Water-stable Soil Aggregates Research Articles

Effects of large-grained activated humic acid fertilizer on soil aggregates and organic carbon in apple orchard soil

The new large-grained activated humic acid fertilizer (LAF) can significantly reduce the amount of chemical fertilizer application and stable fruit yield. Understanding its impacts on soil aggregates and organic carbon is an important basis for revealing its role in driving soil structure of apple orchard. There were four LAF treatments: LAF1 (full fertilization, fertilization period and mass ratio (the same below), germination stage: fruit expansion stage: maturity stage=3:4:3), LAF2 (full fertilization, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF3 (fertilizer application reduction by 1/4, germination stage: fruit expansion stage: maturity stage=2:3:5), LAF4 (fertilizer application reduction by 1/3, germination stage: fruit expansion stage: maturity stage=2:3:5); with no fertilization as control (CK). In a four-year pot experiment, we examined the composition, stabi-lity and organic carbon content of soil aggregates under different fertilization treatments. The results showed that: 1) compared with CK, each treatment of LAF increased the content of >2 mm and 2-0.25 mm aggregate by 53.4%-77.5% and 12.3%-17.0%, respectively. The application of LAF significantly increased the content of soil water stable aggregates, and such effects were positively related with application amount. The content of soil water stable aggregate was the highest in the LAF1 treatment. 2) There was no significant difference in aggregate content of each particle size among LAF treatments, with the proportion of aggregate content of 2-0.25 mm particle size being the highest. 3) Compared with CK, all LAF treatments significantly increased the average weight diameter (MWD) and geometric mean diameter (GMD), and reduced the fractal dimension (D). LAF1 treatment had the highest MWD and GMD values, and had the strongest effect on the stability of soil aggregates. 4) Except for LAF4 treatment, the content of soil organic carbon in other LAF treatments was significantly higher than that in CK, and the content of soil organic carbon in LAF2 treatment was the highest. All LAF treatments increased the organic carbon content of soil aggregates with each particle size. LAF1, LAF2, and LAF3 treatments significantly increased the organic carbon of aggregates with particle size >2 mm. Particle size >2 mm had the highest contribution to the total organic carbon. The contribution rate of water stable large aggregate organic carbon to total organic carbon of LAF treatment was significantly higher than that of CK, which was all higher than 66.0%, and that of LAF1 treatment was the highest. In conclusion, the application of LAF enhanced the formation and stability of water stable aggregates and increased organic carbon content of aggregates in apple orchard soil, with the best performance of the full application. The application of LAF could be used as an effective measure to improve soil structure and fertility in apple orchard.

Nutrient Characterization in Soil Aggregate Fractions with Different Fertilizer Treatments in Greenhouse Vegetable Cultivation

Fertilization affects the formation and stability of soil aggregate, as well as the nutrient status of soil aggregate. However, the potential effect of compost on soil aggregate and its nutrient characteristics is still unclear. In view of this, we conducted a greenhouse vegetable cultivation experiment to evaluate soil water-stable aggregate (WSA) and its stability indices and aggregate nutrient stoichiometry characteristics at 0 to 20 cm soil depth with four treatments: (1) no fertilizer (CK), (2) chemical fertilizer (CF), (3) organic fertilizer (OF), and (4) chemical fertilizer plus organic fertilizer (CO). The results showed that the proportion of the 2 to 0.25 mm fraction was the greatest, followed by 0.25 to 0.053 mm, which accounted for 41.83 to 49.53% and 28.60 to 31.88% by weight, respectively. The mean weight diameter (MWD) value and the proportion of the >0.25 mm fraction in the CF, OF, and CO treatments were significantly higher than in the CK treatment. Within the fertilization treatments, the MWD and the proportion of the >0.25 mm fraction in the CO were significantly higher than those in CF and OF. Among all the aggregates, the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents were the highest in the fraction of 0.25 to 0.053 mm. The CF, OF, and CO treatments significantly increased the SOC, TN, and TP contents compared with the CK treatment. The SOC content of fractions >2 mm and 0.25 to 0.053 mm in the CO treatment was significantly higher than that of the CF and OF treatments, and the TN and TP contents in all the aggregates (except < 0.053 mm) were the highest in the CO treatment. The SOC, TN, and TP contents in the 2 to 0.25 mm and 0.25 to 0.053 mm components contributed greatly to the soil SOC, TN, and TP reserves. There was no noticeable difference in the nutrient stoichiometry of the soil aggregate between the different treatments. Redundancy analysis (RDA) revealed that the soil physicochemical factors, including SOC, TN, TP, and pH, significantly explained the stability of the soil aggregate. To summarize, chemical fertilizer combined with organic fertilizer positively affected the stability and nutrient accumulation of soil aggregates in greenhouse dryland.

