The characterization of magnetic susceptibility (MS) has become an accepted technique in soil science. This review examines the concept of volume and mass-specific MS, magnetism, frequency dependence, and thermal behavior of MS, as they pertain to soil material. A comparison is presented of the two types of instrumentation for measuring soil MS, based on magnetic field and electromagnetic induction (EMI). These are discussed with respect to applications including magnetic granulometry, detection of pollutants, identification of organic matter, the delineation of drainage class, paleo-environmental studies, archaeology, as well as soil erosion and degradation. Instruments that use magnetic fields can precisely measure the MS of small amounts of soil, thinly deposited layers or soil exposures, but cannot effectively measure materials at distances ≥10 cm from the sensor. EMI instruments, instead, are capable of quickly measuring apparent MS of a finite volume of the soil, and are utilized in mapping of soil MS in agricultural and archaeological investigations; however, the measured apparent MS values need to be further processed to give the real volume MS values of soil layers/segments. Although both kinds of instruments are widely used in soil science, their measured data are not interchangeable. Future work should be conducted to increase the understanding of the comparability of these instruments to find better utility among soil scientists.

Palygorskite has been reported in alluvial sediments and in soil clays in Central Iran, but it is not known if it is inherited or formed in situ. Here, we sampled Calcids developed from Triassic and Cambrian dolomitic formations in the southwestern part of Yazd and performed soil and clay characterization by X-ray diffraction and fluorescence, optical and scanning electron microscopy and energy dispersive X-ray spectrometer analyses. Our results suggested palygorskite neoformation in the calcic soil horizons in Calcids. The soils with aridic soil moisture regime and high Mg concentration, during the formation of a calcic horizon by precipitation of secondary calcite, conditions were suitable for authigenic palygorskite crystals of long size (>10–20 μm) and their stability. In addition, the occurrence of short-size (about 2 μm) palygorskite fibers in the lower gypsic horizon probably resulted from its translocation from the upper horizons. Therefore, such results suggested palygorskite neoformation in the calcic soil horizons in these Calcids of Iran.

A long-term field litterbag manipulation experiment was conducted to examine the effects of reduced precipitation (−30% of through-fall), nitrogen (N) addition (50 kg N·ha⁻¹·yr⁻¹), and their combination (−30% of through-fall and 50 kg N·ha⁻¹·yr⁻¹) on the release and immobilization of N and phosphorus (P) in four litter types (Pinus koraiensis (PK), Tilia amurensis (TA), Quercus mongolica (QM), and their mixture (MIX)). The results showed that N addition did not significantly stimulate litter decomposition, whereas precipitation reduction and the interaction significantly inhibited litter decomposition. N immobilization was significantly enhanced by N addition and reduced precipitation in the PK, QM, and MIX litters but was significantly inhibited in the TA litter. N addition, reduced precipitation, and their combination significantly increased the final P concentration of the litter in each sampling period. Furthermore, interestingly, there was a significant exponential correlation between the remaining N and final P concentration in the PK litter and a significant linear correlation for the QM and MIX litters, but no significant correlation for the TA litter, indicating that the dynamic relationship between the remaining N and final P concentration in the litter depended on the litter type. These results suggest that the forest litter layer may alleviate the effects of N deposition by increasing litter N immobilization and aggravating soil P limitation by inhibiting litter P release following N deposition. Reduced precipitation may further affect biogeochemical cycles by inhibiting the release of litter N and P.

Tillage and nitrogen (N) fertilization can influence soil organic matter (SOM) dynamics, but their interactive effects remain contradictory. A long-term (25 yr) corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation was used to investigate the effect of tillage [moldboard plow (MP) and no-till (NT)] and N rates (0, 80, and 160 kg N·ha⁻¹) on soil organic carbon (SOC), total N (STN), respiration, and SOM fractions [particulate organic matter (POMC, POMN), mineral-associated organic matter (MAOMC, MAOMN), and microbial biomass (MBC, MBN)]. Results indicate that NT had 27% higher SOC and 24% higher STN than MP in the 0–20 cm depth. Furthermore, SOC and STN stocks (0–20 cm) were 22% and 20% higher, respectively, under NT than MP. There was significant stratification under NT, with a rather uniform distribution under MP. The SOM fractions and soil respiration were 28%–275% and 20%–83% higher at the 0–5 and 5–10 cm depths, respectively, under NT than MP. Interestingly, N fertilizer rate or its interaction with tillage had no impact, except for respiration (tillage × N rate and N rate × depth). Hence, while N addition was required for adequate grain production and increased cumulative plant C and N inputs, our findings indicate that the vertical distribution of SOC, STN, and SOM fractions was affected by tillage, thereby influencing resource accessibility and subsequent dynamics of SOM fractions. Taken together, our results support the adoption of NT and judicious use of N fertilizers for enhancing topsoil SOM storage and fertility under humid temperate conditions.

