During field application of biochar, the bulk density of tilled soil initially decreases and then increases over time, until reaching the initial level of compacted soil. This study evaluated the optimal biochar particle size for promotion of water infiltration and retention in a saline soil with various bulk densities after application. Corn straw biochar, pyrolyzed at 450 °C for 0.5 h, was prepared in different particle sizes (S1 ≤ 0.25 mm, S2 = 0.25–1 mm, and S3 = 1–2 mm) and separately mixed into the 0–30 cm soil layer at two rates (R1 = 10 g kg^-1 and R2 = 100 g kg^-1), with tilled (D1 = 1.1–1.43 g cm^-3) and compacted (D2 = 1.45 g cm^-3) bulk densities. Five models were applied to simulate water infiltration into biochar-amended soils. Compared with the non-biochar control, the S1 treatment increased cumulative water infiltration by 41% (bulk density = 1.26 g cm^-3) to 11% (bulk density = 1.45 g cm^-3). However, the effect of the S3 treatment on cumulative water infiltration shifted from positive (+19.3%) to negative (–22.4%) with increasing bulk density. The S2 treatment resulted in the highest water retention at the tilled bulk density, whereas a significant increase (12.7%) in water retention was observed in the S1 treatment at the compacted bulk density. The Kostiakov–Lewis, Kostiakov, and United States Department of Agriculture – Natural Resources Conservation Service models performed better than the Philip and Horton models to describe the relationship between cumulative water infiltration and infiltration time, except for the D2R2S1 treatment. This study provides evidence for amelioration of saline soil by straw biochar in the Yellow River Delta.

The influence of surface mulching on soil aggregation and associated carbon (C) and nitrogen (N) varies by mulching materials and crop types. The 6 yr effect of straw mulching (SM), plastic film mulching (PM), and no mulching (CK) on soil aggregation and associated C and N concentrations at 0–20 and 20–40 cm soil layers were studied under dryland winter wheat (Triticum aestivum L.) and spring corn (Zea mays L.) in the Loess Plateau of China. Regardless of crop types, aggregate proportion was greater in macroaggregates (2.00–10.00 mm), but lower in microaggregates (<0.50 mm) with mulching than without in both soil layers. The mean weight diameter of aggregates was greater with SM and PM than CK. Compared with CK and PM, SM increased soil organic C (SOC) and total N (STN) concentrations in both macroaggregates and bulk soil at 0–20 cm. Aggregate proportion and soil C and N concentrations at both depths were more pronounced in winter wheat than spring corn. The recovery rates of bulk soil SOC and STN in aggregates varied from 94% to 107%. Straw and plastic film mulching enhanced soil aggregation compared with no mulching. Straw mulching was more effective in increasing SOC and STN concentrations at the surface layer in dryland winter wheat and spring corn.

The aim of this study is to investigate impact of soil amendments (4% biochar, 0.4% polymer, and a combination of them) on soil moisture and salinity distribution, tomato yield, and water-use efficiency (WUE). Open-field experiments were conducted during two successive growing seasons in 2017 and 2018. The experiment consisted of three levels of irrigation treatments: 100%, 80%, and 60% of crop evapotranspiration (ET_c); and two different water qualities: fresh 0.9 dS m^-1 and saline electrical conductivity 3.6 dS m^-1. Results revealed that at 100% of ET_c, soil water distribution increased by 12.94%, 37.87%, and 42.21% at depths 0–15, 15–30, and 30–45 cm, with the addition of biochar, respectively, compared with control at same depths under freshwater, but the addition of polymer was increased by 6.35%, 16.56%, and 16.37%, respectively. While combination treatments increased by 15.70%, 24.80%, and 41.26%, at the depths aforementioned. Salt concentration was increased by 59.10% with biochar, whereas decreasing by 7.19% and 57.63% with polymer and mixture treatments, respectively. The results also showed that biochar and mixture treatments improved yield compared with the polymer and control, whereas saline water decreased the yield compared with freshwater. With deficit irrigation, WUE was increased by 28.54%, 40.98%, and 68.93% at 100%, 80%, and 60% of ET_c, respectively, indicating it could be used as an irrigation management strategy under arid and semiarid field conditions.