Long-Term Forest Conversion Affects Soil Stability and Humic Substances in Aggregate Fractions in Subtropical China

Soil aggregates are the basic structural components of soil, which are important factors that can predict erosion resistance. However, few researchers have investigated the effects of forest conversion on the stability of soil aggregates, particularly in subtropical forests. In this study, soils from various depths (0 to 30 cm) were collected from four forest types (transformed from broadleaved forests (BMF) to combined coniferous broadleaved (CBMF), Chinese fir (FF), and bamboo forests (BF)) to determine the impacts of forest conversion on the physical and chemical properties of soil, water-stable soil aggregates, and aggregate-associated humic substances. The results showed that forest conversion had no effects on the soil’s physical properties, or the humic substances in bulk soil, but had significant effects on soil aggregates. In addition, the conversion of broadleaved forest to Chinese fir forest increased the soil stability, and to bamboo forest, decreased the soil stability. Finally, the soil’s physicochemical properties were closely related to aggregate-associated humic substances. In summary, specific forest management measures should be applied to strengthen the positive impacts and reduce the negative impacts associated with forest conversion.

The Combined Application of Mineral Fertilizer and Organic Amendments Improved the Stability of Soil Water-Stable Aggregates and C and N Accumulation

Soil aggregate stability is one of the important physical properties affecting rice (Oryza sativa L.) production and soil sustainability. This study was undertaken to evaluate the influence of different medium-term fertilization regimes on soil aggregate stability and aggregate-associated carbon (C) and nitrogen (N) in rhizosphere and bulk soil. This experiment consisted of three treatments, including mineral fertilizer alone (NPK), mineral fertilizer plus rice straw (NPK + RS), and controlled-release blended fertilizer plus cattle manure (CRF + CM). Although higher fertilizer costs were in the CRF + CM treatments, one-time application could save labor costs compared to the conventional split application of chemical fertilizers. The results showed that, compared to the NPK alone, the combined application of NPK with organic amendments improved the proportion of >0.25 mm macroaggregate, soil organic carbon (SOC), total nitrogen (TN) concentrations, and mean weight diameter (MWD) in both rhizosphere and bulk soil during the whole rice growing season. In rhizosphere, the proportion of macroaggregate was significantly positively (p < 0.01) correlated with root biomass while it had no significant correlation with SOC in the proportion of all sizes of aggregates. By contrast, bulk soil had a significantly (p < 0.01) positive relationship between the proportion of >2 mm class and organic C associated with smaller particle-sized aggregates (0.25–2 mm and <0.25 mm). In addition, the organic C associated with 0.25–2 mm showed the largest contribution of the total SOC content in all treatments during the rice growing stage. Overall, the results suggested that the medium-term application of mineral fertilizer with organic amendments was beneficial to improve soil aggregate stability and C and N accumulation.

Grazing altered soil aggregates, nutrients and enzyme activities in a Stipa kirschnii steppe of Inner Mongolia

Grasslands are a major biome on Earth, and their soils play a dominant role in the overall ecosystem functions and dynamics. Though the majority of global grasslands are used for grazing, the impact of grazing on soil structure and soil quality remains unclear due to large variations among grasslands. In this study, we assessed soil nutrient content, enzyme activities and soil aggregates at 0–30 cm depth under different grazing intensities, including a treatment of grazing exclusion. Heavy grazing reduced content of soil nitrogen, potassium, and soil urease and sucrase activities. While grazing increased the mechanical stability of soil aggregates, it reduced the water stability of soil aggregates. With increasing grazing intensity, water stability of the aggregates was correspondingly weakened, as was the erosion resistance of the soil. The soil urease activity, available soil nutrients, mean weight diameter by wet sieving (w-MWD), and geometric mean diameter by wet sieving (w-GMD) showed significant high sensitivity to grazing intensity in this Stipa kirschnii dominated grassland in Inner Mongolia. Overall, the soil quality at the heavy grazing site appeared poor compared with that at the light grazing site. For developing grazing management strategies, it is clear that heavy grazing should be avoided in this type of grasslands, albeit continued monitoring of soil structure is needed to explore the potential long-term consequences of the grazing.

Soil carbohydrate and aggregation as affected by carbohydrate composition of paper mill biosolids

