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Rock pulverization is recommended when converting boreal forests to agricultural land use to facilitate tillage operations. Resulting rock dust incorporation might alter physical, chemical, and biological properties of soils. We assessed soil nematode trophic group abundances and indices, basal and burst respiration, and phosphorus extractability after land use conversion (LUC) and recent pulverization (

Shallow soils occur throughout the world and are recognized as Leptosols at the highest level in the World Reference Base. These soils are notionally characterized as having a lithic contact close to the soil surface. Within the Canadian System of Soil Classification (CSSC), shallow soils are currently handled at the family level according to the depth at which the lithic contact is encountered. At the series level, these soils are usually designated as a shallow phase of a non-shallow soil series, ignoring the hierarchical structure of the CSSC. Shallow soils occur almost anywhere in Canada where the glacial drift is thin. The presence of bedrock close to the surface impacts drainage, the amount of available moisture, depth for rooting, and has a major influence on soil formation. Consequently, it is proposed that the importance of shallow soils be elevated to the order level, to be consistent with the frequency of their occurrence in the Canadian landscape and for consistency with other soil classification systems of the world. This requires integration at the great group and subgroup levels within all orders of the CSSC, as well as changes to the current formal definition of soil. These proposed modifications include nullifying the minimum 10 cm depth requirement as part of the current definition of soil in the CSSC for closer consistency with ecological land classification and other soil classification systems of the world. Proposed modifications to the current key to the soil orders, great groups, and subgroups are presented and discussed.

Biofumigation has been proposed as an alternative to soil fumigation to manage soil-borne diseases including potato early dying disease complex (PED). This study examined the potential of using brown mustard (Mustard juncea) biofumigation to manage PED under rain-fed potato production in New Brunswick, Canada in two trials between 2017 and 2020 in comparison with chloropicrin fumigation and a conventional barley rotation. Biofumigation increased yield in one trial, but not in a second trial where the potato crop experienced severe drought, whereas chloropicrin fumigation increased yield in both trials. Biofumigation was effective in suppressing root-lesion nematode (RLN, Pratylenchus spp.) counts in both trials, but was ineffective in suppressing V. dahliae population density. Chloropicrin fumigation was effective in suppressing RLN counts and V. dahliae population density only in the hill where injected, but the effect was short-lived as the population density of V. dahliae in the hill increased to the level of the control in one potato growing season. Biofumigation may be an alternative to chloropicrin fumigation in managing PED, particularly in fields with high RLN population but relatively low Verticillium population density. However, neither biofumigation nor fumigation used alone may be sustainable in the short-term potato rotations commonly used in New Brunswick, and additional beneficial practices are required to sustain productivity in the long-term.

Soil degradation has been of great concern for New Brunswick's potato farmers, especially on sloped land and shallow soils. In this study, we evaluated the initial response of labile soil carbon (C) fractions (permanganate oxidizable C (POXC) and particulate organic C (POC)) and aggregate stability to two integrated best management practices (BMPIs) composed of the following individual practices: diversion terraces (DT), grassed waterways (GW), and contour tillage (CT) (i.e., DTGW) and DT, GW, CT, and tile drainage (TD) (i.e., DTGW + TD), relative to CT that served as a control. The more water was regulated in the field, the greater the increase in labile C; where DTGW and DTGW + TD gained 19.8% and 50.6% of POXC, respectively, while CT lost 11.2% of POXC. There was an increase in mineral associated organic matter C in the terraced BMPIs, despite the high amount of tillage events that took place during potato cultivation. Two BMPIs had no effect on aggregate stability, most likely due to the short duration of this initial monitoring study that spanned just over two growing seasons. Even though there were no improvements in soil structure, our findings showed that some stabilization of soil C is possible even during the initial two seasons following BMPI implementation.

Stagnating potato tuber yields in Prince Edward Island (PEI) are a major economic concern. Identification of factors influencing within-field yield variation may provide insight into strategies for overcoming yield limitations. A survey approach was used where soil samples were collected from 49 commercial fields from 2014 to 2017 from a total of 289 sampling points, with points identified as having either “high” or “low” yield, determined by yield monitor as being 5.6–11.2 t ha−1 above or below average field yield, respectively. A suite of 33 measures of soil physical and chemical properties and soil pathogens were measured. Principal component analysis identified three principal components (PCs) which accounted for 85.6% of the total variation. The PC1 (reflecting 42.3% of the total variance) was associated primarily with soil texture (i.e., sand, clay) and parameters which were highly correlated with soil texture. Under the rainfed potato production on sandy-loam soils in PEI, finer soil texture is likely related to increased yield through its effect on improved soil water holding capacity. The PC2 (reflecting 29.0% of the total variance) was primarily associated with soil fertility and the PC3 (reflecting 14.4% of the total variance) was associated primarily with soil organic matter quality and soil structure. Although soil pathogens were measured at levels high enough to impact yield, they did not differ significantly between high and low yield locations. The findings of this study highlight the value in using multivariate approaches to overcome the challenges in identifying factors which control within-field yield variability.