N-(n-Butyl)thiophosphoric triamide (NBPT) has been reported to reduce ammonia volatilization from surface-applied urea and urea ammonium nitrate (UAN). A new NBPT formulation (ARM U^™, 18% NBPT) that contains a polymer allowing for lower application rate of NBPT was evaluated for its efficacy relative to Agrotain^® (30% NBPT) and Arborite^® (24% NBPT). Trials consisted of (i) a greenhouse study that compared two rates of ARM U-treated urea (360 and 540 mg NBPT kg^-1 urea) with Arborite- or Agrotain-treated urea (480 and 600 mg NBPT kg^-1 urea, respectively) and (ii) a field study that compared urea and UAN treated with either ARM U (360 mg NBPT kg^-1 urea) or Agrotain (600 mg NBPT kg^-1 urea) at two sites. Static chambers fitted with acid-charged discs were used to measure ammonia volatilization at six or seven dates over 28 d. In the greenhouse study, ammonia volatilization was reduced by 96% with either ARM U or Agrotain and 95% with Arborite. In the field study, ARM U and Agrotain reduced ammonia volatilization from urea by 80% and 66%, respectively, across sites. Similarly, ammonia volatilization from UAN was reduced by 46% and 60% with ARM U and Agrotain, respectively. Despite the lower NBPT application rates with ARM U, ammonia reduction by ARM U, Agrotain, and Arborite was not significantly different. The addition of ARM U to urea and UAN enabled lower application rate of NBPT without compromising its efficacy.

Black soil is inherently productive and fertile but is subject to soil erosion. Understanding the distribution of soil physical and hydraulic properties of the soil profile under various land uses would help reveal the mechanism behind the degradation of black soil. In this study, we investigated the variation in soil physical and hydraulic properties with land uses and soil depths in the black soil area of Northeast China. Disturbed samples and undisturbed soil cores were collected from 0–100 cm soil depths under agricultural land (AL), forestland (FL), and shrub land (SL). Our results showed that the land use and soil depth significantly affected the soil bulk density (BD), field capacity (FC), capillary moisture capacity (CMC), saturated hydraulic conductivity (Ks), and soil water retention curve (θ_s and α). Small macroaggregates accounted for most of the soil mass and were significantly higher in FL but lower in AL for the 0–50 cm of the soil samples. The FC, CMC, and Ks decreased, but the BD increased with the soil depth across the three land-use types. In addition, the soil in AL had a higher BD but lower CMC and Ks than the soil in FL and SL for most soil depths. These results indicated that land use can influence the variation in soil physical and hydraulic properties within the 0–100 cm soil depth, and agricultural use is a major reason for soil degradation in this black soil region.

The disruptive land-use change during forage grass conversion to annual crop can be critical for determining nitrous oxide (N₂O) emissions, but this is an understudied period. We measured soil N₂O fluxes (using closed static vented chambers) together with potential environmental drivers of these fluxes from liquid pig manure (LPM) and solid pig manure (SPM) applied to an annual crop (ANN) and perennial forages (FPP) that was converted to annual crop. Unamended plots were used as a control (CON). The results showed that in 2013, average soil nitrate-N was significantly higher on the recently converted FPP (ranging from 19 to 83 mg N kg^-1) than the continuous ANN plots (from 16 to 35 mg N kg^-1). The recently converted perennial forage system produced three times greater N₂O than the continuous annual system, which is likely a result of accelerated N mineralization from the accumulated soil organic matter (over 4 yr) and grass residues of the recently killed forage grasses. However, during the second year of the study when the FPP plots were reseeded to perennial grasses, the system emitted 30% less N₂O than the ANN system. These results suggest that including perennial forage grass in rotation with annual crops can provide N-saving and climate change mitigation benefits; however, some of the N stored in the soil would be lost when the perennial grass plots are cultivated to grow annual crops.

Bearing capacity is often calculated in dry or saturated conditions, leading to overconservative designs, for a wide range of climates in the world. Extensive researches show that bearing capacity is significantly affected by the soil matric suction. However, in most of the presented models, uniform (and sometimes linear) suction distributions are taken into account for computing the bearing capacity. Also, there is no exact solution in the residual zone of unsaturation. In the present study, a simple method is proposed to predict the bearing capacity of footings placed on unsaturated soil, using the limit equilibrium concept. Linear and uniform variations of matric suction are considered in computations, as well as the nonlinear suction distribution. The framework of the proposed model is analogous to Terzaghi’s equation, and a novel factor is developed, during calculations, as the suction bearing capacity factor. In the case of full saturation, the proposed model is simplified to the Terzaghi’s equation. Estimated results are compared with the experimental and theoretical data available in the literature. Predicted values are in a good agreement with the measured data in the transition zone and residual zone of unsaturation.