Paper mill biosolids (PB) are recognized as a valuable source of carbon for the physical improvement of arable soils. However, little is known about the composition of carbohydrates of these materials and their breakdown in soil, which contributes to soil structural stability. The objectives of this study were to characterize the carbohydrates in PB and to determine under controlled conditions and in the field the soil carbohydrate content and water-stable aggregation. The field experiment consisted of PB applied every year (2000–2008) at 0, 30, and 60 Mg wet weight·ha−1 to annual row crops with soils collected after 3, 6, and 9 yr. The other experiment consisted of PB added at 50 Mg wet weight·ha−1 to two soils, a clay and a sandy loam, and incubated at 25 °C and 60% water-filled pore space for 16 wk. The PB differed in their content in galactose, mannose, and arabinose for total fraction and sum of carbohydrates for water-soluble fraction. In the field, repeated annual PB application increased most of soil total carbohydrates (sum and individuals) after 3 yr and the proportion of >1 mm stable aggregates. The incubation study confirmed results obtained in the field, where the PB richest in carbohydrates induced the highest increases in soil total carbohydrates in both soil types. Soil total and microbial (galactose and mannose)-derived carbohydrates were closely correlated with the percentage of large aggregates, while with water-soluble carbohydrates, they are highly correlated to the amount of microbial carbohydrates applied, thus further contributing to improve soil C quality.

An Environmentally Friendly Soil Amendment for Enhancing Soil Water Availability in Drought-Prone Soils

Applying soil amendments plays a critical role in relieving water stress in arid and semiarid areas. The natural clay mineral attapulgite (ATP) can be utilized to adjust the balance of water and soil environment. In this study, we investigated four different particle size distribution typical soils in the Loess Plateau: (1) lou soil (LS), (2) dark loessial soil (DS), (3) cultivated loess soil (CS), (4) sandy soil (SS). Five ATP application rates (0, 1%, 2%, 3%, and 4%) were selected to test the effect of ATP on the soil water retention curve, soil saturated hydraulic conductivity, and soil structure. The results showed that applied ATP significantly increased the soil clay content, and the relative change of SS with 3% ATP applied increased by 53.7%. The field water holding capacity of LS, DS, CS, and SS with 3% ATP applied increased by 8.9%, 9.6%, 18.2%, and 45.0%, respectively. Although applied ATP reduced the saturated hydraulic conductivity, the values of CS and SS were opposite when the amount of ATP applied was >3%. The relative change in the amount of 0.25–1 mm soil water-stable aggregates of SS was 155.9% when 3% ATP was applied. Applied ATP can enhance soil water retention and soil stability, which may improve limited water use efficiency and relieve soil desiccation in arid and semiarid areas or similar hydrogeological areas.

半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 半干旱黄土区植被恢复对土壤团聚体稳定性及抗侵蚀能力的影响 DOI: 10.5846/stxb202202090324 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省回国留学人员科研资助项目（2021-097）；山西省基础研究计划（20210302123333）；国家自然科学基金项目（41971129） Effect of vegetation restoration on stability and erosion resistance of soil aggregates in semi-arid loess region Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤水稳性团聚体强烈影响土壤过程和功能，是反映土壤质量和土壤抗侵蚀能力的重要指标。为探究半干旱黄土区植被恢复对土壤抗侵蚀能力的影响，以甘肃省定西市龙滩流域为研究区，选取3种恢复方式（天然荒草、自然恢复、人工恢复）7种植被类型（大针茅草地、长芒草草地、赖草草地、苜蓿草地、柠条灌丛、山杏林以及油松林）为研究对象，通过测定0-20 cm、20-40 cm和40-60 cm土壤水稳性团聚体，分析土壤团聚体组成、稳定性及抗侵蚀能力特征。结果表明：1）不同恢复方式不同植被类型间土壤水稳性团聚体稳定性差异显著（P<0.05），自然恢复方式的土壤水稳性团聚体平均重量直径显著高于天然荒草和人工恢复方式，且7种植被类型土壤大团聚体质量百分比均在67.97%-90.12%之间；人工恢复方式土壤水稳性团聚体稳定性较差，其中油松林稳定性最差。2）土壤团聚体破坏率和土壤抗侵蚀能力均表现出自然恢复方式更有利于土壤结构稳定性的提高。3）土壤水稳性大团聚体含量越高，土壤团聚体越稳定，土壤结构稳定性就越好；平均重量直径与土壤可蚀性因子K值呈极显著性负相关（P<0.01）。本研究结果表明自然恢复方式能够显著提高土壤团聚体的稳定性，从而提升土壤的抗侵蚀能力，建议当地在未来植被恢复规划中采取自然恢复方式更有利于生态恢复的有效进行。 Abstract:Soil water-stable aggregates strongly affect soil process and function, which is an important index to reflect soil quality and soil erosion resistance. In order to explore the effect of vegetation restoration on soil erosion resistance in semi-arid loess region, in this study, through three restoration methods (natural grassland, natural restoration, artificial restoration) and seven vegetation types (Stipa grandis grassland, Stipa bungeana grassland, Leymus secalinus grassland, Medicago sativa grassland, Caragana korsinskii shrub, Armeniaca sibirica forest and Pinus tabulaeformis forest) were selected in the Longtan catchment of Dingxi in Gansu Province. The composition, stability and erosion resistance characteristics of soil aggregates were analyzed by measuring 0-20 cm, 20-40 cm and 40-60 cm soil water-stable aggregates. The results showed that:1) there are significant differences in the stability of soil water-stable aggregates among different vegetation types and different restoration methods (P<0.05). The average weight diameter of soil aggregates in natural restoration grassland was significantly higher than that in natural restoration and artificial restoration vegetation, and the mass percentage of soil macroaggregates of the seven vegetation types was 67.97%-90.12%. The stability of soil water-stable aggregates under artificial restoration was poor, among which the stability of Pinus tabulaeformis forest was the worst. 2) The destruction rate of soil aggregates and the ability of soil erosion resistance showed that the natural restoration method was more beneficial to the improvement of soil structure stability. 3) The higher the content of water-stable macroaggregates in soil, the more stable the soil aggregate, the better the soil structural stability; there was a very significantly negative correlation between soil average weight diameter and soil erodibility factor K (P<0.01). The results of this study show that the natural restoration method can significantly improve the stability of soil aggregates, thus improving the soil anti-erosion ability, so as to improve the soil erosion resistance, suggested the plant in the future. 参考文献 相似文献 引证文献

