Increased Soil Bulk Density Research Articles

Effect of Sod Production on Physical, Chemical, and Biological Properties of Soils in North and South China

Lawns play a vital role in urban development, but the impact of sod production on soil properties has always been controversial. In this study, we examined the physical, chemical, and biological properties of sod production bases across different regions and years [including northern China (2.5, 3, 5, 6, 8, 10, 12 years), referred to as N-2.5, N-3, etc., and southern China (3, 10, 11, 14, 17 years), referred to as S-3, S-10, etc.], with tall fescue and Kentucky bluegrass planted in the north and bermudagrass or creeping bentgrass planted in the south. Sod production was found to increase soil bulk density while reducing porosity and field capacity, but these effects did not consistently intensify with longer production periods. Except for available phosphorus and available potassium, other soil nutrients (total carbon, total nitrogen, organic matter, alkali-hydrolyzable nitrogen, etc.) were either unaffected or increased at certain time points (S-11, S-14). Prolonged sod production (S-10, S-17) also boosted microbial content. In northern regions, organic matter and total nitrogen were the key factors influencing microbial community structure, whereas in southern regions, alkali-hydrolyzable nitrogen, electrical conductivity, available potassium, and organic matter were most influential. We also found that crop rotation, sand mulching, and deep plowing could enhance soil nutrient content and microbial activity in sod production.

Synergistic co-evolution of rhizosphere bacteria in response to acidification amelioration strategies: impacts on the alleviation of tobacco wilt and underlying mechanisms.

Soil acidification represents a severe threat to tobacco cultivation regions in South China, exacerbating bacterial wilt caused by Ralstonia solanacearum. The comprehension of the underlying mechanisms that facilitate the restoration of rhizosphere microbial communities in "healthy soils" is imperative for ecologically managing tobacco bacterial wilt. This study focuses on acidified tobacco soils that have been subjected to continuous cultivation for 20 years. The experimental treatments included lime (L), biochar (B), and a combination of lime and biochar (L+B), in addition to a control group (CK). Utilizing rhizosphere biology and niche theory, we assessed disease suppression effects, changes in soil properties, and the co-evolution of the rhizosphere bacterial community. Each treatment significantly reduced tobacco bacterial wilt by 16.67% to 20.14% compared to the control group (CK) (p < 0.05) and increased yield by 7.86% to 27.46% (p < 0.05). The biochar treatment (B) proved to be the most effective, followed by the lime-biochar combination (L+B). The key factors controlling wilt were identified through random forest regression analysis as an increase in soil pH and exchangeable bases, along with a decrease in exchangeable acidity. However, lime treatment alone led to an increase in soil bulk density and a decrease in available nutrients, whereas both biochar and lime-biochar treatments significantly improved these parameters (p < 0.05). No significant correlation was found between the abundance of Ralstonia and wilt incidence. Nonetheless, all treatments significantly expanded the ecological niche breadth and average variation degree (AVD), enhanced positive interactions and cohesion within the community, and intensified negative interactions involving Ralstonia. This study suggests that optimizing community niches and enhancing pathogen antagonism are key mechanisms for mitigating tobacco wilt in acidified soils. It recommends using lime-biochar mixtures as soil amendments due to their potential ecological and economic benefits. This study offers valuable insights for disease control strategies and presents a novel perspective for research on Solanaceous crops.

Impact of winch-assisted logging machinery on soil disturbance in the mountainous forests of Western Carpathians

IntroductionTimber harvesting on steep terrain is a challenge in terms of economic viability, safety, and environmental performance. Felling with chainsaws and use of yarders seems optimal in this environment. However, using mobile traction winches allows for the safe work of ground-based technologies even in these challenging conditions.MethodsOur study assessed the impact of winch-assisted cut-to-length harvesting on soil disturbance in young forest stands (up to 40 years old) across slopes of 14.9°-27.4° (27–52%). Utilizing 78 measurement points (i.e., 234 measurements), we analyzed soil samples from trail ruts, between ruts, and undisturbed areas for soil bulk density (g.cm−3) and soil moisture content (%), simultaneously measuring penetration resistance (MPa), penetration depth (cm) and rut depth (cm).ResultsThe results highlighted that areas without winch assistance experienced the most significant increases in soil bulk density (up to 22.35%) and penetration resistance (up to 26.8%), though these differences were not statistically significant. Linear mixed effects models did not confirm a significant effect (p &amp;gt; 0.05) of a traction winch on the soil bulk density (g cm−3) and penetration resistance (MPa) in the ruts of the forwarding trails. Mean forwarding trail profile depths ranged from 4.63 to 7.28 cm, with the maximum depths between 10.86 and 17.25 cm, showing deeper ruts in non-assisted areas. Moreover, the presence of the traction winch (p &amp;lt; 0.05) significantly affected the maximal depth of the forwarding trail rut.ConclusionThe findings suggest that winch-assisted harvesting may mitigate soil disturbance (rut depths) on steep slopes, offering a sustainable option for utilizing ground-based machinery with reduced environmental impact.

