Andrew S. Ball

Soil Microbial Community Response to Land Use Change in an Agricultural Landscape of Western Kenya

Tropical agroecosystems are subject to degradation processes such as losses in soil carbon, nutrient depletion, and reduced water holding capacity that occur rapidly resulting in a reduction in soil fertility that can be difficult to reverse. In this research, a polyphasic methodology has been used to investigate changes in microbial community structure and function in a series of tropical soils in western Kenya. These soils have different land usage with both wooded and agricultural soils at Kakamega and Ochinga, whereas at Ochinga, Leuro, Teso, and Ugunja a replicated field experiment compared traditional continuous maize cropping against an improved N-fixing fallow system. For all sites, principal component analysis of 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) profiles revealed that soil type was the key determinant of total bacterial community structure, with secondary variation found between wooded and agricultural soils. Similarly, phospholipid fatty acid (PLFA) analysis also separated wooded from agricultural soils, primarily on the basis of higher abundance of monounsaturated fatty acids, anteiso- and iso-branched fatty acids, and methyl-branched fatty acids in the wooded soils. At Kakamega and Ochinga wooded soils had between five 5 and 10-fold higher levels of soil carbon and microbial biomass carbon than agricultural soils from the same location, whereas total enzyme activities were also lower in the agricultural sites. Soils with woody vegetation had a lower percentage of phosphatase activity and higher cellulase and chitinase activities than the agricultural soils. BIOLOG analysis showed woodland soils to have the greatest substrate diversity. Throughout the study the two functional indicators (enzyme activity and BIOLOG), however, showed lower specificity with respect to soil type and land usage than did the compositional indicators (DGGE and PLFA). In the field experiment comparing two types of maize cropping, both the maize yields and total microbial biomass were found to increase with the fallow system. Moreover, 16S rRNA gene and PLFA analyses revealed shifts in the total microbial community in response to the different management regimes, indicating that deliberate management of soils can have considerable impact on microbial community structure and function in tropical soils.

Potential carbon mitigation and income in developing countries from changes in use and management of agricultural and forest lands.

The many opportunities for mitigating atmospheric carbon emissions in developing countries include reforesting degraded lands, implementing sustainable agricultural practices on existing lands and slowing tropical deforestation. This analysis shows that over the next 10 years, 48 major tropical and subtropical developing countries have the potential to reduce the atmospheric carbon burden by about 2.3 billion tonnes of carbon. Given a central price of

Algal growth control by a barley straw extract

10 per tonne of carbon and a discount rate of 3%, this mitigation would generate a net present value of about

The recovery of lignocellulose-degrading enzymes from spent mushroom compost

16.8 billion collectively for these countries. Achieving these potentials would require a significant global effort, covering more than 50 million hectares of land, to implement carbon-friendly practices in agriculture, forest and previously forested lands. These estimates of host-country income potentials do not consider that outside financial investment may or may not be available. Our calculations take no account of the additional benefits of carbon sequestration in forest soils undergoing reforestation, increased use of biomass and reduced use of fossil-fuel inputs and reduced agricultural emissions. In all events, realizing these incomes would necessitate substantially greater policy support and investment in sustainable land uses than is currently the case.

The role of sustainable agriculture and renewable–resource management in reducing greenhouse–gas emissions and increasing sinks in China and India

In recent years, there has been an apparent increase in the occurrence of harmful algal blooms occurring in potable waters. The potential of a simple barley straw extract to inhibit algal growth was assessed. Algal growth in lakewater was inhibited by the addition of barley straw (1% w/v), with the chlorophyll a concentration remaining below the original level (40 micrograms l-1) throughout the experiment. In contrast, in the presence of wheat straw, algal biomass increased, reaching a final chlorophyll a concentration of 1160 micrograms l-1 after 28 days. Analysis of the remaining particulate straw at the end of the experiment showed that the lignin content of barley straw had increased significantly from 10-33% (w/w). Further, a preparation of a simple aqueous extract from the decomposed-barley straw was found to inhibit the cyanobacteria Microcystis sp. and the algal species Scenedesmus, with chlorophyll a levels some 10-fold lower than in untreated flasks. This study shows that a decomposed-barley extract, even in a very dilute concentration (0.005%) was capable of inhibiting the growth of Microcystis sp., a commonly occurring cyanobacterium which produces the toxin microcystin and has been responsible for some of the most serious pernicious algal blooms in the UK.

