Proceedings - Soil Science Society of America最新文献

A precise soil organic carbon (SOC) content estimate is crucial soil quality parameter for agricultural produce and ecological safety. Moreover, geospatial modeling of SOC is critical when there are limited laboratory equipment and chemical reagents for soil analysis. This study used geostatistics—ordinary kriging (OK) and inverse distance weighting (IDW)—to map SOC in Libokemkem area, Northwest Ethiopia, for improved SOC management. About 107 soil samples were obtained from the plow layer at a 20-cm depth and SOC was determined. Statistical Package for Social Sciences version 24.0 was used to generate descriptive statistics, and geostatistical analysis was also performed on the data using ArcGIS platform. The coefficient of determination (R²) and root mean square error (RMSE) derived from the validation of the predicted maps were used to assess the models. The results revealed homogeneity (coefficient of variation < 10%), low (0.12%–1.74%), and optimal (1.74%–4.06%) mean levels of SOC in study area. The OK showed an R² of 0.74 and an RMSE of 13%, and the IDW revealed an R² of 0.69 and an RMSE of 14%. The semivariogram results indicate a moderate dependence for SOC with stable, circular, spherical, exponential, and Gaussian models. We conclude that the sustainable monitoring of SOC is significant in enhancing soil quality. However, further study considering all drivers of spatial variability for SOC in the study and other soil sampling approaches improving performance of the prediction models is needed.

Monitoring changes in soil organic carbon over time is important to many agricultural and environmental goals. Despite decades of measurements, temporal variability in soil carbon measurements has not been studied extensively. In this report, we examine five sets of monthly samples extending up to 3 years each that were collected from field experiments at four locations representative of dryland farming in the Pacific Northwest. The variance from month-to-month was 15%–32% of the random error, averaging 20%. This was often greater than the variance between replicate experimental units (2%–42%, averaging 17%). At certain sites, sequential samples were found to be temporally autocorrelated, but no consistent trend patterned on seasonal factors like precipitation was found. This suggests that a single point-in-time sample can deviate substantially from the long-term average soil carbon at the site. We illustrate this problem with the results of repeated soil samples taken from 12 commercial farm fields. We recommend that confidence intervals for soil organic carbon estimates should include variance based on a large population of samples rather than from a single sample set at one timepoint.

Soil quality monitoring schemes are a useful tool for assessing the potential of soils to perform desired services such as agricultural productivity. When researchers or other stakeholders wish to compare results between different schemes or studies, failure to consider differences in soil sample storage conditions presents a significant potential for error. Here, we compared levels of nitrogen and potassium, as well as pH, in agricultural soil samples stored under three different conditions (refrigerated, frozen, and oven-dried). All tests were performed after 7 and 24 weeks of storage. Nitrate decreased significantly in dried (p < 0.001) samples. When refrigerated, nitrate first increased (p < 0.01) and then decreased (p < 0.001). Nitrate levels where unchanged at Week 7 in the freezer but decreased significantly at Week 24 (p < 0.001). Nitrite and ammonium increased after drying (p < 0.001) and when frozen (p < 0.001 and p < 0.05) but remained stable when refrigerated. There was no significant difference in potassium levels between the fresh control and Week 7 in the freezer, but potassium had increased at Week 24 (p < 0.05). Potassium concentration increased in refrigerated samples (p < 0.001) and fluctuated up and down in dried samples (p < 0.01). pH measurements fluctuated significantly in refrigerated and frozen samples (p < 0.001 and p < 0.01, respectively) but were unchanged in dried samples. We suggest that soil monitoring schemes standardize their sample storage, and we encourage researchers to clearly report soil sample storage conditions in publications, to improve transparency and reproducibility.

The shrub and patch size of moss crusts can significantly affect plant and soil nutrients. The effects and relationships of shrubs and moss crusts on soil multifunctionality are unclear. This study aimed to understand the spatial heterogeneity of soil multifunctionality in moss crust patches and shrubs. Soil organic carbon, nutrient, and enzyme activities under moss crust patches were measured. Interestingly, the soil polyphenol oxidase (PPO) and peroxidase (POD) activities, carbon-related soil multifunctionality index (C-SMF), nitrogen-related soil multifunctionality index (N-SMF), phosphorus-related soil multifunctionality index (P-SMF), and soil multifunctionality index (SMF) increased with increasing patch size in moss crusts. The patch size of moss crusts had no significant effect on the C-SMF, N-SMF, P-SMF, and SMF under the shrub. The soil C-SMF, N-SMF, P-SMF, and SMF under shrubs were significantly higher than that in exposed areas (EAs). The soil PPO, POD, N-SMF, P-SMF, and SMF under dead shrubs were significantly higher than those under living shrubs and in EAs. Evaluation and composition analysis of C-SMF, N-SMF, and P-SMF indicated that moss crust promotes the increase of P-SMF, and that shrub promotes the increase of C-SMF and N-SMF. Moss crust patches mainly affected phosphorus functionality, increasing phosphorus cycling. Shrub promotes soil carbon and nitrogen functionality. This study elucidates the effect of moss crust patch size on soil multifunctionality influenced by shrub growth in desert ecosystems and provides further new insights into the soil processes and functions. Results are beneficial for the comprehensive utilization of fertile islands and its enhancement of beneficial ecological functions, such as maintaining soil nutrition, quality, health, and vegetation restoration, and lay a foundation for future research on nutrient absorption and utilization between mosses and shrubs.

