Dark Brown Chernozemic Research Articles

Once in Three-Year Deep-Banding and Annual Shallow-Banding of P, K and Cu Fertilizer Effects on Crops and Soil Nutrients

Deep-banding of the immobile nutrients (P, K, and Cu) is considered one technique that may improve crop production under temperate dryland systems, where moister soil conditions prevail at seeding followed by relatively drier soil during the growing period. The objectives were to compare growth and yield of canola (Brassica napus L.), field pea’s (Pisum sativum L.) and wheat (Triticum aestivum L.); and nutrient concentrations in crops and soil from once in three-year deep-banding (12.5-15 cm) and annual shallow-banding (3.75 to 5 cm diagonally deeper than seeding depth) of P, K and Cu under direct seeding systems. Small plot trials were conducted at the three sites; representing Brown (Dark Brown Chernozem), Black (Black Chernozem), and Grey (Dark Grey Luvisol) soil zones in Alberta, Canada; which represent crop growing conditions for most areas of western Canada. The nine treatments were annual shallow-banding and once in three year deep-banding of P, K, Cu and PKCU nutrients plus a control (no P, K, or Cu fertilizer). Applied thrice the recommended rate for deep-banding (in 2018) treatments and the recommended rate for the annual shallow-banding treatments in 2018, 2019 and 2020. All three phases of pea’s-wheat-canola rotation were grown at each site to generate nine years of data for each crop. The density, height, NDVI (normalized difference vegetation index) and biomass of plants, yield for crops and nutrient concentrations in seed and biomass of crops and soil showed significantly positive responses to P, K, and PKCu additions in some cases; generally not linked to the deep or shallow placement of tested nutrients. Changes in nutrient concentrations in seed and biomass of crops in response to nutrient additions were not consistent. Treatments with P showed response more often than with the K and Cu. The soil P and Cu concentrations increased in response to their additions in some cases, but no change was observed from the K addition. Once in three-year deep-banding or annual shallow-banding methods were equally effective. The findings provide another option (once in three year deep-banding) for applying the P, K and Cu fertilizers.

Soil responses to inclusion of corn, soybean, and cover crops under rainfed conditions in the northern Great Plains

Crop rotations in the northern Great Plains of North America increasingly include corn ( Zea mays L.) and soybean ( Glycine max (L.) Merr.). Use of cover crops, while less extensive, is also increasing given their purported agronomic and environmental benefits. To date, soil responses to the inclusion of corn, soybean, and cover crops in rainfed cropping systems have not been well documented in the region. Therefore, soil properties were evaluated 6 years after establishment of three crop rotations (spring wheat ( Triticum aestivum L.)–soybean (SW–S), spring wheat–corn–soybean (SW–C–S), and spring wheat–corn–cover crop (SW–C–cc)) each split by no and minimum tillage on a Dark Brown Chernozem near Mandan, ND, USA. Soil responses to treatments were subtle and exclusive to the 0–7.6 cm depth. Soil pH was lower in SW–S than SW–C–cc (5.28 vs. 5.48; P = 0.05), SO4-S was greater under SW–C–cc than SW–C–S (13.4 vs. 11.6 g S kg−1; P = 0.03), exchangeable K was greater under SW–C–S and SW–C–cc than SW–S (0.83 cmol kg−1 vs. 0.52 cmol kg−1; P = 0.05), and water-stable aggregates were greater in SW–S than SW–C–S (26% vs. 19%; P = 0.08). Soil organic carbon (SOC) and total N did not differ among crop rotations or between tillage treatments, while particulate organic matter N was greater under no tillage compared to minimum tillage ( P = 0.08). Between 2012 and 2018, soil pH decreased and SOC increased under SW–C–S. Frequent monitoring of near-surface soil conditions in rotations with soybean every other year is recommended. Furthermore, innovative management practices are needed to enhance soil C and N fractions in rotations with full-season cover crops.