Sorptivity (S) is the fundamental variable controlling the early infiltration process. Besides soil properties, soil initial water content (θ_i) and (or) matric pressure (h_i) are key factors determining extent of S. Assessment of interrelationship among S, h_i, and soil properties can provide a considerable insight into understanding the behaviour of dry soils to rainfall or irrigation water. This study was conducted to evaluate relationship between S and some selected soil parametric and morphometric properties within a range of h_i. Sixteen undisturbed soil samples (5 cm id, 5 cm length) were taken from the topsoil (0–15 cm) of a paddy soil with clay texture. Sorptivity was measured with a mini-disc infiltrometer on the samples equilibrated at h, ranging from −20 to −1500 kPa. A parameter (η), representing the relationship between S and h_i, was introduced. Correlation analysis was conducted between η and selected soil morphometric and parametric properties. Soil structure and clay content appeared the most important soil attributes influencing S–h_i relation between −200 and −1500 kPa. The results provided a fundamental understanding on S–h_i–soil properties interrelations in a clay soil. The methodology developed in this study can be used to evaluate S–h_i relationship across different soils and scales.

Soil microorganisms play an important role in agricultural ecosystem. However, there is little information about the effects of putative allelochemicals on specific soil microorganisms in vivo. Cucumber seedlings were treated with four concentrations of ferulic and p-hydroxybenzoic acids (0–1.0 μmol·g⁻¹ soil) in soil. Effects of ferulic and p-hydroxybenzoic acids on rhizosphere Fusarium community structures and abundance were analyzed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR techniques, respectively. The results showed that ferulic acid at concentrations of 0.25, 0.5, and 1.0 μmol·g⁻¹ soil significantly reduced the number of bands of Fusarium, and ferulic acid at concentrations of 0.5 and 1.0 μmol·g⁻¹ soil significantly reduced Shannon–Wiener and evenness index of Fusarium community. All concentrations of p-hydroxybenzoic acid changed the community structure of Fusarium, including decreasing the number of bands, Shannon–Wiener, and evenness index. Ferulic and p-hydroxybenzoic acids at all concentrations significantly promoted the abundance of Fusarium. Ferulic and p-hydroxybenzoic acids at 0.5 μmol·g⁻¹ soil had the highest Fusarium abundance among all treatments. These results indicate that four concentrations of ferulic acid had various effects on Fusarium, which was different from p-hydroxybenzoic acid, and this may be related to the cucumber autotoxicity, giving us a further understanding of soil sickness.

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.

Broiler chicken litter (BCL) is a cheap manure for vegetable crops in developing countries. Extensive antibiotic use in poultry production could increase antibiotic resistant bacteria (ARB) in manure and eventually in crop root microbiome. We investigated the prevalence of ARB in BCL from medium- and large-scale farms (n = 33) and in carrot (Daucus carota) grown in BCL-applied soils in Sri Lanka. All the BCL samples contained aerobic bacteria resistant to 10 μg·mL⁻¹ of oxytetracycline or enrofloxacin. The abundance of ARB determined by viable plate-count method ranged from 0.05% to 30.10% of aerobic bacterial population. Soil from two fields applied with BLC for 3 yr (short history, SH) and 10 yr (long history, LH) were treated with BCL (10%, w/w) and oxytetracycline (10 and 100 mg·kg⁻¹) in a pot experiment alongside an unamended control. Adding BCL and oxytetracycline had a significant (P < 0.05) effect on the abundance of oxytetracycline-resistant epiphytic and endophytic bacteria (EEB) in carrot roots at harvest. Both total and oxytetracycline-resistant EEB increased significantly (P < 0.05) with the application of BCL to LH soil but not to SH soil. Carrot sold at retailed markets (n = 30) contained epiphytic bacteria resistant to 1 μg·mL⁻¹ oxytetracycline (4.13 ± 0.207 log₁₀CFU·g⁻¹ dry carrot). High minimum inhibitory concentrations for oxytetracycline (≥128 μg·mL⁻¹) were observed in 83% and 50% of ARB isolates obtained from BCL (n = 18) and carrot (n = 24), respectively. Results confirmed that BCL acts as a carrier of ARB, and continuous application of BCL to soil increased the prevalence of ARB among EEB in carrot.