陇东雨养苹果覆膜对土壤团聚体结构稳定性与细根分布的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 陇东雨养苹果覆膜对土壤团聚体结构稳定性与细根分布的影响 DOI: 10.5846/stxb202102190468 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31760555）；财政部和农业农村部：国家现代农业产业技术体系（GARS-27）；农业农村部西北地区果树科学观测实验站（S-10-18） Effects of film mulching on soil aggregate structure stability and fine root distribution of rain-fed apple in eastern Gansu Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:不同的果园管理方式可影响果树根系生长、分布与土壤团聚体稳定性、有机碳固存，进而改变"根-土"复合体响应关系。对西北陇东旱塬不同覆膜年限（2 a、4 a和6 a）苹果园表层土壤（0-20 cm）细根生长进行调查，并采用干筛法和湿筛法相结合的方式对土壤团聚体进行分级（>2 mm，0.5-2 mm，0.25-0.5 mm和<0.25 mm）。计算团聚体稳定性参数[> 0.25 mm机械稳定性团聚体含量（DR0.25）、> 0.25 mm水稳性团聚体含量（WR0.25）、平均重量直径（MWD）、平均几何直径（GMD）、团聚体破坏率（PAD）、水稳系数（WSC）]和团聚体有机碳含量。分析细根生长与土壤物理结构对长期覆膜的响应，探明土壤团聚体稳定性与有机碳固持关系，揭示黄绵土物理结构稳定机制。结果表明：6 a处理通过增加表层土壤黏粒和物理性黏粒比例，改变孔隙结构，抑制细根生长，其根量、根长和根表面积仅为对照（CK）的20.97%、24.66%和41.25%；降低表层土壤团聚体力稳性，其DR0.25、机械稳定性团聚体MWD和GMD仅为CK的82.2%、74.02%和59.38%；对水稳性团聚体的保护作用低于短期覆膜（2 a），其PAD和WSC为2 a处理的121.17%和54.56%。2 a处理可提高土壤团聚体的力稳性、水稳性和土壤团聚程度，使土壤结构得到改善。同时对机械稳定性、水稳性团聚体有机碳提升效果优于6 a处理，为6 a处理的115.66%和116.6%。大团聚体固持有机碳能力高于微团聚体，但由于长期覆膜团聚体稳定性的下降，6 a处理的DR0.25为CK的82.2%，不利于对有机碳的保护，使土壤有机碳水平对团聚体稳定性变异决定性仅为29.55%。连续覆膜引发的频繁干湿交替增加了黏粒对土壤结构稳定性的影响权重，促使表土"隐形"退化，抑制苹果细根在表层土壤中的生长、分布。2 a处理对土壤团聚体结构有良好的保护作用，促进土壤有机碳累积。 Abstract:Different orchard management methods can affect the growth and distribution of fruit roots, the stability of soil aggregates and the ability of organic carbon storage, and then change the response relationship of root-soil complex. The fine root growth of apple orchard surface soil (0-20 cm) with different plastic film mulching years (2 a, 4 a, and 6 a) was investigated in the dry tableland of Longdong, Northwest China. The combination of dry and wet screening methods was used to classify soil aggregates (>2 mm, 0.5-2 mm, 0.25-0.5 mm, and <0.25 mm). The aggregate stability index, including > 0.25 mm Mechanical stability aggregates content (DR0.25), > 0.25 mm water-stabled aggregates content (WR0.25), Mean weight diameter (MWD), geometric mean diameter (GMD), percentage of aggregate destruction rate (PAD), water stability coefficient (WSC), and the content of organic carbon were calculated. The response of soil physical structure and fine root growth to long-term film mulching was analyzed, the relationship between soil aggregate stability and organic carbon sequestration was explored, and the stability mechanism of physical structure of loess soil was revealed. The results showed that film-mulching six years inhibited fine root growth by increasing soil clay, the proportion of physical clay and changing pore structure, and the root weight, root length and root surface area were only 20.97%, 24.66% and 41.25% of conventional tillage (CK); The DR0.25, MWD and GMD of surface soil aggregates were 82.2%, 74.02% and 59.38% of CK; The protective effect of PAD and WSC were 121.17% and 54.56% of film-mulching two years, compared with that of short-term film mulching. Film-mulching two years improved the force stability and water stability of soil aggregates as well as the degree of soil aggregates, and improved the soil structure. At the same time, the organic carbon improvement effect of mechanical stability and water stability aggregates was better than that of film-mulching six years, which was 115.66% and 116.6% of film-mulching six years. Although the ability of large aggregates to hold organic carbon was higher than that of micro aggregates, due to the long-term stability decline of coated aggregates, the DR0.25 of film-mulching six years was only 82.2% of CK, which was not conducive to the protection of organic carbon, so that the decisive effect of soil organic carbon level on the stability variation of aggregates was only 29.55%. The frequent dry-wet alternation caused by continuous film mulching increased the influence weight of clay particles on soil structural stability, promoted the invisible degradation of the topsoil, and inhibited the growth and distribution of fine roots of apple in the topsoil. Film-mulching two years had a good protective effect on soil aggregate structure and promoted soil organic carbon accumulation. 参考文献 相似文献 引证文献