Integrating enhanced efficiency fertilizers and nitrogen rates to improve Canada Western Red Spring wheat

Granular urea fertilizer applied at planting is prone to nitrogen (N) losses in certain environments. Enhanced efficiency fertilizers (EEFs) are developed to mitigate losses and optimize plant uptake. To determine the benefits of EEFs in grain yield and quality enhancement in Canada Western Red Spring (CWRS) wheat, an experiment was conducted from 2019 to 2022 at eight sites in Alberta and Saskatchewan, Canada. The effects of five N sources [urea; urea + urease inhibitor, N-( n-butyl)thiophosphoric triamide (NBPT); urea + nitrification inhibitor, nitrapyrin; urea + dual-inhibitor, NBPT + dicyandiamide; and polymer-coated urea, ESN® (Environmentally Smart Nitrogen®)] and four N rates (60, 120, 180, and 240 kg N ha−1) on CWRS wheat production were examined. Results indicated that N source affected grain yield in Dark Brown Chernozem soils but not in Black Chernozem or Dark Grey Luvisol soils. In Dark Brown Chernozem soils, a dual inhibitor increased grain yield by 3.1% and 3.9% relative to urea and polymer-coated urea, respectively, while all other EEFs attained similar results. The use of a dual inhibitor EEF led to greater net returns compared to urea and polymer-coated urea in the Dark Brown Chernozem soils. Grain protein concentration increased linearly with increasing N rate from 60 to 240 kg N ha−1. Generally, a rate of 120 kg N ha−1 was optimal for CWRS wheat grown in Canadian prairie conditions when coupled with EEFs, particularly a dual inhibitor, and grain yield and protein were often responsive.

Elevation gradient drives distribution of soil carbon in a semiarid grassland of British Columbia

A sequence of Brown, Dark Brown and Black Chernozems spanning a 600 m elevation gradient in a semiarid bunchgrass ecosystem (Lac du Bois Grassland) near Kamloops, British Columbia was first described in 1961. More soil organic carbon (SOC) at higher elevations along the sequence was attributed to increasing effective precipitation with increasing elevation. Since the 1961 study, plant community composition has shifted toward the desired climax community due to improved livestock management instituted in the 1970s; however, changes in soil carbon stocks remain unknown. The objective of this study was to quantify SOC and soil inorganic carbon (SIC) stocks using the same site selection criteria as used in 1961. SOC stocks (kg m−2 ± SD; 0–60 cm) were similar for Brown (5.73 ± 1.7) and Dark Brown Chernozems (5.87 ± 0.76) but increased sharply (10.11 ± 2.5) for the higher elevation Black Chernozems. SIC increased with depth in all three soil zones, representing 33%–50% of total C from the 30–60 cm soil depth. To evaluate changes in SOC (0–20 cm) from the 1961 measurements, three different approaches for calculating SOC stocks were used based on the inclusion or exclusion of coarse fragments. Results varied across the three soil zones from no change to a 20% increase in the Brown, an increase of 7% to a reduction of 26% in the Dark Brown, and a decrease of 12% to 35% in the Black soil zone. Information about soil coarse fragments and the distribution of SOC and SIC stocks within the soil profile is crucial for accurate comparisons across studies or resampling events.

Short-term legacy effects of feedlot manure amendments on surface soil CO2 efflux under irrigated silage barley in Southern Alberta

The short-term legacy effects following long-term (17 yr) feedlot manure application on CO2 efflux for a surface soil (clay loam) were studied over 2 yr (2016–2017) on a Dark Brown Chernozem in southern Alberta. The five treatments were stockpiled (SM) or composted (CM) manure with either straw (ST) or wood-chips (WD) bedding applied at 77 Mg·ha−1 (dry wt.) and an unamended control (CON). Surface soil efflux was measured during the growing season of the 2 yr using the dynamic, closed-chamber method. Ancillary measurements (soil water and temperature, total carbon, bulk density) were also obtained. Soil CO2 efflux was similar (P > 0.05) among the four amended treatments in the first (0.63–0.86 g·m−2·h−1) and second (0.40–0.46 g·m−2·h−1) years. However, soil CO2 efflux was significantly greater for amended than unamended treatments by 54–110% in the first year (CON = 0.41 g·m−2·h−1) and by 33–53% in the second year (CON = 0.30 g·m−2·h−1). Soil CO2 efflux was similar for SM and CM in both years and was significantly greater for WD than ST bedding in the first but not second year. Weak positive correlations (r ≤ 0.39) occurred between soil CO2 efflux and total soil C, water-filled pore space (WFPS), and soil temperature. Overall, our findings suggested that legacy effects of manure may persist for 1–2 yr following discontinued applications, but are mostly restricted to greater soil CO2 efflux for amended than unamended soils.

