beef-Pastures of Southern Piedmont, Georgia. Sustainability. 2021; 13 (9):4844.
Chicago/Turabian StyleSubash Dahal; Dorcas Franklin; Anish Subedi; Miguel Cabrera; Laura Ney; Brendan Fatzinger; Kishan Mahmud. 2021. "Interrelationships of Chemical, Physical and Biological Soil Health Indicators in Beef-Pastures of Southern Piedmont, Georgia." Sustainability 13, no. 9: 4844.
Nitrogen (N) in the agricultural production system influences many aspects of agroecosystems and several critical ecosystem services widely depend on the N availability in the soil. Cumulative changes in regional ecosystem services may lead to global environmental changes. Thus, the soil N status in agriculture is of critical importance to strategize its most efficient use. Nitrogen is also one of the most susceptible macronutrients to environmental loss, such as ammonia volatilization (NH3), nitrous oxide (N2O) emissions, nitrate leaching (NO3), etc. Any form of N losses from agricultural systems can be major limitations for crop production, soil sustainability, and environmental safeguard. There is a need to focus on mitigation strategies to minimize global N pollution and implement agricultural management practices that encourage regenerative and sustainable agriculture. In this review, we identified the avenues of N loss into the environment caused by current agronomic practices and discussed the potential practices that can be adapted to prevent this N loss in production agriculture. This review also explored the N status in agriculture during the COVID-19 pandemic and the existing knowledge gaps and questions that need to be addressed.
Kishan Mahmud; Dinesh Panday; Anaas Mergoum; Ali Missaoui. Nitrogen Losses and Potential Mitigation Strategies for a Sustainable Agroecosystem. Sustainability 2021, 13, 2400 .
AMA StyleKishan Mahmud, Dinesh Panday, Anaas Mergoum, Ali Missaoui. Nitrogen Losses and Potential Mitigation Strategies for a Sustainable Agroecosystem. Sustainability. 2021; 13 (4):2400.
Chicago/Turabian StyleKishan Mahmud; Dinesh Panday; Anaas Mergoum; Ali Missaoui. 2021. "Nitrogen Losses and Potential Mitigation Strategies for a Sustainable Agroecosystem." Sustainability 13, no. 4: 2400.
In agroecosystems, nitrogen is one of the major nutrients limiting plant growth. To meet the increased nitrogen demand in agriculture, synthetic fertilizers have been used extensively in the latter part of the twentieth century, which have led to environmental challenges such as nitrate pollution. Biological nitrogen fixation (BNF) in plants is an essential mechanism for sustainable agricultural production and healthy ecosystem functioning. BNF by legumes and associative, endosymbiotic, and endophytic nitrogen fixation in non-legumes play major roles in reducing the use of synthetic nitrogen fertilizer in agriculture, increased plant nutrient content, and soil health reclamation. This review discusses the process of nitrogen-fixation in plants, nodule formation, the genes involved in plant-rhizobia interaction, and nitrogen-fixing legume and non-legume plants. This review also elaborates on current research efforts involved in transferring nitrogen-fixing mechanisms from legumes to non-legumes, especially to economically important crops such as rice, maize, and wheat at the molecular level and relevant other techniques involving the manipulation of soil microbiome for plant benefits in the non-legume root environment.
Kishan Mahmud; Shiva Makaju; Razi Ibrahim; Ali Missaoui. Current Progress in Nitrogen Fixing Plants and Microbiome Research. Plants 2020, 9, 97 .
AMA StyleKishan Mahmud, Shiva Makaju, Razi Ibrahim, Ali Missaoui. Current Progress in Nitrogen Fixing Plants and Microbiome Research. Plants. 2020; 9 (1):97.
Chicago/Turabian StyleKishan Mahmud; Shiva Makaju; Razi Ibrahim; Ali Missaoui. 2020. "Current Progress in Nitrogen Fixing Plants and Microbiome Research." Plants 9, no. 1: 97.
