Sean M. Smukler

Application of biochar and nitrogen influences fluxes of CO2, CH4 and N2O in a forest soil

Nitrogen (N) fertilization of forests for increasing carbon sequestration and wood volume is expected to influence soil greenhouse gas (GHG) emissions, especially to increase N2O emissions. As biochar application is known to affect soil GHG emissions, we investigated the effect of biochar application, with and without N fertilization, to a forest soil on GHG emissions in a controlled laboratory study. We found that biochar application at high (10%) application rates increased CO2 and N2O emissions when applied without urea-N fertilizer. At both low (1%) and high biochar (10%) application rates CH4 consumption was reduced when applied without urea-N fertilizer. Biochar application with urea-N fertilization did not increase CO2 emissions compared to biochar amended soil without fertilizer. In terms of CO2-eq, the net change in GHG emissions was mainly controlled by CO2 emissions, regardless of treatment, with CH4 and N2O together accounting for less than 1.5% of the total emissions.

A novel methodology to assess land-based food self-reliance in the Southwest British Columbia bioregion

There is a growing awareness that climate change, economic instability, resource limitations and population growth are impacting the capacity of the contemporary global food system to meet human nutrition needs. Although there is widespread recognition that food systems must evolve in the face of these issues, a polarized debate has emerged around the merit of global-versus-local approaches to this evolution. Local food system advocates argue that increasing food self-reliance will concomitantly benefit human health, the environment and local economies, while critics argue that only a globalized system will produce enough calories to efficiently and economically feed the world. This debate is strong in British Columbia (BC), Canada, where residents and food security experts have called for increased food self-reliance while the provincial government largely supports export-oriented agriculture. As elsewhere, however, in BC this debate takes place in absence of an understanding of capacity for food self-reliance. The few studies that have previously evaluated self-reliance in this region have been limited in their approach in a number of ways. In this study we use a novel methodology to assess current (2011) status of land-based food self-reliance for a diet satisfying nutritional recommendations and food preferences that accounts for seasonality of crop production and the source of livestock feed, and applied it to the Southwest BC bioregion (SWBC) as a case study. We found that agricultural land use in SWBC is dominated by hay, pasture and corn silage, followed by fruits and vegetables. Fruit and vegetable production comprise 87% of total food crop production in SWBC by weight, and a substantial amount is produced in quantities beyond SWBC need per crop type, representing an export focused commodity with limited contribution to food self-reliance. Results illustrate that SWBC is a major producer of livestock products, but these industries rely on feed grain imports. The production of feed grain could therefore be considered a major constraint on self-reliance; SWBCs total dietary self-reliance is 12% if discounting livestock feed imports or 40% if including them. Results demonstrate that a diet including foods that cannot be grown in the region or consumed fresh out of season, limits potential food self-reliance. Our methods reveal the value of factoring dietary recommendations and food consumption patterns into food self-reliance assessments and the necessity of accounting for the source of livestock feed to fully understand the self-reliance status of a region.

Cultivating climate resilience: a participatory assessment of organic and conventional rice systems in the Philippines

Climate change poses serious threats to agriculture. As a primary staple crop and major contributor to agriculturally derived greenhouse gas (GHG) emissions, rice systems are of particular significance to building climate resilience. We report on a participatory assessment of climate resilience in organic and conventional rice systems located in four neighboring villages in Negros Occidental, Philippines. The Philippines is one of the foremost countries impacted by climate change, with an increasing incidence of climate-related disturbances and extensive coastlines, high population density and heavy dependence on agriculture. Using the United Nations Food and Agriculture Organizations Self-evaluation and Holistic Assessment of climate Resilience of farmers and Pastoralists (SHARP) tool, we measured 13 agroecosystem indicators of climate resilience, and assessed the degree to which household, farm, and community mechanisms and outcomes impact adaptation capacity, mitigation potential and vulnerability. We used a participatory approach to situate these indicators in their socio-ecological context, and identify targeted interventions for enhancing climate resilience based on local farmer experiences and socio-ecological conditions. Comparison of climate resilience indicators across organic and conventional rice systems in this region indicated that organic rice systems are more climate resilient than their conventional counterparts. As such, increased policy support for the development of organic rice systems are critically important as an adaptive mechanism to augment food security, mitigate GHG emissions and improve climate resilience in the Philippines.