Long-term application of feedlot beef cattle manure amendments to cropland may enhance earthworm abundance by increasing soil organic carbon. The objective of this study was to determine the legacy effects of feedlot manure type [stockpiled (SM) vs. composted (CM)], bedding material [straw (ST) vs. woodchips (WD)], manure rate (13, 39, or 77 Mg ha^-1), unamended control, and inorganic fertilizer treatments on earthworm abundance in a clay loam soil after 3–4 yr of discontinued applications following 17 annual applications. Earthworms were sampled (20 cm depth) in 2 yr (2017–2018), and ancillary soil properties also determined. The Aporrectodea genus was the dominant earthworm identified. Earthworm abundance was similar (P > 0.05) for amended and unamended or inorganic fertilizer treatments. Abundance at the 39 Mg ha^-1 rate in 2018 was significantly (P ≤ 0.05) greater by four times for SM than CM with ST, but it was two times greater for CM than SM with WD. Abundance at the 13 Mg ha^-1 rate in 2017 was significantly greater by 91% for ST than WD, but at the 39 Mg ha^-1 rate, it was 10 times greater for WD than ST. In 2018, abundance was five times greater for WD than ST with CM, but it was similar with SM. Overall, short-term legacy effects occurred on earthworm abundance, but these effects varied with manure rate. Earthworm abundance was not increased by manure application, which suggested a carrying capacity not directly related to food resource.

To address concerns among members of the Canadian Society of Soil Science (CSSS) regarding the discipline’s capacity to train new soil professionals, specifically in pedology and field skills, members of the CSSS’s soil education and pedology committees have proposed to develop a pedology field school. To aid in the selection of learning outcomes that are relevant to professional practice, an online survey was sent to Canadian soil professionals within private industry and governmental organizations. Professional feedback was also requested regarding the creation of a web-based national soil education resource and the certification of soil pedological skills. According to the survey results, the quality of new graduates’ pedology and field skills was perceived as poor. Certain soil field skills and knowledge were thought to be either completely absent from the current Canadian curriculum (e.g., spatial variability of soil processes), or not well mastered by graduates (e.g., interpreting soil survey reports). Important learning outcomes were identified, such as interpreting soil survey information, soil mapping, and soil-landscape classification with soil description–classification and soil genesis content needed as a refresher. Taking into consideration existing regional field schools, we recommend that the CSSS co-create, where needed, and coordinate, where they already exist, regional pedology field schools throughout Canada. We also propose that the CSSS develop a national pedology certification and a web-based soil education resource. Also, further study is necessary to shed light on the contribution of non-disciplinary graduates to the professional practice and the impact this has on the perception of soil education in Canada.

In cool temperate regions, large emissions of nitrous oxide (N₂O), an important greenhouse and ozone-depleting gas, have been observed during freeze–thaw (FT) cycles. However, it is unclear how freezing and thawing rates, freezing intensity, and freezing duration influence N₂O emissions. We used a laboratory incubation to measure N₂O emissions from two soils (sandy loam, silty clay) undergoing a single FT cycle of various freezing and thawing rates [rapid (0.5 °C h^-1) vs. slow (0.017 °C h^-1)], freezing intensity (-1 vs. -3 °C), and freezing duration (24 vs. 48 freezing degree-days). In general, soil carbon dioxide fluxes during freezing were highest when soils were frozen slowly at -1 °C, whereas fluxes after thawing were highest from the soils frozen and thawed rapidly at -3 °C. Soil N₂O emissions during both the freezing and thawing periods were greatest in the soils exposed to rapid freezing to -3 °C, intermediate under rapid freezing to -1 °C and slow freezing to -3 °C, and smallest under slow freezing to -1 °C and the control treatment (constant +1 °C). The similar N₂O emissions between the unfrozen control and the slowly frozen -1 °C treatment was unexpected as previous field studies with similar freezing rates and temperatures still experienced high N₂O emissions during thaw. This suggests that the physical disruptions caused by freezing and thawing of the surface soil are not the primary driver of FT-induced N₂O emissions under field conditions.

There is limited information about the genesis, classification, and properties of calcareous and gypsiferous soils of western Iran. This study investigated the morphological, physical, and mineralogical characteristics of soils on different physiographic units, including plateau, colluvial fans, and piedmont plain in the Aleshtar region. The results indicated that the parent materials (calcareous and gypsiferous) as well as topographic conditions had the most influence on the soil profile development, pedogenic processes, and clay mineralogy. Illite, chlorite, smectite, palygorskite, and kaolinite clay minerals were identified using X-ray powder diffraction, transmission electron microscopy, and scanning electron microscopy. Illite, chlorite, and kaolinite have genetically been inherited from parent rocks. Neoformation of smectite and palygorskite other than genetic inheritance was formed as a result of calcite and gypsum precipitation and poor drainage. Calcareous soils with the petrocalcic horizon and gypsiferous soils contained more pedogenic palygorskite. In conclusion, we suggest adding a new great group of Gypsixerepts to the soil taxonomy to reflect the presence of pedogenic gypsum in Inceptisols.