Generally, improvement in the soil health of pasturelands can result in amplified ecosystem services which can help improve the overall sustainability of the system. The extent to which specific best management practices have this effect has yet to be established. A farm-scale study was conducted in eight beef-pastures in the Southern Piedmont of Georgia, from 2015 to 2018, to assess the effect of strategic-grazing (STR) and continuous-grazing hay distribution (CHD) on soil health indicators and runoff nitrate losses. In 2016, four pastures were converted to the STR system and four were grazed using the CHD system. Post-treatment, in 2018, the STR system had significantly greater POXC (by 87.1, 63.4, and 55.6 mg ha−1 at 0–5, 5–10, and 10–20 cm, respectively) as compared to CHD system. Soil respiration was also greater in the STR system (by 235 mg CO2 m-2 24 h−1) and less nitrate was lost in the runoff (by 0.21 kg ha−1) as compared to the CHD system. Cattle exclusion and overseeding vulnerable areas of pastures in STR pastures facilitated nitrogen mineralization and uptake. Our results showed that the STR grazing system could improve the sustainability of grazing systems by storing more labile carbon, efficiently mineralizing soil nitrogen, and lowering runoff nitrate losses.
Subash Dahal; Dorcas Franklin; Anish Subedi; Miguel Cabrera; Dennis Hancock; Kishan Mahmud; Laura Ney; Cheolwoo Park; Deepak Mishra. Strategic Grazing in Beef-Pastures for Improved Soil Health and Reduced Runoff-Nitrate-A Step towards Sustainability. Sustainability 2020, 12, 558 .
AMA StyleSubash Dahal, Dorcas Franklin, Anish Subedi, Miguel Cabrera, Dennis Hancock, Kishan Mahmud, Laura Ney, Cheolwoo Park, Deepak Mishra. Strategic Grazing in Beef-Pastures for Improved Soil Health and Reduced Runoff-Nitrate-A Step towards Sustainability. Sustainability. 2020; 12 (2):558.
Chicago/Turabian StyleSubash Dahal; Dorcas Franklin; Anish Subedi; Miguel Cabrera; Dennis Hancock; Kishan Mahmud; Laura Ney; Cheolwoo Park; Deepak Mishra. 2020. "Strategic Grazing in Beef-Pastures for Improved Soil Health and Reduced Runoff-Nitrate-A Step towards Sustainability." Sustainability 12, no. 2: 558.
In order to ensure a soil system’s sustained ability to carry out ecosystem services, indicators that assess soil health are needed. We examined the capacity of nematode maturity index (MI), structure index (SI), enrichment index (EI), and trophic groups as measures of soil health, by determining soil nematodes’ sensitivity to cropping systems: rotation, perturbation, fertilization, and inoculation with local effective microorganisms (LEM). Plots were managed for two years under different rotations, annual ryegrass/fallow (ARF) and cereal rye/edamame soybean (CRS). In the third year of the study, all of the plots were managed exactly the same as a wheat/edamame rotation. Data were collected in both winter and summer of this year. In all three years, three inoculant treatments (LEM, False-LEM and No inoculate) were applied. In CRS plots, which received the most tillage and fertilization, there were greater SI values in soils that received LEM application. Nematode community structure described by each MI, SI, and EI were sensitive enough to reflect changes due to differences in soil management practices from previous years. Principal components analysis confirmed that nitrogen mineralization is an important measure to include when using nematode community analysis in the development of a soil health index.
Laura Ney; Dorcas Franklin; Kishan Mahmud; Miguel Cabrera; Dennis Hancock; Mussie Habteselassie; Quint Newcomer; Subash Dahal; Anish Subedi. Sensitivity of Nematode Community Analysis to Agricultural Management Practices and Inoculation with Local Effective Microorganisms in the Southeastern United States. Soil Systems 2019, 3, 41 .
AMA StyleLaura Ney, Dorcas Franklin, Kishan Mahmud, Miguel Cabrera, Dennis Hancock, Mussie Habteselassie, Quint Newcomer, Subash Dahal, Anish Subedi. Sensitivity of Nematode Community Analysis to Agricultural Management Practices and Inoculation with Local Effective Microorganisms in the Southeastern United States. Soil Systems. 2019; 3 (2):41.
