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11 pages, 1025 KB

Open AccessArticle

Shifts in Soil Nutrient Availability and C:N:P Stoichiometry During Long-Term Vegetation Restoration in Mu Us Sandy Land

by Chi Zhang, Xingchang Zhang and Na Zhao

Agronomy 2026, 16(8), 815; https://doi.org/10.3390/agronomy16080815 - 15 Apr 2026

Viewed by 411

Abstract

Vegetation restoration profoundly impacts soil carbon (C)-nitrogen (N)-phosphorus (P) cycling in arid sandy lands, with vegetation type critically regulating accumulation patterns. However, the magnitudes of soil nutrients and stoichiometry for different vegetation types are still largely unknown. Thus, we conducted a regional-scale study [...] Read more.

Vegetation restoration profoundly impacts soil carbon (C)-nitrogen (N)-phosphorus (P) cycling in arid sandy lands, with vegetation type critically regulating accumulation patterns. However, the magnitudes of soil nutrients and stoichiometry for different vegetation types are still largely unknown. Thus, we conducted a regional-scale study to evaluate the soil nutrients and nutrient stoichiometry under four typical vegetation types in the Mu Us Sandy Land (MUS), including monoculture arbor (MA), monoculture shrub (MS), arbor-shrub mixed (MAS), and monoculture herbaceous (MH), with cropland (Cr) and bare sand (Bs) controls. Our results showed that vegetation type significantly affected SOC and TN content. MS (30–40 years), MA (>40 years), and MH exhibited significant increases of 285.5–305.8% in SOC and 293.6–374.6% in TN in the topsoil, respectively. MS (30–40 years) and MH demonstrated increases of 399.1% and 283.3% in SOC and 250.2% and 162.8% in TN in the subsoil. However, MAS had no significant effect on SOC and TN. MA (>40 years) resulted in a higher TP in the subsoil. Compared to Bs, humic substances significantly increased by 111.1–171.6% under MA (>40 years), MS (>40 years), and MH, exhibiting positive correlations with SOC. Moreover, MAS treatment resulted in a higher C:N, while the MH resulted in a higher C:P and N:P in the topsoil. Despite stable total phosphorus (TP), elevated C:P and N:P ratios under MH indicated emerging P limitation in restoration. Therefore, long-term monoculture shrub, arbor, and herbaceous vegetation effectively enhances soil fertility in arid sandy lands through long-term SOC accumulation and humic substance formation. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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14 pages, 2081 KB

Open AccessArticle

Comparative Effects of Biochar and Humic Acid on the Soil–Wheat System in Mildly Saline Soils

by Leping Bai, Ru Zhang, Shengcai Wu, Bin Liu, Yuyi Li, Xiquan Wang and Baoping Zhao

Agronomy 2026, 16(5), 550; https://doi.org/10.3390/agronomy16050550 - 28 Feb 2026

Viewed by 656

Abstract

Soil salinization is a major constraint on global crop production. While organic amendments are used in mildly saline soils, their seasonal effects require further study. This research applied biochar (BC) and humic acid (HA) annually in 2022 and 2023 separately, with an unamended [...] Read more.

Soil salinization is a major constraint on global crop production. While organic amendments are used in mildly saline soils, their seasonal effects require further study. This research applied biochar (BC) and humic acid (HA) annually in 2022 and 2023 separately, with an unamended control (CK), to assess impacts on soil quality and wheat yield. BC significantly reduced soil salt content by 28.1% and 17.5% in 2022 and 2023 at a rate of 7.5 Mg·ha⁻¹, while increasing organic matter and total phosphorus. In contrast, HA lowered soil pH by 3.1% in 2022 and enhanced available nitrogen, potassium, and phosphorus. Both BC and HA increased alkaline phosphatase activity by 7.6% and 6.9% in 2023, respectively. Notably, grain yield showed no direct link to soil nutrients but was positively correlated with phosphatase activity in 2023. Consequently, BC did not improve the soil quality index but raised grain yield by 12.9% and 20.7% over two years, primarily via increased 1000-grain weight. In contrast, HA both improved the soil quality index by 16.1% in 2023 and increased grain yield by 17.2%, driven by enhanced aboveground biomass. In conclusion, soil chemical properties and crop productivity were decoupled in these mildly saline–alkaline soils, highlighting the potential for site-specific application of organic amendments. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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24 pages, 5007 KB

