Biochar offers several benefits as a soil amendment, including increased soil fertility, carbon s... more Biochar offers several benefits as a soil amendment, including increased soil fertility, carbon sequestration, and water-holding capacity in nutrient-poor soils. Here, we performed a series of enzyme assays on pine biochar-amended soils, comparing multiple enzyme activities (EAs) simultaneously determined in the same soil sample vs. the sum of individual EAs involved in the C, N, S, and P cycles to provide information of the impacts of biochar on biogeochemical cycling. The combination of these four EAs has been considered an indicator of soil health due to their role in the reactions that release bioavailable nutrients in the cycling of C (β-glucosidase), N and C (β-glucosaminidase), P (acid phosphomonoesterase), and S (arylsulfatase) in soils. Comparisons of the theoretical EAs and the CNPS activity assay approaches in the biochar-modified soil revealed similar activity trends with the different concentrations of added biochar. Two years after adding biochar, study results showed the amended soils did not retain more pNP substrate than the un-amended control soils in three different pH buffers (5.5, 5.8, and 6.5) commonly used in EA reactions. Finally, we performed a third experiment to determine if the biochar previously added to the EAs interfered with the reactions' enzyme or substrate. The results indicated that greater activity was measured using the combined assay, which suggests the CNPS activity method was less affected by biochar than the individual EAs. Our findings indicate that the potential soil biochemical-health index, CNPS activity (combination of four enzymes) assay is more robust than the individual EAs and can be used as an alternative tool to monitor soil functioning.
Prescribed burning and tree thinning are commonly used restoration practices for US forests manag... more Prescribed burning and tree thinning are commonly used restoration practices for US forests management to increase forest productivity and enhance plant and animal diversity. The impact of these practices in Alabama's Bankhead National Forest (BNF) to soil microbial components and overall forest soil health are unknown. We hypothesized that microbial assemblages and enzyme activities are continuously changing in forest ecosystems especially due to management selections. Therefore, the objective of this study was to assess changes in microbial community compositions (fungal vs bacterial populations) via fatty acid methyl ester (FAME) profiling and several enzyme activities (β-glucosaminidase, acid phosphatase, arylsulfatase, β-glucosidase, xylanase, laccase, and manganese peroxidase) critical to soil organic matter (SOM) dynamics and biogeochemical cycling. In this forest, heavily-thinned plots without burning or less frequent burning treatments seemed to provide more favorable conditions (higher pH and lower C:N ratios) for C and N mineralization. This may explain a slight increase (by 12%) detected in fungi:bacteria (F:B) ratio in the heavily-thinned plots relative to the control. Thinned (lightly and heavily) plots showed greater ligninolytic (laccase and MnP) activities and lower β-glucosidase and β-glucosaminidase activities compared to the no-thinned plots probably due to increase depositions of woody recalcitrant C materials. We observed significant but negative correla-
Sulfatases which cleave sulfate esters in biological systems are key enzymes that deserve special... more Sulfatases which cleave sulfate esters in biological systems are key enzymes that deserve special attention due to their significant roles in organic sulfur (OS) mineralization and inorganic sulfur ( 2 4 SO -) release. In this study, in-vitro experiments were conducted to evaluate S bonded substrate hydrolysis by a commercially available arylsulfatase (EC 3.1.6.1) from Aerobacter aerogenes. The enzyme-substrate interactions were assessed to determine: 1) rate of hydrolysis, 2) catalytic efficiency, 3) thermal stability, and 4) optimal pH of this enzyme. Arylsulfatase exhibited substrate hydrolysis with a high affinity for p-nitrophenyl sulfate (potassium 4-nitrophenyl sulfate (pNPS)). The optimum activity for the enzyme was observed to occur at a pH of 7.1. The optimal temperature was 37˚C but ranged from 35˚C -45˚C. The apparent K m and K cat of the enzyme for pNPS hydrolysis at the optimal pH, and temperature were determined to be 1.03 mM and 75.73 µM/min, respectively. This work defines the catalytic and kinetic properties of arylsulfatase (EC 3.1.6.1) and confirms the optimal conditions for sulfatase activity testing. The resulting information is useful in elucidating the contributions that individual enzymes have for specific reactions rather than relying on traditional total enzyme activity measurements.