Nitrogen Use Efficiency in Parent vs. Hybrid Canola under Varying Nitrogen Availabilities

Improving nitrogen use efficiency (NUE) is essential for sustainable agriculture, especially in high-N-demanding crops such as canola (Brassica napus). While advancements in above-ground agronomic practices have improved NUE, research on soil and below-ground processes are limited. Plant NUE—and its components, N uptake efficiency (NUpE), and N utilization efficiency (NUtE)—can be further improved by exploring crop variety and soil N cycling. Canola parental genotypes (NAM-0 and NAM-17) and hybrids (H151857 and H151816) were grown on a dark brown chernozem in Saskatchewan, Canada. Soil and plant samples were collected at the 5–6 leaf stage and flowering, and seeds were collected at harvest maturity. Soil N cycling varied with phenotypic stage, with higher potential ammonium oxidation rates at the 5–6 leaf stage and higher urease activity at flowering. Seed N uptake was higher under higher urea-N rates, while the converse was true for NUE metrics. Hybrids had higher yield, seed N uptake, NUtE, and NUE, with higher NUE potentially owing to higher NUtE at flowering, which led to higher yield and seed N allocation. Soil N cycling and soil N concentrations correlated for improved canola NUE, revealing below-ground breeding targets. Future studies should consider multiple root characteristics, including rhizosphere microbial N cycling, root exudates, and root system architecture, to determine the below-ground dynamics of plant NUE.

Effect of Manure from Cattle Fed 3-Nitrooxypropanol on Anthropogenic Greenhouse Gas Emissions Depends on Soil Type

Cattle production is a large source of greenhouse gas (GHG) emissions from the Canadian livestock sector. Efforts to reduce CH4 emissions from enteric fermentation have led to modifications of diet composition for livestock, resulting in a corresponding change in manure properties. We studied the effect of applying manure from cattle fed a barley-based diet with and without the methane inhibitor supplement, 3-nitrooxypropanol (3-NOP), on soil GHG emissions. Three soils common to Alberta, Canada, were used: a Black Chernozem, a Dark Brown Chernozem, and a Gray Luvisol. We compared the supplemented (3-NOPM) and non-supplemented manure (BM) amendments to a composted 3-NOPM (3-NOPC) amendment and a control with no manure amendment (CK). In an 84-day laboratory incubation experiment, 3-NOPM had significantly lower cumulative CO2 emissions compared to BM in both the Black Chernozem and Gray Luvisol. The cumulative N2O emissions were lowest for 3-NOPC and CK and highest for 3-NOPM across all soil types. Cumulative CH4 emissions were only affected by soil type, with a net positive flux from the fine-textured Gray Luvisol and Dark Brown Chernozem and a net negative flux from the coarse-textured Black Chernozem. Cumulative anthropogenic GHG emissions (CO2-equivalent) from soil amended with 3-NOPM were significantly higher than those for both BM and CK amendments in the Black Chernozem, while the cumulative anthropogenic GHG emissions from the 3-NOPC treatment were similar to or significantly lower than those for the BM and CK treatments across all soil types. We conclude that soil GHG emissions resulting from the 3-NOPM amendment are dependent on soil type and 3-NOPM could potentially increase soil GHG emissions compared to BM or CK. Although we show that the composting of 3-NOPM prior to soil application can reduce soil GHG emissions, the composting process also releases GHGs, which should also be considered in assessing the life-cycle of manure application. Our results provide a first look at the potential effect of the next stage in the life cycle of 3-NOP on GHG emissions. Further research related to the effect of soil properties, particularly in field studies, is needed to assess the best management practices related to the use of manure from cattle-fed diets supplemented with 3-NOP as a soil amendment.

Corrigendum: Wheat yield and soil properties reveal legacy effects of artificial erosion and amendments on a dryland Dark Brown Chernozem

Corrigendum: Wheat yield and soil properties reveal legacy effects of artificial erosion and amendments on a dryland Dark Brown Chernozem

Wheat yield and soil properties reveal legacy effects of artificial erosion and amendments on a dryland Dark Brown Chernozem

Erosion leads to substantial loss of soil productivity. To abate such decline, amendments such as manure or fertilizer have been successfully employed. However, the longevities of erosion and soil amendment legacy effects are not well quantified. In 1957, a Dark Brown Chernozem soil at Lethbridge, AB, was land-levelled, creating three degrees of topsoil removal or erosion: noneroded, moderate erosion, or severe erosion. Two amendment studies (1980–1985 and 1987–1991) were superimposed on the erosion treatments. Both studies were cropped to spring wheat (Triticum aestivum L.) from 1993–2010 to examine legacy effects of erosion and soil amendments on wheat yield and soil properties. Without amendment, mean wheat yield under moderate erosion was 40% of the noneroded treatment, whereas severe erosion was 34% of the noneroded treatment, 36–42 yr (1993–1999) after erosion. Under moderate or severe erosion, the restorative power of manure diminished substantially in the first 10–15 yr following cessation of addition, but then levelled off resulting in wheat yields up to 35% higher than equivalent nonamended treatments. Legacy effects of erosion (54 yr) and amendment (27–31 yr) on soil organic carbon and total nitrogen were also observed.