Open AccessArticle

Microbial Agents Enhance Sugar Beet Yield and Quality as an Alternative to Chemical Fertilizers

by Zijian Zhang, Chao Li, Shangzhi Li, Yaqing Sun, Ningning Li and Guolong Li

Agronomy 2025, 15(12), 2838; https://doi.org/10.3390/agronomy15122838 - 10 Dec 2025

Viewed by 605

Abstract

Sugar beet (Beta vulgaris L.) is an important economic crop and a primary source of sugar in northern China, characterized by strong stress tolerance and high nutritional value. Microbial inoculants can promote crop growth by regulating soil enzyme activities, enriching dominant beneficial [...] Read more.

Sugar beet (Beta vulgaris L.) is an important economic crop and a primary source of sugar in northern China, characterized by strong stress tolerance and high nutritional value. Microbial inoculants can promote crop growth by regulating soil enzyme activities, enriching dominant beneficial bacterial genera in rhizosphere soil, and improving the availability of soil nutrients. This study aimed to investigate the role of microbial inoculants in sugar beet production and their potential to replace chemical fertilizers and put forward the scientific hypothesis that microbial inoculants can increase soil nutrients and improve the soil microenvironment. A two-year field experiment was conducted: in 2022, treatments with different application rates of Bacillus subtilis and Trichoderma spp. inoculants were set up to screen the optimal inoculant and its dosage (M1); in 2023, based on this optimal inoculant (M1), treatments with reduced chemical fertilizer input were established to explore the mechanisms underlying the maintenance of sugar beet yield and quality. The results showed that the M1N2 (75 kg/ha fertilizer and 20% less nitrogen fertilizer) treatment significantly increased nitrogen, phosphorus, and potassium agronomic use efficiencies by 91.48%, 51.94%, and 53.50%, respectively, compared with the control (CK). Soil urease, catalase, and sucrase activities were significantly enhanced by 14.57%, 66.84%, and 222.46%, respectively. The treatment also significantly increased the relative abundance of beneficial bacterial genera such as JG30-KF-CM45 and KD4-96, while sugar beet yield was significantly increased by 5.53% relative to the CK. This study provides a theoretical basis for the application of microbial inoculants and the reduction in chemical fertilizers in sugar beet production. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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21 pages, 2080 KB

Open AccessArticle

Assessment of the Plant Growth-Promoting Potential of Three Pseudomonas and Pantoea Isolates to Promote Pepper Growth

by Ayman F. Omar, Adil H. A. Abdelmageed, Ahmad Al-Turki, Ahmed M. Aggag, Medhat Rehan and Noha M. Abdelhameid

Agronomy 2025, 15(10), 2419; https://doi.org/10.3390/agronomy15102419 - 18 Oct 2025

Cited by 2 | Viewed by 1731

Abstract

Plant growth-promoting bacteria (PGPB) have a wide range of applications in agriculture and environmental management. They act as biostimulants and biofertilizers to enhance crop quality and yields in a more sustainable way. The present research aimed at isolating three active strains from the [...] Read more.

