Key Soil Chemical Properties Research Articles

Afforestation-Induced Shifts in Soil Bacterial Diversity and Community Structure in the Saihanba Region.

Afforestation plays a pivotal role in ecosystem restoration, exemplified by the Saihanba Mechanized Forest Farm, the world's largest planted forest; however, the assembly mechanisms and interactions of soil microbial communities in such forests remain inadequately understood. This study aimed to elucidate the impact of different afforestation tree species, namely Larix gmelinii var. principis-rupprechtii, Picea asperata, and Pinus sylvestris var. mongolica, on soil bacterial diversity and community structure in comparison to grassland. Sixty soil samples were collected at a 20 cm depth, and high-throughput sequencing was employed to identify bacterial communities and assess their interactions with environmental factors. A total of 6528 operational taxonomic units (OTUs) were identified, with Solirubrobacter, Conexibacter, Bacillus, Massilia, Gaiella, Acidibacter, and Vicinamibacter being the dominant genera. Afforestation significantly impacted soil bacterial alpha diversity, with notable influence from key soil chemical properties, including available phosphorus (AP), cation exchange capacity (CEC), and the carbon-to-nitrogen ratio of soil organic matter (SOM-C/N). The Mantel test highlighted pH, the Normalized Difference Vegetation Index (NDVI), and spatial variable (dbMEM) as primary environmental factors influencing dominant bacterial genera. The bacterial community structure demonstrated deterministic homogeneous selection, wherein SOM-C/N emerged as a significant factor influencing the dissimilarity of soil bacterial communities. Furthermore, plantation soils exhibited a more complex network structure than grassland soil, highlighting the crucial role of bacterial communities in vegetation changes and providing valuable insights into their response to environmental factors during the reforestation process.

Growth and Productivity of Pigeon Pea Genotypes under Different Plant Geometry and Its Residual Impact on Some Soil Chemical Properties

Field experiments were conducted during the 2020 and 2021 cropping seasons at the research fields of CSIR-Savanna Agricultural Research Institute located at Nyankpala in the Guinea savannah agroecology of Ghana. The objective was to test the effect of genotype and plant geometry on the growth and productivity of pigeon pea and its residual effect on some soil chemical properties. The work involved three pigeon pea genotypes (L-2015-2, L-2015-3 and ICP-8863) and four spacing levels; 100 cm x 30 cm, 100 cm x 45 cm, 100 cm x 60 cm and 100 cm x 75 cm. Analysis of variance indicated a significant interaction effect of genotype, year and spacing effect on number of branches per plant, pod length, grain yield, 1000 seed weight and harvest index. Genotype x spacing effect was significant for all traits except the number of seeds per pod. (294.7 cm) whilst genotype L-2015-3 at 100 cm x 60 cm produced the shortest plants (222.9 cm). Genotype L-2015-2 at 100 cm x 60 cm in 2021 had the highest grain yield (2311 kg/ha) whilst genotype ICP8863 at 100 cm x 60 cm in 2020 had the lowest grain yield (391 kg/ha). A post-2020 cropping season soil analysis revealed improvement in key soil chemical properties, explaining the better crop performance in 2021. Genotype L-2015-2 had the highest overall average grain yield (1484 kg/ha) whilst ICP8863 had the lowest overall grain yield. The study indicated that the different genotypes required different spacing for their optimum yield due to differences in plant architecture, growth and branching habit. Spacing had significant influence on plant height, number of leaves at flowering, number of pods per plant and number of seeds per pod which were significantly and positively correlated with grain yield. Therefore, each genotype should be matched with its preferred spacing for optimum growth and maximum grain yield.

Graphene oxide influences bacterial community and soil environments of Cd-polluted Haplic Cambisols in Northeast China