Mention of trade names or commercial products is solely for the purpose of providing specifi c in... more Mention of trade names or commercial products is solely for the purpose of providing specifi c information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer. Assigned to Associate Editor Robert Dungan.
Prescribed burning and thinning were implemented in an Alabama forest (Bankhead National Forest) ... more Prescribed burning and thinning were implemented in an Alabama forest (Bankhead National Forest) as a management strategy to control pest and disease outbreaks and also to increase forest productivity. However, using fire as a control mechanism in this forest may alter soil nutrient cycling, soil organic matter (SOM), and soil microbial populations. There is the need for continuous research on forest ecosystems to bridge knowledge gaps in our understanding of SOM transformations and microbial processes in a repeatedly burned forest ecosystems. The objectives of this study were to assess and document the impact of prescribed burning and thinning on soil labile organic matter fractions, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), potential carbon mineralized (PCM), enzymatic activity, and energy (ATP) potentials. Labile organic carbon was isolated using the density method, whereas enzyme activities were determined as described in Bottomley et al. (Methods of s...
Prescribed burning and thinning were implemented in an Alabama forest (Bankhead National Forest) ... more Prescribed burning and thinning were implemented in an Alabama forest (Bankhead National Forest) as a management strategy to control pest and disease outbreaks and also to increase forest productivity. However, using fire as a control mechanism in this forest may alter soil nutrient cycling, soil organic matter (SOM), and soil microbial populations. There is the need for continuous research on forest ecosystems to bridge knowledge gaps in our understanding of SOM transformations and microbial processes in a repeatedly burned forest ecosystems. The objectives of this study were to assess and document the impact of prescribed burning and thinning on soil labile organic matter fractions, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), potential carbon mineralized (PCM), enzymatic activity, and energy (ATP) potentials. Labile organic carbon was isolated using the density method, whereas enzyme activities were determined as described in Bottomley et al. (Methods of s...
Activity measurements of selected soil enzymes (cellulase, glucosidase, amidohydrolase, phosphata... more Activity measurements of selected soil enzymes (cellulase, glucosidase, amidohydrolase, phosphatase, arylsulfatase) involved in carbon, nitrogen, phosphorus, and sulfur cycling in the biosphere, hold potential as early and sensitive indicators of soil ecological stress and restoration, These measurements are advantageous because the procedures are simple, rapid, and reproducible over time. Enzyme activities are sensitive to short-term changes in soil and kind-use management. Enzyme activities have also been observed to be closely related to soil organic matter proposed as an index of soil quality.
The presence of oxyanions such as phosphate (P) in soils is believed to have effects on lead (Pb)... more The presence of oxyanions such as phosphate (P) in soils is believed to have effects on lead (Pb) interaction with minerals and is often considered as a remediation method for Pb immobilization in soil. In this study, the effect of P on Pb sorption on kaolinite was investigated using batch equilibrium studies and an equilibrium sorption ionexchange model. Batch equilibrium studies indicated that sorption on pristine and P-pretreated kaolinite surfaces was highly pH dependent. Sorption equilibrium was attained within 10 min for both surfaces. The amount of Pb sorbed significantly increased at low pH (pH range, 4-6) when presorbed P was present on the surface. Preferential sorption of Pb onto pristine kaolinite is likely when Pb is present in ionic Pb hydroxy forms in solution, apparently due to the stronger affinity of PbOH + species to the surface relative to Pb 2+. At different pH values, solution speciation of Pb as well as a Pb sorption model suggest solid precipitation of Pb(OH) 2 (s) and/or adsorption of various aqueous Pb(OH) x species to the surface at pH greater than 6. Modeling studies also suggest the possibility of formation of a surface complex similar to pyromorphite at low pH (pH 4) when P is on the surface. Lead sorption on pristine kaolinite was endothermic, whereas sorption on P-presorbed surface was exothermic. Lead sorption onto P-presorbed kaolinite resulted in a lower entropy ($S ;) of the system compared with the pristine kaolinite, which is indicative of a stronger binding of Pb to a Ppresorbed surface.