Plant growth-promoting bacteria (PGPB) have a wide range of applications in agriculture and environmental management. They act as biostimulants and biofertilizers to enhance crop quality and yields in a more sustainable way. The present research aimed at isolating three active strains from the arid rhizosphere soil to act as biofertilizer. The plant growth-promoting features were evaluated in vitro and their implementation on pepper growth and yield were assessed and measured. Regarding IAA and ammonia production, the three designated isolates (P21, P22-1 and P58) showed patterns of high IAA production, producing 154.47 µg/mL, 155.03 µg/mL, and 188.65 µg/mL, respectively. Furthermore, considerable amounts of ammonia were detected in the supernatant of peptone water medium after 72 h of growth. Isolate P21 produced the maximum amount and generated 17.38 μmol/mL, whereas both P22-1 and P58 displayed lower amounts (15.47 and 15.92, respectively), without significant differences. P-solubilization efficacy calculated 18.7% (isolate P21), 64% (isolate P22-2), and 54% (isolate P58) when compared with un-inoculated medium. The molecular identification by 16S rRNA displayed that the three isolates belonged to Pseudomonas alkylphenolica strain P21 (PX257452), Pantoea agglomerans strain P22-1 (PX257453), and Pantoea brenneri strain P58 (PX257454). Applying the selected strains with sweet pepper in the presence of rock phosphate (RP) was assessed under greenhouse conditions. Three treatments (adding bacterial suspension at 0, 10 and 20 days after transplanting) from P21, P22-1, and P58 strains revealed that P21(3), P21(2), P22-1(3), and P58(3) treatments are considered the most promising treatments related to plant height, root length, leaf area, number of leaves per plant, leaf P-uptake, and stem P-uptake in addition to total plant P-uptake. In addition, the PCA biplot showed that MSP (mono-super phosphate), P22-1(3), and P58(3) are closely associated with high phosphorus uptake, indicating their effectiveness in enhancing phosphorus absorption by solubilizing insoluble forms. Eventually, PGPB will help the environment by improving soil fertility and structure, decreasing the need for toxic chemical fertilizers, and improving ecosystem health overall. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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20 pages, 3069 KB

Open AccessArticle

Assessing the Synergy of Spring Strip Tillage and Straw Mulching to Mitigate Soil Degradation and Enhance Productivity in Black Soils

by Zhihong Yang, Lanfang Bai, Tianhao Wang, Zhipeng Cheng, Zhen Wang, Yongqiang Wang, Fugui Wang, Fang Luo and Zhigang Wang

Agronomy 2025, 15(6), 1415; https://doi.org/10.3390/agronomy15061415 - 9 Jun 2025

Cited by 1 | Viewed by 1087

Abstract

To address the critical challenges of wind erosion mitigation and sustainable soil management in the fragile agroecosystem of the black soil region in the foothills of the Daxing’anling Mountains, this study evaluated five tillage practices—conventional ridge tillage (CP), no tillage with straw removal [...] Read more.

To address the critical challenges of wind erosion mitigation and sustainable soil management in the fragile agroecosystem of the black soil region in the foothills of the Daxing’anling Mountains, this study evaluated five tillage practices—conventional ridge tillage (CP), no tillage with straw removal (NT), no tillage with straw mulching (R+NT), autumn strip tillage with straw mulching (R+ST_A), and spring strip tillage with straw mulching (R+ST_S)—across two landforms: gently sloped uplands and flat depressions. The results demonstrated that R+ST_S achieved superior performance across both landscapes, exhibiting a 42.99% reduction in the wind erosion rate, a 48.88% decrease in soil sediment discharge, and a 52.26% reduction in the soil creep amount compared to CP. These improvements were mechanistically linked to the enhanced surface microtopography (aerodynamic roughness increased by 1.8–2.3 fold) and optimized straw coverage (68–72%). R+ST_S also enhanced the topsoil fertility, increasing the total nitrogen (TN), soil organic carbon (SOC), alkaline nitrogen (AN), available phosphorus (AP), and rapidly available potassium (AK) by 22.07%, 12.94%, 14.92%, 32.94%, and 9.52%, respectively. Furthermore, it improved maize emergence and its yield by 10.04% and 9.99% compared to R+NT. Mantel tests and SEM revealed strong negative correlations between erosion and nutrients, identifying nitrogen availability as the key yield driver. R+STS offers a sustainable strategy for erosion control and productivity improvement in the black soil region. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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16 pages, 8200 KB