Studies examining the influence of disturbance and management history on pasture soils across a large sampling area are uncommon. We report on the soil properties found in 102 northern temperate pastures sampled in central Alberta, Canada, and relate these attributes to ongoing pasture management practices compiled from producer surveys and aboveground measures of rangeland health (RH). Tame pastures, typically seeded to introduced forages, were associated with higher soil fertility (total carbon, nitrogen, and organic matter) than semi-native grasslands, which were associated with coarse-textured soils. Soil properties remained independent of most grazing and pasture management practices, including the grazing systems, class of livestock, fertilization, and stocking rate. However, manure application, often combined with harrowing, was associated with improved soil fertility and increased electrical conductivity (salinity). Soils with a fire history reported by land managers, largely in the Boreal natural region, were characterized by a greater soil C:N ratio. Soil surface properties (litter cover, litter depth, and bare soil) were responsive to grazing management, with growing season and year-round grazing associated with a thinner litter layer having less cover, and bare ground twice as high under continuous grazing compared with pastures rotationally grazed. Further, variation in soil surface cover was associated with contrasting RH classes (healthy, healthy with problems, and unhealthy), whereas soil attributes remained unrelated to RH. This study demonstrates that soils within these northern temperate grasslands are relatively insensitive to many pasture management practices, and highlights that existing RH assessments may provide limited insight into differences in mineral soil properties.

Assessment tools are needed to evaluate the effect of farming practices on soil health, as there is increasing interest from growers to improve the health of their soils. However, there is limited information on the efficacy of different soil health indicators on commercial farms and perhaps less so on organic farms. To assess efficacy, three organic growers in cooperation with the Ecological Farmers Association of Ontario’s Farmer-Led Research Program tested management sensitivity, measurement repeatability, and consistency of interpretation of different soil health indicators. On each farm, we compared permanganate-oxidizable carbon (active carbon), organic matter, wet aggregate stability, phospholipid fatty acid analysis, Haney soil health test, and Haney nutrient test on one field of grower-perceived high productivity, one field of grower-perceived low productivity, and one reference site (undisturbed, permanent cover). Our results were consistent with previous research that showed grower perception of productivity and soil health associated with management-sensitive soil health indicators. Of the indicators tested, active carbon was the only indicator that was sensitive, repeatable, and consistent across the three farms, and soil organic matter was highly repeatable and consistent to detect differences greater than 0.5% organic matter. This study highlights differences among soil health indicators on commercial farms, and it concludes that active carbon and organic matter were the most useful soil health indicators for these organic farms. Participating growers intend to use results to benchmark current soil status and to help guide land management decisions towards improved soil health.

Phosphorus (P) loss to freshwater is a key driver of eutrophication, and understanding the scale and spatial distribution of potential P sources is a key pre-requisite for implementing policies for P management to minimize environmental impacts. Soil test P (STP) is a useful indicator of the accumulation of P in soils, but these data are not readily available for most agricultural land in Canada, so the cumulative P balance (P inputs as manure or fertilizer minus removal of P in crops) is calculated as a proxy for this value. Cumulative P balance is an important calculation within the indicator of risk of water contamination by P, so allocations of manure and fertilizer P to cropland were updated within the calculation of P balance, and for Ontario, data from 1961 to 1980 were added to account for P applications during that period. The STP concentrations were calculated from the resulting cumulative P balances. When compared with reported STP concentrations, the predicted concentrations showed a statistically significant regression at the national (R² = 78%) and provincial scale (Ontario, R² = 36%; Prince Edward Island, R² = 36%; Manitoba, R² = 72%; British Columbia, R² = 40%). There was significant variation in the cumulative P balance across Canada, with the highest values corresponding with areas of high livestock density, whereas large zones of P deficit were detected across the Prairies.