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO2 respiration rates, CH4 and N2 O fluxes. The study documents studies that measure GHG fluxes from the soil (n = 372) from various land uses, groundwater levels and environmental conditions. We found that total soil respiration was larger in managed peat ecosystems (median = 52.3 Mg CO2 ha-1 year-1 ) than in natural forest (median = 35.9 Mg CO2 ha-1 year-1 ). Groundwater level had a stronger effect on soil CO2 emission than land use. Every 100 mm drop of groundwater level caused an increase of 5.1 and 3.7 Mg CO2 ha-1 year-1 for plantation and cropping land use, respectively. Where groundwater is deep (≥0.5 m), heterotrophic respiration constituted 84% of the total emissions. N2 O emissions were significantly larger at deeper groundwater levels, where every drop in 100 mm of groundwater level resulted in an exponential emission increase (exp(0.7) kg N ha-1 year-1 ). Deeper groundwater levels induced high N2 O emissions, which constitute about 15% of total GHG emissions. CH4 emissions were large where groundwater is shallow; however, they were substantially smaller than other GHG emissions. When compared to temperate and boreal peatland soils, tropical peatlands had, on average, double the CO2 emissions. Surprisingly, the CO2 emission rates in tropical peatlands were in the same magnitude as tropical mineral soils. This comprehensive analysis provides a great understanding of the GHG dynamics within tropical peat soils that can be used as a guide for policymakers to create suitable programmes to manage the sustainability of peatlands effectively.

Non-marketable crops are increasingly being used as a tool to promote agroecosystem services and sustainable agriculture. Nevertheless, crops vary greatly in the traits by which they capture resources and influence the local ecosystem. Here we report on the traits and associated soil microbial communities that relate to aboveground biomass production, nutrient capture, weed suppression, erosion control and building particulate organic matter of 22 different full-season cover crops. All agroecosystem services were positively correlated with maximum canopy height and leaf area. Rooting density was positively associated with indices of bacterial diversity. While some legumes produced the greatest standing N and P in aboveground biomass, they were also poor at capturing soil nitrate and promoted high levels of potential plant fungal pathogens. Conversely, Brassicaceae crops had the lowest levels of potential plant fungal pathogens, but also suppressed saprophytic fungi and rhizobia. Thus, not all crops are equal in their ability to promote all agroecosystem services, and while some crops may be ideal for promoting a specific agroecosystem service, this could result in a trade-off with another. Nonetheless, our study demonstrates that plant functional traits are informative for the selection of crops for promoting agroecosystem services.

Without accurate data on soil heterotrophic respiration (Rh), assessments of soil carbon (C) sequestration rate and C balance are challenging to produce. Accordingly, it is essential to determine the contribution of the different sources of the total soil CO2 efflux (Rs) in different ecosystems, but to date, there are still many uncertainties and unknowns regarding the soil respiration partitioning procedures currently available. This study compared the suitability and relative accuracy of five different Rs partitioning methods in a subtropical forest: (1) regression between root biomass and CO2 efflux, (2) lab incubations with minimally disturbed soil microcosm cores, (3) root exclusion bags with hand-sorted roots, (4) root exclusion bags with intact soil blocks and (5) soil δ13C–CO2 natural abundance. The relationship between Rh and soil moisture and temperature was also investigated. A qualitative evaluation table of the partition methods with five performance parameters was produced. The Rs was measured weekly from 3 February to 19 April 2017 and found to average 6.1 ± 0.3 MgCha-1yr-1. During this period, the Rh measured with the in situ mesh bags with intact soil blocks and hand-sorted roots was estimated to contribute 49 ± 7 and 79 ± 3 % of Rs, respectively. The Rh percentages estimated with the root biomass regression, microcosm incubation and δ13C–CO2 natural abundance were 54 ± 41, 8–17 and 61 ± 39 %, respectively. Overall, no systematically superior or inferior Rs partition method was found. The paper discusses the strengths and weaknesses of each technique with the conclusion that combining two or more methods optimizes Rh assessment reliability.

