H. H. Janzen

• Researcher at Agriculture and Agri-Food Canada

The words we choose to describe our research ultimately directs its course. A dominant term in soil science now, is ‘sequestration’, referring to the removal of carbon (C) from air and its irreversible seclusion in soil, ideally as stable soil organic carbon (SOC). An emerging view, however, now sees SOC as an inherently dynamic assemblage of forms...

Identifying the primary regulators of plant litter decay in agricultural soils is important for understanding ecosystem function now and for managing post-harvest litter in a warmer world. We conducted a litter decay study at 11 sites in Canada and New Zealand with diverse soils and climates. We incorporated 13 C-labelled barley litter into the sur...

Cropping systems with perennial forages and reduced fallow frequency generally increase soil organic carbon and thus subsequent soil health and crop yield. We evaluated the impact of prior cropping systems on subsequent yields and soil properties in a semiarid region by using crop yields as a bioassay of soil health following the termination of a 2...

The rigorous scrutiny Minasny et al. (2022) devote to our paper (Janzen et al., 2022) is both gratifying and edifying. The issue we addressed – the prospects for soil C sequestration to mitigate climate change – is so complex, ecologically and technically, that its underlying science is never fully settled. Any paper, including our own, is therefor...

How much C can be stored in agricultural soils worldwide to mitigate rising carbon dioxide (CO2) concentrations, and at what cost? This question, because of its critical relevance to climate policy, has been a focus of soil science for decades. The amount of additional soil organic C (SOC) that could be stored has been estimated in various ways, mo...

Variable results have been reported on the effects of crop residue loads on soil microbial properties. We investigated changes in soil bacterial composition, β‐glucosidase enzyme activity and nutrient bioavailability in response to wheat residue loading. The treatments included three levels of above‐ground wheat residues (removed, retained or suppl...

Crop residue input plays a central role in regulating soil organic carbon (SOC) storage. Ten long-term field experiments were used to ascertain the changes in SOC in response to differing rates of crop residues. The amount of C input from crop residues varied significantly between and within sites due to soil-environmental conditions, management an...

Long-term field trials are ideal for characterising soil microbial communities because lasting communities in a given cropping system evolve over a long time. However, the soil microbiome has not been characterized in most long-term trials. We used a field trial established in 1911 to identify the core soil bacteria and their functioning in century...

Study region This study used data collected from three cropland sites (two in Manitoba and one in Prince Edward Island) in Canada. Study focus In efforts to accurately describe the water dynamics in agricultural soils, most of the agri-hydrological models developed are highly complex, such that they require detailed input data, of which most of th...

Soil temperature affects the rate of C-cycle processes by influencing the activities of microbial communities but little is known about whether the effects on these communities are consistent in different soils. We studied bacterial and fungal communities in six different soils, originating from two different Canadian climatic regions and incubated...

‘Soil health’ has become a dominant, pervasive phrase in soil and environmental sciences. But despite its ubiquity, the concept remains elusively ambiguous, largely because ‘health’ here is a metaphor, not a literal scientific construct. So we ask: can this imagery nevertheless still advance research toward stewardship of soils globally? To address...

Nitrogen (N) is an essential ingredient for the production of food in agricultural systems. As the use of industrial fertilizers has risen over time, so too have concerns relating to N losses from these systems and the contamination of air and water, climate change impacts and biodiversity losses these cause. In order to balance continuing and impr...

Producing food to meet rising global demand requires a more thorough understanding of how farming systems can ensure food security without compromising economic, environmental, and social sustainability. This dilemma can be addressed through a social-ecological systems approach to ecosystem service assessment, which assesses the linkages between th...

The soil microbial community regulates decomposition of plant litter, but little is known about how the composition of the community responds to litter quality. To evaluate this, we applied 13 C-labelled oat [Avena sativa] leaf or stem litter to soil at a rate of 5 mg C g −1 soil and incubated it at 20°C for 170 days. We measured total C mineralize...

Understanding the mechanisms controlling the formation and persistence of soil organic matter (SOM) is important for managing soil health and sustainable food production. The formation of SOM and the degree to which it is protected from decomposition are important for determining the long-term persistence of SOM. We used soils collected in a ¹³C-la...

Climate change may profoundly influence soil organic carbon (SOC) dynamics through effects on soil temperature and water, but the mechanisms and magnitude of those effects remain uncertain. We measured the response of residue-C and native SOC in six soils with diverse texture subjected to artificial heating after transplanting to a common field sit...

