Proceedings - Soil Science Society of America最新文献

Carbon footprints from plants, soil, and the environment are needed to evaluate C balance of an agroecosystem, which indicates if a system is a C source or sink for mitigating climate change. There is scarce information about C footprint and C balance in dryland agroecosystems. We measured C storage of above- and belowground crop biomass, CO₂ fluxes, soil C sequestration rates, and C balances of three long-term (34-year-old) dryland cropping sequences from 2016 to 2018 in the US northern Great Plains. Cropping sequences were no-till continuous spring wheat (NTCW; Triticum aestivum L.), no-till spring wheat–pea (NTWP; Pisum sativum L.), and conventional till spring wheat–fallow (CTWF). Carbon storage in grain, straw, root, and rhizodeposit were 29%–61% greater for NTCW and NTWP than CTWF. The CO₂ flux peaked immediately after tillage, planting, fertilization, and intense precipitation (>10 mm) for 3 months in 2016–2017. Cumulative annual CO₂ flux was 8%–37% greater for NTCW than NTWP and CTWF in 2016–2017, but was not different among cropping sequences in 2017–2018. Soil C sequestration rate at 0–10 cm measured from 2012 to 2019 was in the order: NTCW (0.27 Mg C ha⁻¹ year⁻¹) > NTWP > CTWF (−0.23 Mg C ha⁻¹ year⁻¹). Carbon balance remained negative and was not significantly different among cropping sequences but varied by year. Carbon loss increased with increased precipitation, regardless of cropping systems. Although a C source, the legume–nonlegume rotation can reduce C loss due to greater grain C output than other cropping sequences in the semiarid region of the northern Great Plains.

In this study, we investigated the bacterial diversity and plant growth-promoting (PGP) properties of bulk soil bacteria of Vachellia tortilis subsp. raddiana collected from the Taidalt and Amazloug nature preserves area in southern Morocco. Using repetitive extragenic palindromic polymerase chain reaction fingerprinting and 16S rDNA sequencing, 93 strains were identified. They belonged mainly to the genera Bacillus and Peribacillus. In vitro tests for PGP traits showed high levels of activity for strains belonging to the genera Bacillus and Pseudomonas. It was relevant that several Bacillus strains produced auxin (maximum amount 262.61 µg mL⁻¹ for Bacillus sp. LMR1097), solubilized phosphate (maximum amount 22.10 µg mL⁻¹), or produced siderophores, while three strains were able to fix atmospheric nitrogen (LMR1145, LMR1013, and LMR1015). Inoculation of V. tortilis subsp. raddiana plants with selected bacterial strains (LMR881 and LMR1097) increased shoot and root growth parameters. The strain Pantoea sp. LMR881 had the highest mean values for shoot and root length (24.60–14.80 cm) and shoot dry weight (1.31 g), whereas Bacillus sp. LMR1097 showed the lowest mean shoot dry weight. Overall, these results highlight the potential of using selected native bacterial inoculants for improving growth of candidate tree plants to be used in restoration programs of arid degraded areas.

Conventional farming practices have negatively impacted micronutrient fertility and overall soil health. Metal lactates are an organic micronutrient amendment that provide both a labile carbon substrate as well as mineral nutrition for plant and microbial growth. To determine the ability of metal lactates to provide readily available micronutrients, Zn, Cu, Mn, Ni, and Co in lactate and chloride salt form were amended to soils and incubated for 28 days. Operationally defined speciation was determined using sequential extraction on samples incubated for 1, 5, or 28 days. The results show a comparable distribution of metals in chloride and lactate form; however, differences were detected in water-soluble and exchangeable Ni and Zn at each timepoint. For example, in the water exchangeable fraction, there was 2.6%–2.9% less Ni and 0.2%–0.3% less Zn in the metal lactate-treated soil compared to soil treated with metal chlorides. Furthermore, carbonate-bound Ni averaged 4.1% and 4% less in metal lactate-treated soils as compared to metal chloride-treated soils on days 1 and 5, and Cu decreased 2.9%–3.3% during the treatment period for the lactate-bound form. Additionally, microbial phospholipid fatty acid (PLFA) was performed and found a stimulatory effect of metal lactates on bacterial biomass with an increase of 12%–18% relative to the metal chloride treatment. Results from this study support the use of metal lactates as a sustainable alternative to conventional fertilizers by providing bioavailable micronutrients for plant nutrition in addition to a labile carbon source to support the growth of microbial populations.