To reveal the characteristics of nitrogen loss and their coupling relations in the process of surface flow and interflow under various rainfall intensities in gray fluvo-aquic soil areas, the coupling loss characteristics of total nitrogen (TN), nitrate nitrogen (NO₃⁻-N), and ammonium nitrogen (NH₄⁺-N) in the surface flow and interflow under three rainfall intensities (60, 80, and 110 mm·h⁻¹) at a slope of 5° were studied using an artificial rainfall simulation. The results showed that (1) runoff yield and TN concentration were proportional to the rainfall intensity, with higher runoff concentrations of TN in the initial stage, and (2) surface flow yield, which was the main output mode of farmland runoff, was higher than interflow yield under a range of rainfall intensities. The average concentration of NO₃⁻-N in surface flow decreased with increasing rainfall intensity, whereas the opposite was true in interflow. The main loss path of NO₃⁻-N was interflow, whereas the main loss path of NH₄⁺-N was the surface flow; NO₃⁻-N was the main form of TN loss. The surface flow was the main loss path of soil nitrogen loss in farmland, and the runoff yield was an important factor in controlling nitrogen loss.

Farmers are looking for appropriate tools for assessing and interpreting the health status of their soils; however, there is no standardized and prairie-based soil health scoring framework. Accordingly, we focused on developing one for arable cropping systems in Saskatchewan. In 2018, soil samples (0–15, 15–30, and 30–60 cm depths) were collected from 55 arable fields across Saskatchewan, along with native prairie samples. Various soil chemical, physical, and biological attributes were measured (23 attributes in total). Based on the data distribution for each attribute, we developed scoring functions. The results from multivariate analyses were used to determine the weighting factors needed to integrate the individual scores from each soil attribute into a single Saskatchewan Assessment of Soil Health score. Soil carbon (C) and nitrogen (N) indices (soil organic C, active C, total N, and soil protein) and total phosphorus produced the highest weighting factors. We also tested if there were linkages between the soil health and crop productivity by assessing the cereal yields for the past 10 years as reported from the same rural municipalities where the soil samples were collected. A positive relationship between soil health and yields was most apparent during dry years; thus, we recommend further research to explore this linkage at a finer scale. Overall, this research forms the foundation of a promising framework that can be built upon, and in due course, lead to the development of a tool for producers who are interested in tracking soil health and using the results to inform management.

Understanding the relationship between soil fungal communities and soil function is vital to establish a sustainable and ecologically friendly tea (Camellia sinensis L.) cultivation. However, there is limited research on the response of soil fungal communities to tea-fungus intercropping, particularly how it is related to soil biodiversity and fertility. Here, we assessed and compared the fungal communities using a metabarcoding technique, soil properties in three plantations (1, 2, and 5 yr of tea-Pleurotus intercropping plantations), and a 5 yr chemically fertilized monoculture plantation. We obtained a total of 3493 operational taxonomic units (OTUs) from four tea plantations. Five hundred and ninety-three fungal OTUs are shared by all plantations, and the other 471 fungal OTUs are shared by three plantations. The largest number of OTUs was recorded in 5 yr tea-Pleurotus intercropped plantations (N = 2040), followed by 2 yr (N = 2024) and then 1 yr (N = 1471), while the chemically fertilized plantation recorded 1823 OTUs. Tea-Pleurotus intercropping showed a significant effect on the increased diversity of soil fungal diversity compared with the monoculture tea cultivations. Fungal groups Basidiomycota, Ascomycota, and Mortierellomycota were the most abundant taxonomic groups recorded in all soil samples. Principal coordinate analysis revealed that fungal community composition in tea-Pleurotus intercropped plantations and monoculture tea plantations was significantly different. Besides, redundancy analysis revealed that soil nutrients significantly influence soil fungal community composition. Our results demonstrate that tea-Pleurotus intercropping may offer long-term benefits to soil biodiversity and sustainable benefits in the tea plantations.