Effect of frequent clearcutting on some soil properties, temperatures, and herbaceous vegetation and the potential of their recovery in a short time.

Harvesting or degradation of forest ecosystems directly affects the microclimate, causing changes in air and soil temperatures and soil moisture in the forestlands. The objectives of this study were to investigate the effect of frequent clearcutting of forest cover on some selected soil properties, ambient and soil temperatures, soil moisture, and herbaceous vegetation cover and determine their recovery in a short period in the area subject to frequent clearcutting under the powerline corridors (PLCs). The study was conducted in the research forest of Istanbul University-Cerrahpaşa, Faculty of Forestry. The treatment plots were selected from the clearcut area, and control plots were selected from an untouched oak-hornbeam forestland. Soil temperature and moisture and maximum and minimum ambient temperatures were measured in the treatment and control plots between 2020 and 2021 and topsoil sampled between 2019 and 2021. Data were analyzed using analysis of variance (ANOVA) to test the effects of clearcutting on some selected soil properties in the short term after cutting. Clearcutting caused a significant increase in soil bulk density (BD) and a decrease in the soil total porosity (TP), soil hydraulic conductivity (HC), and saturation capacity (SC). Forest cover removal significantly decreased the soil organic matter (SOM) content by 3%, increased average soil temperature by 2.1°C, and the difference between maximum and minimum temperatures by 8.8°C. Additionally, clearcutting reduced the average soil moisture from 36 to 35%. The findings revealed that clearcutting negatively affected some hydro-physical soil properties and soil microclimate conditions that may not recover to their previous states within the next few years.

Residual plastic film decreases crop yield and water use efficiency through direct negative effects on soil physicochemical properties and root growth

Film mulching has been extensively used to improve agricultural production in arid regions of China. However, without sufficient mulch film recovery, large amounts of residual film accumulated in the farmland, which would affect crop yield and water use efficiency (WUE). In order to comprehensively analyze the effects of residual film on crop yield and WUE, and clarify its influencing mechanism, present study adopted a meta-analysis to systematically evaluate the impacts of residual film on soil physicochemical properties, crop root growth, yield, and WUE. The results showed that residual film significantly increased soil bulk density and the soil moisture content in 0–20 cm soil layer, but decreased soil porosity, soil organic matter, soil total nitrogen content, and soil moisture content in >20 cm soil layer, especially when residual film amount was >400 kg ha−1. Residual film significantly reduced crop root dry weight, root length, root diameter, root volume and root surface area. Generally, crop yield and WUE decreased with the increase of residual film amount; and crop yield was reduced by about 14.00 % when the residual film amount increased by 1000 kg ha−1. In average, crop yield and WUE under film residual condition were significantly decreased by 13.46 % and 9.21 %, respectively. The negative effects of residual film on root growth, yield and WUE were greater for cash crops (cotton, tomato and potato) than for cereal crops (wheat, maize). The structural equation model indicated that residual film generated indirect negative effects on crop yield and WUE by directly affecting soil physicochemical properties and crop root growth, with the standard path coefficients of −0.302 and − 0.217, respectively. The results would provide a theoretical basis for reducing residual film pollution on farmland and promoting the green and sustainable development of agriculture.

