Exchangeable Base Cations Research Articles

Response of soil nutrient content, organic matter characteristics and growth of pine and spruce seedlings to logging residues

The aim of this study was to determine the effects of different amounts of logging residues on soil properties and growth of Scots pine and Norway spruce seedlings 10years after clear-felling. The field experiments consisted of two Scots pine and four Norway spruce experiments. The treatments, on three replicate 8m∗8m plots in all field experiments, were whole-tree harvesting, i.e. harvesting all the above-ground biomass with no logging residue left on the site (R0), stem-only harvesting, leaving logging residues on the site (R1), and stem-only harvesting with double the amount of logging residues left on the site (R2). In the R1 treatment the amount of logging residue in the spruce stands was 39–54Mgha−1 dry mass and in the pine stands, 11–18Mgha−1 dry mass. Over all sites, logging residues had no consistent effects on seedling growth, amounts of soil carbon and nutrients or organic matter characteristics. In some spruce experiments, however, logging residues increased the average diameter, height and height growth (last three years), as well as the number of seedlings, stem volume and biomass. In pine experiments, logging residues had no effect on tree or stand characteristics. In one pine experiment the amounts of exchangeable base cations increased, and there were also changes in the quality of organic matter: the C/N ratio decreased, and NH4–N, microbial biomass N and C mineralization increased due to residues. In the spruce experiments and the other pine experiment, the effect of logging residues on the soil properties measured was slight. Logging residues did not affect NO3–N concentrations or rates of net nitrification, which in most soils were both negligible. Seedling height and height growth correlated strongly and positively with net N mineralization and its ratio to microbial biomass N. All in all, logging residues improved tree and stand characteristics generally in spruce stands, but the effects on soil properties and processes, if any, occurred mostly in one pine stand. This poor correspondence may point to other changes brought on by the logging residues, such as changes in physical environment or decreased competition with ground vegetation, being more important for seedling growth than nutrient status was.

Geochemical characteristics of soils in Fezzan, Sahara desert: Implications for environment and agriculture

An investigation was conducted to geochemically characterize the soils in Fezzan of the Sahara desert in order to assess (a) the role of the soils as a carbon store, (b) the potential risk of the fine-grained soil fraction as a dust source, and (c) the potential soil constraints for the development of irrigation agriculture. The results show that, on average, there was about 0.7% of carbon stored in the topsoil with approximately 1/3 being inorganic carbon and 2/3 being organic carbon. The fine-grained soil fraction contained 2.13% of Fe and 252mg/kg of phosphorus, indicating that the Fezzan area could be an important source of ocean iron and phosphorus. Manganese and strontium were identified as the major chemical pollutants potentially present in the dusts. The soils were generally alkaline and saline. Sodium dominated the soluble basic cations with a mean sodium adsorption ratio >16. Calcium dominated the exchangeable basic cations with a mean exchangeable sodium percentage of 6.52, suggesting that most of the topsoils were not sodic. However, there was a tendency that sodicity increased with depth for some soils. Different strategies are proposed for reclaiming the soils using the groundwater from the Great Man-made River Project.

Ameliorating Effects of Fungus Chaff and Its Biochar on Soil Acidity

A biochar was generated from fungus chaff at 300 °C, and the ameliorating effects of fungus chaff and its biochar on an acidic Ultisol were compared using incubation experiments. Incorporation of fungus chaff and its biochar significantly increased soil pH and soil exchangeable base cations but decreased soil exchangeable acidity. The ameliorating effect was greater for the biochar than the fungus chaff, and thus the biochar was a better amendment for acidic soil than its feedstock of fungus chaff. The biochar ameliorated soil acidity mainly through the release of its contained alkaline substances, while fungus chaff increased pH of acidic soils through two mechanisms: release of alkaline substances and inhibition of soil nitrification. The incorporation of fungus chaff increased soil-available organic carbon and thus accelerated the microbial assimilation of inorganic nitrogen, while incorporation of fungus chaff biochar enhanced nitrification due to increased soil pH.