Evaluation of Soil Physico-Chemical and Biological Properties under Different Tea (Camellia sinesis) Gardens of Himachal Pradesh, India

Assessment of different soil attributes provides an insight into the soil-related constraints and potentials for sustainable agricultural planning. In the present investigation, 37 tea gardens were selected at random from tea growing areas of Himachal Pradesh during 2017-19 to evaluate the status of different soil attributes in surface (0-0.30 m) and sub-surface (0.30-0.60 m) soils. All the collected soil samples were analyzed for particle density, porosity, water stable aggregates, electrical conductivity, exchangeable Ca and Mg and microbial count as per standard procedures. The particle density, porosity and water stable aggregates in soils of tea gardens varied from 2.58 to 2.64 Mg m3, 39 to 57% and 26 to 58%. The electrical conductivity, exchangeable Ca and Mg were in the range of 85 to 210 dS m-1, 1.2 to 4.0 cmol (p+) kg-1 and 0.6 to 2.3 cmol (p+) kg-1 with a mean value of 134±35.8, 2.7±0.8 and 1.4±0.4, respectively. With regards to microbial count, the bacterial population ranged from 49 to 71 x 106 CFU, fungal population ranged from 36 to 69 x 104 CFU and actinomycetes population varied from 31 to 58 x 104 CFU.

Earthworm (Pheretima guillelmi)-mycorrhizal fungi (Funneliformis mosseae) association mediates rhizosphere responses in white clover

Earthworms and arbuscular mycorrhizal fungi (AMF) are beneficial organisms in the soil and play an important role in improving soil fertility and plant growth. The objective of this study was to analyze the response of single versus dual inoculation of earthworms (Pheretima guillelmi) and AMF (Funneliformis mosseae) on mycorrhizal growth, root morphology, and rhizosphere properties of white clover (Trifolium repens). Addition of earthworms significantly increased the degree of root AMF colonization, while decreased hyphal length and spore number in the soil. Single or dual inoculation of F. mosseae and P. guillelmi significantly increased root traits (total length, area, volume, and average diameter), soil phosphatase activities (acid, neutral, and alkaline), easily extractable and total glomalin-related soil protein content, the percentage of soil water-stable aggregates at the size of 2–4 mm, 1–2 mm and 0.5–1 mm, aggregate stability, Bray-P, and soil organic carbon (SOC) contents. Among them, the dual inoculation further amplified the effect on glomalin production, phosphatase activity, and aggregate stability, but did not show a superposition effect on root improvement, Bray-P, and SOC. Our study, hence, suggested that AMF and earthworms have synergistic roles in elevating rhizosphere properties vis-à-vis agronomic responses of white clover.

Impact of Chitosan on Water Stability and Wettability of Soils.