For centuries, scientists have been probing the nature and dynamics of organic matter in soil and sediment. A prominent approach in this research has been to extract humic substances using a strong alkaline solution. The continuing merits of this time‐honored approach, however, has prompted some recent debate. Does the study of humic substances, as...

Soil organic carbon (SOC) in agricultural lands is vital for global food production and greenhouse gas (GHG) mitigation. Accurate quantification of the change in SOC stocks at regional or national scales, which depends heavily on reliable spatiotemporal carbon (C) input data, remains a big challenge. Here we use the process-based RothC model to est...

Globally, consumption of bovine meat is projected to increase by 1.2% per annum until 2050, a demand likely met in part by increased Canadian beef production. With this greater production on a finite agricultural land base, there is a need to weigh the contribution of this industry to the Canadian economy against the full range of positive and nega...

Soil organic carbon (SOC) changes slowly, and final management influences can be measured only after decades. Analysis of archived samples from a site established on grassland in 1911 showed that SOC, under wheat systems, approached steady state after several decades, and that its amount reflected the inputs of residue C.

To improve the estimates of C and N inputs to soil, we developed new estimates of partitioning between the harvested portion, aboveground residue, and belowground residue for 11 major crops based on depth-adjusted root/shoot ratios and grain yield-adjusted harvest indices. We updated the mean N concentration of each partition.

We planted continuous wheat, with and without nitrogen fertilizer, onto a preceding long-term (44 yr) experiment with contrasting cropping systems, and measured soil organic carbon (SOC) after 6 yr. Changes in SOC were driven mostly by cumulative plant C inputs, as influenced by yield response to added nitrogen.

Understanding how soil fertility and current practices affect microbial function in different soils is important for the development of sound management recommendations. However, interactions of the soil matrix with topography and climate obscure these interpretations. A long-term soil quality experiment was established in 1990 at Lethbridge, AB to...

Soil organic matter (SOM) is a major driver of key agroecosystem functions. Our objective was to examine the dynamics of organic matter in whole soil, particulate (POM; >53 μm size), and mineral-associated (MAOM) fractions under varying crop rotations and nutrient managements at two long-term experimental sites (Breton and Lethbridge). Soil samples...

Agricultural is essential to feed the human world but it can also degrade the physical world. Therefore, we need widely-accepted metrics to assess how prospective practices influence sustainability. We hypothesized that emergy and energy analyses considered together provide a robust, comprehensive measure of sustainability, and evaluated this hypot...

Before recommending a feeding strategy for greenhouse gas (GHG) mitigation, it is important to conduct a holistic assessment of all related emissions, including from those arising from feed production, digestion of these feeds, managing the resulting manure, and other on-farm production processes and inputs. Using a whole-systems approach, the Holo...

Grazing is a common practice in the beef cattle industry and is an integral component of pasture and rangeland management. The objective of this study was to evaluate impacts of grazing management scenarios on greenhouse gas (GHG) intensity [kg carbon dioxide equivalents (CO2e) kg− 1 beef] at the farm-gate for beef production systems in western Can...

Abstract Managing the land properly can help conserve the soil which is critical for sustaining our life and the global society. However, measuring the quality of the soil explicitly is still a challenge. Therefore, this study was conducted to identify suitable soil quality indicators among contrasting land managements (i.e., simple vs. complex cro...

Wheat (Triticum aestivum L.) is a major food source supplying nutrients required for adequate human nutrition. Changing fertility and cropping practices could alter the concentration of essential elements in wheat grain. This study utilized two long-term field experiments to determine the effect of nitrogen (N) and phosphorus (P) fertilization and...

Managing nitrogen (N) inputs to sustain high yields whileminimizing losses to adjacent environments remains among the foremost aims in agroecosystems. We studied the N balance in a study established in 1911 at Lethbridge, AB, Canada. The experiment includes three cropping systems - continuous wheat (W), fallow-wheat-wheat (FWW), and fallow-wheat (F...

We assessed the extent to which summer fallow in the Dark Brown soil zone is likely to return as a response to net return (NR) risk. An economic model was used to identify, delineate, and quantify the effects of changes in product prices and input costs on the long-term economic performance of cereal, legume forage, and legume green manure rotation...

Soil carbon (C) balance largely depends on the amount of crop residue inputs into soils and those inputs are affected by harvest index (HI), the ratio of harvested product to total shoot dry matter. The objective of this study was to establish the relationship between HI and yield for major crops to improve the estimation of aboveground crop residu...

Core Ideas We report long‐term SOM change in different soils transplanted to one plot. Mainly, initial SOM concentrations highly influence change over time. Sand and land management history influence SOM change. High C soils lose C and low C soils gain C; thus, soils converge to new equilibrium. Light‐fraction OM converges at a faster rate than C a...