Recent flooding of agricultural land in the northern Prairie Pothole Region – coupled with intensification of agriculture – has resulted in renewed efforts to drain Prairie Potholes. Drainage is used to improve growing conditions and increase the amount of land that can be cultivated. The aim of this study was to determine if duration of agricultural drainage improved growing conditions and nutrient availability, by measuring physical (i.e. structure and bulk density) and chemical properties (i.e. C, N, and P). Forty-two wetlands and paired midslopes were selected in the Prairie Pothole Region in the Black soil zone of southeastern Saskatchewan. Drainage duration of wetlands ranged from 0 to 50 years. Results suggest drainage does improve growing conditions and nutrient availability for agricultural production, but these changes vary across wetlands drained for different durations of time. Compared with undrained soils, changes were greatest in soils drained from 20 to 34 years, but decreased after 36 years becoming more similar to cultivated midslope positions. Some drainage benefits include increased nitrification and greater available PO 4 −3 at a depth of 0–15 cm. Phosphorus sorption decreased with drainage duration and P desorption increased in soils drained from 7 to 34 years. This could result in greater available N and P for crop uptake, but could also lead to greater nutrient losses. Additionally, bulk density increased and microaggregates decreased with drainage duration. Compared with undrained soils, drainage did not have a significant effect on macroaggregates, soil organic carbon, water extractable organic carbon, light fraction, total N, NO 3 − , and mineralization. It is likely other agricultural practices used in conjunction with drainage, such as tillage, fertilizer additions, and crop removal, are affecting how these soil properties change over time. The resulting quantitative data from this study provides an excellent resource for planning management strategies to improve nutrient use efficiency and reduce losses to the environment.

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO

Increasing oil palm (OP) plantation establishment on tropical peatlands over the last few decades has major implications for the global carbon (C) budget. This study quantified total and heterotrophic soil carbon dioxide (CO 2 ) emissions in an industrial OP plantation (7 year old, 149 trees ha − 1 ) on peat located in the eastern coast of the Sumatra Island (Jambi district), Indonesia, after two doses of nitrogen (N) fertilizer application at rates typical of local practice. The first dose applied in March 2012 (first Fertilization event FE) consisted of 0.5 kg urea per palm (equivalent to 371 kg N ha − 1 at the base of the palm which when extrapolated across the plantation was 35 kg N ha − 1 ) and the second dose applied in February 2013 (second FE) amounted to 1 kg urea per palm. Soil CO 2 fluxes were measured using an infrared gas analyzer (IRGA) in dark closed chambers. The measurements were made daily from 1 day before to 7 days after fertilizer application. Soil heterotrophic respiration (Rh) and total soil respiration (Rs) were measured in trenched plots (where root respiration was excluded) and non-trenched plots, respectively. Concomitant with CO 2 flux measurements, air and soil temperatures, rainfall and the water table level were measured. To estimate the fertilizer effect during the different times of the day, CO 2 fluxes were monitored every 3 h during a 24 h period on days 2 and 3 after fertilizer application during the second FE. Shortly after fertilizer application, substantial pulses of CO 2 were detected in the IRGA chambers where the fertilizer was applied. Even though the fertilized area represents 9.4% of the plantation area only, the impact of fertilizer application at the plantation scale on CO 2 fluxes was noteworthy when compared to non-fertilized control treatments. The Rs was 36.9 kg CO 2 –C ha − 1 (7 days) − 1 greater in the fertilized than in the non-fertilized plots after the first FE but no enhancement was observed after the second FE (− 72.2 kg CO 2 –C ha − 1 7 days − 1 ). The Rh was 340.5 and 98.9 kg CO 2 –C ha − 1 (7 days) − 1 greater in the fertilized than in the non-fertilized plots after the first and second FE, respectively. The larger CO 2 flux enhancement in Rh as compared to Rs may be the result of fertilizer uptake by the palm roots in the un-trenched plots, while in the trenched ones where roots were absent, microorganisms used the fertilizer to accelerate soil organic matter mineralization. Although the response of Rh to N addition and the priming effect were high as compared to results in the literature, the impacts were short-term only and may not have implications on the annual C budget of the plantation.

Soil carbon sequestration can be estimated from field to global scale using numerical soil/ecosystem models. In this chapter, we describe the structure and development of models that have been widely used at international level, from simple models that include carbon only to models that include descriptions of the dynamics of a range of nutrients. We also present examples of the application from field to global scale of different models to answer a range of different questions on the impact of land use and climate changes on soil carbon sequestration.A full discussion of the impact of soil carbon modeling on political and socioeconomical aspects is included to emphasize the need of a close interaction between model developers, researchers, land owners/users and policy makers to ensure the development of robust approaches to climate change, food security and soil protection.Whatever type of models are used to meet future challenges, it is important that they continue to be tested using appropriate data, and that they are used in regions and for land uses where they have been developed and validated.

