Proceedings - Soil Science Society of America最新文献

The susceptibility of surface soil to drying when rainfall is scarce has prompted evaluation of deeper placement (20 cm) of fertilizers within the profile to where soil moisture is more likely to be stored. However, concerns arise regarding potential chemical challenges to P availability in the subsurface. This study examined differences in chemical conditions between the soil surface (0–10 cm) and subsurface (15–25 cm), and investigated the effect on the diffusion and extractability of banded P. Analysis of surface and subsurface samples from 15 sites revealed substantial differences in characteristics that influence P behavior between depths. The phosphorus buffering index (PBI) was largely explained by concentrations of amorphous Al and Fe (hydr)oxides and CaCO₃. The measured diffusion distance of P from monoammonium phosphate (MAP) granules was found to be inversely related to PBI. Consequently, significant differences in diffusion distances were typically observed between soil layers characterized by marked PBI variations. The measured diffusion radii were used to calculate the mean P concentrations of surface-banded and deep-banded MAP in a field scenario, which were replicated in a 4-week laboratory incubation. The resulting lability of applied P was determined through isotopic exchange, and although significantly higher P recoveries were measured from the subsurface at two sites where large pH differences existed between depths, no significant differences were measured between depths at all other sites. Hence, the subsurface is not a more hostile zone for deep-placed P.

The soil mantle of the tropical karstic landscapes of Southern Mexico was shaped by specific processes of pedogenesis and long-term human impacts of ancient Maya agriculture. To understand the interaction between natural and human-induced soil-forming processes in the calcareous mountains of Chiapas state, we studied soil toposequences around the Classic Maya site of Budsilhá and related them to the archaeological evidence of settlement and land-use distribution. Soil chemical analysis, micromorphological observations, and clay mineral identification were carried out in key soil profiles at the main geoforms. Limestone hills are occupied by shallow Rendolls which are usually perceived as incipient soils. However, high content of silicate clay composed of kaolinite and vermiculite and ferruginous clayey soil material observed at macro- and microscale backed the hypothesis that these soils were formed from the residues of thick Terra Rossa after their erosion. Swampy lowlands are occupied by thick clayey gleyic soils with clay mineral assemblages similar to those in the upland Rendolls. We suppose that the mineral matrix of the lowland soils is largely derived from the pedosediments of eroded upland Terra Rossa, which lost original ferruginous pigmentation and aggregation due to redoximorphic processes. Some wetland soils contain neoformed gypsum that is atypical for humid tropics; sulfide-sulfate transformation under fluctuating redox conditions could promote gypsum synthesis. Ancient Maya land use was closely related to soil-geomorphic conditions: settlements with homegardens occupied calcareous hills, whereas the primary agricultural domain was developed on lowland soils after their drainage by artificial canals.

Drew A. Scott, Mark A. Liebig, Nicanor Z. Saliendra, David Toledo, Michael DeGreef, Chantel Kobilansky, Justin Feld. Soil Science Society of America Journal, 88, 779–791. https://doi.org/10.1002/saj2.20646

Correspondence Email: [email protected]

The authors noted an error in Figure 4 of the original article. The correct version of Figure 4 is reproduced below.

Soil structure dynamics during a season depend on management practices and environmental factors. A lightweight autonomous robot (total mass: 3300–4100 kg, wheel load: 700–1200 kg, contact areas: 0.125 m², inflation pressures: 60–280 kPa) was used for sowing (October 2021) and weeding (May 2022) operations on an annually plowed sandy loam field. We took 579 cm³ soil cores at 10- to 18-cm depth in the crop area and wheel tracks before and after the operations to assess the impact from traffic and the potential recovery of topsoil structural properties. We measured air permeability and effective air-filled porosity in the laboratory, and X-ray CT scanned the samples to evaluate soil pore functionality. The first operation (conducted on a moist seedbed) had the largest impact, significantly compacting and reducing the air-filled porosity by 42% (from 0.21 to 0.12 m³ m⁻³) and decreasing air permeability by 75.8% (from 130 to 31.5 µm²). After 7 months, the crop area and wheel track showed signs of soil consolidation due to environmental factors but not decompaction. The second operation occurred on drier (water content 0.06 g g⁻¹), stronger soil conditions (degree of compactness 100.8%), and recompaction of the wheel track was not observed. Traffic in weak soils can result in seasonal topsoil compaction despite the lighter wheel loads. However, due to the milder impacts, recovery rates might be faster for lightweight machinery than for heavy tractors. Multi-season studies are needed to assess the real potential of lightweight robots to minimize soil compaction risk.