Managers increasingly seek to increase forest soil carbon but long-term controls on soil organic matter (SOM) sources and stability are weakly understood. We used a 30-year detrital input/removal treatment experiment in a deciduous forest to evaluate the importance of root and leaf litter to SOM. Inputs were assessed by excluding roots and leaves (litter) or by doubling litter inputs. In mineral soil, %SOM differed only at 0–10 cm (p = 0.11), with concentrations in the no litter and no roots treatments of 26% and 9%, respectively, lower than the controls. Cessation of litter inputs had a stronger effect on SOM than cessation of root inputs, but root litter inputs may contribute stable SOM. Doubled litter increased mineral SOM.

Mollisol is crucial for solving food security issues, but long-term excessive application of chemical fertilizers has led to severe Mollisol degradation in Northeast China, especially a rapid decline in soil organic carbon (SOC). In context of the use of crop-herbage intercropping and straw return as alternatives for some chemical fertilizers, it is important to understand how crop-herbage intercropping and straw return combined with chemical fertilizers influence labile organic carbon (LOC) fractions that improve SOC. To address this, this study explored how the combined application of maize (Zea mays L.)–Melilotus officinalis intercropping, straw return, and chemical fertilizers affect LOC fractions and mineralized carbon (MC) from the perspective of physical property-mediated pathways. Thus, a field experiment with six treatments was established in the Songnen Plain of Northeast China: (1) maize monoculture without chemical fertilizers and straw return (CK), (2) maize monoculture with chemical fertilizers and no straw return (CF), (3) maize monoculture with chemical fertilizers and straw return (CFS), (4) maize–M. officinalis intercropping and straw return combined with full application of chemical fertilizers (CFSM), (5) maize–M. officinalis intercropping and straw return combined with half application of chemical fertilizers (1/2CFSM), and (6) maize–M. officinalis intercropping and straw return without chemical fertilizers (SM). The CF and CFS groups had no effect on bulk density and porosity but reduced specific gravity. The CFSM group increased water contents, porosity, LOC fractions, SOC, MC, and CO₂ release rate and decreased bulk density and specific gravity. Compared with the CF group, the 1/2CFSM group enhanced water contents, microbial biomass carbon, and water-soluble organic carbon (WSOC) to 6.36%, 17.91%, and 11.6%, respectively. We found that maize–M. officinalis intercropping, straw return, and reducing chemical fertilizers application improved LOC fractions to increase SOC by positively affecting bulk density, specific gravity, and water contents. Further analysis indicated that WSOC was a key determinant of SOC and maize yields. These findings provide a strategy to increase SOC and rehabilitate degraded soils through crop-herbage intercropping and straw return combined with reducing chemical fertilizers application, which will contribute to a sustainable and environmentally friendly agriculture.

Sandy loamy soils are widely distributed in fluvial floodplains and experience flooding events frequently, resulting in a large amount of nitrous oxide (N₂O) emissions. This case is more serious when the soil use is changed to paddies. It is of great significance to figure out the N₂O consumption and its influencing factors in sandy loamy paddy soils to mitigate N₂O emissions. In this study, three sandy loamy paddy soils (0–5 cm) originated from lake deposits were selected (S1, S2, and S3) as objectives. A certain concentration of exogenous N₂O was added at the bottom of the flooded soil column to monitor the dynamics of N₂O and nitrogen (N₂) on the soil surface. Total N₂O consumption, N₂O uptake, and N₂ production were quantified, and the abundance of nitrous oxide reductase genes (nosZI, and nosZII) and other soil properties (ammonium-nitrogen, nitrate-nitrogen, and dissolved organic carbon [DOC] content) were analyzed. The results showed that the sandy loamy paddy soil column with a depth of 0–5 cm could intercept more than 95% of the exogenous N₂O under the flooded anaerobic condition, indicating that the three sandy loamy paddy soils all had extremely strong N₂O consumption capacities. And the increment of N₂ accounted for 68.73%–76.09% of the total N₂O consumption, which had a stronger relationship with the increase of nosZI gene abundance than nosZII gene. In addition, the total N₂O consumption and N₂ increment of S1 and S3 soils were significantly higher than those of S2 soil. This difference was mainly related to soil organic matter content, total nitrogen content, DOC consumption, and the increase of nosZI gene abundance (p < 0.05). The strong N₂O consumption potential of sandy loamy soils can provide feasible solutions for regulating N₂O emissions in a wide range of similar environments in fluvial floodplains.