The decomposition of Lolium perenne in soils exposed to elevated CO2: comparisons of mass loss of litter with soil respiration and soil microbial biomass.

The recovery of lignocellulose-degrading enzymes from spent mushroom compost was assessed using a variety of physical and chemical treatments. Maximum recoveries of active xylanase activity were detected in extracts from spent compost which had been physically treated by blending. A range of lignocellulose-degrading activities was also recovered from blended compost extracts; peroxidases, the xylan-debranching enzymes acetylesterase and arabinofuranosidase, and the cellulose-degrading activities endoglucanase, cellobiohydrase and β-glucosidase. The compost extract was also shown to be capable of releasing reducing sugars (12 nmol min−1 g compost−1) from wheat straw. Characterization of the stability of this enzyme activity showed that maximum activity could be detected between pH 7 and 9 and after 1 h incubation at 65°C. The activity and stability of the enzymes suggest a potential role for enzyme cocktails from compost extracts in the biological upgrading of grass lignocelluloses to animal fodder.

Solubilisation and mineralisation of [14C]lignocellulose from wheat straw by Streptomyces cyaneus CECT 3335 during growth in solid-state fermentation

This paper contains an analysis of the technical options in agriculture for reducing greenhouse–gas emissions and increasing sinks, arising from three distinct mechanisms: (i) increasing carbon sinks in soil organic matter and above–ground biomass; (ii) avoiding carbon emissions from farms by reducing direct and indirect energy use; and (iii) increasing renewable–energy production from biomass that either substitutes for consumption of fossil fuels or replaces inefficient burning of fuelwood or crop residues, and so avoids carbon emissions, together with use of biogas digesters and improved cookstoves. We then review best–practice sustainable agriculture and renewable–resource–management projects and initiatives in China and India, and analyse the annual net sinks being created by these projects, and the potential market value of the carbon sequestered. We conclude with a summary of the policy and institutional conditions and reforms required for adoption of best sustainability practice in the agricultural sector to achieve the desired reductions in emissions and increases in sinks. A review of 40 sustainable agriculture and renewable–resource–management projects in China and India under the three mechanisms estimated a carbon mitigation potential of 64.8 MtC yr−1 from 5.5 Mha. The potential income for carbon mitigation is

Optimization of extracellular lignocellulolytic enzyme production by a thermophilic actinomycete Thermomonospora fusca BD25

324 million at

Mixed aerobic and anaerobic microbial communities in benzene‐contaminated groundwater

5 per tonne of carbon. The potential exists to increase this by orders of magnitude, and so contribute significantly to greenhouse–gas abatement. Most agricultural mitigation options also provide several ancillary benefits. However, there are many technical, financial, policy, legal and institutional barriers to overcome.

Is the solubilized product from the degradation of lignocellulose by Actinomycetes a precursor of humic substances

Abstract Two key questions regarding the effects of elevated atmospheric CO2 on soil microbial biomass are, (a) will future levels of elevated CO2 affect the amount of microbial biomass in soil? and (b) how will any observed changes impact on C-flux from soils? These questions were addressed by examining soil microbial biomass, and in situ estimations of soil respiration in grassland soils exposed to free air carbon dioxide enrichment (60 Pa). Corresponding measurements of plant litter mass loss were taken using litter bags, ensuring that ambient litter was decomposed in ambient soil, and elevated CO2 grown litter was decomposed in soils exposed to elevated CO2. Significantly greater levels of microbial biomass (p