PH effects of the addition of three biochars to acidic Indonesian mineral soils

Soil acidity may severely reduce crop production. Biochar (BC) may increase soil pH and cation exchange capacity (CEC) but reported effects differ substantially. In a systematic approach, using a standardized protocol on a uniquely large number set of 31 acidic soils, we quantified the effect of increasing amounts (0–30%; weight:weight) of three types of field-produced BCs (from cacao (Theobroma cacao. L.) shell, oil palm (Elaeis guineensis. Jacq.) shell and rice (Oryza sativa. L.) husk) on soil pH and CEC. Soils were sampled from croplands at Java, Sumatra and Kalimantan, Indonesia. All BCs caused a significant increase in mean soil pH with a stronger response and a greater maximum increase for the cacao shell BC addition, due to a greater acid neutralizing capacity (ANC) and larger amounts of extractable base cations. At 1% BC addition, corresponding to about 30 tons ha−1, the estimated increase in soil pH from the initial mean pH of 4.7 was about 0.5 units for the cacao shell BC, whereas this was only 0.05 and 0.04 units for the oil palm shell and rice husk BC, respectively. Besides depending on BC type, the increase in soil pH upon the addition of each of the three BCs was mainly dependent on soil CEC (low CEC resulting in stronger pH increase), and to a lesser extent on initial soil pH (higher initial pH resulting in stronger pH increase). Addition of BC also increased the amount of exchangeable base cations (cacao shell ≫ oil palm and rice husk) and CEC. Through this systematic screening of the effect of BC on pH and CEC of acidic soils, we show that a small addition of BC, in particular if made of cacao shell, to acidic agricultural soils increases soil pH and CEC. However, the response is highly dependent on the type, quality and amount of the added BC as well as on intrinsic soil properties, mainly CEC.

The Potential Of The Soil For Stabilisation Of Organic Carbon In Soil Aggregates

Abstract Carbon stabilisation in soil is the result of interaction between the chemical and physical mechanisms of protection and the dominance of the mechanism depends not only on the long-term constant characteristics of soil but also on the properties, which can be partly influenced by human activities. In this study, the potential of the soil for stabilisation of carbon (Ps) in different soil types depending on soil properties was compared. Experiment included six soils (Eutric Fluvisol, Mollic Fluvisol, Haplic Chernozem, Haplic Luvisol, Eutric Cambisol, and Rendzic Leptosol) of different land uses (forest, meadow, urban, and agro-ecosystem) in Slovakia. Ps was determined with dependence on the ratio of labile and stable fractions of carbon in the soil macro-aggregates. Ps was in an exponential dependence (r = 0.942; P < 0.01) with production potential of the soil, and the fractions of dry-sieved aggregates larger than 3 mm play an important role in the first stages of the carbon stabilisation. The suitable parameter, which reflects the changes in carbon stability in the soil is the ratio of the labile carbon and non-labile carbon in the soil macro-aggregates (L/NL). Lower values of L/NL that indicate a higher stability of carbon were determined at a higher pH, at the higher content of carbonates and exchangeable basic cations, and at a higherportion of humic acids free and bound with mobile sesquioxides R2O3.

Effects of different harvesting intensities on the macro nutrient pools in aged oak coppice forests

Improved knowledge concerning nutrient removals through harvesting in former coppice forests is crucial for the sustainable management of these forests. This is especially true if the resumption of coppicing is being considered to serve increasing fuel wood demands. In this study the nutrient contents of various tree compartments of sessile oak (Quercus petraea (Mattuschka) Liebl.) and hornbeam (Carpinus betulus L.) from two sites differing in soil fertility were determined using allometric equations to calculate nutrient removal associated with different harvesting intensities.Stand level nutrient contents in tree compartments were comparable between both study sites. The results for exchangeable base cations, plant available P, and total N indicate that coppicing is not a priori an unsustainable forest management system. On sites with large soil nutrient pools, even whole trees may be harvested without substantial reductions in ecosystem nutrient pools. However, on sites with a low nutrient capital, current harvesting practices would result in relatively high rates of nutrient export. In these stands, harvesting intensity should be based on careful selection of the tree compartments removed, e.g. stem only, to conserve nutrients on site.This study describes the impact of simulated tree harvesting on soil nutrient pools in aged coppice forest for the first time. Based on our findings, general assumptions related to soil sustainability of coppicing are replaced by clear recommendations regarding silvicultural nutrient management. Considering the large areas of aged coppice forests in Europe this study provides a methodological template which is needed to enhance their sustainable management.