The production of bioproduct feedstocks such as switchgrass (Panicum virgatum L.) and willow (Salix spp.) on degraded lands provides an opportunity to grow dedicated bioenergy crops with the potential to capture and store carbon in the soil while reducing competition with land for food production. However, how the production of these crops alters plant–soil–microbe interactions that govern soil C accumulation in highly degraded soil is underexplored. The objectives of this study were to examine select biological and chemical properties related to stable soil organic matter (SOM) production from the growth of switchgrass and willow on marginal soil over two growing seasons and whether biochar amendment can positively affect these parameters. To address our objectives, paired former surface mined lands and non-mine impacted marginal agriculture sites were selected across West Virginia, USA, and biochar and unamended control treatments were imposed. Through the first two growing seasons, microbial activity and demand for carbon (C) increased and was accompanied by a shift in extracellular enzyme investment for decomposition-associated enzymes. Mineral-associated organic matter C increased over the two growing seasons, and this increase was greater in the mine sites compared to the agriculture sites. Compared to each site's previous land use, C losses were observed under bioproduct systems in the agriculture, but not the mine sites. Biochar amendments did not impact microbial activity but did increase the C:N of SOM. Overall, our results suggest that the early growth of switchgrass and willow can result in C accumulation in marginal and highly degraded lands.

Wind erosion and variable weather challenge crop production in the northern Great Plains. Management that increases residue cover might mitigate wind erosion during the cash crop growing season. We evaluated horizontal sediment flux (modified Wilson and Cooke samplers) and cash crop yield across a single rotation of corn (Zea mays L.)–soybean (Glycine max (L.) Merr.)–spring wheat (Triticum aestivum L.) in paired fields with contrasting management. One field included cover crops and retained spring wheat straw (aspirational), while the other excluded both conservation practices over the 3-year rotation (business-as-usual). Horizontal sediment flux rapidly decreased with days after cash crop planting (increasing crop canopy), regardless of management treatment. In 2 years (2020 corn and 2022 spring wheat), there was greater horizontal sediment flux, lower cash crop grain yield, and lower cash crop aboveground biomass in the aspirational versus business-as-usual field. In 2021 soybean, there was lower horizontal sediment flux, greater cash crop yield, and greater cash crop aboveground biomass in the aspirational versus business-as-usual field. Higher yield and lower horizontal sediment flux responses corresponded with the management treatment that produced the higher cash crop aboveground biomass. Additionally, our short-term study indicated that in drought years, cover crops worsened the adverse effects of abnormally low precipitation on yield and biomass of 2020 corn but not 2021 soybean.

The acidic soils of western Newfoundland require liming for successful production of most crops. Locally sourced paper mill waste wood ash (WA) and paper sludge (SL) have potential as cheaper alternatives to limestone (LIME). Two greenhouse experiments evaluated WA and SL as liming and soil conditioning amendments for annual ryegrass (Lolium multiflorum) production. At 55 days after seeding, soil pH in WA (6.2 and 6.3) and wood ash and paper sludge (WASL) (6.0 and 6.3) were not different from that in LIME (6.0 and 6.5) for Experiments 1 and 2, respectively. However, pH in SL was 0.4 and 0.3 points lower than in LIME. Compared to LIME, WA, SL, and WASL produced 31%–52% and 57%–74% greater biomass yield in Experiments 1 and 2, respectively. N uptake was greater in WA (60 and 129 kg N ha⁻¹) and WASL (51 and 97 kg N ha⁻¹) compared to LIME (40 and 85 kg N ha⁻¹), in Experiments 1 and 2, respectively. SL did not differ from LIME in Experiment 1, but reduced N uptake by 57% in Experiment 2. The results show significant potential of WA as an alternative amendment for liming and yield improvement of annual ryegrass grown in NL podzolic soils. However, SL has limited potential due to the risk of increasing N immobilization and residual soil mineral N when growing conditions are limiting. Combining SL with WA or biochar seemed to alleviate these risks. Overall, the adoption of these amendments for field production systems warrants serious consideration, following supplemental field studies to determine optimal application rates and timing.