Soil thermal properties, which determine heat transport, can influence soil health parameters and crop productivity. The objective of this study was to evaluate the 2-year effects of no-till cover crops (CCs) and no-till no cover crop (NC) on soil thermal properties (thermal conductivity (λ), volumetric heat capacity (C_V), and thermal diffusivity (D)). Two levels of CCs were used for this study: CC versus NC. The CCs included crimson clover (Trifolium incarnatum L.), hairy vetch (Vicia villosa Roth.), winter peas (Lathyrus hirsutus L.), oats (Avena sativa), winter wheat (Triticum aestivum L.), triticale (Triticale hexaploide Lart.), flax (Linum usitassimum L.), and barley (Hordeum vulgare L.). Soil samples were collected at 0–10, 10–20, and 20–30 cm depths and their λ, C_V, and D were measured in the laboratory. Additionally, soil organic carbon, bulk density (BD), and volumetric water content (ϴ) at saturation, −33 kPa, and −100 kPa soil water pressures were measured. Results showed that BD was 18% and 14% higher under CC compared with NC management during 2021 and 2022, respectively. Furthermore, ϴ at all measured soil water pressures was slightly higher under CC compared with NC management during both years. As a result, λ and D were significantly higher under NC compared with CC management, while C_V was significantly higher under CC compared with NC management, during both years and at all measured soil water pressures. Generally, soil thermal properties were directly proportional to ϴ, suggesting that ϴ may be the most important factor influencing soil thermal properties.

Soil and crop management influence soil organic carbon (SOC), chemical composition, and overall soil quality. In a Mediterranean region, a study initiated in 1994 examined the long-term effects of conventional tillage (CT) versus no-tillage (NT) practices. Initially focusing on continuous durum wheat cultivation until 2009, the experiment later introduced a 2-year rotation of durum wheat and Vicia faba L. cover crops in half of the CT and NT fields. SOC was monitored from 2008 to 2018, while microbial biomass (as dsDNA), soluble nitrogen (N), and enzyme activities (EAs) were monitored from 2011 to 2014 to evaluate the rotation’s impact. Between 2009 and 2018, CT yields were on average 15% higher than NT, especially during high rainfall years. NT significantly increased SOC content in the 0–30 cm soil layer, along with higher levels of soluble N, dsDNA, and EAs at 0–10 cm depth. NT led to a 23% and 10% increase in SOC stock and SOC stock per equivalent soil mass compared to CT. EAs increased by over 50% under NT, indicating enhanced biological activity. The SOC increase due to NT was limited to the top 10 cm, with a decrease at deeper depths (up to 50 cm). Introducing cover crops over 4 years did not yield significant impacts, suggesting the need for a longer period to observe noticeable effects. Overall, adopting NT practices resulted in higher SOC concentration, enhanced soil biological activity, and improved biogeochemical cycles, emphasizing the positive impact of NT on soil health and sustainability.

Soil health encompasses the collective functioning of chemical, physical, and biological properties in soil. The extent to which soil management affects soil health and the links with agronomic outcomes remain unclear. This project aimed to understand the interrelations of tillage systems, soil health, and agronomic properties in Portage la Prairie, MB, Canada. Tillage systems were cultivation, deep tillage, raised beds, and vertical tillage. Soybean (Glycine max (L.) Merr), corn (Zea mays L.), and canola (Brassica napus L.) were all grown in 2020, 2021, and 2022. Crop yield, seed protein content, and seed oil content were measured each year. Soil samples were taken in spring 2021, fall 2021, and fall 2022 and analyzed for nitrate-N, ammonium-N, total N, ACE protein, water extractable organic N, water extractable total N, water extractable ammonium N, soil organic matter, soil organic carbon, calcium carbonate equivalent, CO₂ burst, permanganate oxidizable carbon, water extractable organic C, pH, salts, Olsen P, K, S, sand, silt, and clay. Tillage system had a significant impact on agronomic properties in seven crop by sampling combinations. Tillage system effected soil nitrate-N concentration at five crop by sampling combinations, three more than any other soil property. Soybean agronomic properties correlated with soil health indicators more frequently than for corn and canola. This suggests that the utility of soil health indicators may be crop specific. Further research is needed to understand the mechanisms underpinning the ability of soil health indicators to predict agronomic outcomes and to benchmark soil health indicator values with time.