Chitosan has become increasingly applied in agriculture worldwide, thus entering the soil environment. We hypothesized that chitosan should affect the water stability of soil. Since this problem has not been studied to date, we examined, for the first time, the influence of chitosan on the water stability and wettability of soil aggregates. The aggregates were prepared from four soils with various properties amended with different amounts of two kinds of powdered chitosan, and subjected to 1 and/or 10 wetting–drying cycles. The water stability was measured by monitoring air bubbling after aggregate immersion in water, and the wettability was measured by a water drop penetration test. The biopolymer with a lower molecular mass, lower viscosity, and higher degree of deacetylation was more effective in increasing the water stability of the soil than the biopolymer with a higher molecular mass, higher viscosity, and lower deacetylation degree. After a single wetting-drying cycle, the water stability of the soil aggregates containing chitosan with a higher molecular mass was generally lower than that of the soil; after ten wetting–drying cycles, the water stability increased 1.5 to 20 times depending on the soil. The addition of low-molecular-mass chitosan after a single wetting-drying cycle caused the water stability to become one to two hundred times higher than that of the soil. A trial to find out which soil properties (pH, C and N content, bulk density, porosity, and particle size distribution) are responsible for the effectiveness of chitosan action was not successful, and this will be the objective of further studies.

Saturated hydraulic conductivity and water-stable aggregates in some forest reserves of South western Nigeria

A study was carried out along a toposequence in three forest reserves under Teak and Gmelina of Osun Grove, Onigambari, and Omo in south Western Nigeria to evaluate changes in saturated hydraulic conductivity (Ksat) and percent soil water-stable aggregates (WSA%). Three points: upper slope, middle slope, and lower slope were delineated and samples for soil analysis were collected from pedogenetic horizon using core samplers and auger. Samples were analyzed for soil properties like; Ksat and WSA (%) Data from the analysis were subjected to ANOVA using GenStat and means were separated using Duncan’s multiple range test at P &lt;0.05. Results indicated that there were significant differences in the saturated hydraulic conductivity both under teak and Gmelina plantation along toposequence at Onigambari and Osun grove. But at area J4, upper slope subsurface soil under Gmelina plantation and lower slope surface soil were superior to other slope segments. Meanwhile, middle slope subsurface soil and upper slope surface soil under teak plantation were significantly different from other slope positions. The structural stability and erosion resistance of the soil in area J4 were higher than those of the soil in the Onigambari and Osun sacred grove.

The impact of agricultural land afforestation on soil water content in Central Bohemia

In the Czech Republic, the afforestation of agricultural land has been supported by providing subsidies from the government and the European Union. Afforestation of less-productive agricultural land provides many benefits including carbon sequestration, soil erosion control, biodiversity, water retention, cooling, social benefits, decreasing noise and light pollution, increasing air quality, wind speed reduction, oxygen production, wood production and non-wood products. In some aspects, it is possible to produce wood of the same quality on former agricultural land compared to permanent forest land. In this study, we attempted to find out the course of temperatures and volumetric water content as well as some other physical soil properties (at depths of 20, 40 and 60 cm) 9 years after the afforestation of agricultural land (warm, mild dry region of the Czech Republic) with a mixture of broadleaved tree species (Quercus robur L., Quercus rubra L. and Acer platanoides L.) or monospecific Pinus sylvestris L. stand; the study was performed in the period from April to the beginning of November 2020. Concerning the studied physical soil properties, the value of bulk density was higher (and total porosity lower) at a depth of 20 cm in Pinus sylvestris L. compared with agricultural land or the mixture of broadleaves; the water stability of soil aggregates was higher after the afforestation with the mixture of broadleaves. The temperature was lower in the soil of afforested plots (at all studied depths) compared to the agriculturally used land. Differences in rainfall interception, transpiration, soil&lt;br /&gt;(and forest floor) properties and other factors could influence the obtained values of water content in the soil of the studied plots. The average volumetric water contents were the highest in the plots with Scots pine (depth of 20 cm) and broadleaves (depth of 40 cm), and on the control plot (depth of 60 cm). The volumetric water content at a soil depth of 20 cm was not significantly (P &amp;gt; 0.05) different when the plot with Scots pine and agriculturally used land were compared. In all other cases and depths, the differences between plots were significant (P &amp;lt; 0.05).

Distribution characteristics and stability of soil aggregates as compounded by soft rock and sand under different planting years of corn in Mu Us sandy land in China

Field plot experiments of compound soil mixing with soft rock and sand with ratios of 1 : 1, 1 : 2 and 1 : 5 during 2010-2018 years of corn cultivation in Mu Us Sandy Land in china., was carried out to observe the change characteristics of composition, distribution and mean weight diameter (MWD) of compound soil water stable aggregate (WSA) under different corn planting years. The results showed that with the increase of planting years, the content of WSA in composite soils of three portions with a particle size of &lt; 0.25 mm gradually decreased, and WSA with a particle size of &gt; 0.25 mm showed a continuous increasing trend. The WSA with a particle size of 0.25 - 0.5 mm accounted high for the maximum ratio, which plays an important role in the agglomeration of the compound soil. After 9 years of planting, the MWD of 1 : 1, 1 : 2 and 1 : 5 compound soil WSA increased by 1.13, 1.85 and 1.58 times, respectively, and t 1:2 compound soil WSA with particle size &gt; 0.25 mm and MWD increase at a faster rate, which lead to a higher soil agglomeration and stability. The interaction between the mixture ratio of soft rock to sand and the planting years of corn has a significant impact on the formation and stability of WSA in the compound soil. With the increase of planting years of corn, the agglomeration effect of compound soil in different proportions was found to enhance, and the development of soil structure improve continuously. Bangladesh J. Bot. 50(3): 917-923, 2021 (September) Special

Effects of different nitrogen application rates on soil water stable aggregates and N2O emission in winter wheat field.

