Soil Research最新文献

Green manure crops have the potential to improve phosphorus (P) use efficiency in agroecosystems by enhancing the mobilisation of soil P reserves.

This study investigated and quantified the short-term mobilisation and uptake of soil P in the rhizosphere of several green manure crops.

Five plant species/varieties (Lupinus angustifolius (lupin – early and late flowering varieties), Pisum sativum (pea), Cicer Arietinum (chickpea), and Fagopyrum escolentum (buckwheat)) were grown in two contrasting soils, pumice (1100 mg total P kg⁻¹, anion storage capacity 39%) and volcanic ash (2800 mg total P kg⁻¹, anion storage capacity 95%) in rhizosphere study containers. After 40 days, rhizosphere (0–5 mm) and bulk (>5 mm) soils were sampled and subjected to P fractionation. Organic anions were collected from the rhizoplane using an anion exchange membrane.

Dry matter yield, P uptake, and rhizoplane organic anion exudation were affected by plant species, soil type, and their interaction. Rhizosphere P changes of labile inorganic organic P and stable inorganic P were influenced by plant species and soil type, while moderately labile inorganic P was affected by only plant species. Interaction between plant species and soil type had no effect on rhizosphere P depletion or accumulation. The quantities and composition of organic anions determined in rhizoplane exudates were highly variable (0.01–0.1 μmol cm⁻² h⁻¹). However, significant correlations were observed between the depletion of moderately labile and stable soil inorganic P and concentrations of malate in exudates.

The findings of this study clearly demonstrated the capacity of green manure crops (especially blue lupin) to rapidly mobilise and deplete different forms of soil P across the soil types.

Forest restoration has been adopted by governments and local communities across the globe to restore ecological functions and as a measure to mitigate climate change.

This study investigated the spatial variation in landscape, vegetation, soil characteristics, and soil carbon storage under young restoration plantings across a hillslope in northern New Zealand.

Soil samples (0–10 cm, 10–20 cm, and 20–30 cm) were taken from 121 locations across 5–20-year-old restoration plantings, remnant and regenerating bush and pasture. Samples were analysed for bulk density, pH, and soil carbon concentration and soil carbon stocks were calculated. Ordinary kriging and multiscale geographically weighted regression (MGWR) were used to predict and explain soil carbon stocks across the landscape.

Soil carbon stocks (0–10 cm depth) across the study area ranged from 1.9 to 7.1 kg m⁻². Spatial analysis revealed that elevation, slope, stem density, bulk density, and pH had a significant effect on the magnitude and distribution of soil carbon stocks.

This study has shown that topography had a strong effect on soil carbon stocks across the young restoration plantings. The outcome of this study highlights the importance of taking landscape and soil characteristics into account when planning a forest restoration project.

The cementation of spodic horizons (ortstein) has long been studied through chemical analysis in disturbed soil samples of <2 mm (soil structure destructuring).

Use of the undisturbed samples and selective chemical extractions to study the soil organic matter (SOM) and short-range order phase (SROP) cementing the spodic horizon.

The study was carried out in a Spodosol (ortstein) from southern Brazil in undisturbed cubes (1.5 cm × 1.5 cm × 1.5 cm). The undisturbed cubes were separated in two visual colour standards (yellow colour (YC – 10YR 6/8) and yellow dark colour (YDC – 10YR 4/3)) and were submitted to four SROP chemical extractions (pyrophosphate (PYR), ammonium oxalate (AO), NaOH 0.5 mol L⁻¹, and water).

The choice of selective SROP extraction in two colour standards of undisturbed samples enabled the identification of cementation details of the ortstein : (1) SOM illuviation also increases Fe, Al, Mn, Si, Ca, and Mg contents; (2) the SRO-Fe and Al oxides cover the SOM and/or there is a larger proportion of mineral in relation to OC in the organo/mineral association; (3) SRO-Al oxides were the main compounds responsible for cementation; and (4) the illuvial SOM associated with SRO-Fe oxides did not contribute to ortstein physical stability.

The best extractions to study the samples were AO for YC colour and NaOH for YDC colour. We recommend the use of undisturbed samples and the inclusion of NaOH 0.5 mol L⁻¹ in the chemical protocol for analysis to better understand which organic and mineral phases clog the ortstein pores in different pedogenetic conditions around the world.