Modeling Barley Yield in a Dark Brown Chernozem after Discontinuation of Long‐term Manure Application

Core Ideas Soil properties at the discontinuation of manuring adequately explained subsequent grain yield. Soil TOC, TP, TN, and NO3–N were most influential and consistent in explaining yield variability. No evidence of convergence in grain yield among the discontinued manure treatments after 7 yr. Fertilizer application on soils that have received long‐term manure application is often not necessary and typically not advised for environmental reasons. Soil properties at the discontinuation of manure application may assist in modeling crop yield trends on such soils in subsequent years. The data used in this study were from a long‐term field experiment initiated in 1973 at the Agriculture and Agri‐Food Canada Research and Development Centre in Lethbridge, Alberta. Soil and plant samples were collected annually from 1973 through 2010 from irrigated plots that were cropped to barley (Hordeum vulgare L.) every year. Soil properties measured at the start of the experiment in 1973 were used to model yield in the control plots while soil properties measured at the end of annual manure applications in 2003 were used as predictors in partial least squares (PLS) regressions to model barley yield in subsequent years in plots in which manure application was discontinued. Soil total N, organic carbon, P, and NO3–N concentrations were the most important soil properties for modeling annual barley grain yield in manured soils using PLS regression. Our results indicate that initial measured soil properties can be a useful tool in modeling yearly crop yield. During the 7 yr following discontinuation of manure application, there was no evidence of convergence in grain yield among amendment treatments, reflecting that the soil nutrient levels were above agronomic thresholds for optimum yields. Long‐term monitoring of yield will assist in the development of models for predicting when nutrient application will become necessary.

Phytoextraction of nitrogen and phosphorus by crops grown in a heavily manured Dark Brown Chernozem under contrasting soil moisture conditions

ABSTRACTPhytoextraction of excess nutrients by crops in soils with a long history of manure application may be a viable option for reducing the nutrient levels. This greenhouse study examined the effectiveness of six growth cycles (40 d each) of barley, canola, corn, oat, pea, soybean, and triticale at extracting nitrogen (N) and phosphorus (P) from a Dark Brown Chernozem that had received 180 Mg ha−1 (wet wt.) of beef cattle feedlot manure annually for 38 years. Moisture content during the study was maintained at either 100% or 50% soil field capacity (SFC). Repeated cropping resulted in an overall decrease in dry matter yield (DMY). The decrease in N and P uptake relative to Cycle 1 was fastest for the cereal grains and less pronounced for the two legumes. However, cumulative N uptake values were significantly greater for corn than the other crops under both moisture regimes. The reduction in soil N was greater under the 100% than the 50% SFC. These results indicate that repeated cropping can be a useful management practice for reducing N and P levels in a heavily manured soil. The extent of reduction will be greater for crops with high biomass production under adequate moisture supply.

Quantifying Optimal Rates of Litter Retention to Maximize Annual Net Primary Productivity on Mixed-Grass Prairie

Optimal rates of litter retention for maximizing annual aboveground net primary productivity (ANPP) were investigated in native mixed-grass rangelands in Saskatchewan, Canada. The study was conducted on 18 independent study sites on brown and dark brown Chernozem (Mollisol) soils during the 2011 and 2012 growing seasons. Each site contained 30 treatment plots with two control plots and 28 treatment plots receiving between 1 and 2 290 g/m2 of added plant litter sourced from a reference site. Soil moisture values were recorded for each plot in May, June, and July, while forb, graminoid, and total ANPP were harvested at the end of the growing season. Soil moisture-litter relationships were driven by weather patterns with significant differences between years. Graminoid ANPP-litter relationships were nonlinear with peaks in productivity between 54 and 412 g/m2 of litter mass in the brown soil zone and between 27 and 157 g/m2 of litter mass in the dark brown soil zone. Forb ANPP was highest at the lowest litter masses and was not significantly influenced by study year or soil zone. The recommended litter retention rates in provincial range health assessment guidelines are accurate for the dark brown soil zone but are lower than the levels identified here for the more arid brown soil zone.