Infrared spectroscopy is increasingly being adopted as a technology for soil analysis. However, laboratories worldwide are equipped with different infrared spectrometers, leading to variations that hinder the global application of soil spectroscopy. This study evaluates the transferability of soil spectra from a global dataset collected using four mid-infrared spectrometers. To evaluate the efficacy of five spectral transfer functions (direct standardization, piecewise direct standardization, spectral space transformation [SST], principal components-canonical correlation analysis [PC-CCA], and domain-invariant partial least square [DIPLS] regression), two datasets were used: dataset A (n = 224; standardized samples) was scanned using one primary spectrometer and three secondary spectrometers; dataset B (n = 1904; legacy samples) was scanned only using the primary spectrometer. The first set of chemometrics models was developed using dataset A to compare the performance of different spectrometers. The second set of models was developed using dataset B to evaluate the effectiveness of spectral transfer functions. Both models were developed using partial least squares regression. Spectral transfer functions developed using dataset A indicate that the PC-CCA method was the best in converging spectra collected from four instruments into a similar space projected using Uniform Manifold Approximation and Projection. Spectral transfer did not result in consistent improvement in the prediction of soil properties compared to the direct use of spectra collected from different spectrometers. These findings carry significant implications for the utilization of legacy models, enabling laboratories to concentrate on acquiring new samples and spectral measurements using established protocols without the need for spectral transfer.

The present study examined how the use of soil color can help build and evaluate clay content prediction models from laboratory visible and near infrared spectroscopic data. This study was based on a regional database containing 449 soil samples collected over Karnataka state in India, which has been divided into red soils (240 samples) and black soils (209 samples) based on their Munsell soil color. Partial least squares regression models were calibrated and validated from both the regional datasets and subsets stratified as red and black soils. In addition, a random forest model was used to classify the validation soil samples into black and red classes to evaluate models’ performance. First, while the clay content predicted by the regression model built from regional data was evaluated as correct at regional scale (R²_val of 0.75), this model was evaluated as more accurate over black (R²_val of 0.8) than red (R²_val of 0.63) soil samples. Second, the regression models built from subsets stratified per soil color provided different performances than the regression model built from the regional data, both at the regional scale and soil color scale. In conclusion, this study demonstrated that (1) predictions are highly dependent on calibration data, (2) the interpretation of prediction performances relies heavily on validation data, and (3) pedological knowledge, such as soil color, can be effectively employed as an encouraging covariate in both the construction and evaluation of regression models.

Manure relocation strategies are needed to mitigate excessive phosphorus (P) application to agricultural land in areas of intensive animal agricultural production. This requires conceptual frameworks such as the manureshed, which categorizes agricultural areas according to the potential to export or receive manure for P fertilization. To further understand how the manureshed concept could be utilized, assessments of the potential implementation and necessity of the manureshed model are needed. With North Carolina at the center of the largest manureshed in the United States, North Carolina is an ideal test case to identify areas of concern for manure relocation under the manureshed framework. Swine and poultry dominate North Carolina's agricultural production, and because the vast majority of North Carolina producers are not required to limit manure applications to a P-based rate, P accumulates. Therefore, soil test data from samples submitted to the North Carolina Department of Agriculture and Consumer Services (NCDA&CS) from 2017 to 2019 were used to determine how manureshed classes defined by Spiegal et al. correspond to current soil test P levels. It was determined that 36% of counties experience very high (>100 mg P kg⁻¹; N = 36) median P concentrations in soil. Furthermore, fields cultivated with warm-season forages had the highest mean P concentration (188 mg kg⁻¹) and high median P trended toward counties with high animal production. Lastly, while mean soil P for all manureshed classifications fell into the very high category, manure source counties had the highest mean soil P concentrations (188 mg kg⁻¹), which was 39%–52% higher than the other classifications. This suggests that, in addition to manuresheds classification, soil test data are needed to design and promote manure redistribution strategies.

Proper soil sampling is critical for accurate fertilizer recommendations. Samples collected in extremely wet or dry conditions may compromise the integrity of the sample and influence analytical results. We evaluated the effects of six soil moistures, two sampling depths (0–10 and 0–15 cm), and two soil probes on soil core uniformity and soil test results. Moisture treatments encompassed a range from dry (11.2%–18.5% moisture) to saturated conditions in Captina, Dewitt, Calhoun, and Calloway silt loam soils. Core depth and dry core weight were measured in all soils, and pH and Mehlich-3 extractable P, K, S, and Zn were assessed for Calhoun and Calloway soils. Soil moisture, probe, or their interaction influenced core depth and weight, while chemical properties were significantly affected only by soil moisture. Sampling very dry or saturated soils compromised the collection of uniform cores mainly for the 0- to 15-cm depth. Soil pH tended to increase with increasing moisture, but the mean values fluctuated only ±0.3 units. Across soils and depths, extractable S consistently decreased by 16%–48% as soil moisture at sampling time increased. Phosphorus was affected by soil moisture for 0–15 cm samples in both soils but showed no clear pattern. Soil moisture at the time of sampling affected soil test K for both soils and sample depths with individual cores varying up to 47 mg kg⁻¹ (i.e., 59–106 mg kg⁻¹). Greater soil test P and K variability occurred for very dry and wet conditions, which often prohibit collecting samples to the proper depth and could impact fertilizer rate recommendations.