Excessive nitrogen application would deteriorate soil structure and increase greenhouse gas emission. We set up six treatments, i.e., N0, N120, N180, N240, N300and N360(nitrogen application rates of 0, 120, 180, 240, 300 and 360 kg·hm-2, all straws returned into the field in situ) in the nitrogen fertilizer experimental site to investigate the effects of different nitrogen application rates on soil N2O emission, soil water-filled porosity (WFPS), soil temperature, nitrate and ammonium contents, composition and stability of water stable aggregates in winter wheat filed in 2018-2020. The results showed that there was a significant positive correlation between soil N2O emission and nitrogen application rate. There was no correlation between WFPS and nitrogen application rate. Soil temperature in the 0-10 cm layer decreased significantly with the increases of nitrogen application rates. There was a significant positive correlation between nitrate and ammonium contents and nitrogen application rate. With the increases of nitrogen application rates, the content of water stable aggregates with diameter &gt;2 mm decreased, while that of water-stable aggregates with diameter &lt;0.5 mm increased. The particle size of soil water-stable aggregates also decreased gradually. There was a significant negative correlation between nitrogen application rate with mean weight diameter (MWD) and geometric mean diameter, while no correlation with fractal dimension. The fitting equation between MWD and N2O emission flux was y=3928.3e-2.171x (R2=0.55, P&lt;0.001), indicating that N2O emission increased markedly as MWD decreasing. The increases in nitrogen application rate reduced soil temperature in the 0-10 cm layer, increased nitrate and ammonium contents, decreased the average particle size of soil water stable aggregates, and the stability of soil aggregates, and increased soil N2O emission.

The Effects of Crops Together with Winter Cover Crops on the Content of Soil Water-Stable Aggregates in Organic Farming

The stability of the soil aggregates is an important soil quality indicator, as it affects the soil’s overall functionality. As the soil aggregates are highly affected by agricultural practices, it is essential to know how crops interact with the aggregation process. Therefore, for obtaining more knowledge, this research was conducted in Estonia in an organic crop rotation field experiment from 2012/2013 through 2015/2016 to study the effects of crops (potato → spring barley undersown with red clover → red clover → winter wheat → pea) under different treatments (TC—control; TW—winter cover crops; TW+M—TW with farmyard manure 40 Mg ha−1 per crop rotation). The results showed that in the topsoil (5–10 cm), the soil water-stable aggregate (WSA) content (determined by the wet sieving method) from highest to lowest was following: pea (61.7%), winter wheat (61.6%), spring barley (61.5%), red clover (59.3%), potato (57.1%); whereas in the subsoil (30–35 cm): potato (50.6%), pea (48.5%), red clover (47.9%), spring barley (47.7%), winter wheat (46.4%). Therefore, potato was a noticeable crop, as among the crops, it had the lowest WSA content in the topsoil, while highest in the subsoil. The results shown gave an assumption that the after-effects of some crops (foremost with pea) were noticeable in the soil properties during the following crop. In the topsoil, the differences between crops were significant among crops just for TW and TW+M treatments. In TW, potato was lower than spring barley and winter wheat, but not significantly lower than pea or red clover. In the subsoil, significant differences between crops were observed for TC and TW treatments: in TC, potato was just significantly greater than red clover (but similar to other crops), and in TW, significantly greater than winter wheat. Furthermore, in the topsoil the soil organic carbon (SOC) content was not significantly affected by crops, and the use of winter cover crops generally increased the SOC content while concurrently decreased the WSA content and the soil maximum water holding capacity. This was probably caused by the additional tillage operations which cancelled out the possible benefits for the soil aggregates. As a consequence of the constantly declining SOC content, caused by the weakened soil aggregates, the plant-available P and K contents, especially in the absence of manure applications, decreased as well, probably due to the combination of fixation and removal of plant biomass. Therefore, it is expected that by continuing this trend, the plant growing conditions decline, which in turn will have a negative effect for the aggregate formation and carbon sequestration, which are essential for plant growth.

