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Browsing by Author "Lehmann, Johannes"

Now showing 1 - 10 of 10
  • Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal: A review
    Glaser, B.; Lehmann, Johannes; Zech, W. (Biology and Fertility of Soils, 2002)
    Rapid turnover of organic matter leads to a low efficiency of organic fertilizers applied to increase and sequester C in soils of the humid tropics. Charcoal was reported to be responsible for high soil organic matter contents and soil fertility of anthropogenic soils (Terra Preta) found in central Amazonia. Therefore, we reviewed the available information about the physical and chemical properties of charcoal as affected by different combustion procedures, and the effects of its application in agricultural fields on nutrient retention and crop production. Higher nutrient retention and nutrient availability were found after charcoal additions to soil, related to higher exchange capacity, surface area and direct nutrient additions. Higher charring temperatures generally improved exchange properties and surface area of the charcoal. Additionally, charcoal is relatively recalcitrant and can therefore be used as a long-term sink for atmospheric CO2. Several aspects of a charcoal management system remain unclear, such as the role of microorganisms in oxidizing charcoal surfaces and releasing nutrients and the possibilities to improve charcoal properties during production under field conditions. Several research needs were identified, such as field testing of charcoal production in tropical agroecosystems, the investigation of surface properties of the carbonized materials in the soil environment, and the evaluation of the agronomic and economic effectiveness of soil management with charcoal.
  • Assessing and managing soil quality for sustainable agricultural system
    Motavalli, Peter P.; Jintaridth, Bunjirtluk; Lehmann, Johannes; Goyne, Keith W.; Gilles, Jere L. (2008)
    Soil quality assessment is a process by which soil resources are evaluated on the basis of soil function. Soil organic matter (SOM) is one of the most widely knowledge indicators of soil quality(Gregorich et al., 1994). In general, SOC varies across landscapes, soil types and climatic zones. It is characterized by high levels of C in recalcitrant or humified forms and small changes in SOC resulting from changes in soil management are difficult to measure. An approach to evaluate the impact of agricultural management of SOM dynamics is to separate SOM into pools which will depend on differences in decomposition rates (Wander et al., 1994). In two-pool exponential decomposition models, the pool with the smallest size and most rapid turnover is termed labile and the larger pool with slow turnover is termed recalcitrant. The lability of SOM is defined as the ease and speed with which it is decomposed by microbes and depends on both chemical recalcitrance and physical protection from microbes. Changes in labile fractions of SOC provide an early indication of soil degradation or improvement in response to management practices (Islam and Weil,2000). In this research, soil samples will be collected from representative degraded and non- degraded soils at ongoing SANREM field sites, establish in-field and laboratory capacity to test soil quality, and develop analytical methodologies for the spectroscopic-based procedures. Collaboration with CGIAR system (i.e., ICRAF), USDA-ARS and USDA-NRCS are also important goals of this project due to the ongoing efforts and resources being invested at these institutions in developing low-cost methods for soil quality evaluation.
  • Assessing and managing soil quality for sustainable agricultural systems: SANREM CRSP Cross Cutting initiative
    Motavalli, Peter P.; Jintaridth, Bunjirtluk; Lehmann, Johannes; Goyne, Keith W.; Gilles, Jere L. (2008)
    A presentation about the SANREM CRSP Cross Cutting initiative in terms of assessing and managing soil quality for sustainable agricultural systems in the Altiplano of Peru and Bolivia.
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    Bringing carbon back into nutrient management
    Lehmann, Johannes (2009)
    This presentation discusses biochar as an example of the integration of household energy and soil improvement.
  • Community Markets for Conservation (COMACO) links biodiversity conservation with sustainable improvements in livelihoods and food production
    Lewis, Dale; Bell, Samuel D.; Fay, John; Bothi, Kim L.; Gatere, Lydiah; Kabila, Makando; Mukamba, Mwangala; Matokwani, Edwin; Mushimbalume, Matthews; Moraru, Carmen I.; Lehmann, Johannes; Lassoie, James; Wolfe, David; Lee, David R.; Buck, Louise; Travis, Alexander J. (The National Academy of Sciences, 2011)
    In Zambia's Luangwa Valley, past economic development initiatives and household coping strategies have severely depleted natural resources and, in turn, hindered further development. The Community Markets for Conservation (COMACO) Model has been developed to improve and shift livelihoods to ventures that also protect and conserve natural resources. The program trains the least food-secure in sustainable agriculture practices, identifies and trains those responsible for the greatest amount of resource depletion, and helps provide access to extension and markets to both of these groups. Although the program is still in progress, numerous indicators have been identified that signal its effectiveness, such as the stabilization of certain animal species and adoption of sustainable agriculture practices.
  • Environmental variables affecting the success of conservation farming in Zambia
    Gatere, Lydiah; Delve, Robert; Hobbs, Peter R.; DeGloria, Steve; Lehmann, Johannes (2008)
    This presentation discusses conservation farming methods in Zambia. The research highlights how conservation farming methods may help to negate environmental variables that hinder crop production, such as lack of rainfall and poor soil quality. The study compares conservation farming practices with variable amendments, including cow manure, gliricidia leaves, biochar, and fertilizer applications.