Estimating daily solar radiation from common meteorological variables plays an important role in agricultural applications, such as driving crop growth models. Relatively simple and accurate estimation methods, which use only daily air temperature together with precipitation, are often required. Based on all available solar radiation data across Canada, the most common and representative solar radiation models were evaluated. All estimation models provided more accurate estimates, in terms of all performance statistics used in this study, than those extracted directly from a high-resolution global dataset of meteorological forcings for land surface modelling. The DS model adapted from one originally developed for the Canadian Prairies performed better than other representative models for all stations. The DS model was then adapted for regional use in southern Canada, mostly the major agricultural regions. We compared simulated crop yields using the CSM–CERES–wheat and CSM–CROPGRO–canola models driven by observed and estimated daily solar radiation data, and we found a difference of approximately 5% for spring wheat (Triticum aestivum L.) and 12% for canola (Brassica napus L.). Based on the results for two locations under different climate regimes with relatively long records (45 and 40 yr, respectively) of solar radiation data, the models using daily temperature range and precipitation were found to be robust for daily solar radiation estimation for the entire time periods of the data records.

Little research has been conducted on the effect of beef feedlot manure amendments on runoff hydrology and soil loss during the transition between continuous and legacy application phases. We conducted a 6 yr (2013–2018) study and utilized surface (0–5 cm) soil collected from a long-term (since 1998) field experiment on a clay loam soil in southern Alberta, Canada. The treatments were stockpiled or composted feedlot manure with straw (ST) or wood-chip (WD) bedding applied at 13, 39, and 77 Mg ha^-1 (dry weight). There was also an unamended control and inorganic fertilized treatment (IN). Disturbed surface soil was collected from all treatments after 15 (C15), 16 (C16), and 17 (C17) continual annual applications (2013–2015), and then 1 (L1), 2 (L2), and 3 (L3) yr (2016–2018) after manure applications were discontinued in 2015. The soil was packed into runoff trays, and a Guelph rainfall simulator (70 mm h^-1) was used to generate 30 min of runoff. The time to runoff, total runoff depth, and flow-weighted mean concentrations (FWMCs) and mass loads of total suspended solids (TSS) were determined. Mean values of runoff variables were significantly greater for ST than WD in certain years for time to runoff (by 28%–127%), runoff depth (44%), TSS FWMCs (58%–137%), and FWMC loads (28%–230%). Mean TSS was generally significantly greater at the two lower than highest manure rates for FWMC (48%–135%) and loads (21%–253%). Overall, choice of bedding material showed the most potential to maximize infiltration and reduce water and sediment loss.

The conversion of forested areas into cropping systems modifies the soil physical attributes and affects the environmental and economic sustainability of agricultural activity. Thus, this work aimed to evaluate the modifications caused in the physical attributes of the soil in the area of guarana, cupuacu, and annatto compared with forest area in southern Amazonas. In the areas of forest and guarana meshes of 90 m × 70 m and regular spacing between the sampling points of 10 m × 10 m, in the area of annatto meshes of 90 m × 56 m and spacing of 10 m × 8 m, for cupuacu meshes of 54 m × 42 m, with spacing between the sampling points of 6 m × 6 m. The samples were collected in the depths of 0.00–0.05, 0.05–0.10, and 0.10–0.20 m, with 80 sampling points in each area, making 960 samples in the four areas. The cupuacu area most closely resembled the most diverse aspects of soil physical attributes with the forest area, and this was noticeable through the averaging test along with the principal component analysis, thus indicating that this crop is the least harmful to the studied soil, as well as the adopted systems of cultivation cause modifications mostly superficially, being these modifications little noticeable in layers superior to 10 cm.

A 21 yr field study comparing zone tillage (ZT), no-tillage (NT), and moldboard plow tillage (MP) was used to elucidate tillage effects on soil hydrophobicity (SH) and soil water repellency index (RI) in a cool, humid clay loam soil in southwestern Ontario. The SH was 38% (P ≤ 0.05) greater for ZT and NT than MP, and it was similar between crop row (0.34) and crop inter-row (0.37) for ZT. The RI values were not different among tillage systems, or between the crop row versus crop inter-row positions under the three tillage systems.

Mid-infrared spectroscopy in the transmission mode was used to predict inorganic nitrogen (N), organic N, and total N in soil leachate. The developed predictions were accurate and robust for total N, NH₄⁺, NO₃^-, inorganic N (NH₄⁺ + NO₃^-), and organic N (total N - inorganic N) with high determination coefficients (R² = 96.7 - 99.0) and residual prediction deviation (RPD = 5.47 - 9.96). The proposed method simultaneously estimates the concentrations of dissolved nitrogen species in soil leachates accurately and with significant savings in time, cost, and chemicals relevant to conventional methods.