Open AccessArticle

Enhancing Soil Phosphorus and Potassium Availability in Tea Plantation: The Role of Biochar, PGPR, and Phosphorus- and Potassium-Bearing Minerals

by Wen Wei, Kunyu Li, Changjun Li, Siyu Wang, Lulu Li, Jinchuan Xie, Ting Li, Zijun Zhou, Shirong Zhang, Yulin Pu, Yongxia Jia, Xiaojing Liu, Xiaoxun Xu and Guiyin Wang

Agronomy 2025, 15(6), 1287; https://doi.org/10.3390/agronomy15061287 - 23 May 2025

Cited by 4 | Viewed by 2524

Abstract

The co-application of biochar, plant growth-promoting rhizobacteria (PGPR), and phosphorus- and potassium-bearing minerals has emerged as a promising strategy for improving soil nutrient availability. However, the synergistic effects and impact factors that facilitate this optimization are yet to be fully elucidated. To address [...] Read more.

The co-application of biochar, plant growth-promoting rhizobacteria (PGPR), and phosphorus- and potassium-bearing minerals has emerged as a promising strategy for improving soil nutrient availability. However, the synergistic effects and impact factors that facilitate this optimization are yet to be fully elucidated. To address this knowledge gap, we conducted a pot experiment to evaluate the effects of these amendments on tea yield and phosphorus (P)/potassium (K) availability, while employing Random Forest (RF) and Partial Least Squares Structural Equation Modeling (PLS-SEM) to reveal the underlying mechanisms driving these improvements. The results demonstrated that the tripartite combination significantly enhanced tea yield, leaf P/K concentrations, and soil available P (AP)/available K (AK) levels compared to individual applications or pairwise combinations. Analytical modeling identified Chloroflexi bacteria containing pqqc functional genes as key drivers of AP enhancement. The AP was further modulated by β-glucosidase activity, NaHCO₃-P, and AK levels. Critical determinants of AK dynamics included phosphorus-solubilizing bacterial populations, catalase activity, and fundamental soil chemical properties. In summary, our research conclusively shows that the co-application of phosphorus- and potassium-bearing minerals, PGPR, and biochar represents an effective approach to enhancing P and K accessibility in soil, thereby offering a viable alternative to conventional P and K fertilizers in tea cultivation. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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29 pages, 5713 KB

Open AccessArticle

Relationships Between Carbon Fractions and Soil Nutrients in Organic Cassava Cultivation in the Sandy Soil of Northeastern Thailand

by Suphathida Aumtong, Chanitra Somyo, Kanokorn Kanchai, Thoranin Chuephudee and Chakrit Chotamonsak

Agronomy 2025, 15(5), 1069; https://doi.org/10.3390/agronomy15051069 - 28 Apr 2025

Cited by 2 | Viewed by 1729

Abstract

This research investigated the interaction between the labile and stable fractions of soil organic carbon (SOC) during the cultivation of organic cassava in sandy soil in northeastern Thailand over a period of five years. We collected surface soil samples (0–30 cm) from this [...] Read more.