Core Ideas Sustainability can only be measured over long time periods. To evaluate sustainability, therefore, we need a way of keeping track—a memory. Soil offers such a memory because the soil stays. An underlying aim of soil science is to extract and describe soils' memories. Terrestrial ecosystems worldwide face mounting stresses and upheavals,...

Widespread global changes, including rising atmospheric CO2 concentrations, climate warming and loss of biodiversity, are predicted for this century; all of these will affect terrestrial ecosystem processes like plant litter decomposition. Conversely, increased plant litter decomposition can have potential carbon-cycle feedbacks on atmospheric CO2...

Ruminants raised for meat and milk are important sources of protein in human diets worldwide. Their unique digestive system allows them to derive energy and nourishment from forages, making use of vast areas of grazing lands not suitable for arable cropping or biofuel production and avoiding direct competition for grain that can be used as human fo...

Ammonia (NH 3 ) volatized from livestock manure is affiliated with ecosystem and human health concerns and decreased fertilizer value of manure and can also be an indirect source of greenhouse gas. Beef cattle feedlots, where thousands of cattle are grouped together to enable greater control of feed management and production, are hot spots in the a...

After 47 yr of no-till and reduced summerfallow at Lethbridge, Alberta, soil organic carbon concentration and stocks increased 2.14 g kg⁻¹ and 2.22 Mg ha⁻¹, respectively, in the surface 7.5 cm layer. These findings confirmed the conservation value of reducing tillage and summerfallow. The annual changes were relatively small.

Inter-relationships among soil erosion, soil quality, soil resilience, and legacy effects of organic amendments have not been adequately quantified. Topsoil was mechanically removed (cuts) to simulate erosion in semiarid southern Alberta in 1990. Three cuts (0, 10, and 20 cm) superimposed with three one-time (1990 only) amendment treatments (check,...

Our goals in this study were to track the incorporation of plant residue into soil organic matter (SOM) and test the effectiveness of different fractionation methods to evaluate this transformation. We incubated soil amended with 13C-labelled barley (Hordeum vulgare L.) residue and used three fractionation methods based on size (> 250, 53-250, 5-53...

Root distribution pattern plays an important role in understanding and estimating of soil C allocation and the effect of crop roots C input on soil carbon balance in agroecosystems. A database of 96 profiles was compiled and root distribution pattern were fitted to a modified logistic dose response curve for 11 temperate crops. A slight linear decr...

The Habere-Bosch process for synthesizing fertilizer nitrogen (N) is among themost importantmodern discoveries because it has enabled us to growenough food for several billion more of us. At the same time, however, profusion of added "reactive" N has become a prominent ecological threat, globally, because a large fraction of appliedNis lost fromagr...

The Canadian ammonia (NH3) emissions model and a survey of dairy farm practices were used to quantify effects of management on emissions from dairy farms in Ontario Canada. Total NH3 emissions from dairy farming were 21 Gg NH3-N yr-1 for the four ecoregions of the province. Annual emission rates ranged from 12.8 (for calves in ecoregions of Manitou...

Long-term cropping system studies offer insights into soil management effects on agricultural sustainability. In 1995, a 6-yr bioassay study was superimposed on a long-term crop rotation study established in 1951 at Lethbridge, Alberta, to determine the impact of past cropping systems on soil quality, crop productivity, grain quality, and the relat...

A long-term, 42-yr study was used to determine the impacts of crop rotation and fertility management on wheat yield and profitability. Crop rotations included continuous wheat (W), fallow-wheat (FW), and fallow-wheat-wheat (FWW). Original plots were split for nitrogen (N) and phosphorus (P) fertility treatments, a two-factor factorial for N (0 and...

The prospect, so alluring, of sequestering carbon (C) to mitigate CO2 build-up in air has prompted a flurry of soil studies, but questions still linger about whether early optimism was fully justified. My objectives are to review briefly the mechanisms of carbon accrual, consider constraints on soil C sequestration for mitigating climate, and conte...

Stewart, A. A., Alemu, A. W., Ominski, K. H., Wilson, C. H., Tremorin, D. G., Wittenberg, K. M., Tenuta, M. and Janzen, H. H. 2014. Whole-farm greenhouse gas emissions from a backgrounding beef production system using an observation-based and model-based approach. Can. J. Anim. Sci. 94: 463–477. Backgrounding, raising weaned beef cattle in preparat...