Soufrière Hills volcano is an active andesitic volcano located in the south-central part of Monts... more Soufrière Hills volcano is an active andesitic volcano located in the south-central part of Montserrat Island, West Indies. Phosphorus (P)-rich ash emitted from the Soufrière Hills volcano is expected to have effects on P retention and distribution in highly acidic soils surrounding the areas inundated with ash for several years. Phosphorus forms in ash varied with year of deposition with highest percent of P as CaP. Generally, the predominant forms of inorganic P in ash/soil mixtures and volcanic ashYderived soil were Ca-bound P 9 Al-or Fe-bound P 9 residual P 9 labile P 9 water-soluble P. Low soil pH in severely affected volcanic area soils suggests that CaP may exist in a partially dissolved form and will be the primary source of P for vegetation. Significantly high free Fe and Al oxides in these soils imply that bulk of P will remain as fixed P at the soil pH. High amounts of free Fe and Al oxides in soil may also play an important role in P adsorption and retention in these soils over time. The cation exchange capacity and pH of surface material from severely affected areas suggest that surface material mainly consists of a high percentage of ash (primary mineral). Total inorganic P was relatively less in areas minimally affected by the volcano. Both watersoluble and labile P pools in the minimally affected areas were relatively higher than those in severely affected areas.
International agriculture and rural development Our world is changing exponentially and unleashin... more International agriculture and rural development Our world is changing exponentially and unleashing sets of complicated problems, challenges, and opportunities. In view of this, international agriculture and rural development experiences have become critical in the training of food and agriculture majors. Professor. Dr. Zachary Senwo and colleagues have spent nearly two decades initiating and leading overseas studies programs in such countries as Brazil, China, Honduras, Kenya, and Costa Rica and continue to mentor scholars worldwide including Malawi, China, Brazil, Senegal, Rwanda, South Africa, Cameroon, and Gabon.
Canola is cultivated both during winter and spring seasons in the United States and this exposes ... more Canola is cultivated both during winter and spring seasons in the United States and this exposes the crop to winter kill, frost, and high temperatures, during the reproductive period. The temperatures during winter and spring are known to influence all the crucial steps of the reproductive cycle including gametogenesis, pollination, fertilization and embryogenesis (Angadi, 2000). Winter rapeseed has been successfully grown in the Pacific Northwest, southern Great Plains, Midwest, and southeast regions of the USA. The hardiest cultivars will routinely survive winters in the north east of USA but survival is inconsistent further south (Rife et al., 2001). Winter-grown canola (Brassica napus L.) production is limited mostly by frost and winter-kill in the southern canola-growing regions of the United States (Singh et al., 2008). For instance, the late freeze in 2007 resulted in significant damage to most of the winter canola cultivars at the National Winter Canola Variety Trials in Alabama, U.S. (Cebert and Rufina, 2007). Winter hardiness and freezing tolerance are a major concern for improving production consistency in many regions of the canola growing countries.
Evaluation of the soil rhizosphere has been limited by the lack of robust assessments that can ex... more Evaluation of the soil rhizosphere has been limited by the lack of robust assessments that can explore the vast complex structure and diversity of soil microbial communities. Our objective was to combine fatty acid methyl ester (FAME) and pyrosequencing techniques to evaluate soil microbial community structure and diversity. In addition, we evaluated biogeochemical functionality of the microbial communities via enzymatic activities of nutrient cycling. Samples were taken from a silt loam at 0-10 and 10-20 cm in an organic farm under lettuce (Lactuca sativa), potato (Solanum tuberosum), onion (Allium cepa L), broccoli (Brassica oleracea var. botrytis) and Tall fescue pasture grass (Festuca arundinacea).