Management can affect soil quality through changes in carbon (C) stock, especially in protected C fractions of soil aggregates. Soil aggregation and C sequestration may be improved with soil correction (liming and gypsum) and nitrogen (N) fertilization, but it is not clear how these factors might interact to affect humic substances. The objective of the study was to evaluate the effects of calcium (Ca), magnesium (Mg), and N fertilizatilizer amendments on the accumulation of C, N, and humic substances in soil aggregates from an Oxisoil in Brazil. The production system was no-till soybean [Gycine max (L.) Merr.] double-cropped with maize (Zea mays L.) and intercropped with forage grass since 2016. Treatments were no amendment, lime only, and lime + phosphogypsum, factorially arranged with and without annual N fertilization of maize. Soil was collected at 0–10, 10–20, 20–40, and 40–60 cm 6 years after initiation of the experiment. The combination of lime, gypsum, and N led to 13% greater total C stock and 20% greater total N stock within the 0–60 cm soil profile than the control. Levels of fulvic acid (FA) and humic acid (HA) were similar among aggregate classes, but humin was greatest in larger aggregates. Liming plus N decreased FA and HA, but gypsum application mitigated this negative effect. Application of limestone, gypsum, and N increased humin, mainly in the soil surface (0–10 cm). Soil C storage and stabilization was enhanced in large soil aggregates with the combined use of lime, gypsum, and N fertilization in humid tropical soils.

While many studies note the positive effects of soil organic matter (SOM) on crop yields, there is limited quantitative information on the influence of increased SOM on potato (Solanum tuberosum L.) productivity in sandy soil. This study estimated the impact of varying SOM on potato productivity in sandy soils and explored whether nitrogen (N) mineralization served as a primary mediator. Soil from nine fields in Wisconsin (SOM range of 1.1%–3.8%) was collected for a greenhouse study. Both NH₄-N and NO₃-N extracted from ion strips and potentially mineralizable nitrogen (PMN) were used as the proxies for N mineralization. Linear mixed effect models indicated that fresh matter whole biomass and dry matter vine biomass were 0.45 and 0.54 times greater at 3.8% SOM compared to 1.1% SOM at an optimal soil pH of 5.2, respectively. Similarly, total N uptake in the whole and vine biomass was 0.51 and 1.0 times higher at 3.8% SOM than 1.1% SOM, respectively. While PMN demonstrated a positive correlation with SOM, it only partially mediated the effect of SOM on productivity, specifically in N uptake in the vines. However, for most productivity measures, including PMN with SOM in the models did not substantially reduce the estimated SOM effect on productivity, indicating that SOM affected productivity mostly through mechanisms other than N acquisition by plants available through mineralization of OM. The study underscored the complex interplay between SOM and potato productivity, urging further research into the multifaceted roles of SOM in sandy soils.

Management practices such as relay cropping, cover crops, and no-tillage may promote soil health in the North Central United States. However, soil health indicators in corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] systems involving multiple management practices are not well documented. The objective of this study was to determine the sensitivity of soil health metrics and the Soil Management Assessment Framework (SMAF) to contrasting management systems with different tillage, crops, and fertilization in a North Central US Mollisol. Different management systems, including conservation tillage and nitrogen fertilization strategies, cover cropping, and camelina [Camelina sativa (L.) Crantz] relay intercropping, were compared to a conventional corn–soybean system. Different systems did not affect most soil health indicators compared to the conventional system. Aggregate stability was the only indicator to change due to management, where no-till with cover crops increased aggregate stability by 38% compared with camelina relay cropping. The SMAF scores for all the soil quality indices were unaffected by treatments but displayed high values of over 90%. Overall, crop yields were more closely related to weather conditions and management systems than to soil health indicators. Soybean yields were decreased (between 1 and 2 Mg ha⁻¹) in the camelina relay cropping system, while corn yields were lower (up to 70%) in the treatment that received no N fertilization. Ultimately, these findings suggest that soil health indicators are resilient to change due to management in these highly productive Mollisols and may not be closely associated with crop yields.