This research investigated the interaction between the labile and stable fractions of soil organic carbon (SOC) during the cultivation of organic cassava in sandy soil in northeastern Thailand over a period of five years. We collected surface soil samples (0–30 cm) from this sandy region, utilizing a combination of cow and chicken manure along with dried distilled grains (DDGs) from cassava fermentation for ethanol production, to monitor and compare the effects of continuous mixed organic fertilization on SOC, carbon fractions, soil pH, and nitrogen and phosphorus levels throughout a five-year period of varying land use ages (LUA) to the pre-fertilization state. This study proposed that the use of a combination of organic fertilizers could increase soil organic carbon levels. This study indicates that the continuous application of organic fertilizers over five years does not lead to a significant increase in soil carbon; however, it may result in temporary alterations in different organic carbon fractions. The study showed that the mixed organic fertilization could the increase carbon fractions. Labile carbon (LBC) fraction was at its lowest before fertilization, peaking at LUA 3 and increasing by 5.44–25.50% after organic fertilizer addition. The first year revealed high non labile carbon (NLBC) levels, exceeding 60%, in comparison to the pre-fertilizer period. In the second year, NLBC levels declined to LUA 5, a change that was not statistically significant. After pre-fertilization, the concentration of recalcitrant carbon (REC) did not significantly decrease. Nitrate (NO₃⁻-N) concentrations exhibited no significant fluctuation pre-and post-fertilization. Furthermore, the Bray II-extractable phosphorus (P(B)) decreased (i.e., LUA 1 and 4). The pH levels dropped after the addition of organic fertilizer, particularly in the second year. We found strong positive links between SOC and carbon fractions such as NLBC (r = 0.54 ***) and POXC (r = 0.49 ***). However, neither LBC nor less labile carbon fraction (LLBC) showed any significant correlations with SOC. The negative correlations were observed between ammonium (NH₄⁺-N) and NO₃⁻-N with labile carbon types, such as LBC, LLBC, and POXC, while positive correlations were noted with stable carbon fractions, such as NLBC, and REC. From the application of this organic fertilizer, there are various amounts of organic carbon which cause the following effects: The inclusion of LBC from mixed organic fertilization seems to enhance SOC decomposition rather than accumulation. NLCB may persist in sandy soil for a longer duration than LBC, resulting in the retention of SOC in sandy soil. Our results suggested the implementation of a systematic soil testing strategy to monitor temporal variations in carbon fractions and nutrient levels. Using the right amounts of both LBC and NLBC would improve soil health and help store carbon through organic fertilizers. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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12 pages, 3104 KB

Open AccessArticle

Rheological Characterization of Structural Stability for Black Soils from Northeast China

by Jian Sun, Lin Zhou, Yuyang Yan, Chenyang Xu, Zhe Liu, Zhenghong Yu, Jiangwen Li and Feinan Hu

Agronomy 2025, 15(5), 1050; https://doi.org/10.3390/agronomy15051050 - 27 Apr 2025

Cited by 2 | Viewed by 1155

Abstract

Soil structural stability is fundamentally linked to soil functionality and sustainable productivity. Rheological properties describe the deformation and flow behavior of soil under external stress, playing a crucial role in understanding soil structure stability. Despite their importance, the studies about rheological properties of [...] Read more.

Soil structural stability is fundamentally linked to soil functionality and sustainable productivity. Rheological properties describe the deformation and flow behavior of soil under external stress, playing a crucial role in understanding soil structure stability. Despite their importance, the studies about rheological properties of black soils in Northeast China remain limited. This study aims to assess the rheological properties of two kinds of black soil with different degrees of degradation in Northeast China. The rheological parameters of these soils under various water contents and shearing were quantified by conducting Amplitude Sweep Tests (ASTs) and Rotational Sweep Tests (RSTs). Both AST and RST results showed that as soil water content and shear rate increased, shear strength, viscosity, and hysteresis area all decreased in Keshan and Binxian black soils. The increase in soil water content reduces the friction between soil particles, leading to a decrease in soil structure stability. Additionally, the viscosity and hysteresis area of the two soils decreased with the increase in water content, making it more flowable and exhibiting shear-thinning behavior. Keshan black soil exhibited stronger recovery and shear strength compared to Binxian black soil; this is mainly due to the higher organic matter content in Keshan soil, which could increase structural stability by bonding the soil particles at the micro-level. These findings enhance our understanding about the structure stability of the black soils based on the rheological parameters via rheometer. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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18 pages, 3886 KB

Open AccessArticle

Effect of Combined Application of Desulfurization Gypsum and Soil Amendment KIA on Saline-Alkali Soil Improvement

by Qinghong Xiao, Wei Wei, Hao Wu, Kunyue Wu, Xue Gong, Meng Li, Shiwen Wang and Lina Yin

Agronomy 2025, 15(1), 53; https://doi.org/10.3390/agronomy15010053 - 28 Dec 2024

Cited by 7 | Viewed by 4260

Abstract

Saline-alkali soil imposes severe adverse effects on soil utilization and agriculture production worldwide. Amelioration of saline-alkali soil is crucial to ensure global food security and promote sustainable agricultural development. Here, the effects of the combined application of soil amendment desulfurization gypsum (G) and [...] Read more.