Problems arising from conventional tillage (CT) systems (such as soil erosion, decrease of organi... more Problems arising from conventional tillage (CT) systems (such as soil erosion, decrease of organic matter, environmental damage etc.) have led many farmers to the adoption of no-till (NT) systems that are more effective in improving soil physical, chemical and microbial properties. Results from this study clearly indicated that NT, mulch tillage (MT), and winter rye cover cropping systems increased the activity of phosphatase, β-glucosidase and arylsulfatase at a 0-10 cm soil depth but decreased the activity of these enzymes at 10-20 cm. The increase in enzyme activity was a good indicator of intensive soil microbial activity in different soil management practices. Poultry litter (PL) application under NT, MT, and rye cropping system could be considered as effective management practices due to the improvement in carbon (C) content and the biochemical quality at the soil surface. The activities of the studied enzymes were highly correlated with soil total nitrogen (STN) soil organic carbon (SOC) at the 0-10 cm soil depth, except for acid phosphatase where no correlation was observed. This study revealed that agricultural practices such as tillage, PL, and cover crop cropping system have a noticeable positive effect on soil biochemical activities under cotton production.
Canola is cultivated both during winter and spring seasons in the United States and this exposes ... more Canola is cultivated both during winter and spring seasons in the United States and this exposes the crop to winter kill, frost, and high temperatures, during the reproductive period. The temperatures during winter and spring are known to influence all the crucial steps of the reproductive cycle including gametogenesis, pollination, fertilization and embryogenesis (Angadi, 2000). Winter rapeseed has been successfully grown in the Pacific Northwest, southern Great Plains, Midwest, and southeast regions of the USA. The hardiest cultivars will routinely survive winters in the north east of USA but survival is inconsistent further south (Rife et al., 2001). Winter-grown canola (Brassica napus L.) production is limited mostly by frost and winter-kill in the southern canola-growing regions of the United States (Singh et al., 2008). For instance, the late freeze in 2007 resulted in significant damage to most of the winter canola cultivars at the National Winter Canola Variety Trials in Ala...
Soil Microbial Communities and Metabolic Function of a Northern Alabama Forest Ecosystem
ABSTRACT Thinning, prescribed burning, and their combinations, are common forest management pract... more ABSTRACT Thinning, prescribed burning, and their combinations, are common forest management practices to restore degraded forest communities and to prevent uncontrollable wildfires. However, their impacts on soil microbial communities, which are vital to global element cycling, are traditionally overlooked. In this study, the effects of thinning and burning on microbial communities and metabolic functions was evaluated in a forest ecosystem using ester-linked fatty acid methyl ester (EL-FAME) coupled with assays of enzymes important in carbon, nitrogen, phosphorus, and sulfur cycling, such as laccase, manganese peroxidase (MnP), xylanase, β-glucosidase, β-glucosaminidase, acid phosphatase, and arylsulfatase. The treatments comprised of three burning patterns (no burn, 3yr- and 9yr- burn cycles) and three levels of thinning (no thin, lightly thinned, and heavily thinned) in a completely randomized design layout located at the Bankhead National Forest of Alabama. Five years after treatments were initiated, microbial communities increased in the lightly-thinned plots and decreased in the burn-only plots compared to the no-burn/no-thinned (reference) plot. Thinning promoted soil ligninolytic enzymatic activities, as both lightly- and heavily-thinned treatments exhibited greater laccase and MnP activities than the no-thinned plots. There was increase in hydrolysis of hemicellulose with thinning, as demonstrated by xylanase activities. Lower activities of β-glucosidase in the heavily-thinned treatments correspond to an increase in the deposition of woody material with restricted access to cellulose. Geometric mean enzyme activity (GMea) index of all seven enzymes were greater under the lightly thinned plots than the heavily-thinned and no-thinned plots, with implications of potential higher metabolic function under those practices. Overall, the light thinning increased the relative abundance of the microbial communities, and the metabolic capacity of the soil.
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