Risk assessment of soil compaction due to machinery traffic used in infield transportation of sugarcane during mechanized harvesting

Soil stress imposed by tire-soil contact from transshipment vehicles used in mechanized sugarcane harvesting results in increase in the degree of compactness. In this study we aimed to: (i) estimate the magnitude and propagation of vertical stress into soil caused by sugarcane transshipment wheeling; and (ii) assess the risk and occurrence of soil compaction in an Oxisol of southeastern Brazil. Three tractor-trailers with a carrying capacity of 10, 21, and 30 Mg, and an autonomous truck-trailer with a carrying capacity of 20 Mg were evaluated as field traffic treatments. For each treatment, magnitude and distribution of vertical soil stress (σz) and soil strength (precompression stress, σp) were predicted by modeling estimation and risk of compaction was assessed by σp/σz relationship. The occurrence of soil compaction was evaluated based on measured changes in the bulk density and macroporosity (equivalent pore diameter > 50 μm) up to 0.70 m deep after wheeling. Estimates indicated that the autonomous truck applied stresses that reached 595 kPa at the soil surface beneath the centerline of the tire, imposing the greatest risk of compaction up to a depth of 0.35 m depth. The stresses at the soil surface beneath the centerline from the tractor-towed trailer tires ranged from 275 to 279 kPa, imposing a risk of compaction that did not exceed 0.29 m depth. All assessed transshipment configurations promoted soil compaction, detected by increases in the soil bulk density and decreases in the macroporosity, even at greater depths where risk prediction had not alerted to the soil compaction. The most significant impact on soil compaction was observed for the autonomous truck-trailer and the tractor-towed trailer with a carrying capacity of 30 Mg, also affecting subsoil, as evidenced by a relative increase in soil bulk density of 5 % and 7 % in the 0.30−0.50 m and 0.50−0.70 m layers, respectively, and a relative reduction in macroporosity of 40 % and 50 % in these same soil layers.

Responses of soil microbial community activities and soil physicochemical properties to coal fly ash soil amendment

BackgroundHundreds of millions of tons coal fly ash are produced annually to support economic development and industrial production. However, directly applying coal fly ash to agricultural production can decrease the land productivity and pose a threat to the ecosystem due to the poor physicochemical properties and seriously heavy metal pollution.MethodsIn this study, a field experiment to investigate the effects of coal fly ash as a soil amendment was conducted in Hebei province, China. The coal fly ash (CFA) soil field was mixed with the carrier soil (CS, without containing coal fly ash) at different rates (0–40% mass content) in the 0–20 cm layer of top soil and then mixed with a rotovator. The soil was then amended with 0.45–1.80 kg·m− 2 of G1 soil amendment for planting corn.PurposeThe purpose of this study is to investigate the response mechanism of soil microbial community activities, and soil physicochemical properties to soil amendment and carrier soil in coal fly ash soil.Key resultsThe study found that the G1 amendment, which consisted of humic acid, polyacrylamide, zeolite powder, and FeSO4·7H2O, improved the soil chemical properties and physical structure by increasing soil bulk density and macroaggregates. The highest corn yield was observed in B5 (20% CS and 1.3500 kg·m− 2 G1). Meanwhile, the abundance of microorganisms that facilitate the circulation of soil nutrients such as Acidobacteria (77.05%), Sphingomonas (25.60%), Nitrospira (20.78%), Streptomyces (11.32%), and Gaiella (10.20%) was increased.ConclusionsOverall, our results indicate that the use of coal fly ash soil as a amendment can enhance soil sustainability by improving soil microbial functions. These findings provide a reference for the development and application of coal fly ash soil amendments.

Dairy cattle grazing compacts soil surface without reducing subsequent crop yield

Integrated crop-livestock systems are being increasingly used to intensify food production and make it more sustainable. On the other hand, most studies have focused on extensive systems. This paper analyzed the effects of different managements on soil and plants in an intensive integrated system for milk production. An experiment of management systems was installed in southern Brazil, Rio Grande do Sul, on a Latossolo Vermelho (Oxisol), in 2015 to evaluate: rotational grazing of dairy cows in the winter; rotational grazing of dairy cows in winter followed by soil chiseling; and ungrazed area (control). Soil physical properties and yields of crops were evaluated. Trampling by dairy cows increased soil bulk density by 24 % (0.0-0.05 m), but did not influence yields of subsequent soybean or maize. Chiseling reduced the bulk density of the uppermost layer by 19 %, but did not affect the yields of subsequent crops. It was concluded that in years with abundant water, dairy cattle grazing in an integrated crop-livestock system in Southern Brazil compacts the soil surface, but does not compromise the soil physical processes related to the growth and development of subsequent crops.