Chicago/Turabian StyleLaura Ney; Dorcas Franklin; Kishan Mahmud; Miguel Cabrera; Dennis Hancock; Mussie Habteselassie; Quint Newcomer; Subash Dahal; Anish Subedi. 2019. "Sensitivity of Nematode Community Analysis to Agricultural Management Practices and Inoculation with Local Effective Microorganisms in the Southeastern United States." Soil Systems 3, no. 2: 41.
Uneven spatial distribution of soil N in conventionally managed pastures is a function of various biotic and abiotic factors and results in poor land use efficiency. In this study, we measured soil inorganic N (at depths of 0–5, 5–10, and 10–20 cm) in a 50-m grid and specific areas of interest from eight conventionally managed beef pastures (∼17 ha each), four near Eatonton and four near Watkinsville in the southern Piedmont of Georgia, USA, to assess the effects of management, landscape, and cattle locus in spatial distribution of soil inorganic N. Significant spatial autocorrelation was observed in the soil inorganic N indicating that the regions of high inorganic N deposition were near (within 91 m of) one or more pasture equipage (hay, shade, and water). In the Watkinsville pastures, inorganic N was 65% higher within 5 m of shade than the rest of the pastures, down to a 10-cm soil depth. In the Eatonton pastures, inorganic N (0–5 cm) was 22% higher within 30 m of a hay-feeding areas than the rest of the pasture. Cattle locus calculated as cattle density (cow ha−1 yr−1) was a function of pasture equipage and had a significant positive relationship with soil inorganic N. Landscape parameters (slope and elevation) significantly affected inorganic N distribution; however, the effect was small and was masked by management factors. Our results suggest that strategic placement of pasture equipage (hay, shade, and water) can effectively distribute N where needed in beef pastures, thereby increasing land use efficiency. Copyright © 2018. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
Subash Dahal; Dorcas H. Franklin; Miguel L. Cabrera; Dennis W. Hancock; Lawton Stewart; Laura C. Ney; Anish Subedi; Kishan Mahmud. Spatial Distribution of Inorganic Nitrogen in Pastures as Affected by Management, Landscape, and Cattle Locus. Journal of Environmental Quality 2018, 47, 1468 -1477.
AMA StyleSubash Dahal, Dorcas H. Franklin, Miguel L. Cabrera, Dennis W. Hancock, Lawton Stewart, Laura C. Ney, Anish Subedi, Kishan Mahmud. Spatial Distribution of Inorganic Nitrogen in Pastures as Affected by Management, Landscape, and Cattle Locus. Journal of Environmental Quality. 2018; 47 (6):1468-1477.
Chicago/Turabian StyleSubash Dahal; Dorcas H. Franklin; Miguel L. Cabrera; Dennis W. Hancock; Lawton Stewart; Laura C. Ney; Anish Subedi; Kishan Mahmud. 2018. "Spatial Distribution of Inorganic Nitrogen in Pastures as Affected by Management, Landscape, and Cattle Locus." Journal of Environmental Quality 47, no. 6: 1468-1477.
Laura Ney; Dorcas Franklin; Kishan Mahmud; Miguel Cabrera; Dennis Hancock; Mussie Habteselassie; Quint Newcomer. Examining trophic-level nematode community structure and nitrogen mineralization to assess local effective microorganisms’ role in nitrogen availability of swine effluent to forage crops. Applied Soil Ecology 2018, 130, 209 -218.
AMA StyleLaura Ney, Dorcas Franklin, Kishan Mahmud, Miguel Cabrera, Dennis Hancock, Mussie Habteselassie, Quint Newcomer. Examining trophic-level nematode community structure and nitrogen mineralization to assess local effective microorganisms’ role in nitrogen availability of swine effluent to forage crops. Applied Soil Ecology. 2018; 130 ():209-218.
Chicago/Turabian StyleLaura Ney; Dorcas Franklin; Kishan Mahmud; Miguel Cabrera; Dennis Hancock; Mussie Habteselassie; Quint Newcomer. 2018. "Examining trophic-level nematode community structure and nitrogen mineralization to assess local effective microorganisms’ role in nitrogen availability of swine effluent to forage crops." Applied Soil Ecology 130, no. : 209-218.