Graphene oxide (GO), a carbon nanomaterial that is widely used in the environment and other industries, may pose potential risks to ecosystems, especially the soil ecosystem. Some soils in Northeast China are frequently polluted with cadmium (Cd) metal. However, there is no study on the influence of GO on the Cd-contaminated soil microbial community and soil chemical properties. In this study, Cd (100 mg kg−1)-polluted soils were treated with different concentrations of GO (0, 25, 50, 150, 250, and 500 mg L−1, expressed as T1, T2, T3, T4, T5, and T6, respectively) for 40 days. The treatment without Cd pollution and GO served as the control (CK). Then, we investigated the influence of the GO concentrations on the bacterial community and chemical properties of Cd-polluted Haplic Cambisols, the zonal soil in Northeast China. After GO addition, the richness and diversity indexes of the bacterial community in Cd-contaminated Haplic Cambisols initially increased by 0.05–33.92% at 25 mg L−1, then decreased by 0.07–2.37% at 50 mg L−1, and then increased by 0.01–24.37% within 500 mg L−1 again. The species and abundance of bacteria varied with GO concentration, and GO significantly increased bacterial growth at 25 and 250 mg L−1. GO treatments influenced the bacterial community structure, and the order of similarity of the bacterial community structure was as follows: T4 = T5 > T1 = T6 > T2 > T3 > CK. Proteobacteria and Acidobacteria were the dominant bacteria, accounting for 36.0% and 26.2%, respectively, of soil bacteria. Different GO treatments also significantly affected the metabolic function of bacteria and further influenced the diversity of the bacterial community structure by affecting several key soil chemical properties: soil pH, organic matter and available potassium, phosphorus, and cadmium. Our results provide a theoretical basis for scientific and comprehensive evaluation of the environmental impacts of GO on the zonal forest soils of Northeast China.

Can highly saline irrigation water improve sodicity and alkalinity in sodic clayey subsoils?

The concept of irrigating crops with saline irrigation water is not new, but impacts of this practice on soil properties remain debatable, particularly the use of highly saline water. In this work, key soil chemical properties were assessed to a depth of 300 cm following 2.5 years of application of highly saline irrigation to a sodic texture-contrast soil (Brown Sodosol) in south-eastern Tasmania, Australia. Control plots (rainfall only) were compared to irrigation treatments of low (0.8 dS/m) and high salinity (16 dS/m) waters at application rates of both 200 and 800 mm/year. Whilst significant increases in both electrical conductivity and chloride concentration occurred throughout the soil profile in the high salinity treatment, these values were well below those of the irrigation water, indicating effective deep leaching. In the upper soil profile, 0–50 cm, of the high salinity treatments both the exchangeable Na+ and its ratio to total base cations (ESP) were significantly increased whilst the lower soil profile between 50 and 200 cm, was improved via both reduced alkalinity and sodicity. Leaching of the exchangeable base cations Ca2+, Mg2+ and K+ was significant in the upper soil profile (0–50 cm). As expected, the low salinity treatment (0.8 dS/m) had minimal impacts on soil chemical properties. The upper topsoil (0–10 cm) total organic carbon was significantly reduced in the high salinity plots and was negatively correlated with Cl− concentration. The data confirms the general concerns about application of saline irrigation, namely increased whole profile salinisation and upper soil profile (0–50 cm) sodicity, but they also show unexpected and desirable reductions in the lower soil profile (> 50 cm) alkalinity and sodicity. It appears the Na+ ions present in the saline waters led to differential leaching of base cations from the rooting zone, especially Ca2+ which then ameliorate the alkalinity and sodicity deeper in the soil profile (> 50 cm). Thus, surface application of gypsum may help sustain the application of highly saline waters; alternatively, subsurface irrigation above the sodic clayey subsoils could be trailed.

Three long-term trials end with a quasi-equilibrium between soil C, N, and pH: an implication for C sequestration

The aim of this study was to assess the long-term changes in some key soil chemical properties at the completion of three long-term trials in south-eastern Australia and the relationship between those soil properties. From a soil organic matter perspective, the build-up of carbon (%C) requires an accumulation of nitrogen (%N), and the build-up of %C and %N fertility comes at the cost of soil acidity. Rotation, tillage, and stubble practices combine to alter the quantity, quality (C : N), and the depth distribution of organic matter in a soil, but the three soil chemical properties reported here seem to also be in quasi-equilibrium at the three long-term sites. The consequence is that if the build-up of soil organic matter leads to soil acidification, then the maintenance of agricultural production will require liming. The emission of CO2 when limestone reacts with soil acids, plus the C cost of limestone application, will negate a proportion of the gains from C sequestration as organic matter in soil. Such cautionary information was doubtless unforeseen when these three long-term trials were initiated.

Anthropogenic effects on the physical and chemical properties of subtropical coastal urban soils

AbstractWe investigated the effects of various anthropogenic factors on urban soil properties in subtropical, coastal Tampa, FL, USA. Specifically, we explored the influence of (i) urbanization as measured by land use, land cover, population density and years since urban development and (ii) socioeconomic conditions as reflected in household income and property values on bulk density (BD) and several key soil chemical properties. Results indicate that Tampa’s urban soils were affected to varying degrees by these factors with chemical properties being more variable than BD. Across land uses significant differences were found for Mehlich‐1 (M1) extractable P, Ca and Na. A similar trend was observed for land‐cover classes, although significant differences were also found for pH and M1‐Cu. Soil properties had no statistically significant relationship with population density. However, time since urbanization did with M1‐P and Na varying significantly across age categories. For our socioeconomic analyses, M1‐K and Mg levels differed significantly by household income while pH, P, Ca and Na values differed significantly by property value. Overall, our findings indicate that despite their inherent heterogeneity, there are identifiable patterns among subtropical coastal urban soil properties. We suggest that a more thorough understanding of these patterns and their drivers is an essential first step towards developing soil management strategies aimed at maintaining environmental quality and ecosystem services in subtropical cities.