Short‐term effects of double‐layer ploughing reduced tillage on soil structure and crop yield

AbstractSoil tillage is widely acknowledged to affect soil characteristics and agricultural productivity. This research investigates the short‐term effects of various tillage methods on soil physical properties and crop yields at a Central German field site with a dry climate (mean temperature 9.5°C; annual precipitation 470 mm). Three tillage approaches were evaluated: conventional plough tillage (25 cm depth), cultivator tillage (18 cm depth), and double‐layer plough tillage (15 and 30 cm depth). We assessed soil physical properties through standard laboratory analyses, compression tests, soil pore structure via X‐ray computed tomography (X‐ray CT) and crop yields over 3 years. The results indicate that cultivator tillage approach increased soil bulk density relative to conventional tillage, especially in the second year, though this effect diminished over time. Double‐layer plough tillage emerged as a viable short‐term alternative to conventional tillage, achieving comparable soil bulk density. Saturated hydraulic conductivity values were generally higher for soils under conventional tillage or double‐layer plough tillage than for cultivator tillage, highlighting their soil loosening effect. Classical soil analysis methods combined with X‐ray computed tomography provided valuable insights into tillage induced changes to soil structure. Cultivator tillage resulted in a distinct pore structure with reduced macroporosity and pore connectivity. Despite notable soil property variations, crop yields remained consistent across the tillage methods. Overall, double‐layer plough tillage presents a sustainable option, moderately improving soil physical properties while maintaining crop yields. This study highlights the need to assess the short‐term effects of tillage on soils and contributes to the broader dialogue on optimizing tillage strategies for effective soil management and crop production.

Land use legacies affect early tropical forest succession in Mexico

AbstractQuestionsAgricultural expansion is one of the dominant drivers of forest and biodiversity loss, and shifting cultivation is the most widely used form of agriculture in many tropical forest regions. Where forests have been cleared, they have the potential to recover once the land is abandoned. However, legacies of land use are often overlooked in successional studies, and a deeper understanding of this legacy effect is needed to define efficient restoration practices using natural or assisted regeneration. Here, we analysed how land‐use history affects soil properties and early succession on abandoned agricultural fields in two contrasting Mexican socio‐ecological systems.LocationMexico, Oaxaca and Chiapas.MethodsWe sampled soil and monitored vegetation for 2 years after agricultural abandonment, and interviewed landowners about their land‐use practices.ResultsLand‐use practices were clearly influenced by landowners’ social context (residence time, rural or urban origin), and topography and soil type also constrained or facilitated land‐use practices. Soil characteristics were strongly affected by three land‐use practices: mechanical tillage decreased soil N and K; frequent herbicide and pesticide use increased N and K; and for pasture systems, stocking density increased soil bulk density and decreased pH and N. High‐intensity land management practices, specifically use of machinery, had the highest impact on early forest succession. When machinery was not used, the frequency of land‐use practices, particularly weeding frequency, is the main factor influencing tree cover and sapling diversity.ConclusionsTo facilitate post‐agricultural forest recovery, we recommend restoration efforts using natural regeneration in areas with low previous land‐use intensity and frequency.

The effect of paraquat dichloride and carbosulfan on soil conditions and population dynamic of soil microbes in a cornfield: a case study in Sumedang, West Java

Paraquat dichloride (PC) is one of the herbicides active ingredients that is widely used by farmers to control various types of weeds, while carbosulfan (CS) is one of the insecticide’s active ingredients that is widely used to control various types of insect pests. The objective of this study is to analyze the impact of pesticides for PC and CS on the chemical and physical conditions of the soil and the dynamics of fungi and soil bacteria population in a corn field in Sumedang district, West Java. The experiment took place between August and October, during the dry season, concluding just as the rainy season began. The PC concentrations used were 0 mL/L, 3.33 mL/L, 4 mL/L, 4.66 mL/L and 5.33 mL/L, while the CS concentrations used were 0 mL/L, 0.5 mL/L, 1 mL/L, 1.5 mL/L and 2 mL/L. Soil sampling was conducted before and after the application of pesticides. The total abundance of fungi and bacteria was analyzed using the total plate count (TPC) method. The application of PC to the cornfield slightly decreased soil bulk density from 1.354 g/cm3 to 0.816 g/cm3, while the application of CS slightly increased soil bulk density. A decrease in bulk density is considered positive for the physical conditions of the soil for plant cultivation. In general, the result indicated that the application of PC and CS did not show a significant effect on the chemical characteristics of the soil, and also it did not affect the population of fungi and bacteria. Weather conditions, i.e. dry season (June-September) and rainy season (started from October) seem to affect more on soil conditions as well soil microbial population than the application of the pesticides.