Protection from wintertime rainfall reduces nutrient losses and greenhouse gas emissions during the decomposition of poultry and horse manure-based amendments

ABSTRACT Manure-based soil amendments (herein “amendments”) are important fertility sources, but differences among amendment types and management can significantly affect their nutrient value and environmental impacts. A 6-month in situ decomposition experiment was conducted to determine how protection from wintertime rainfall affected nutrient losses and greenhouse gas (GHG) emissions in poultry (broiler chicken and turkey) and horse amendments. Changes in total nutrient concentration were measured every 3 months, changes in ammonium (NH4+) and nitrate (NO3−) concentrations every month, and GHG emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) every 7–14 days. Poultry amendments maintained higher nutrient concentrations (except for K), higher emissions of CO2 and N2O, and lower CH4 emissions than horse amendments. Exposing amendments to rainfall increased total N and NH4+ losses in poultry amendments, P losses in turkey and horse amendments, and K losses and cumulative N2O emissions for all amendments. However, it did not affect CO2 or CH4 emissions. Overall, rainfall exposure would decrease total N inputs by 37% (horse), 59% (broiler chicken), or 74% (turkey) for a given application rate (wet weight basis) after 6 months of decomposition, with similar losses for NH4+ (69–96%), P (41–73%), and K (91–97%). This study confirms the benefits of facilities protected from rainfall to reduce nutrient losses and GHG emissions during amendment decomposition. Implications: The impact of rainfall protection on nutrient losses and GHG emissions was monitored during the decomposition of broiler chicken, turkey, and horse manure-based soil amendments. Amendments exposed to rainfall had large ammonium and potassium losses, resulting in a 37–74% decrease in N inputs when compared with amendments protected from rainfall. Nitrous oxide emissions were also higher with rainfall exposure, although it had no effect on carbon dioxide and methane emissions. Overall, this work highlights the benefits of rainfall protection during amendment decomposition to reduce nutrient losses and GHG emissions.

Determining Greenhouse Gas Emissions and Removals Associated with Land-Use and Land-Cover Change

This chapter reviews methods and considerations for quantifying greenhouse gas (GHG) emissions and removals associated with changes in land-use and land-cover (LULC) in the context of smallholder agriculture. LULC change contributes a sizeable portion of global anthropogenic GHG emissions, accounting for 12.5 % of carbon emissions from 1990 to 2010 (Biogeosciences 9:5125–5142, 2012). Yet quantifying emissions from LULC change remains one of the most uncertain components in carbon budgeting, particularly in landscapes dominated by smallholder agriculture (Mitig Adapt Strateg Glob Chang 12:1001–1026, 2007; Biogeosciences 9:5125–5142, 2012; Glob Chang Biol 18:2089–2101, 2012). Current LULC monitoring methodologies are not well-suited for the size of land holdings and the rapid transformations from one land-use to another typically found in smallholder landscapes. In this chapter we propose a suite of methods for estimating the net changes in GHG emissions that specifically address the conditions of smallholder agriculture. We present methods encompassing a range of resource requirements and accuracy, and the trade-offs between cost and accuracy are specifically discussed. The chapter begins with an introduction to existing protocols, standards, and international reporting guidelines and how they relate to quantifying, analyzing, and reporting GHG emissions and removals from LULC change. We introduce general considerations and methodologies specific to smallholder agricultural landscapes for generating activity data, linking it with GHG emission factors and assessing uncertainty. We then provide methodological options, additional considerations, and minimum datasets required to meet the varying levels of reporting accuracy, ranging from low-cost high-uncertainty to high-cost low-uncertainty approaches. Technical step-by-step details for suggested approaches can be found in the associated website.