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    Microscale spatial distribution and soil organic matter persistence in top and subsoil
    Inagaki, Thiago M.; Possinger, Angela R.; Schweizer, Steffen A.; Mueller, Carsten W.; Hoeschen, Carmen; Zachman, Michael J.; Kourkoutis, Lena F.; Kogel-Knabner, Ingrid; Lehmann, Johannes (Pergamon-Elsevier Science, 2023-03)
    The spatial distribution of organic substrates and microscale soil heterogeneity significantly influence organic matter (OM) persistence as constraints on OM accessibility to microorganisms. However, it is unclear how changes in OM spatial heterogeneity driven by factors such as soil depth affect the relative importance of sub-strate spatial distribution on OM persistence. This work evaluated the decomposition and persistence of 13C and 15N labeled water-extractable OM inputs over 50 days as either hotspot (i.e., pelleted in 1-2 mm-size pieces) or distributed (i.e., added as OM < 0.07 mu m suspended in water) forms in topsoil (0-0.2 m) and subsoil (0.8-0.9 m) samples of an Andisol. We observed greater persistence of added C in the subsoil with distributed OM inputs relative to hotspot OM, indicated by a 17% reduction in cumulative mineralization of the added C and a 10% higher conversion to mineral-associated OM. A lower substrate availability potentially reduced mineralization due to OM dispersion throughout the soil. NanoSIMS (nanoscale secondary ion mass spectrometry) analysis identified organo-mineral associations on cross-sectioned aggregate interiors in the subsoil. On the other hand, in the topsoil, we did not observe significant differences in the persistence of OM, suggesting that the large amounts of particulate OM already present in the soil outweighed the influence of added OM spatial distribution. Here, we demonstrated under laboratory conditions that the spatial distribution of fresh OM input alone significantly affected the decomposition and persistence of OM inputs in the subsoil. On the other hand, spatial distribution seems to play a lower role in topsoils rich in particulate OM. The divergence in the influence of OM spatial distribution between the top and subsoil is likely driven by differences in soil mineralogy and OM composition.
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    Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency
    Possinger, Angela R.; Bailey, Scott W.; Inagaki, Thiago M.; Koegel-Knabner, Ingrid; Dynes, James J.; Arthur, Zachary A.; Lehmann, Johannes (2020-10-01)
    The response of mineral-stabilized soil organic carbon (SOC) to environmental change is a source of uncertainty in the understanding of SOC cycling. Fluctuating wet-dry cycles and associated redox changes in otherwise well-drained soils may drive mineral dissolution, organic carbon (OC) mobilization, and subsequent OC mineralization. However, the extent to which rapid fluctuations between water-saturated and unsaturated conditions (i.e., flashy conditions) result in long-term changes in mineral composition and organo-mineral interactions is not well understood. In this study, the effect of variable saturation frequency on soil mineral composition, mineral-associated OC, and OC mineralizability was tested using selective dissolution, bulk spectroscopy, microscale imaging, and aerobic-anaerobic incubation experiments. Previous water table fluctuation measurements and diagnostic profile characteristics at Hubbard Brook Experimental Forest (NH) were used to identify soils with high, medium, and low saturation frequency regimes (defined by historical water table cycling frequency; i.e., water table presence and recession in the upper B horizon). We found the amount of OC released during extractions targeting non-crystalline minerals was of similar magnitude as extracted iron (Fe) in lower saturation frequency soils. However, the magnitude of extracted OC was 2.5 times greater than Fe but more similar to extractable aluminum (Al) in higher saturation frequency soils. Bulk soil Fe was spatially more strongly correlated to soil organic matter (SOM) in lower saturation frequency soils (Spearman Rank r(s) = 0.62, p < 0.005), whereas strong correlations between Al and SOM were observed in higher saturation frequency soils (r(s) = 0.88, p < 0.005) using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging. Characterization of bulk soil Fe with X-ray absorption spectroscopy showed 1.2-fold greater Fe(II) and 1-fold lower contribution of Fe-organic bonding in soils with high saturation frequency. Fe(III) interactions with carboxylic and aromatic C were identified with C-13 nuclear magnetic resonance (NMR) spectroscopy Fe(III) interference experiments. Additionally, carboxylic acid enrichment in high saturation frequency soils quantified by C K-edge X-ray absorption spectroscopy point towards the role of carboxylic functional groups in Al-organic in addition to Fe-organic interactions. In our incubation experiments, a doubling in short-term CO2 evolution (per unit total soil C) was detected for high relative to low saturation frequency soils. Further, an order of magnitude increase in CO2 evolution (per unit water-extractable OC) following anaerobic incubation was only detected in high saturation frequency soils. The observed shift towards Al-dominated SOC interactions and higher OC mineralizability highlights the need to describe C stabilization in soils with flashy wet-dry cycling separately from soils with low saturation frequency or persistent saturation.
  • Reversibility of soil productivity decline with organic matter of differing quality along a degradation gradient
    Kimetu, J. M.; Lehmann, Johannes; Ngoze, S. O.; Mugendi, D. N.; Kinyangi, James M.; Riha, S.; Verchot, L.; Recha, J. W.; Pell, A. N. (Springer, 2008)
    This study investigates the reversibility of soil productivity decline using additions of labile organic matter (green and animal manure) to add nutrients to the soil, and stable organic matter (biochar and sawdust) to stabilize the soil and enhance the soil organic carbon (SOC). The overall goal was to test and compare the impact of these additions on the productivity of crops and to investigate ways to improve soil quality. In western Kenya, agriculture is very important and the use of continuous cropping after forest clearing has greatly affected soil fertility by decreasing the amount of nutrients and carbon in the soil. Restoring the soil organic matter content is essential for maintaining crop productivity in the long-term and creating a sustainable food source in this region.