Conservation agriculture (CA) is increasingly promoted to build soil organic matter (SOM) based on findings from predominantly small-plot long-term agroecosystem experiments (LTAEs), with minimal on-farm data. Using commercial producer fields (n = 20) in the Brown Chernozemic soil zones of Saskatchewan, Canada, which were sampled before (1996) and after (2018) adopting direct-seeding and continuous cropping (1997), we examined changes in soil organic carbon (SOC) and soil total nitrogen (STN) stocks, along with C and N stocks in particulate (POM) and mineral-associated organic matter (MAOM), and compared them to an LTAE in the same soil zone. After 21 years, SOC and STN stocks (0–30 cm depth) increased by 13% and 21%, respectively, in commercial producer fields, and were more pronounced in finer- than coarser-textured soils. Conversely, there were no significant changes (0–30 cm depth) after 18 years (1998–2016) with CA (continuous wheat and pulse-wheat under no-tillage (PW-NT)) in the LTAE, except that STN stock for PW-NT decreased by 7.7%. The estimated rate of change to 30 cm depth was similar between the commercial fields and LTAE for SOC (0.28 and 0.16 Mg C ha⁻¹ year⁻¹, respectively), but not STN (0.04 and −0.03 Mg N ha⁻¹ year⁻¹, respectively). Changes were more evident in the MAOM than POM fraction in both cases. Although the impact of CA may be similar, as observed for SOC, actual on-farm changes will depend on site-specific factors, and specific CA practice. Therefore, on-farm monitoring studies are needed for more accurate assessments of SOM changes and C sequestration potentials.

Prairie cordgrass (PCG) is a perennial crop which has the potential for biofuel production under marginal lands. The intercropping of a perennial legume, kura clover (KC) with PCG can reduce the use of chemical fertilizer while maintaining the soil hydro-physical conditions. The objective of this study was to compare the soil hydro-physical properties and greenhouse gas (GHG) fluxes under PCG intercropped with KC (PCG–KC), and PCG fertilized with graded levels of N (0, 75, 150, and 225 N kg ha⁻¹). During the summer of 2021, soil samples (0–10 cm) were collected. Additionally, gas samples were collected weekly from April through September of the same year. Soil water retention, saturated hydraulic conductivity (K_sat), thermal conductivity (λ), soil organic carbon (SOC), and total N (TN) concentrations were measured. Soil pore characteristics were measured using X-ray computed tomography. The PCG–KC had 1.42 g kg⁻¹ TN and 24 g kg⁻¹ SOC at 0–10 cm, non-significant to PCG-75, 150, and 225 N. Nonetheless, TN significantly increased in both PCG–KC and other fertilized treatments compared to the control. Intercropping boosted macroporosity (0.024 cm³ cm⁻³), K_sat (+50%), and lowered λ (−1%), compared to the N fertilized treatments. Soil cumulative CO₂ under PCG–KC (1012.67 kg C ha⁻¹) was similar to PCG-75, 150 N, but lower than PCG-225 N (1418.66 kg C ha⁻¹). Overall, this study showed that PCG–KC can be a sustainable option over the use of N fertilizers since they had similar levels of hydro-physical characteristics and had a comparable ability to mitigate GHG emissions.