Visual evaluation of soil structure is a reliable method to detect changes in the soil quality of Colombian Amazon pasturelands

AbstractThe visual evaluation of soil structure (VESS) is an affordable and easy‐to‐use method for assessing soil quality that could help in the early detection of soil quality changes in pasturelands of less developed countries where ranchers cannot afford quantitative soil studies. Here, we assessed the soil quality of three pasture areas in the Colombian Amazon region using the VESS method and tested its suitability through a correlation analysis with key physical and biochemical soil indicators of quality measured at the same study locations. Moreover, by integrating all assessed soil indicators, we determined a soil quality index (SQI) to correlate with VESS scores. A forest area was used as a reference to evaluate changes in soil indicators and soil quality due to pasture use for &gt;25 years. Our results revealed high VESS scores, indicating poor soil quality in pasture areas and suggesting a compaction process that starts at 6.5 cm soil depth, corroborated by increases in soil bulk density, soil resistance to penetration, and reduction in soil porosity. Soil C and N contents were 35% and 33% lower in pasture than forest. This same pattern was observed in the geometric mean of the enzymatic activity. The VESS scores were significantly correlated with most of physical and biochemical soil indicators and with the overall SQI, demonstrating the ability of VESS to integrate and reflect attributes related to the essential physical, chemical, and biological functioning of soils from the Colombian Amazon region, becoming a useful tool for detecting signs of soil quality degradation in pasturelands.

Woody debris removal modifies carbon stocks and soil properties in a fragmented tropical rainforest

AbstractWe examined whether and how woody debris removal for domestic fuel affects carbon storage and soil properties in an Indian rainforest. Fuelwood removal reduced aboveground carbon stocks, increased soil bulk density, and possibly reduced soil phosphorus stocks. Equitably balancing this subtle trade‐off between climate‐regulating and vital, widely utilized provisioning functions, is a challenge for tropical forest research and management.

Developing crown width model for mixed forests using soil, climate and stand factors

Abstract The tree crown is a useful measure of tree vigour and is highly relevant to a tree's environmental adaptability. Crown allometry depends on environmental and stand conditions. Several studies have focussed on the effects of climate change and competitive intensity on the crown, but the regulatory role of soil resources and diversity on crown allometry and carbon allocation has been neglected. Data from 20,994 trees in 232 mixed forests collected between 2011 and 2019 were located near four major mountain ranges in northeast China. The proposed crown width model includes the stand developmental stage, soil, climate, competition intensity, species mixture, species diversity, structural diversity and their interactions. We observed that the cross‐species allometric scaling exponent does not conform to the universal scaling law. Our results showed that crown width increased with increasing soil bulk density, quadratic mean diameter and coefficient of diameter variation but decreased with increasing de Martonne aridity index, basal area, Simpson index and species mixture. The interaction between quadratic mean diameter and soil bulk density had a significant negative effect on crown width. The influence of a particular factor within the interaction term on crown width was modulated by the gradients of other factors. Furthermore, soil bulk density contributed more to crown width modelling than the aridity index, and structural diversity had a greater effect on crown width than species diversity. Synthesis. Our results provide new insights into the environmental variability of crown allometry in mixed forests under global change, which is critical for improving regional and global estimates of forest biomass and carbon stocks.

Long-term warming altered soil physical structure and soil organic carbon pools in wheatland field

Summary The impacts of long-term warming on soil physical structure and soil organic carbon (SOC) pools are currently disputed and uncertain. We conducted an eleven-year warming experiment in wheatland field in Henan, China. We found that long-term warming significantly increased soil bulk density by 4.5%, and significantly decreased total porosity and non-capillary porosity by 3.4% and 5.0%, respectively. Besides, long-term warming decreased the &gt;2 mm fraction proportion and increased &lt;0.053 mm fraction proportion of dry and wet aggregates. The mean weight diameter value for dry and wet aggregates in long-term warming treatment was significantly decreased by 7.0% and 6.7%, respectively. Moreover, long-term warming significantly decreased the total SOC, very labile pool (F1) and labile pool (F2) content by 10.6%, 30.6%, and 43.6%, and significantly increased the less labile pool (F3) and non-labile pool (F4) content by 94.2% and 21.1%, respectively. Long-term warming increased the passive carbon pool percentage but decreased the active carbon pool (ACP) percentage. Our results suggest that long-term warming negatively affected the soil's physical structure and impaired soil ACP accumulation. The findings of this study help improve our understanding of the response of farmland soils in northern China to climate change and provide scientific basis for establishing carbon management measures in farmland.