Limestone is the most widely used agricultural input for soil acidity correction and calcium (Ca) and magnesium (Mg) fertilization. However, other materials have the potential to fulfill these purposes, such as steel slags, also known as silicates. Silicates have higher solubility than limestone, serving as agents for increase pH in no-till, in addition to being a source of Ca, Mg, and silicon (Si). This study aimed to compare the effects of surface application of dolomitic lime and calcium magnesium silicate on soil chemical properties, soybean [Glycine max (L.) Merr.] nutritional status, and grain yield under no-till. The experiment was installed in the northwest Paraná State, Brazil, on a Rhodic Eutrustox. Lime and silicate rates were applied by broadcasting before the sowing of soybean. Silicate treatment increases soil Ca²⁺, pH, and base saturation up to a depth of 0.10 m. By contrast, liming effects on soil chemistry were restricted to the 0.05 m top layer after 24 months of application. The acidity correction and Ca²⁺ supply to greater soil depths and the increased leaf Si as a beneficial element provided by silicate treatment contributed to increasing soybean yield in the 2018/2019 and 2019/2020 seasons. Lime application, regardless of the rate, did not improve soybean yield. Waste from the steel industry can be used as acidity correctives and source of Si, Ca, and Mg, improving the agronomic performance of soybean.

RETRACTION: Ibrahim, A. & Horton, R. (2021). Biochar and compost amendment impacts on soil water and pore size distribution of a loamy sand soil. Soil Sci Soc Am J., 85, 1021–1036. https://doi.org/10.1002/saj2.20242

The above article, published online on 16 March 2021 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal's Editor, William Horwath, the Soil Science Society of America's Editor-in-Chief, Craig Rasmussen, the Soil Science Society of America, and Wiley Periodicals LLC.

The retraction has been agreed following concerns raised from the corresponding author of (Al-Omran et al., 2021), who claimed that he was omitted as an author and was unaware of the article's submission as he pursued the publication of (Al-Omran et al., 2021) in another journal. An investigation by the journal, society, and Wiley observed that (Al-Omran et al., 2021) is based on the same research as this article, with evidence of significant overlap. Therefore, these parties consider this a duplicate publication.

Additionally, further investigation by the author's institution concluded that the article does not disclose the university's funding, nor does it appropriately acknowledge the omitted author. As such, the institution formally requested that the article be retracted.

Corresponding Author A. Ibrahim disagreed with the retraction. Co-author R. Horton collaborated during the investigation and agreed to the retraction.

Biochar may improve the health of environmentally sensitive soils (i.e., low C, sandy, sloping) especially if combined with cover crops (CCs), but research is scant. We assessed how wood biochar (836 g C kg⁻¹) applied at 0, 6.25, 12.5, 25, and 50 Mg ha⁻¹ to sandy, sloping, and semi-arid soils with and without CCs affects soils and crop yields in the central US Great Plains for 3 years. We measured crop yields and CC biomass each year, and most soil properties in Years 1 and 3. Biochar did not interact with CCs, suggesting the combination was no better than biochar or CC alone. In the semi-arid soil, crop and CC did not establish due to persistent droughts. Biochar benefits were highly site-specific. Biochar improved some soil properties but only in the sandy and sloping soils and at the biochar application depth (0- to 15-cm soil depth). The 50 Mg biochar ha⁻¹ improved the soil's ability to sorb water (0.08 cm s^−1/2). Also, in the sandy soil, it increased soil organic matter concentration (2.5 g kg⁻¹), soil pH (0.65 units), and available water (0.07 m³ m⁻³) only in Year 1, suggesting a biochar benefit in sandy soils is short-lived. In the sloping soil, >25 Mg biochar ha⁻¹ reduced bulk density (0.16 Mg m⁻³) and increased soil mean weight diameter of water-stable aggregates (0.58 mm), organic matter concentration (11.42 g kg⁻¹), infiltration (9.35 cm), CC biomass production (0.27 Mg ha⁻¹), and some microbial biomass groups. Biochar did not affect crop yields. Overall, >25 Mg biochar ha⁻¹ improved properties in some soils without interacting with CCs.