The first International Peat Congress (IPC) held in the tropics – in Kuching (Malaysia) – brought together over 1000 international peatland scientists and industrial partners from across the world (“International Peat Congress with over 1000 participants!,” 2016). The congress covered all aspects of peatland ecosystems and their management, with a strong focus on the environmental, societal and economic challenges associated with contemporary large-scale agricultural conversion of tropical peat.

This study quantified the fate of new carbon (C) in four crop sequences (lentil–wheat, canola–wheat, pea–wheat, and continuous wheat). Lentil–wheat and continuous wheat were grown in intact soil cores from a Brown Chernozem (BCz) and canola–wheat, pea–wheat, and continuous wheat in cores from a Dark Brown Chernozem (DBCz). In the first growing cycle, plants were pulse-labeled with 13C-CO2. Soil 13C pools were measured once after the labeled growing cycle to quantify root biomass contribution to soil organic matter (SOM) in a single cycle and again after a second growing cycle to quantify the fate of labeled root and shoot residues. 13C was quantified in four SOM fractions: very light (VLF), light (LF), heavy (HF), and water extractable organic matter (WEOM). For BCz lentil, BCz wheat, DBCz canola, DBCz pea, and DBCz wheat in the labeling year, root-derived C estimates were 838, 572, 512, 397, and 418 mg of C per kg soil, respectively. At the end of the second growing cycle, decreases in root-derived C were greater in the VLF, which lost 62 to 95 % of its labeled 13C, than the LF (lost 21 to 56 %) or HF (lost 20 to 47 %). Root-derived C in WEOM increased 38 to 319 %. On DBCz, even though wheat and pea produced less aboveground biomass than canola, they generated similar amounts of SOC by fraction indicating that their residues were more efficiently stabilized into the soil than canola residues. Combining 13C repeat-pulse labeling and SOM fractionation methods allowed new insights into C dynamics under different crop sequences and soil types. This combination of methods has great potential to improve our understanding of soil fertility and SOM stabilization.

Pulse crops represent an ever-increasing proportion of cropping systems in the Northern Great Plains. Previous studies have noted apparent benefits associated with pulse crop production that extend beyond the reduced need for N fertilizer in the year of production; these benefits have been attributed to the quality of pulse residues and their effects on N dynamics in subsequent years. This study used isotope dilution techniques to quantify the N-cycling effects of pulse crops in the rotation. Gross N mineralization was measured over three growing seasons at two Agriculture and Agri-Food Canada research sites in Saskatchewan, Canada: Scott (four rotations; one with pulse crop) and Swift Current (three rotations; one with pulse crop). Gross nitrification and the relative contribution of nitrification vs. denitrification to N2O emissions were also measured. Across all dates and rotations, the average gross mineralization rate at Scott was 2.0 ± 4.0 mg NH4+-N kg−1 soil d−1 and at Swift Current was 1.4 ± 3.9 mg NH4+-N kg−1 soil d−1. At both sites, rates were highly variable across the growing season, but tended to be higher at anthesis than either pre-seeding or post-harvest. The only significant difference among rotations was at Swift Current, where the fertilized continuous wheat rotation had the highest gross mineralization rates (rotation average: 2.3 mg NH4+-N kg−1 soil d−1). The lack of difference among most rotations was particularly notable given the differences in residue quantity among the crops. Ultimately, the lower quantity of residues produced by pulse crops appears to be offset by their higher quality.

Tropical peatlands are among the largest pedologic pools of organic carbon. This study compared soil CO2 fluxes in an intact peat swamp forest, a transitional logged drained forest and an oil palm plantation located on the same alluvial peat plain (peat dome) in Jambi, Sumatra, Indonesia. Dynamic closed chambers were used to measure soil CO2 efflux from January to September 2012. Chambers were placed in pairs, with one close to a tree/palm and the other at mid-distance to the next tree/palm. In the oil palm plantation additional chambers were placed in frond decomposing lines and tertiary drainage canals. During the experiment, air and soil temperatures, water table level and rainfall were recorded. The fluxes were significantly larger in the oil palm plantation (28.4 ± 1.2 Mg C-CO2 ha-1 y-1) than in the transitional logged drained forest (18.5 ± 0.7 Mg C-CO2 ha-1 y-1) and in the intact peat swamp forest (16.0 ± 1.2 Mg C-CO2 ha-1 y-1). The CO2 fluxes were spatially variable according to distance to tree/ palm or when emitted from tertiary drainage canals but no clear trend was detected. A significant but weak relationship was found between CO2 fluxes and water table level in the peat swamp forest. Soil CO2 emissions in oil palm plantations were higher than those reported from Borneo by other authors. The soil CO2 flux should be separated into its auto- and heterotrophic components and balanced with C inputs and other C outputs in further studies to determine soil net atmospheric impacts on the climate system of this land-use change.