Evaluation of tractor traffic on soil physical properties and their relationship with white oat yield in no-tillage

In a no-tillage system, the absence of soil disturbance combined with increased machine traffic has led to soil compaction in the top layer, negatively affecting its physical quality and hampering crop growth and production. This experiment aimed to assess the impact of tractor traffic, occurring under a no-tillage system, on soil physical properties and their relationship with the growth and yield of white oat crops. The research was conducted in an Oxisol, utilizing a randomized block design with five replications. The treatments consisted of ten consecutive years of no-tillage and additional traffic by 2, 4, 6, and 8 passes of a tractor wheel across the entire plot area. Various soil parameters were evaluated in two soil layers, including soil bulk density, total porosity, macroporosity, and soil resistance to penetration. Additionally, plant height, stem diameter, dry plant mass, mass of one thousand grains, and grain yield were determined. The collected data were analyzed using analysis of variance and linear regression. The results indicated that higher tractor traffic intensity led to increased soil bulk density and reduced macroporosity and soil resistance to penetration in the 0-0.10 m layer compared to the 0.10-0.20 m layer. In the 0-0.10 m layer, bulk density values exceeding 1.44 Mg m-3 were found to restrict the growth and yield of white oat crops, while in the 0.10-0.20 m layer, grain yield was limited when soil bulk density surpassed 1.35 Mg m-3. Our results show that farmers should be aware of the consequences of machine traffic on soil properties as it can have negative effects on crop yields, especially those of white oats grown in clayey soil similar to the one evaluated in this experiment.

Long-term fire and grazing regimes modify soil physical properties and root traits in North American tallgrass prairie

The native Konza tallgrass prairie is maintained by two key natural processes, periodic fire and ungulate grazing. As a potential crucial feedback mechanism, how fire and grazing influence plant root traits and soil properties in the tallgrass prairie ecosystem remains less known. Here, we investigated the effects of long-term fire and grazing regimes on soil physical properties and root traits at the Konza Prairie Biological Station, near Manhattan, KS, USA. Soil cores were collected under control (unburned and ungrazed), fire (annually burned), grazing (annually grazed), and fire + grazing (annually burned and grazed) treatments. Soil water retention, total root volume, specific root length, specific root area, and root biomass were measured. We found that both fire and grazing significantly reduced soil water retention, increased soil bulk density and soil microporosity (<50 μm), and reduced macroporosity (>50 μm) compared to the unburned and ungrazed treatment. Fire and grazing also significantly reduced litter accumulation by 79 % (burned), 57 % (grazed), and 77 % (burned and grazed). Fire increased specific root area by 15 %. Grazing and fire + grazing significantly decreased specific root length by 40 % and 29 %, and specific root area by 33 % and 24 %, respectively. Litter production was positively related to soil volumetric water content and soil pore volume of 300–50 μm, but negatively related to soil bulk density and soil pore volume of less 50 μm. Soil volumetric water content was positively correlated to specific root lengths, and soil bulk density was negatively related to specific root length and specific root area. There was a significant negative relationship between root diameter and soil volumetric water content under burned and grazed treatment. The SEM model showed that fire, grazing, and fire + grazing regimes were associated with dead root biomass (R2 = 0.38) and root length density (R2 = 0.40) indirectly through soil bulk density and litter accumulation. Our findings suggested that the annual fire + grazing regime seriously leads to the degradation of tallgrass prairie by influencing soil physical properties, reducing root trait functions and root biomass, and altering the relationship between root diameter and soil volumetric water content.