Cultivation of forage grasses intercropped with maize (Zea mays) improves soil quality and yield of subsequent crops. However, for the Cerrado of north-east Brazil, little is known about the effects of this practice on soil chemical and biological attributes and on succeeding soybean crop’s yield and nutrition.

This study aimed to evaluate the influence of intercropping maize with forage grasses on soil chemical and biological properties and on the nutritional status and yield of succeeding soybean in the Cerrado of Piauí, Brazil.

In the 2016/2017 cropping season, maize (M) was grown in monoculture and intercropped with Megathyrsus maximus cvs Zuri, Massai, Tanzania, and Tamani; Urochloa brizantha cv. Marandu, and Urochloa ruziziensis cv. Ruziziensis. In the 2017/2018 and 2018/2019 cropping seasons, soybean (Glycine max) was grown on the same plots.

In the 2017/2018 cropping season, highest soil K concentrations in the 0–0.1 m depth were observed following M + Zuri and M + Massai. In the 2018/2019 cropping season, soybean grown after monoculture maize, M + Zuri, M + Tanzania and M + Ruziziensis promoted the highest soil basal respiration. Intercropping maize with forage grasses of the genus Urochloa increased the soil humic substances and carbon concentrations. The M + Tanzania treatment increased soybean leaf P and K concentrations in the 2017/2018 cropping season.

Intercropping maize with forage grasses improved soil fertility and increased cumulative soybean grain yield by 15%.

Maize intercropped with forage grasses, especially of the genus Urochloa, increases humic fractions and total soil organic carbon, and is thus a feasible agricultural management.

Neutralising native soil Al³⁺ is crucial in subtropical agriculture before implementing no-tillage (NT).

The aim of this study was to monitor variations in soil Al saturation and crop yields over 34 years in a field trial under NT, to define the best rate and frequency of lime reapplication for maximum productivity of grain and forage crops.

We measured the soil Al³⁺ saturation in 11 soil sampling seasons in three soil layers (0–5, 5–10, and 10–15 cm). From these 11 soil samplings, the Al saturation was extrapolated for the harvesting day of each crop by fitting a sigmoid model with five parameters. Then, Al saturation values of each year were plotted against the relative crop yields. From that, the critical Al saturation at which crop yield declined by more than 5% was estimated by a linear plateau model.

We observed that the yields of six of the 10 soybean crops, and all corn, millet, and black oat crops were not decreased even though the soil had been cultivated for 34 years without reapplying lime. The critical Al saturation values in the 10–15 cm soil layers for soybean, wheat, and cover crops were 44, 24 and 20%, respectively.

The soybean, corn, and wheat varieties available for Brazil’s subtropical region are tolerant to high Al³⁺ saturation, but responsive to liming. It is possible to maintain high crop yields in the long term by reapplying limestone on the soil surface.

It is imperative to establish an agronomic soil profile without Al³⁺ when adopting NT for a diverse crop rotation system. The combination of NT, Al-tolerant varieties, and reapplication of surface limestone is a suitable strategy to optimise both grain and forage yields.

Acid drainage (AD) production from sulfide rich materials can impact the environment, particularly the surrounding mine areas. A suitable evaluation of AD is warranted to prevent and remediate its impacts. The methods that estimate AD and its kinetics are time consuming.

To identify chemical and mineralogical features that influence the AD dynamics, and propose a fast method to estimate the AD generation.

Chemical analyses of sulfides rocks and thiomorphic soil samples included pH, contents of major elements and the acid-base accounting (ABA). Mineral identification was performed by X-ray diffractometry (XRD) and scanning electronic microscopy (SEM). The rate of sulfide oxidation in samples was evaluated through simulated weathering (SW) tests performed with different contents of H₂O₂, with and without CaCO₃. Supernatant was drained to determine pH, acidity and S-sulfate.

Generation of AD was affected by carbonates and sulfides contents in samples, crystal sizes and types. Coal and thiomorfic soil produces more AD, due to framboidal pyrites and small sized sulfides.