Long-term (47 yr) effects of tillage and frequency of summerfallow on soil organic carbon in a Dark Brown Chernozem soil in western Canada

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.

Long-term cropping system impact on quality and productivity of a Dark Brown Chernozem in southern Alberta

Smith, E. G., Janzen, H. H. and Larney, F. J. 2015. Long-term cropping system impact on quality and productivity of a Dark Brown Chernozem in southern Alberta. Can. J. Soil Sci. 95: 177–186. 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 relationship of yield productivity to soil quality. All plots from 13 long-term crop rotations were seeded to wheat (Triticum aestivum L.) in a strip plot design [control, nitrogen (N) fertilizer]. Prior to seeding, soils were sampled to determine soil chemical properties. Total wheat production for the last 4 yr of the study was used as the measure of productivity. The 1995 soil analysis indicated crop rotations with less frequent fallow and with N input had higher soil quality, as indicated by soil organic carbon (SOC) and light fraction carbon (LF-C) and N (LF-N). SOC had a positive relationship to total wheat yield, but was largely masked by the application of N in this bioassay study. Frequent fallow in the previous crop rotation lowered productivity. The concentration of LF-C had a negative relationship, whereas LF-N had a positive relationship to total wheat yield, with and without N fertilization in this bioassay study. Grain N concentration was higher with applied N and when the long-term rotation included the addition of N by fertilizer, livestock manure, annual legume green manure or legume hay. This study determined that long-term imposition of management practices have lasting effects on soil quality and crop productivity.

Unsaturated water flux at mid and lower slope positions within an inclined landscape of the Dark Brown soil zone in southern Alberta

Miller, J. J. and Chanasyk, A. S. 2015. Unsaturated water flux at mid and lower slope positions within an inclined landscape of the Dark Brown soil zone in southern Alberta. Can. J. Soil Sci. 95: 27–36. Little research has quantified vertical-unsaturated water flux below the root zone for mid and lower slope positions within inclined, low-relief, and longer-slope landscapes of the Dark Brown soil zone of the Canadian prairies. We measured soil moisture (0.23–1.22 m) in the field at mid and lower slope positions in southern Alberta from May to October in 1985 and 1986. Undisturbed soil cores were taken from soil horizons and saturated hydraulic conductivity and soil moisture retention were determined in the laboratory. Vertical-unsaturated water flux below the root zone was calculated between 1.07 and 1.22 m depths below ground surface using the hydraulic gradient method. Water fluxes for the 2 yr ranged from <10−11 to 10−10 m s−1 at the mid slope position, and from <10−11 m s−1 to 10−9 m s−1 at the lower slope position, and were consistent with some other studies. Cumulative water flux was dominantly downward (−2.2 to −3.4 mm) at the mid slope position and this flow direction was consistent with this Orthic Dark Brown Chernozemic soil that was located in a “recharge area”. Cumulative water flux was dominantly upward at the lower slope position in 1985 (1.4 mm) and dominantly downward but of very low magnitude in 1986 (−0.1 mm), and this flow direction was consistent with this saline Gleyed Regosol and “saline seep”. Cumulative water fluxes as a percentage of annual precipitation were 0.8 to 1.8% at the mid slope position and 0.3 to 0.5% at the lower slope position.

A Bioassay of Nitrogen Availability in Soils Amended with Solid Digestate from Anaerobically Digested Beef Cattle Feedlot Manure

Anaerobically digested manure (ADM) from biogas plants is often applied to cropland at rates equivalent to those for raw manure. However, the digestion process may alter nutrient release patterns, necessitating adjustment of application rates. We tested this hypothesis using five cycles of forage barley (Hordeum vulgare L.) grown in pots containing a Dark Brown Chernozem (mixed Typic Haploboroll) or a Black Chernozem (Typic Haplocryoll) amended with beef cattle (Bos taurus) feedlot manure, solid digestate (SD, that is, the separated solids fraction of ADM), pelletized SD (PSD), and urea + monoammonium phosphate (UMAP) at rates equivalent to 400 and 800 mg total N kg⁻¹ soil. Biomass yields did not differ significantly among manure, SD, and UMAP (mean = 32 g kg⁻¹ soil) and were lowest for PSD (18 g kg⁻¹ soil). Overall, apparent N recovery (ANR) from amendments over the five crop cycles decreased in the order: UMAP (53%) > manure (35%) ≈ SD (20%) > PSD (−7%) in the Dark Brown Chernozem; and UMAP (45%) ≈ manure (42%) > SD (26%) > PSD (−13%) in the Black Chernozem. Apparent net mineralization of organic N was higher in the Black Chernozem than the Dark Brown Chernozem and, in both soils, higher for manure (33% of initial total organic N) than SD (24%) and PSD (−16%). Although biomass yields were similar for manure and SD, slower organic N mineralization and lower apparent N recovery in SD-amended soils may limit the N supply capacity of SD. It may be prudent to apply SD at higher rates than manure or to supplement the SD with mineral N fertilizer to ensure adequate available N for plant uptake.