Saline-alkali soil imposes severe adverse effects on soil utilization and agriculture production worldwide. Amelioration of saline-alkali soil is crucial to ensure global food security and promote sustainable agricultural development. Here, the effects of the combined application of soil amendment desulfurization gypsum (G) and KIA (K, an industrial organic by-product) on soil improvement and plant growth were investigated. Two experiments, a soil column leaching test and a pot experiment for plant growth, were carried out. The results showed that the combined application of G and K reduced soil pH significantly. Although the soil Na⁺ contents had no change in the combined treatments, the K⁺, Ca²⁺ and Mg²⁺ contents were significantly higher, and the HCO₃⁻ and Cl⁻ contents were significantly lower, compared to the control. Furthermore, maize plants exhibited a higher photosynthetic rate and greater dry weight in the combined treatments. Additionally, after plant growth, the soil enzyme activities increased. These results showed that the combined application of G and K could have a more favorable impact on soil improvement by reducing soil pH, enhancing soil ion exchange, increasing soil nutrient contents, and promoting plant growth. Our study suggests that KIA is an effective and eco-friendly soil amendment for improving saline-alkali soil. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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18 pages, 7464 KB

Open AccessArticle

Soil Greenhouse Gas Emissions and Nitrogen Dynamics: Effects of Maize Straw Incorporation Under Contrasting Nitrogen Fertilization Levels

by Zhengyu Wang, Jiaxin Shang, Xuelian Wang, Rongqi Ye, Dan Zhao, Xiangyu Li, Yadong Yang, Hongyu Zhang, Xiangwei Gong, Ying Jiang and Hua Qi

Agronomy 2024, 14(12), 2996; https://doi.org/10.3390/agronomy14122996 - 16 Dec 2024

Cited by 6 | Viewed by 1811

Abstract

Straw is widely incorporated into conservation agriculture around the world. However, its effects on greenhouse gas emissions (GHGs) and nitrogen dynamics under soils formed by the long-term application of different amounts of nitrogen (N) fertilizer are still unclear. An incubation experiment was conducted [...] Read more.

Straw is widely incorporated into conservation agriculture around the world. However, its effects on greenhouse gas emissions (GHGs) and nitrogen dynamics under soils formed by the long-term application of different amounts of nitrogen (N) fertilizer are still unclear. An incubation experiment was conducted on soils collected from a field study after 6 years of contrasting N fertilization of 0 (low N), 187 (medium N), and 337 kg N ha⁻¹ (high N), with and without maize straw. Straw amendment significantly stimulated both nitrous oxide (N₂O) and carbon dioxide (CO₂) fluxes (p < 0.05), and increased cumulative emissions by 0.8 and 19.0 times on average compared to those without straw incorporation. Medium-N soil observably weakened N₂O emissions (23.8 μg kg⁻¹) compared to high-N soil (162.7 μg kg⁻¹), and increased CO₂ emissions (1.9 g kg⁻¹) compared to low-N soils (2.3 g kg⁻¹) with straw amendment. Soil NH₄⁺-N and NO₃⁻-N invariably increased with rising soil N level, whereas straw promoted the turnover of mineral N by enhancing soil N fixation capacity. From the first day until the end of incubation, NH₄⁺-N decreased by 79.0% and 24.7%, while NO₃⁻-N showed a decrease of 58.8% or an increase of 75.2%, depending on whether straw was amended or not, respectively. Moreover, partial least squares path modeling and random forest mean predictor importance were used to find that straw affected GHGs by altering the N turnover capacity. Straw amendment increased GHGs and diminished the risk of losing mineral N by enhancing its turnover. Combining straw with medium-N soil could mitigate the greenhouse effect and improve the N and carbon (C) balance in farming systems compared to low- and high-N soils. This is recommended as a farmland management strategy in Northeast China. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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17 pages, 2260 KB