Plants figure prominently in efforts to promote C sequestration in agricultural soils, and to mitigate greenhouse gas (GHG)emissions. The objective of the project was to measure the transformations of plant carbon in soil through controlled laboratory experiments, to further understand (1) root-associated CO2 and N2O production during a plant’s lif...

2014. Transforming plant carbon into soil carbon: Process-level controls on carbon sequestration. Can. J. Plant Sci. 94: 1065Á1073. Plants figure prominently in efforts to promote C sequestration in agricultural soils, and to mitigate greenhouse gas (GHG) emissions. The objective of the project was to measure the transformations of plant carbon in...

Plants figure prominently in efforts to promote C sequestration in agricultural soils, and to mitigate greenhouse gas (GHG) emissions. The objective of the project was to measure the transformations of plant carbon in soil through controlled laboratory experiments, to further understand (1) root-associated CO 2 and N 2 O production during a plant's...

Backgrounding, raising weaned beef cattle in preparation for finishing in a feedlot, is a common practice in western Canadian beef production systems. The objectives of this study were: (i) to assess the whole-farm greenhouse gas (GHG) emissions from a pasture-based backgrounding system using an observation-based and model-based approach and (it) t...

Animal feeding operations have been identified as the primary contributor of anthropogenic ammonia (NH 3) emissions in North America. Quantifying NH 3 volatilization from each stage of livestock manure management is important for developing corresponding technologies and methods to reduce emissions and nutrient losses. A regionally specific mass ba...

Greenhouse gas (GHG) emissions remain an important field of agricultural research. Apart from measuring, simulations are frequently used to investigate management impacts on GHG emissions. The HOLOS model has been developed (using country specific emission factors) to explore potential mitigation practices with respect to GHG emission reduction or...

This project was designed to provide information about the efficiency of nitrogen (N) management practices for western Canadian winter wheat producers. Three factors were included in Experiment 1: 1) urea type (urea, urea+urease inhibitor -‘Agrotain’; urea+urease and denitrification inhibitor – ‘SuperU’, polymer-coated urea – ‘ESN’, and urea ammoni...

The objective of this study was to conduct a life-cycle assessment (LCA) of greenhouse gas (GHG) emissions from a typical nongrazing dairy production system in Eastern Canada. Additionally, as dairying generates both milk and meat, this study assessed several methods of allocating emissions between these coproducts. An LCA was carried out for a sim...

Field Experiments conducted over the past 100 years in the Canadian Prairie provinces have resulted in voluminous agronomic knowledge that has propelled Canada to become a major exporter of agricultural products. Hundreds of scientific publications have been produced and this knowledge is now being used to address emerging issues such as climate ch...

â–º Consistent farm scale data with respect to soil, weather, and farm operation data. â–º Stochastic simulation of variability in farm scale GHG emission sources. â–º Soil N2O emission was the largest source of GHG emissions per unit area and per kg DM. â–º Soil C change contributed most to the variability in GHG emission intensities among farms i...

The arbuscular mycorrhizal (AM) fungal resources present in wheat fields of the Canadian Prairie were explored using 454 pyrosequencing. Of the 33 dominant AM fungal operational taxonomic units (OTUs) found in the 76 wheat fields surveyed at anthesis in 2009, 14 clustered as Funneliformis – Rhizophagus, 16 as Claroideoglomus, and 3 as Diversisporal...

Soil erosion by wind or water removes valuable topsoil and decreases soil productivity. What is the value of this topsoil in terms of maintaining crop yield? When restoring eroded soils, how long do the effects of one-time applications of soil amendments last and is the magnitude or longevity of these effects influenced by the level of erosion? Thi...

A field bioassay of soil quality was established in 1990 at the Lethbridge Research Centre to study how measured differences in soil quality affect yield. At each of two sites, 36 diverse soils were deposited onto subsurface soil, and spring wheat was grown, with and without added nitrogen, to measure yield responses. The experiment shows that plan...

A number of scientists have named our age the Anthropocene because humanity is globally aff ecting Earth systems, including the soil. Global soil change raises important questions about the future of soil, the environment, and human society. Although many soil scientists strive to understand human forcings as integral to soil genesis, there remains...

Organic amendments are often used to mitigate the effects of soil degradation caused by erosion. In spring 1992, a desurfaced soil (∼15 cm depth mechanically removed to simulate erosion) received one-time applications of amendments (20 Mg ha -1 dry wt), and was subsequently seeded annually to spring wheat (Triticum aestivum L.). By 2009, six treatm...