Paper mill biosolids (PB) are recognized as a valuable source of carbon for the physical improvement of arable soils. However, little is known about the composition of carbohydrates of these materials and their breakdown in soil, which contributes to soil structural stability. The objectives of this study were to characterize the carbohydrates in PB and to determine under controlled conditions and in the field the soil carbohydrate content and water-stable aggregation. The field experiment consisted of PB applied every year (2000–2008) at 0, 30, and 60 Mg wet weight·ha⁻¹ to annual row crops with soils collected after 3, 6, and 9 yr. The other experiment consisted of PB added at 50 Mg wet weight·ha⁻¹ to two soils, a clay and a sandy loam, and incubated at 25 °C and 60% water-filled pore space for 16 wk. The PB differed in their content in galactose, mannose, and arabinose for total fraction and sum of carbohydrates for water-soluble fraction. In the field, repeated annual PB application increased most of soil total carbohydrates (sum and individuals) after 3 yr and the proportion of >1 mm stable aggregates. The incubation study confirmed results obtained in the field, where the PB richest in carbohydrates induced the highest increases in soil total carbohydrates in both soil types. Soil total and microbial (galactose and mannose)-derived carbohydrates were closely correlated with the percentage of large aggregates, while with water-soluble carbohydrates, they are highly correlated to the amount of microbial carbohydrates applied, thus further contributing to improve soil C quality.

The Bt horizon is the diagnostic horizon of the Luvisolic Order in Canada. According to the Canadian System of Soil Classification (CSSC), the Bt must be formed from clay illuviation through the processes of lessivage (i.e., physical transport of clay). In a study of a Luvisol catena in the central Saskatchewan, we demonstrate that Ae/Bm horizons overlying IIBt horizons are formed in a sandy mantle overlying till (i.e., a lithological discontinuity) and that the sandy mantle contributed negligible amounts of illuvial clay despite the presence of clay skins on ped surfaces in the IIBt horizon. We extended the results of this study to the regional scale by examining sand fractions in 63 pedons of Luvisol-dominated soil associations from soil surveys in the Northern Forest Reserves (between latitudes 53°N and 55°N). Of the 63 pedons, 13 had lithological discontinuities identified in their profile description and a further 27 had discontinuities identified through shifts in the sand fractions between horizons. For the profiles with discontinuities, inherited particle size differences are a more likely cause of coarse-over-fine textural contrasts than lessivage. A regional analysis of the distribution of Luvisol-dominated associations showed distinct zonations that account, in part, for the differences in the occurrence of lithological discontinuities. Based on these results, we suggest that the criteria for Bt horizons in the CSSC should be broadened to include nonilluvial coarse-over-fine texture-contrast horizons and that the criteria for the Luvisolic order also be broadened to include these nonilluvial Bt horizons.

The soil family was developed in the 1960s as the fourth level of taxa within the hierarchical structure of the Canadian System of Soil Classification. The original aim of the soil family category was to provide a framework for checking and establishing limits for soil series while providing a link between the series and the subgroup level. Its intended use was to define and group numerous soil series based on soil characteristics important for the purpose of applying appropriate management practices. In the current Canadian System of Soil Classification, taxa at the family level represent subdivisions of the subgroups. Classification of mineral soils at the family level is based on properties of the parent materials which include particle size; soil mineralogy; reaction (soil pH); calcareousness; depth to bedrock and permafrost; as well as climactic factors: soil temperature and soil moisture regimes. The soil family particle-size classes were originally intended as a compromise between both agronomic and engineering influences; however, the resulting product has limited functionality because of differences in definitions between engineering and agronomic grain sizes and non-alignment with soil textural classes. Consequently, classification and use of the family taxon have largely been ignored. Some adjustments to the family taxon for mineral soils and terric layers in organic soils are proposed including realignment of classes in the current family particle-size triangle to follow the divisions of the soil textural classes. Minor adjustments to mineralogy classes and depth to bedrock are also proposed.