Open AccessArticle

Impact of a Single Lignite Humic Acid Application on Soil Properties and Microbial Dynamics in Aeolian Sandy Soils: A Fourth-Year Study in Semi-Arid Inner Mongolia

by Lei Zhou, Junqi Chu, Yufen Zhang, Qi Wang, Yanting Liu and Baoping Zhao

Agronomy 2024, 14(11), 2581; https://doi.org/10.3390/agronomy14112581 - 1 Nov 2024

Cited by 6 | Viewed by 3088

Abstract

Humic acid (HA) is considered a promising soil amendment for improving soil fertility. However, the effects of HA application on the microbial community, especially in aeolian sandy soils of semi-arid regions, remain insufficiently elucidated. To address this gap, a field experiment was conducted [...] Read more.

Humic acid (HA) is considered a promising soil amendment for improving soil fertility. However, the effects of HA application on the microbial community, especially in aeolian sandy soils of semi-arid regions, remain insufficiently elucidated. To address this gap, a field experiment was conducted to investigate the changes in soil properties, bacterial and fungal diversity, and community structure in a buckwheat field in the fourth year after a single application of lignite humic acid (L-HA) at 0 (L-HA0), 2 (L-HA1), 4 (L-HA2), and 6 (L-HA3) ton·ha⁻¹ in an aeolian sandy soil in Inner Mongolia, China. The results demonstrated that four years after L-HA application, there was a significant (p < 0.05) decrease in soil pH, accompanied by an increase in soil water content and nutrient levels, including organic matter and total N, available P, and K. Additionally, the application of L-HA enhanced microbial biomass C and N and stimulated enzyme activities, such as urease and invertase, with these effects being more pronounced at higher application rates (L-HA2 and L-HA3). However, HA addition did not significantly (p < 0.05) affect soil microbial biomass P or alkaline phosphatase activity. The L-HA amendment enhanced the α-diversity indices of soil bacteria but did not significantly (p < 0.05) affect soil fungal diversity. The addition of L-HA induced significant changes in the composition of the soil microbial community at both the phylum and genus levels, with significant variability in microbial responses observed across the different L-HA application rates. The incorporation of L-HA notably enriched the composition of bacterial and fungal communities at the phylum level, particularly those involved in carbon cycling, including the bacterial phyla Proteobacteria and Actinobacteriota and the fungal phyla Ascomycota and Rozellomycota. At the genus level, higher L-HA application rates, specifically L-HA2 and L-HA3, exerted statistically significant (p < 0.05) effects on most bacterial and fungal genera. Specifically, these treatments increased the abundance of bacterial genera, such as Rokubacterium and fungal genera, including Plectosphaerella, Tausonia, Talaromyces, and Clonostachys. Conversely, the relative abundance of the bacterial genera Vicinamibacter and Subgroup_7, as well as the fungal genus Niesslia, was significantly reduced. Redundancy analysis (RDA) indicated that bacterial community compositions were closely associated with soil parameters, such as available P (AP), microbial biomass carbon (SMC), microbial biomass nitrogen (SMN), microbial biomass phosphorus (SMP), and invertase, while all tested soil parameters, except for alkaline phosphatase, significantly influenced the fungal community structure. Given that the changes in these soil parameters were highly correlated with the amounts of L-HA addition, this suggests that the impacts of long-term L-HA amendment on the soil bacterial and fungal communities were linked to alterations in soil physicochemical and biological properties. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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Review

Jump to: Research

32 pages, 1920 KB

Open AccessEditor’s ChoiceReview

A Comparative Evaluation of Soil Amendments in Mitigating Soil Salinization and Modifying Geochemical Processes in Arid Land

by Amira Batool, Kun Zhang, Fakher Abbas, Arslan Akhtar and Jiefei Mao

Agronomy 2026, 16(2), 222; https://doi.org/10.3390/agronomy16020222 - 16 Jan 2026

Cited by 1 | Viewed by 1340

Abstract

Salinization is a growing global problem, particularly in arid and semi-arid areas, where salt concentration interferes with the soil structure, altering natural cycling, decreasing agricultural outputs, and threatening food security. Although many soil amendments have been studied, there is still a limited understanding [...] Read more.