Direct evidence-based approaches are vital in understanding the involvement of abiotic/biotic factors and evaluating the newly proposed theories on soil carbon (C) stabilization. Microaggregates (150–250 µm) collected from a corn system (>22 years; Kansas, USA), which had been under no-till with different nitrogen (N) treatments were analyzed (N treatments: manure/compost, urea, zero fertilizer). We studied C stabilization in free soil microaggregates (with preserved aggregate architecture), directly using scanning transmission X-ray microscopy coupled with near edge X-ray absorption fine structure (STXM-NEXAFS) spectroscopy. Submicron scale findings were complemented with bulk chemical analysis. The STXM-NEXAFS analysis revealed soil organic carbon (SOC) preservation inside nano- and micro-pores and organo–mineral association, various degrees of humification, and high molecular diversity. The presence of microbial-derived C was found in manure-/compost-added microaggregates highlighting the contribution of organic amendments in facilitating microbial diversity. The incidence of aragonite-like minerals suggested the biologically/chemically active nature of microaggregate cores. Bulk analysis of free microaggregates showed a higher concentration of SOC (6.5%), ammonium oxalate extractable Fe/Al/Si), and higher aliphaticity of humic acid in manure-/compost-added soils compared to inorganic fertilizer (3% SOC) and control (2.7% SOC) treatments. The co-existence of elements (calcium [Ca]/C, iron [Fe]/N, Fe/C, aluminum [Al]/C, and silicon [Si]/C) was partially supported by bulk chemical analysis that indicated a strong association between ammonium oxalate extractable Fe/Al/Si and SOC (R² = 0.63—0.77). Overall, our study provided direct/indirect evidence for the complex and interactive involvement of chemical, mineralogical, and biological mechanisms that may have been stimulated by the long-term addition of compost/manure in stabilizing SOC.

No-till (NT) alleviates adverse effects of agricultural production on environmental quality, improves soil health, and reduces greenhouse gas emissions, yet this has not been demonstrated in humid subtropical Mississippi. Research objectives were to evaluate nutrient and C dynamics and soil quality via Soil Management Assessment Framework (SMAF) following 15 years of continuous management under corn (Zea mays L.) (2008–2018) and soybean [Glycine max (L.) Merr.] (2019–2022) on a Dundee silt loam soil. After 15 years, soil organic carbon (SOC) stocks (0- to 30-cm depth) under NT were 25% higher than conventional tillage (CT). Between 2020 and 2022, SOC stocks increased 3 Mg ha⁻¹ under NT and decreased 2 Mg ha⁻¹ under CT. Increased SOC retention under NT could represent an opportunity for increasing the systems’ profitability as C markets expand. Greater SOC and aggregation scores improved SMAF soil quality index (SQI) under NT (71%), compared to CT (66%), underscoring the critical role of organic matter in soil functioning in managed agrosystems. Soybean yields were not linked to SMAF SQI (p > 0.05), suggesting that crop yields are mostly affected by non-edaphic factors (e.g., climate extremes). SMAF illustrated positive impacts of NT on SOC sequestration and soil health, which may foster its adoption as a conservation practice in the Lower Mississippi River basin. As such, NT stands as a climate-smart management practice that allows for sustainable intensification in humid subtropical regions.

Historic atmospheric acidic deposition resulting from the combustion of fossil fuels may alter the pools of important nutrients and base cations in sensitive forest soils. This raises concern that chronic acidic deposition, particularly when coupled with intensive forest biomass harvesting, may diminish long-term soil fertility, forest productivity, and carbon storage potential. To address these concerns, the Fork Mountain long-term soil productivity experiment was initiated in 1996 at the Fernow Experimental Forest, West Virginia. The replicated experimental design consists of 16 plots (0.2 ha) that receive one of four treatments: (1) whole-tree harvesting (removal of all aboveground biomass, WT plots); (2) whole-tree harvesting + ammonium-sulfate fertilization (WT + NS plots); (3) whole-tree harvesting + ammonium-sulfate fertilization + dolomitic lime (WT + NS + Lime plots); and (4) untreated reference plots. We present forest floor and soil chemistry responses after ∼25 years of treatment and evaluate the temporal changes to illuminate these results. Soil acidification has occurred, and base cation movement through the soil profile was observed, with effective cation exchange capacity increasing slightly in the deepest soil horizon by the end of the 25 years. However, some of our hypotheses were not supported. In particular, soil C did not increase over time with fertilization/soil acidification but was mainly altered by WT harvesting, as were other nutrients. Dolomitic lime provided some amelioration of acidification, but surprisingly, most of the changes in base cations appeared to be the results of Mg, not Ca, likely due to greater tree requirements and uptake of Ca.