Soil microbial and nutrient properties in the rhizosphere of coffee under agroforestry management

The integration of shade trees in coffee production can positively contribute to increased yields in these cropping systems. However, little work has examined nutrient-microbial dynamics in the rhizosphere of coffee under shade trees. In this study, we compared nutrient concentrations and nitrifier populations in rhizosphere soil of coffee under shade and in monoculture as well as in rhizosphere versus bulk soils. Our study was performed in a low altitude, wet coffee zone of Costa Rica, at a 12-year-old agroforestry experimental farm with coffee (Coffea arabica) grown under full sun and under the commonly used dinitrogen (N2) fixing shade tree, Erythrina poeppigiana. Rhizosphere and bulk soils were collected and analyzed for inorganic N, available P, exchangeable base cations and pH status. Real-time PCR was used to determine the relative abundance of ammonia oxidizing bacteria (AOB). We show a nutrient increase (11–158%), particularly nitrates, in the rhizosphere soil compared to bulk soil of coffee. Moreover, this accumulation was greater in the rhizosphere of coffee associated with E. poeppigiana than under monoculture. AOB abundance was strongly related to soil pH (r=0.83; P=0.002) across both treatments, while AOB abundance varied with soil ammonium:nitrate ratios (r=−0.82; P=0.0420) exclusively under monoculture coffee. Our study, for the first time to our knowledge, illustrates soil nutrient differences and nutrient–microbial relationships under coffee in monoculture and in a N2-fixing shade tree system.

Wood ash and N fertilization in the Canadian boreal forest: Soil properties and response of jack pine and black spruce

Wood ash fertilization has yet to be investigated in Canadian boreal forests. Ash often improves soil acid–base status, but without N addition it seldom increases tree growth on poor mineral soils. We report results of a large scale experiment conducted in a boreal jack pine (Pinus banksiana Lamb) stand growing on sandy acidic soil in Northeastern Canada. The experiment was completely random with four replications (1ha each) of five treatments (0, 1, 2, 4 and 8 dry Mgha−1) of loose fly ash with and without urea (280kgNha−1). Soils were sampled in the 0, 2, and 8Mgha−1 treatment up to eight years after application. Foliar nutrition and stand growth were assessed in all treatments one and two years and five years after treatment, respectively.Even under low ash loading, forest floor exchangeable base cations, pH, and base saturation increased within a year of application. Ash application also resulted in a swift decrease in forest floor organic C and an increase in N potential net mineralization rate. The initial dominant pattern of upper mineral soil properties in relation to ash loading was a curvilinear relationship with the highest values observed in the 2Mgha−1 treatment. Eight years after ash application, significant linear relationships were found between ash loading and base cations and base saturation in the forest floor and mineral soil (0–10cm, 10–20cm). Contrary to N fertilization, ash had no effect on jack pine foliar nutrition and on its five-year growth. However, a decrease of 30% in relative growth rate was observed between the control and the 8Mgha−1 ash treatment for large (⩾10cm DBH) black spruces (Picea mariana (Mill.) BSP). Black spruce is the dominant commercial species of Canadian eastern boreal forests and thus, additional studies are needed to validate the deleterious effect of ash on spruce growth and to elucidate the mechanisms involved.

Initial effects of thinning on soil carbon storage and base cations in a naturally regenerated Quercus spp. forest in Hongcheon, Korea

Thinning can affect soil carbon (C) and base cation balances by reducing tree density and altering microclimate and organic matter budget; however, the subsequent changes in soil C and base cation contents after thinning are not well elucidated. Thus, this study investigated the effects of thinning on C storages in soil (at 0–10 cm, 10–20 cm, and 20–30 cm depths) and forest floor and concentrations of soil exchangeable base cations (Ca2+, Mg2+, K+, and Na+). Thinning treatments of different intensities based on the removed basal area (no thinning: control, 15% thinning: T15, and 30% thinning: T30) were applied to a naturally regenerated 31 to 40-year-old Quercus spp. forest. Soil C concentrations at 10–20 cm and 20–30 cm depths were significantly higher in T15 and T30 than in the control after 39 months, but not after 4 months. T15 and T30 treatments seemed to increase soil C storage at 0–30 cm after 39 months, but did not significantly change forest floor C storage after 4 and 39 months. Concentrations of exchangeable K+ of T15 and exchangeable base cations except for Ca2+ of T30 depth were significantly lower than those of the control at 0–10 cm after 4 months, but not after 39 months. This study shows that thinning treatments on a naturally regenerated Quercus spp. forest could increase soil C concentration after a few years but temporally decrease concentrations of soil exchangeable base cations.