Salinization is a growing global problem, particularly in arid and semi-arid areas, where salt concentration interferes with the soil structure, altering natural cycling, decreasing agricultural outputs, and threatening food security. Although many soil amendments have been studied, there is still a limited understanding of their interaction with soil after mixture application and the geochemical processes and long-term sustainability that govern their effects. To address this knowledge gap, this review elucidated the effectiveness and sustainability of soil amendments, biochar, humic substances, and mineral additives in restoring saline and sodic soils of arid and semi-arid region to explore the geochemical processes that underlie their impact. A systematic search of 174 peer-reviewed studies was conducted across multiple databases (Web of Science, Google Scholar, and Scopus) using relevant keywords and the findings were converted into quantitative values to evaluate the effects of biochar, gypsum, zeolite, and humic substances on key soil properties. Biochar significantly improved cation exchange capacity, nutrient retention, microbial activity, and water retention by enhancing soil porosity and capillarity, thereby increasing plant-available water. Gypsum improved phosphorus availability, while zeolite facilitated the removal of sodium and supported microbial activity. Humic substances enhanced soil porosity, water retention, and aggregate stability. When applied together, these amendments improved soil health by regulating salinity, enhancing nutrient cycling, while also stabilizing soil conditions and ensuring long-term sustainability through improved geochemical balance and reduced environmental impacts. The findings highlight the critical role of multi-functional amendments in promoting climate-resilient agriculture and long-term soil health restoration in saline-degraded regions. Further research and field implementation are crucial to optimize their effectiveness and ensure sustainable soil management across diverse agricultural environments. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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13 pages, 1238 KB

Open AccessReview

Effects of Biochar on Gaseous Carbon and Nitrogen Emissions in Paddy Fields: A Review

by Yidi Sun, Xuetao Wang, Chenxia Yang, Xiaoping Xin, Junlin Zheng, Tao Zong and Chaoyin Dou

Agronomy 2024, 14(7), 1461; https://doi.org/10.3390/agronomy14071461 - 5 Jul 2024

Cited by 10 | Viewed by 3387

Abstract

The paddy field is a major source of gaseous carbon and nitrogen emissions, and reducing these emissions is of great significance for mitigating greenhouse effects and non-point source pollution in farmland. Biochar, derived from agricultural waste, possesses a stable structure, large specific surface [...] Read more.

The paddy field is a major source of gaseous carbon and nitrogen emissions, and reducing these emissions is of great significance for mitigating greenhouse effects and non-point source pollution in farmland. Biochar, derived from agricultural waste, possesses a stable structure, large specific surface area, abundant pore structures, and surface functional groups. These characteristics could enhance soil physicochemical properties and microbial activity, thereby facilitating the dual goals of increasing crop yield and reducing emissions. Based on numerous studies, this review summarizes the effects of biochar on the emissions of carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and ammonia volatilization (NH₃), as well as on global warming potential (GWP) and greenhouse gas emission intensity (GHGI). It elucidates the mechanism of emission reduction by biochar amendment from the perspective of carbon and nitrogen conversion processes and soil physicochemical and biological properties. Numerous studies showed the application of 5~40 t ha⁻¹ biochar reduced CO₂, CH₄, N₂O, and NH₃ emissions by 1.64~89.6%, 8.6~89.6%, 10~90%, and 12.27~53%, respectively. A small number of studies found that the application of 5~48 t ha⁻¹ biochar increased CO₂, CH₄, N₂O, and NH₃ emissions by 12~37%, 19.85~176%, 13~84.23%, and 5.47~70.9%, respectively. Most scholars have found that biochar has varying degrees of emission reduction capabilities in different parts of the world. Therefore, future research directions have been suggested for utilizing biochar to reduce carbon and nitrogen emissions in paddy fields. Full article

(This article belongs to the Special Issue Organic Amendments to Low-Fertility Soils: Current Status and Future Prospects)

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