Soil organic carbon and nitrogen reduction through cattle-path induced erosion in montane grasslands, KwaZulu-Natal, South Africa

The impact of daily cattle migration from homesteads to higher altitude pastures creates severe erosion in the montane grasslands of the predominantly subsistence agricultural rural communities of KwaZulu-Natal, Drakensberg, South Africa. This study quantifies the impact of a degraded cattle path at up, mid and downslope positions on SOC and N distribution in the soil profile and within the soil aggregates. An attempt to evaluate sites of erosion and deposition using excess lead-210 (210Pbex) to support our findings was conducted. On average, the degraded cattle path reduced SOC and N in the bulk soil (by 3–4 times, respectively) and was associated with 53% reduction in aggregate stability and a 14% increase in soil bulk density over the non-degraded reference site. These results reflect the loss of vegetation cover (correlated positively to SOC and N (r ≈ 0.94)), which were triggered by cattle grazing and trampling leading to top-soil loss. Cattle hoofs damage the grass and breakdown soil aggregates, exposing the fertile topsoil particles to detachment and consequential transportation via rill and sheet erosion. This is supported by the loss of 210Pbex in the topsoil of the degraded slope positions relative to the reference site. Consistent down core mixing of 210Pbex activity in degraded slope sites supports evidence of cattle mediated soil mixing. Our findings highlight the accelerated land degradation that results from uncontrolled grazing and movement of cattle on sloping lands in the Okhombe Valley. Developing an integrated management strategy co-led by local communities to develop proactive participatory sustainable land use practices is critical for long-term landscape maintenance and recovery in the region.

Microstructural changes in Oxisols under long-term different management systems

ABSTRACT There has long been a discussion about the effects of soil management on its structure. Since changes can occur due to management and time of use, more accurate assessments can be achieved if carried out in long-term experiments. This study investigated the long-term effects of soil management on the physical quality of a Cerrado Oxisol (Latossolo Vermelho), focusing on microstructural changes. Micromorphology and computed tomography techniques were used to assess the soil's microstructure. The study compared areas under long-term and different soil management practices, including disc plowing, no-tillage, and disc harrow+subsoiler. A native Cerrado area was considered as the reference. Micromorphology revealed some changes in the pedological features of soil aggregates, but the granular structure showed good resistance even after two decades of use and management. It also indicated a decrease in larger pores and an increase in the surface soil layer micropores for the disc plowing and no-tillage treatments. These results were consistent with traditional laboratory evaluations of soil porosity. Computed tomography was limited due to increased soil bulk density in the cultivated treatments, but it showed potential for assessing soil porosity and pore connectivity. We concluded that micromorphology effectively identifies microstructural changes in Oxisols with small and strong granular structures, and the granular soil aggregates displayed resilience even after long-term management. The micromorphometric evaluation corroborates with traditional methods and suggests loss of pores associated with the disc harrow+subsoiler treatment.

Linking soil physical quality to shoot and root biomass production in scenarios of sugarcane straw removal

Understanding how sugarcane straw removal affects soil physical attributes and root development over successive cultivation years is critical for sustainable straw-based bioenergy production. The aim of this study was to evaluate the effects of straw removal on soil physical quality and its relationship with sugarcane root development and crop yield in soils with contrasting textures. Three straw removal rates corresponding to total removal (TR), moderate removal (MR), and no removal (NR) were arranged in a randomized block design with four replicates. Soil was sampled at depths of 0–0.10, 0.10–0.20, and 0.20–0.40 m to determine soil bulk density, macro- and microporosity, soil penetration resistance, and carbon stock. Annual assessments of sugarcane root and stalk dry biomass were conducted. Overall, excessive straw removal rates were detrimental to soil porosity, C stock, and increased bulk density in the surface layer over successive years compared to moderate and no removal rates. Higher soil penetration resistance levels were observed under total removal, reaching values of 2.6 MPa in the 0–0.10 m layer in both soils. Average reductions in root biomass of 23–33% were verified at moderate and total removal rates in both soils, which affected sugarcane stalk yield, with maximum losses of 24% over crop cycles in the clayey soil. In the sandy loam soil, increases in soil C were correlated with reduced soil penetration resistance, which positively influenced root biomass production. Soil compaction over the years was particularly detrimental in the clayey soil, where the biomass production performance of sugarcane roots and stalk yield decreased in response to increased soil bulk density. Our results suggest that reductions in root biomass may occur in response to straw removal, as well as the loss of soil physical quality induced by soil compaction, with negative effects on C accumulation and soil resistance to root penetration.