Weather stations often provide key information related to soil moisture; temperature and evaporation are used by farmers to decide farm operations of nearby agricultural fields. However, the site conditions at the weather stations where data are recorded may not be similar with these nearby fields. The objective of this study was to determine the level of discrepancies in surface soil moisture between weather stations and nearby agricultural fields based on (i) the soil texture, crop residue cover, crop type, growth stages and (ii) temporal dependency of soil moisture to recent rainfall and evaporation rates. Soil moisture from 25 weather stations in the North Dakota Agricultural Weather Network (NDAWN) and 75 nearby fields were measured biweekly during the 2019 growing season in Red River Valley. Field characteristics including soil texture, crop residue cover, crop type, and growth stages along with rainfall and PET were collected during the study period. The regression analysis between surface soil moisture at weather station and nearby field showed higher values for corn at V10 stage (r² = 0.92) and for wheat at flowering stage (r² = 0.68) and opposite was observed with soybean. We found the regression coefficient of soil moisture with 4-d cumulative rainfall slightly increased to 0.51 with an increase in percent residue cover resulting in a decreased root mean square error (RMSE) to 0.063 m³·m⁻³. In general, we observed that surface soil moisture at weather stations could reasonably predict moisture in nearby agricultural fields considering crop type, soil type, weather, and distance from weather station.

The complementary nature of different teaching approaches in facilitating student learning is rarely discussed in the literature. This study compared diverse teaching approaches in soil science education to explore how a combination of instructional approaches can support student learning. Student perspectives on lectures, problem-based learning, and experiential learning in three upper-level university soil science courses were assessed through student enrolment data and survey responses. Results emphasize the benefits of integrating theory and practice and support the integration of concepts from soil physics, chemistry, and biology within individual courses. All respondents who took two or more courses indicated that the distinct teaching approaches and the integration of soil physics, chemistry, and biology within individual courses were beneficial to their learning. Lectures and problem-based learning were seen as pedagogically reciprocal, with theory supporting the application of knowledge for 75% students, while others noted that having the management course first provided context for learning additional theory. A subset of students (n = 9) indicated the relevance of the interdisciplinary nature of the courses for their current employment. Our findings suggest that combining knowledge-based and competency-based approaches may support both student learning and workforce demands and that diverse teaching approaches can work together to support student learning. The research outcomes call for fellow instructors to diverge from the dichotomy of passive and active learning and to consider the complementary nature of distinct teaching strategies.

Soil water repellency (SWR) was measured for a 28 yr field study under irrigation on a clay loam Dark Brown soil in southern Alberta. The objectives were to study the effect of legume–cereal crop rotations, feedlot manure, and phosphorus (P) fertilizer application on soil hydrophobicity (SH) and soil water repellency index (RI) under irrigation. Mean SH and RI were similar (P > 0.05) for a legume–cereal and cereal rotation and were unaffected by P fertilization. However, P fertilization shifted the RI classification from slight to subcritical. In contrast, SH was significantly greater for manured than nonmanured treatments, while RI was unaffected. Soil organic carbon (SOC) concentration was significantly (P ≤ 0.05) correlated with SH (r = 0.74), but not with RI (r = −0.17). This suggested a closer association between the quantity of SOC and quantity of hydrophobic compounds (SH method) compared with the hydrophobic coatings inhibiting infiltration of water (RI method). No significant correlation between SH and RI (r = −0.09) suggests that SH is not a good predictor of SWR using the RI method. Overall, manure application increased SH and P fertilization shifted the RI classification from slight to subcritical. In contrast, legume–cereal rotations had no influence on SH and SWR using RI method compared with continuous cereal.