Adsorption of the herbicide terbuthylazine across a range of New Zealand forestry soils

The growing importance of environmental certification in plantation forestry is increasing the pressure to discontinue the use of chemicals including herbicides classified as highly hazardous. One of these herbicides is terbuthylazine, a triazine used widely to control a broad range of weeds in plantation forests in New Zealand. Using soil samples obtained from a national trial series, the key objectives of this study were to (i) determine the variation in soil adsorption of terbuthylazine as measured by distribution constant (Kd) across a range of soil types and (ii) develop a multiple regression model to predict Kd from key soil chemical properties. Across the 34 sampled sites, Kd averaged 21.9 L·kg–1 and ranged 38-fold from 3.9 to 146.7 L·kg–1. There was a highly significant (P < 0.0001) relationship between organic carbon and Kd, which was best described by a power function, that explained 86% of the variance in Kd. Addition of pH to the model using an exponential decay function was significant and increased the R2 for the model to 0.99. Across soil orders, Kd varied significantly by 10-fold. Values of Kd were lowest on Raw and Recent soil orders, which have low soil organic carbon and a relatively high pH.

Differences in soil chemical properties with distance to roads and age of development in urban areas

The main objective of this study was to characterize variation in soil chemical properties with length of urbanization period and distance to roads. Urban boundaries from 1920’s (old), 1960’s (middle) and 2000’s (new) were identified for three cities in northeast Ohio: Massillon, Wooster and Canton. Within each identified historic boundary, soil samples were collected from two road-side and two interior lawns in one public school site in each city. Thus, there were three urban age and two distance-to-roads classes. Soil particle composition and basic chemical properties including pH, available phosphorus (P), exchangeable potassium (K), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC), nitrate, total carbon (C), total nitrogen (N), and soil organic matter (SOM) were measured. Two notable spatio-temporal patterns appeared repeatedly in the data set. First, total C, total N and SOM were higher in the soils of old (>50 years) urban sites than of newly developed sites. Similar, but not always significant, trends in soil pH, and exchangeable Ca were also observed. Second, road-side soils had higher pH, Ca, total C and N than interior sites regardless of urban age. These data indicate that key soil chemical properties can vary in predictable ways with urban age and distance-to-roads classes. Such variations in key soil chemical properties may influence or reflect soil biota and biogeochemical processes in urban soils.

Soil protection with logging residues during mechanised harvesting of native forests in Tasmania: a preliminary study

Summary In Tasmania, Australia, mechanised forest harvesting operations often use ‘cording’ to limit soil disturbance. This means logs are laid across the snig tracks, perpendicular to the flow of traffic, providing a rigid barrier between the machinery and the ground surface. At the conclusion of harvesting, the cording material is lifted using an excavator and burnt on site. This latter procedure enhances soil nutrition through the ‘ash-bed’ effect, whilst increasing the area of seedbed available for forest regeneration. To date, the efficacy of cording in protecting soil values remains largely untested. The shallow and stony nature of many forest soils, and the presence of logging residues and cording material along snig tracks, make the investigation of soil physical properties difficult. In response, this study was undertaken to assess the effectiveness of cording by using forest regeneration (density of seedlings and seedling height) as an indicator of productivity along former snig tracks protected with cording. Available seedbed (%) and seedling form, including the incidence of browsing and disease, were recorded and key soil chemical properties (0–10 cm soil depth: organic carbon, total nitrogen and total phosphorus), were measured. In the absence of physical soil testing, the theoretical distribution and attenuation of machine loads by the cording are discussed. Forest regeneration along the former snig tracks was consistently inferior in quantity and quality compared to that of the untrafficked control areas. This was attributed largely to: (a) a reduction in the available seedbed (%) due to incomplete combustion of the cording material and retention of logging residues, both on the ground surface and mixed with the upper soil layers, and (b) poor growing conditions—the combined effects of lowered organic carbon, nitrogen and phosphorus concentrations along the former snig tracks. Operational recommendations based on this study include: (a) avoiding trafficking of bare ground during the construction of cording, (b) beginning with a layer of small—diameter material to help spread machine loads more evenly and (c) where appropriate, leaving permanent snig tracks.