Effects of biochar and straw application on the soil structure and water-holding and gas transport capacities in seasonally frozen soil areas

To explore the effects of different regulation modes on the soil structure and gas transport characteristics in seasonal permafrost regions, freeze-thaw cycles (FTCs) were used as boundary conditions and three typical soils on the Songnen Plain were used: black soil, baijiang soil and meadow soil. Four treatments were established: biochar addition (B1), straw addition (S1), biochar combined with straw addition (B1S1) and an untreated control (CK). The changes in the proportion of soil water-stable aggregates, total soil porosity (TP), soil water characteristic curves (SWRCs), soil dissolved organic carbon (DOC) and soil air permeability (PL) were analyzed. The results showed that biochar and straw influenced the structure of the three soil types. The proportions of large (2–0.5 mm) and medium (0.5–0.25 mm) aggregates increased significantly. The soil aggregate stability indexes of the treated soils were better than those of the CK, and the three-phase ratios of the treated soils were closer to ideal. The different treatments had particularly obvious effects on the black soil; the generalized soil structure index (GSSI) values reached 95.59, 94.36 and 98.74 in the B1, S1 and B1S1 treatments, respectively. An interaction effect was observed between biochar and straw. B1S1 had a stronger effect than the other treatments, and the soil water holding capacity was significantly improved (FC = 0.317 cm3 cm−3). Under the B1S1 treatment, the DOC contents in black soil, baijiang soil and meadow soil were 160.78 mg/kg, 272.828 mg/kg and 271.912 mg/kg, respectively. Moreover, biochar and straw combined effectively reduced PL fluctuations under FTCs and improved the long-term stability of the soil structure. These results can aid in rational straw and biochar use to achieve comprehensive agricultural waste utilization.

Exogenous Glomalin-Related Soil Proteins Differentially Regulate Soil Properties in Trifoliate Orange

Glomalin-related soil protein (GRSP) is a specific glycoprotein secreted into the soil by hyphae and spores of arbuscular mycorrhizal fungi that have many potential functions. It is not clear whether exogenous GRSP has an effect on plant growth and soil properties or whether the effects are related to the type of GRSP used. In this study, trifoliate orange (Poncirus trifoliata L. Raf.) seedlings were used to analyze the effects of easily extractable GRSP (EE-GRSP) and difficultly extractable GRSP (DE-GRSP) at a quarter-, half-, and full-strength concentration on shoot and root biomass as well as soil properties The results showed that, at different strengths, exogenous EE-GRSR significantly increased shoot and root biomass compared to the control, which displayed the most significant effects from the half-strength EE-GRSP. In contrast, DE-GRSP, at various strengths, significantly reduced shoot and root biomass. Furthermore, the application of exogenous EE-GRSP stimulated soil water-stable aggregate (WSA) content at 2–4 mm and 0.5–1 mm sizes, while DE-GRSP strongly reduced WSA content at the 2–4 mm, 1–2 mm, 0.5–1 mm, and 0.25–0.5 mm sizes, consequently leading to an increase or decrease in the WSA stability, according to the mean weight diameter. However, exogenous EE-GRSP decreased soil pH and DE-GRSP increased it, which was related to WSA stability. Exogenous EE-GRSP almost significantly increased soil acidic, neutral, and alkaline phosphatase activity at different strengths, while exogenous DE-GRSP, also at different strengths, significantly inhibited soil acidic phosphatase activity. The application of both exogenous EE-GRSP and DE-GRSP increased the organic carbon content of the soil. This study concluded that exogenous GRSP exerted differential effects on plant biomass and soil properties, and EE-GRSP can be considered as a soil stimulant for use in citrus plants. To our knowledge, this is the first report on the negative effects of exogenous DE-GRSP on plant biomass and soil properties.

Effectiveness of grassland crop rotation in the submontane area of the Republic of North Ossetia Alania

In conditions of the submontane zone of The Republic of North Ossetia Alania the investigated cultures of grassland crop rotation made positive effect on structurally-aggregate properties of soil, water stability of soil aggregates, and also on fruitfulness and energetic potential of cultivated crops. The most favorable impact on soil structure was made by clover and winter wheat, which are having more lengthy periods of vegetation, well developed root system, ensuring the better protection of soil in autumn and spring from the destructive effect of atmospheric precipitation. Intertilled cultures had low evaluation in this context. The capacity for structure formation is more weakly expressed in potatoes. In result of research it was revealed that the soil under study has good structural condition because it contains from 52.1 to 55.8% of water-stable aggregates. It was established that the weight by volume kept changing in all cultures of crop rotation. By the end of vegetation, the tendency of increasing weight by volume has been observed practically in all variants. In general, the average soil density under all cultures has been optimal during the whole period of research. The maximum output of feed units was marked among the following options: oat + clover – 9.83 t/ha, clover – 9.49 t/ha, corn – 9.49 t/ha. The more quantity of digested protein was contained in the crop of clover, for the rest of the cultures the index was approximately at the same level. The grass rotation where the pickup of feed units and digested protein was credibly exceeding the indices of intertilled rotation, was the more fruitful (7.96 t/ha – rotation grass and 6.33 t/ha – intertilled rotation).