Balancing the weighting of various components of phosphorus loss in models is a critical but often overlooked step in accurate estimation of risk of P loss under field conditions. This study compared the P loss coefficients used to predict dissolved P losses from desorption from accumulated P in the soil, and those incidental to applications of P as fertilizer or manure, with extraction coefficients determined from actual P losses reported in literature for sites in Canada, with the addition of some sites with similar soils and climate from some northern states. The extraction coefficients for dissolved P measured in runoff water were 6.5× greater in year-round edge-of-field (EoF) measurements than in runoff boxes, indicating that models using P extraction coefficients derived from runoff box experiments will be underestimating the magnitude of losses from P accumulation in soil. Differences among the measurement methods (runoff box, rainfall simulator, or EoF) were not evident for incidental losses from applied P, but current models appear to overpredict the losses of applied P. Good agreement between measured and predicted dissolved P (DP) concentrations using the equations in the Annual Phosphorous Loss Estimator model were achieved by applying coefficients of 0.275 to the fertilizer equations and 0.219 to the manure equations, implying that 72.5% of fertilizer P and 78% of manure P are not available for runoff. This study underlines the importance of considering the relative weights of the various components of P loss as new models are developed and validated.

The effect of environmental pollutants on living organisms can be assessed by studying the changes in the indigenous microbial community. Therefore, in this study, cultivatable bacterial community in nonpolluted as well as household sewage and industrially polluted water of Lai Nullah flowing through Islamabad and Rawalpindi, Pakistan was analyzed. Bacterial community composition and population present in the polluted water were significantly different from the nonpolluted water (P < 0.05). Nonpolluted water had much fewer species and population of bacteria compared with polluted water. Sequence analysis of bacterial 16S rRNA gene revealed that Citrobacter freundii, Klebsiella pneumoniae, Escherichia coli, Lactobacillus plantarum, Geobacillus stearothermophilus, Enterococcus faecalis, Acinetobacter guillouiae, Ralstonia sp., Comamonas sp., and Stenotrophomonas maltophilia were specific to the polluted water. On the other hand, Aeromonas veronii, Exiguobacterium sp., and Lysinibacillus macroides were only found in the nonpolluted water. Among measured physicochemical parameters, higher colony count in the polluted water was best correlated with higher biological oxygen demand, phosphate, sodium, and chloride values (Spearman’s rho = 0.85). Concentration of heavy metals such as cadmium, chromium, copper, nickel, and lead were below 0.03 μg·mL⁻¹ at all the study sites. During plate assay, bacterial strains found at polluted sites showed resistance to selected heavy metals with highest minimum inhibitory concentration for lead (8 mmol·L⁻¹) followed by copper (5 mmol·L⁻¹), nickel (3 mmol·L⁻¹), and cadmium (1 mmol·L⁻¹). All the bacterial isolates also showed various levels of resistance against antibiotics ampicillin, tetracycline, ciprofloxacin, and vancomycin using broth microdilution method. Current research provides new insight into the effect of household sewage and the industrially polluted water of Lai Nullah on the indigenous bacteria.

Nitrification inhibitors (NI) are aimed at improving N-fertilizer use efficiency in cropping systems. This study aimed to assess the nitrification inhibition potential and non-target effects of dry leaf powders (botanicals) of 10 plant species (neem (Azadirachta indica), lantana (Lantana camara), karanda (Pongamia pinnata), Brachiaria (Brachiaria humidicola), cinnamon (Cinnamomum verum), clove (Syzygium aromaticum), wild-sunflower (Tithonia diversifolia), mee (Madhuca longifolia), nutmeg (Myristica fragrans), and pepper (Piper nigram)). The effect of botanicals on the growth of three ammonia oxidizing bacteria isolates (M4, M5, and M7) and NO₃⁻ formation in soil were tested in laboratory experiments. In a pot-experiment, botanicals were applied with urea to assess their effect on vegetative-growth of tomato and capsicum. The non-target effects of botanicals on soil bacteria and fungi, and seed germination were assessed separately. Dicyandiamide (DCD) was used as the positive control in all experiments. Only the growth of M7 was significantly suppressed by all botanicals except neem, Brachiaria, and pepper. The highest shoot-biomass of tomato was obtained when urea was applied with pepper. Nitrate leaching from pots was significantly reduced (P < 0.05) when urea was added with botanicals except for clove and wild-sunflower at basal-dressing. The abundance of culturable fungi and bacteria were not affected significantly by botanicals while seed germination was reduced significantly and consistently by clove only. From the 10 botanicals tested leaf powders of nutmeg, lantana, cinnamon, mee, and pepper were identified as materials with better potential to suppress nitrification with minimum non-target effects.