Sulfides oxidation rate and AD generation increased from the metamorphic and igneous intrusive rocks to sedimentary-volcanic and then the supergenic geomaterials, from bigger to smaller crystal sizes. Carbonates and arsenic inhibit AD kinetics. The ABA failed to predict the AD in geomaterials, especially the ultramafic. The SW dynamic tests were suitable to assess AD kinetics and the stoichiometry of acidity production.

Carbonates and sulfides are important features to predict AD in several geological environments. Using H₂O₂ can abreviate the time consuming tests to assess the AD kinetics.

Soil and water conservation (SWC) measures have been widely practiced on cultivated lands across regions but evidence on their effects is inadequate.

To examine the effects of variously aged SWC measures on cultivated land.

A total of 122 farm households were interviewed. At the 0–20 cm layer, soil samples (n = 59) were collected from soil bunds of <5 years, 5–10 years, and 10–15 years old, and no-bund adjacent fields and analysed in the laboratory.

Approximately 40% of respondents perceived soil erosion as a severe problem in their area. The respondents (70%) practiced the introduced SWC measures such as soil bunds. The introduced SWC measures are beneficial in improving soil fertility (78%) and thus 96% of the respondents were interested in repairing and sustaining it. The soil pH, soil organic carbon, total nitrogen, and available phosphorous were significantly (P < 0.05) greater in the fields with bunds of 10–15 years old than the fields with bunds of less than 10 years. The 10–15 year old bund showed greater soil organic carbon (37%), total nitrogen (40%), and available phosphorous (27%) than adjacent no-bund fields, implying that SWC can show effects on soil in the long term.

The results of the study revealed that the effects of physical SWC measures on soil properties can be observed after a decade of managing them.

Farmers are advised to repair and retain bunds if the erosion-prone areas are used for cultivating annual crop.

Oribatid mites are the most abundant taxon in forest soils that rely on porosity and organic matter availability. Exotic forests of Pinus radiata and Eucalyptus globulus planted over native grasslands in the Pampas region of Argentina have produced modification in soil properties, which can affect the composition and structure of native oribatids communities.

To compare oribatid communities in soils under artificial woodlands of pine and eucalyptus and to assess the vertical distribution of oribatids in relation to edaphic variables.

In each forest, oribatids were collected from three levels of the A horizon: (1) litter layer; (2) 0–5 cm; and (3) 5–10 cm. Edaphic variables measured were penetration resistance, bulk density, total porosity, pH and water content and luminosity at soil level. Density, species richness, diversity and evenness of oribatids were calculated in each level of each forest. Comparisons were made through multivariate analyses.

Edaphic variables showed no significant differences between plots but litters were structurally different. Richness and diversity showed no differences between plots whereas evenness was significantly higher in plot P. Density had higher values in the litter layer of both forests. Canonical Analysis of Principal Coordinates (CAP) showed that Pine plots had a more defined vertical distribution.

The structure and composition of litters promoted differences in the vertical distribution of oribatids. In Pinus, thick unaltered litter showed a marked vertical gradient of mites along levels while in Eucalyptus, thin and easily decomposing litter, showed no vertical patterns.

Assessment and management of soil biodiversity in artificial woodlands.

Laser-induced breakdown spectroscopy (LIBS) is a rapid, multielement analytical technique. It is particularly suitable for the qualitative and quantitative analyses of heavy metals in solid samples.

To validate the technique, the LIBS data were compared with the data obtained via conventional inductively coupled plasma (ICP) spectroscopy for the same soil samples.

In this study, standard and unknown soil samples from contaminated areas were prepared and fixed to an adhesive tape for LIBS analysis. The soils were also digested with acids for ICP analysis. The emission intensity of one selected line for each of the two analytes, i.e. lead (Pb) and zinc (Zn), was normalised to the background signal and plotted as a function of the concentration values previously determined via ICP analysis.

The data demonstrated good linearity for the calibration lines drawn, and the correlation between the ICP and LIBS data was confirmed by the satisfactory agreement between the corresponding values.

The concentration coefficient of determination (R²) between LIBS and ICP-aqua regia digestion analysis or ICP-total digestion analysis were >0.86 and >0.89 for Pb and Zn, respectively. The total analysis time for the LIBS method was 310 min, which was 54.40% shorter than that for the ICP method (680 min).

Consequently, LIBS can be used to measure Pb and Zn in soils without any chemical preparation.