Humic acid (HA), a fairly stable product of decomposed organic matter that consequently accumulates in ecological systems, enhances plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA derived from lignite on growth and macronutrient uptake of wheat (Triticum aestivum L.) grown in earthen pots under greenhouse conditions. The soils used in the pot experiment were a calcareous Haplustalf and a non-calcareous Haplustalf collected from Raisalpur and Guliana, respectively, in Punjab Province, Pakistan. The experiment consisted of four treatments with HA levels of 0 (control without HA), 30, 60, and 90 mg kg^−1^ soil designated as HA0, HA1, HA2, and HA3, respectively. In the treatment without HA (HA0), nitrogen (N), phosphorus (P), and potassium (K) were applied at 200, 100, and 125 mg kg^−1^soil, respectively. Significant differences among HA levels were recorded for wheat growth (plant height and shoot weight) and N uptake. On an average of both soils, the largest increases in plant height and shoot fresh and dry weights were found with HA2 (60 mg kg^−1^ soil), being 10%, 25%, and 18%, respectively, as compared to the control without HA (HA0). Both soils responded positively towards HA application. The wheat growth and N uptake in the non-calcareous soil were higher than those of the calcareous soil. The HA application significantly improved K concentration of the non-calcareous soil and P and NO3-N of the calcareous soil. The highest rate of HA (90 mg kg^−1^ soil) had a negative effect on growth and nutrient uptake of wheat as well as nutrient accumulation in soil, whereas the medium dose of HA (60 mg kg^−1^ soil) was more efficient in promoting wheat growth.

cross-posted from: https://slrpnk.net/post/2639190

ABSTRACT

Land reclamation following surface mining in the Athabasca oils sands region will be extensive, with various challenges specific to local reclamation cover soils. The high economic costs associated with pre-disturbance soil salvage and placement in reclamation necessitates judicious management and application of salvaged cover soils. Soil microbial community activity and bioavailable nutrient supply are largely overlooked in reclamation analyses despite their potential in providing a sensitive measurement of ecosystem function. This study evaluates these parameters by comparing two continuous cover soils, a coarse-textured forest floor mineral mix (FFM) and an organic matter-rich peat soil (PM) at Syncrude Canada's Aurora Soil Capping Study. Shallow (10 cm) and Deep (20–30 cm) placement depths of FFM and PM were compared to a control receiving no cover soil and a harvested jack pine site as a reference. Soil function was assessed by measuring bioavailable nutrient supply rates, soil respiration, phospholipid fatty acid analysis (PLFA), and community level physiological profiles (CLPP). Non-metric multidimensional scaling (NMS) was used to quantify functional similarity with reference conditions. NMS revealed the greatest similarity between FFM and the reference site for bioavailable nutrient supply, PLFA, and CLPP. Deep FFM application shared greatest PLFA similarity to the reference site, while Shallow FFM was more similar in CLPP. Shallow PM was more similar to reference conditions than Deep for all parameters measured, suggesting that shallow cover soil applications might be sufficient for the reclamation target. Soil respiration rates were greatest in FFM, followed by the reference site and PM treatments, with no difference attributable to placement depth. PM had greater nitrogen and sulfur availability, but was lower in phosphorus and potassium when compared to FFM and the reference site. Ecosystem function was more similar in cover soils that mimicked the reference site conditions as much as possible, which in this case meant shallow placement and material salvaged from upland forests

Formed from shrinking and swelling clays, prismatic structure differs from columnar in that it is not induced through sodium deposition and does not have a rounded cap on the top. columnar

diagram

Re-uploaded.

ABSTRACT

Some areas with historically mesic climates are predicted to experience more climate extremes, including longer droughts combined with hotter days and more intense precipitation. Drought and rewetting are known to alter carbon (C) and nitrogen (N) cycling. However, little information is available on how the effects of drought on C and N cycling differ with temperature and land use in soils from humid regions. We evaluated several metrics of C and N cycling under drought with or without heat stress in a forest site and conventionally and organically managed arable sites. We sampled undisturbed soil cores from 0 to 10 cm and incubated them under either reference conditions (REF), drought (DRT), or drought combined with heat stress (D + H). Metrics of C and N cycling, including actual and potential mineralization, enzyme activities, microbial biomass, and dissolved organic C and N, and microbial community structure were assessed at the end of the stress period and 14 and 28 d after rewetting. We found that the effects of D + H differed in magnitude and direction from those of DRT: cumulative C and N mineralization followed the order DRT < REF ≤ D + H. Land management affected stress response: mineralization was always greater in the forest and organic sites than in the conventional site. Post-wet pulses of C and potential net N mineralization were 1.7 and 3.6 times higher, respectively, in the D + H soils than DRT soils, and were greatest at the forest site. Only the organic site was sensitive to DRT alone. Across sites, microbial biomass N was reduced more by stress than C, and only N-cycle parameters failed to reach reference levels after the recovery period. In agreement with previous studies, the N cycle was more affected than the C cycle. Our results suggest that climate change-induced heatwaves during drought have implications for ecosystem C and N balance in mesic climates.

In soils with very high 2:1 clay contents, the soils expand and contract as they are wetted and dried. This creates shear faces called slickenslides, like the one shown above. Essentially they clay expands so much it's forced to shear somehow, and this is the resulting shear plane.

Look how thick the Ae (first) horizon is!

Profile description:

Ah: 0-2 cm; 10YR 2/1; SCL; Weak Fine Granular; Friable

R 2-100 cm

Solonetzic soils are formed when sodium rich ground water causes 2:1 clays to disperse, forcing columns to form

The structure is caused by sodium in groundwater dispersing the clay in the soil. These soils are hard to manage since the structure creates a hardpan, which causes water to pool in the subsurface and drown agronomic plants

Note the layer of carbonates (white) in the lower profile

This is a typical forest subsoil for the boreal, but the structure is a lot stronger than normal.