Changes in Nitrogen Availability in Chernozemic Soils Amended with Anaerobically Digested Cattle Manure

Anaerobically digested manure (ADM) is a nutrient-rich coproduct from manure-based biogas plants. The ADM is often separated into a solid fraction, known as solid digestate (SD), and a liquid fraction, which could be applied to cropland at rates equivalent to those for raw manure. Application of SD could result in different nitrogen (N) mineralization patterns compared to raw manure due to biophysicochemical changes occurring during anaerobic digestion. The objective of this laboratory incubation experiment was to characterize changes in the availability of N in a Dark Brown Chernozem (Typic Haploboroll clay loam) and a Black Chernozem (Typic Haplocryoll silty clay) amended with raw beef cattle (Bos taurus) feedlot manure, SD, pelletized SD (PSD), and urea plus monoammonium phosphate (UMAP) at rates equivalent to 400 and 800 mg N kg⁻¹ soil. Across rates, net mineralized N concentrations after 70 d in soils amended with UMAP, manure, SD, and PSD were 44, 18, −5, and -13% of added N, respectively, in the Dark Brown Chernozem and 45, 29, 6, and -18%, respectively, in the Black Chernozem. The lower N mineralization potential of SD and PSD compared with manure implies that anaerobic digestion alters the nutrient release patterns of manure and suggests that these digested manure forms may have to be either applied at higher rates compared with raw manure or should be supplemented with inorganic N fertilizer to ensure adequate N supply for plants.

Carbon input from 13C-labeled crops in four soil organic matter fractions

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.

The impact of erosion on the classification of Mollisols in Iowa

Fenton, T. E. 2012. The impact of erosion on the classification of Mollisols in Iowa. Can. J. Soil Sci. 92: 413-418. The fertile black soils in the Great Plains and Western States of the United States are dark brown Chernozems in the Canadian system of soil taxonomy and Mollisols, when a mollic epipedon is present, according to the United States soil taxonomy. Other primary criteria are organic carbon content, color, structure, and thickness of the mollic epipedon. Accelerated erosion can affect all of these properties and is especially critical for soils that have slope gradients of more than 2%. Accelerated erosion and erosion phases are recognized in field mapping based on the amount of A horizon remaining but criteria provided in the Soil Taxonomy guidelines conflict with procedures outlined in the Soil Survey Field Manual and result in a dichotomy between the classification system and field mapping practices. Soil map unit data for the five most extensive Mollisol soil series in Iowa that have multip...

The impact of erosion on the classification of Mollisols in Iowa

Fenton, T. E. 2012. The impact of erosion on the classification of Mollisols in Iowa. Can. J. Soil Sci. 92: 413–418. The fertile black soils in the Great Plains and Western States of the United States are dark brown Chernozems in the Canadian system of soil taxonomy and Mollisols, when a mollic epipedon is present, according to the United States soil taxonomy. Other primary criteria are organic carbon content, color, structure, and thickness of the mollic epipedon. Accelerated erosion can affect all of these properties and is especially critical for soils that have slope gradients of more than 2%. Accelerated erosion and erosion phases are recognized in field mapping based on the amount of A horizon remaining but criteria provided in the Soil Taxonomy guidelines conflict with procedures outlined in the Soil Survey Field Manual and result in a dichotomy between the classification system and field mapping practices. Soil map unit data for the five most extensive Mollisol soil series in Iowa that have multiple phases of slope and erosion were summarized and variations between the taxonomic and survey principles were identified. Eroded units comprise 26 to 77% of the total mapped area of the series studied and do not qualify as Mollisols under the taxonomic system. However, under the principle of following the genetic thread to classify soils, the taxonomic system should be modified to accommodate the eroded units that have the same genetic pathway as their uneroded counterparts. This could be accomplished by placing primary emphasis on the organic carbon content and waiving the color requirement for eroded soil map units.