The application of organic amendments to agricultural soils enables the recycling of nutrients, further reducing the inputs of synthetic fertilizers for crop production. However, the production of N₂O emissions is a concern that arises from such a practice. A 35 d incubation experiment was conducted with soils receiving three contrasting types of biosolids — mesophilic anaerobic digested (BM), composted (BC), and alkaline-stabilized (BA) — at four water-filled pore spaces (WFPS): 28%, 40%, 52%, and 64%. A zero-N-addition control was also evaluated. Across all the three types of biosolids, N₂O production increased with soil moisture content, with BM and BC producing the overall highest N₂O fluxes. The most intense pulses of N₂O production were exhibited by BC at the beginning of the incubation. The highest cumulative N₂O production was found with 64% WFPS and from BC- (409 μg N₂O–N·kg⁻¹ soil) or BM-amended soils (390 μgN₂O–N·kg⁻¹ soil), which produced more than four and two times the emissions from the control and BA-amended soils at 64% WFPS, respectively. We also found the highest nitrification rates in the BM- and BC-amended soils. The total N₂O production was exponentially associated with the NO₃⁻–N concentration present at the end of the experiment (R² = 0.83). Changes in the concentration of the soil available N indicated the occurrence of mineralization, nitrification, and denitrification over the incubation. These results provided insight into the interacting responses of N₂O production to soil moisture contents, biosolids treatment stabilization and properties, and soil N availability.

Aggregate stability (AS) was measured in the 25th year of a long-term organic — conventional comparison field study. Located in southern Manitoba, the study includes two, four-year crop rotations under conventional and organic management, plus a grassland. The forage-grain rotation includes alfalfa (Medicago sativa)–alfalfa–wheat (Triticum aestivum)–flax (Linum usitatissimum). The grain only rotation includes wheat–flax–oat (Avena sativa)–soybean (Glycine max); hairy vetch (Vicia villosa) is substituted for soybean in the organic system. Composted manure was added every 4 yr to half of the organic forage-grain rotation to correct a phosphorus deficiency. The wheat and flax phases were sampled at depths (0–10 cm; 10–20 cm) in spring 2017, and wet aggregate stability was measured using the Yoder method with stacked sieves. Mean weight diameter (MWD) was calculated. AS in the organic systems was never lower than that of comparable conventional systems, but had more large aggregates in only a few cases. Our hypothesis that including alfalfa would increase AS was supported in only a few instances. The largest aggregates (1–2 mm and 2–6.3 mm) and the fewest smallest aggregates (0.25–0.5 mm) were observed in the grassland. For the intermediate aggregate size class (0.5–1 mm), the organic forage-grain systems had levels similar (P > 0.05) to the grassland. While adding manure increased plant growth by about 40% in the organic forage-grain rotation, no AS differences were observed. Limited AS response in the arable systems may be due to suboptimal soil C contents; only the grassland had a C content above the minimum 35 g·kg⁻¹ postulated for Vertisols.

According at the characteristics of large subsoiling resistance and small subsoiling range, a pneumatic subsoiling mechanism was designed to disturb the soil with different air pressure. To achieve the purpose of pneumatic subsoiling, first, the aerodynamic model of subsoiling was established, and then the feasibility of the design was verified by experiments. Using the dynamic telemetry data of the sensor, the effects of tillage depth (25, 30, and 35 cm), pressure (4, 6, and 8 MPa), and working speed (2.5, 3.0 and 3.5 km·h⁻¹) on traction resistance were analyzed. The test results showed that under the condition pneumatic subsoiling, the traction resistance was reduced by 7.28%–22.37%, and the soil disturbance coefficient was 55.49%. The effect of pneumatic subsoiling showed that it has met the design requirements. Pneumatic subsoiling not only improved the problem of small stress of traditional subsoiling but also increased the disturbance of gas to soil on the basis of traditional subsoiling, so as to achieve the effect of subsoiling and reducing resistance and consumption.