Previous studies showed that the program of converted forestland from cropland (CFC), initiated by the Chinese government in 1999, has been a significant contributor to China’s efforts towards carbon neutrality. Here, the 20-year CFCs of two aspects (sunny and shady) and three positions (upper, middle, and lower) hillslopes, adjacent maize (Zea mays L.) cropland, and natural secondary Castanea mollissima forest (CCF) within southern Qinling-Daba Mountains region (Qinba) had been selected as the targets. The soil bulk density (SBD), soil organic carbon concentration (SOCC), total nitrogen (TN), and total phosphorus (TP) had been determined. The results showed that SBD increased with depth, and other parameters decreased, which varied largely with the aspect and position. The SOC stocks (SOCS) of CCF, cropland, and CFC were 152.81 ± 5.17, 168.19 ± 11.87, and 183.92 ± 35.69 Mg C hm⁻², respectively. The SOCCs of CCF, cropland, and CFC were 17.71 ± 4.38, 20.23 ± 5.28, and 21.89 ± 7.33 g kg⁻¹, respectively. The CFC increased the correlations between SOC and TP, and decreased the correlations between SOC and TN. The CFC shifted the relationships of lg SOC versus lg N:P and lg SOC versus lg TP from decreasing returns of cropland to isometric. Overall, the CFCs enhanced SOC, especially in the middle shady hillslopes within the southern middle-mountain of Qinba. In contrast, SOC levels decreased in the sunny upper hillslopes. We presented the evidence that hillslopes aspect and position had significant effects on SOC, which was regulated by soil phosphorus.

Rice is sensitive to salt stress, commonly caused by high concentrations of sodium (Na) in soils. However, the concentration and spatial variability of exchangeable Na in lowland paddy fields of Sri Lanka are not known. This study examined the interactive effects of the agro-climatic zones (ACZs), soil orders, and water sources on exchangeable Na in lowland paddy fields in Sri Lanka using 8566 soil samples. Exchangeable Na was extracted using 0.01 mol/L CaCl₂ solution and detected using inductively coupled plasma-mass spectrophotometry. Exchangeable-Na concentration ranged from 0.05 to 4814 mg kg⁻¹ with a mean concentration of 140.7 mg kg⁻¹, and these values were within the optimal range reported for tropical paddy soils. The distribution of exchangeable Na was right skewed with 44%, 35%, and 9.3% of samples falling into 0–100, 100–200, and 200–300 mg kg⁻¹, respectively. Samples from the Low country Dry zone had the highest (157 mg kg⁻¹) Na concentration while that in the Upcountry Intermediate zone was the lowest (13 mg kg⁻¹) (p < 0.05). Vertisols recorded the highest (255 mg kg⁻¹) and Ultisols recorded the lowest (81 ± 5.0 mg kg⁻¹) among soil orders. Soils receiving supplementary irrigation in Low country Dry zone had lower Na than that in rainfed systems. Exchangeable-Na concentration was positively correlated with soil pH (p < 0.05). Even though the concentrations of Na in soil samples were within the optimal range, agronomic decisions based on ACZ, soil order, and water source need to be made to minimize the potential development of saline–sodic soils in the study areas.

Pavement design methods based on principles of unsaturated soil mechanics take into account high soil shear strength due to matric suction resulting in more economical design especially in long roads. In this study, the bearing capacity of two-layer unsaturated sand was investigated using both analytical and experimental methods. At first, using the limit equilibrium method an analytical formula was proposed to determine the bearing capacity of two-layer unsaturated sand in which linear suction profile was considered in soil layers. It should be considered that the constant matric suction distribution assumed by the previous researchers does not show the real profile of matric suction within the soil, sometimes resulting in miscalculated unsaturated bearing capacity. Also, the bearing capacity of two-layer unsaturated poorly graded sand was investigated experimentally in different suctions by a special unsaturated chamber apparatus (UCA) designed for this purpose. The results show more than double increase of unsaturated soil bearing capacity with S_r = 25% compared to saturated soil. The formation of failure wedges in all experiments was investigated by image processing. An acceptable agreement was obtained between the theoretical and experimental bearing capacity results.