This publication is a timely update of the landmark 2004 CAST Task Force Report, Climate Change and Greenhouse Gas Mitigation: Challenges and Opportunities for Agriculture. Modern-day environmental issues include the need to decrease concentrations of carbon dioxide (CO2) and other greenhouse gases (GHGs) in Earth’s atmosphere. Agriculture is in th...

Agroecosystems provide a range of benefits that are strongly influenced by cropping practice. Crop productivity and C, N, and greenhouse gas (GHG) balances were evaluated in an 18-yr cropping system study on an Aridic Haplustoll in the northern Great Plains. Application of synthetic fertilizers consistently increased crop yield and soil organic car...

Numerous mitigation strategies are proposed to reduce greenhouse gas (GHG) emissions from ruminants, with many aimed at reducing enteric CH4. Before implementing such practices, it is critical to evaluate their net impact on total farm GHG emissions. Thus, a life cycle assessment (LCA) was conducted using HOLOS (i.e., a whole farm model based on In...

Humanity is quickly encroaching upon the finite limits of the biosphere. As our numbers and appetites grow, food supplies become less secure, reserves of clean energy dwindle, pools of freshwater evaporate, the atmosphere's capacity to absorb our emissions diminishes and space for human and biotic habitat grows scarce. In response, some are now ask...

Bt (Bacillus thuringiensis) corn is reported to produce lignin-rich residues, compared to non-Bt (NBt) corn, suggesting it is more resistant to decomposition. As the Bt gene is expressed selectively in stem and leaf tissue, it could affect lignin distribution in corn, which naturally has greater lignin content in roots than in stems and leaves. Our...

The depth of sampling has recently been highlighted as critical to making accurate measurements of changes in SOC stocks. This paper aimed to determine the effects of land management changes (LMC) on soil organic carbon (SOC) by re-sampling long-term agoecosystem experiments (LTAEs) across Canada using identical sampling and laboratory protocols. T...

Several long-term agroecosystem experiments (LTAEs) across Canada have been maintained for periods of up to a century. Much scientific knowledge of changes in soil properties through time has been learned from these few, highly productive LTAEs. We determined the effects of land management changes (LMC) on soil organic carbon (SOC) by re-sampling 2...

The biosphere, our fragile and exquisite home, is changing abruptly and irrevocably, largely from human interference. Most or all of the coming stresses have links to the land, so finding hopeful outcomes depend on wide and deep understanding of soils. In this review, we pose eight urgent issues confronting humanity in coming decades: demands for f...

To understand how pulse and oilseed crops might use nitrogen (N) more efficiently under varying levels of water and N availability in soil, we conducted a 2-year field study to monitor N accumulation in aboveground (AG-N) and root material at five growth stages, for canola (Brassica napus L.), mustard (Brassica juncea L.), chickpea (Cicer arietinum...

A life cycle assessment (LCA) was conducted to estimate whole-farm greenhouse gas (GHG) emissions from beef production in western Canada. The aim was to determine the relative contributions of the cow-calf and feedlot components to these emissions, and to examine the proportion of whole-farm emissions attributable to enteric methane (CH4). The simu...

Long-term ecological sites are ‘listening places’– places where we press our ears to the earth and strain to hear its pulse. Such sites will be needed especially in coming decades, as ecosystems throughout the world face mounting stresses, mostly from human influences. My aim, in these musings, is to elicit conversation, by way of seven questions,...

Managing crop fertilization may be an important component of integrated weed management systems that protect crop yield and reduce weed populations over time. A field study was conducted to determine the effects of various timings and application methods of nitrogen (N) fertilizer on weed growth and spring wheat yield. Nitrogen fertilizer was appli...

Gan, Y. T., Campbell, C. A., Janzen, H. H., Lemke, R., Liu, L. P., Basnyat, P. and McDonald, C. L. 2009. Root mass for oilseed and pulse crops: Growth and distribution in the soil profile. Can. J. Plant Sci. 89: 883-893. Crop roots transport water and nutrients to the plants, produce nutrients when they decompose in soil, and provide organic C to f...

In the recent decades NH3 emission from animal production has increased substantially worldwide and there has been indications of its adverse effect on vegetation especially near intensive livestock operations. In this study, the effect of NH3 deposition on soil and on two forage species, crested wheatgrass (CWG) (Agropyron cristatum L. Gaertn.) an...

As agriculture contributes about 0·08 of Canada's greenhouse gas (GHG) emissions, reducing agricultural emissions would significantly decrease total Canadian GHG output. Evaluating mitigation practices is not always easy because of the complexity of farming systems in which one change may affect many processes and associated emissions. The objectiv...