An inadequate soil sampling time leads to difficulties in interpreting soil tests, to incorrect recommendations for soil amendments and fertilizers, and to inappropriate environmental protection restrictions. Soil samples may be collected from agricultural fields before, during, or after the crop growth period. Since the time of soil sample collection can affect soil tests results, the objective of this study was to evaluate the effect of sampling time on measurements representativity of 15 fertility indicators in two fields located in La Pocatière (Québec, Canada). The soils were of fine (G1) and medium (G2) textural groups and were sampled weekly for 33 weeks per year during four years. Data analyses included descriptive statistics, time-series decomposition, and time autocorrelation function (ACF). Since results of these analyses showed a clear seasonal effect only for Mehlich-3 extracted phosphorus (P_M3), soil phosphorus saturation index (SPS) for both G1 and G2 soils, and for pH_W for G1 only, we recommend that the sampling calendar should be restricted to the first five weeks of spring (until the end of May) and to the entire fall period (starting in early September). Also, the temporal autocorrelation was four weeks on average. This implies that, for an initial year, whichever date is chosen for the sampling, the following annual sampling should be done within a four-week time window (i.e., two weeks before until two weeks after the initial sampling date). Time series are an important element to consider in selecting a representative sampling period for soil fertility indicators.

In humid regions, the number of macroaggregates on the soil surface could decline because of rainfall disturbance, or increase due to rainfall-activated chemical and biological stabilization. We took digital images of macroaggregates at the surface of clay and organic soils six times during a 68 d period with 264 mm natural rainfall. Based on the constant or increasing number of surface macroaggregates during the five time intervals, rainfall did not disturb macroaggregates. Macroaggregate persistence was positively correlated with cumulative rainfall (both soils) and soil moisture (organic soil), so we infer that rainfall promoted macroaggregate assemblage through chemical and biological processes.

Canola (Brassica napus L.) is a nitrogen (N)-demanding crop, so tissue N analysis should be related to soil N supply. We evaluated canola N uptake in relation to soil N pools in plots receiving 0, 50, 100, and 150 kg N·ha^?1 from urea at three sites in eastern Canada in 2012. Soil N pools varied significantly at the rosette, flowering, pod filling, and maturity stages, but responded less predictably to urea. Canola N uptake was inconsistently related to soil N pools and urea input. This confirms the importance of site-specific N fertilizer management when growing canola in eastern Canada.

The objective was to quantify the effect of crop rotations, crop type, life cycle, nitrogen fertilizer, manure application, and fallow on soil hydrophobicity (SH). The SH was measured for a long-term (16 yr) dryland field experiment on a Dark Brown clay loam soil in southern Alberta, Canada. Mean SH was significantly (P ≤ 0.05) greater in rotations with grass, perennial crops, manure application, and continuous cropping; whereas cereal–legume rotations and N fertilizer effects were undetectable. A strong, positive correlation occurred between SH and soil organic carbon concentration (r = 0.73). Soil water repellency should be measured on these plots using water-based methods.

Estimating soil nitrogen (N) mineralization is critical to balance fertilizer N requirements and their environmental impacts. In this study, net N mineralization was examined in soils under different crop rotations with each phase of the rotation present every year with biologically based incubations in 2011 and 2015. Net N mineralization was significantly different among treatments when the current crop was soybean, and the effect was dependent upon the previous crop and the cropping sequence. In particular, net increases in inorganic N were greater when the previous crop was winter wheat with or without red clover than if it were corn, and greater for the first year of soybean compared with the second year for rotations with two consecutive years of soybean in the 2011 incubation. However, cropping history did not influence net soil N mineralization when the current crop was corn, winter wheat, or winter wheat with red clover. In 2015, the presence of red clover in the rotation increased net N mineralization in all phases of the rotation. These results suggest both current and previous crops should be considered when estimating the N supplying capacity (net mineralization) of the soil. Net mineralizable N was found to be significantly correlated with total amino sugars (P < 0.001), glucosamine (P < 0.001), and galactosamine (P = 0.003), which suggests that amino sugars could be used as an indicator of the N supplying capacity of soil.