Greater Impacts of Incubation Temperature and Moisture on Carbon and Nitrogen Cycling in Poultry Relative to Horse Manure-based Soil Amendments

Manure-based soil amendments (MBSAs) must be managed optimally to maximize N concentration and availability while minimizing environmental impacts (e.g., greenhouse gas [GHG]) emissions. We conducted an 83-d incubation study to determine the effects of different moisture (60 or 120% of water-holding capacity [WHC]) and temperature (4 or 20°C) conditions during the decomposition of MBSAs. We measured CO, CH, and NO emissions and total C, total N, NH, and NO during the decomposition of chicken MBSA and two understudied MBSAs (turkey and horse). Total N decreased by 38 to 50% after 83 d in poultry MBSAs incubated at 20°C and 120% WHC, whereas NH concentration peaked at 30 d. In contrast, poultry MBSAs incubated at 60% WHC or 4°C had limited N losses but higher CO and/or NO emissions. Horse MBSA incubated for 83 d at 20°C and 60% WHC had two- to threefold higher C losses, 53 to 68% higher total N, and two to three orders of magnitude higher NO concentrations than at wetter and/or colder incubation conditions. Horse MBSA incubated at 20°C and 60% WHC had 13- to 130-fold (CH) and 4- to 70-fold (NO) higher emissions than horse MBSA incubated at 4°C. In contrast, CH emissions peaked at 120% WHC and 20°C. Overall, incubating horse MBSA at 20°C and 60% WHC minimized tradeoffs between maximizing N concentration and availability and minimizing GHG emissions during decomposition, whereas we found no ideal decomposition conditions for poultry MBSAs.

One-time Application of Biosolids to Ungrazed Semiarid Rangelands: 14-year Soil Responses

Abstract: Biosolids have been shown to improve forage production and soil quality on semiarid rangelands in the short term, but less is known about longer-term impacts of one-time biosolids applications. The objective of this study was to determine the effects of a single, surface biosolids application (at 20 dry Mg ha-1) on stability of soil aggregates, bulk density, total carbon (C) and nitrogen (N), permanganate-oxidizable carbon (POXC), polysaccharides, pH, nutrient availability, and soil water content (all at 0–7.5 cm depth) 14 yr following application to ungrazed rangelands in the Central interior of British Columbia. Fourteen years following the biosolids application, aboveground plant biomass was almost two times greater with biosolids application than on control, while exposed mineral soil and microbiotic crust significantly decreased in biosolids plots. Despite differences in aboveground biomass, there was no difference in total soil C and N, POXC, and polysaccharides between biosolids and control plots. Biosolids-amended soil did exhibit significantly greater mean weight diameter of water-stable aggregates, lower pH, increased spring soil water content, and increased availability of Fe3+, Zn2+, Cu2+, and phosphate ions. These findings indicate that the long-term improvements to soil on ungrazed rangeland are possible even from a single biosolids application.

Native bacterial communities and Listeria monocytogenes survival in soils collected from the Lower Mainland of British Columbia, Canada

Soil is an important reservoir for Listeria monocytogenes, a foodborne pathogen implicated in numerous produce-related outbreaks. Our objectives were to (i) compare the survival of L. monocytogenes among three soils, (ii) compare the native bacterial communities across these soils, and (iii) investigate relationships between L. monocytogenes survival, native bacterial communities, and soil properties. Listeria spp. populations were monitored on PALCAM agar in three soils inoculated with L. monocytogenes (∼5 × 106 CFU/g): conventionally farmed (CS), grassland transitioning to conventionally farmed (TS), and uncultivated grassland (GS). Bacterial diversity of the soils was analyzed using 16S rRNA targeted amplicon sequencing. A 2 log reduction of Listeria spp. was observed in all soils within 10 days, but at a significantly lower rate in GS (Fishers least significant difference test; p < 0.05). Survival correlated with increased moisture and a neutral pH. GS showed the highest microbial diversity. Acidobacteria was the dominant phylum differentiating CS and TS from GS, and was negatively correlated with pH, carbon, nitrogen, and moisture. High moisture content and neutral pH are likely to increase the ability of L. monocytogenes to persist in soil. This study confirmed that native bacterial communities and short-term survival of L. monocytogenes varies across soils.

Comparison of selected soil properties following grassland set-aside and annual crop rotations in the Fraser River Delta of British Columbia

Abstract: Selected soil properties were compared after 2–6 yr of grassland set-aside (GLSA) management and an annual cropping system (potato). In general, GLSA and nearby arable cropping fields had similar soil properties, with some improvements of aeration porosity, aggregate stability, bulk density, and mechanical resistance following short-term GLSA management.