Sheep manure application increases soil exchangeable base cations in a semi-arid steppe of Inner Mongolia

The long-term productivity of a soil is greatly influenced by cation exchange capacity (CEC). Moreover, interactions between dominant base cations and other nutrients are important for the health and stability of grassland ecosystems. Soil exchangeable base cations and cation ratios were examined in a 11-year experiment with sheep manure application rates 0–1,500 g/(m2·a) in a semi-arid steppe in Inner Mongolia of China, aiming to clarify the relationships of base cations with soil pH, buffer capacity and fertility. Results showed that CEC and contents of exchangeable calcium (Ca2+), magnesium (Mg2+), potassium (K+) and sodium (Na+) were significantly increased, and Ca2+ saturation tended to decrease, while K+ saturation tended to increase with the increases of sheep manure application rates. The Ca2+/Mg2+ and Ca2+/K+ ratios decreased, while Mg2+, K+ and Na+ saturations increased with increasing manure application rates. Both base cations and CEC were significantly and positively correlated with soil organic carbon (SOC) and soil pH. The increases of SOC and soil pH would be the dominant factors that contribute to the increase of cations in soil. On a comparison with the initial soil pH before the experiment, we deduced that sheep manure application could partly buffer soil pH decrease potentially induced by atmospheric deposition of nitrogen and sulfur. Our results indicate that sheep manure application is beneficial to the maintenance of base cations and the buffering of soil acidification, and therefore can improve soil fertility in the semi-arid steppes of northeastern China.

Amelioration of an Ultisol profile acidity using crop straws combined with alkaline slag.

The acidity of Ultisols (pH <5) is detrimental to crop production. Technologies should be explored to promote base saturation and liming effect for amelioration of Ultisol pH. Column leaching experiments were conducted to investigate the amelioration effects of canola straw (CS) and peanut straw (PS) in single treatment and in combination whether with alkaline slag (AS) or with lime on Ultisol profile acidity. The treatment without liming materials was set as control, and the AS and lime in single treatment are set for comparison. Results indicated that all the liming materials increase soil profile pH and soil exchangeable base cations at the 0-40-cm depth, except that the lime had amelioration effect just on 0 to 15-cm profile. The amelioration effect of the liming materials on surface soil acidity was mainly dependent on the ash alkalinity in organic materials or acid neutralization capacity of inorganic materials. Specific adsorption of sulfate (SO4(2-)) or organic anions, decarboxylation of organic acids/anions, and the association of H(+) with organic anions induced a "liming effect" of crop residues and AS on subsoil acidity. Moreover, SO4(2-) and chloride (Cl(-)) in PS, CS, and AS primarily induced base cations to move downward to subsoil and exchange with exchangeable aluminum (Al(3+)) and protons (H(+)). These anions also promoted the exchangeable Al to leach out of the soil profile. The CS was more effective than PS in decreasing soil acidity in the subsoil, which mainly resulted from higher sulfur (S) and Cl content in CS compared to PS. The CS combined with AS was the better amendment choice in practical agricultural systems.

Characterization of 27 mycotoxin binders and the relation with in vitro zearalenone adsorption at a single concentration.

The aim of this study was to characterize 27 feed additives marketed as mycotoxin binders and to screen them for their in vitro zearalenone (ZEN) adsorption. Firstly, 27 mycotoxin binders, commercially available in Belgium and The Netherlands, were selected and characterized. Characterization was comprised of X-ray diffraction (XRD) profiling of the mineral content and d-spacing, determination of the cation exchange capacity (CEC) and the exchangeable base cations, acidity, mineral fraction, relative humidity (RH) and swelling volume. Secondly, an in vitro screening experiment was performed to evaluate the adsorption of a single concentration of ZEN in a ZEN:binder ratio of 1:20,000. The free concentration of ZEN was measured after 4 h of incubation with each of the 27 mycotoxin binders at a pH of 2.5, 6.5 and 8.0. A significant correlation between the free concentration of ZEN and both the d-spacing and mineral fraction of the mycotoxin binders was seen at the three pH levels. A low free concentration of ZEN was demonstrated using binders containing mixed-layered smectites and binders containing humic acids.

Soil Fertility Status and Productivity Trends Along a Toposequence: A Case of Gilgel Gibe Catchment in Nadda Assendabo Watershed, Southwest Ethiopia

The Impact of landscape positions and land use type on properties as well as land productivity are commonly observed in Ethiopia. The study was therefore conducted to quantify soil fertility and productivity trends under three land uses along the gradient (lower, middle and upper slope positions) of Nadda Assendabo watershed, Southwest Ethiopia. Thus field survey was covered a total of 54 composite soil samples using split plots (for soil physical properties) and split-split factorial arrangements with randomized complete block design from woodlot, grazing and crop land following topographic positions then different parameters were analyzed. The highest mean soil moisture content (56.68%) and porosity (71.09%) were observed for woodlot at the lower slope while the highest soil bulk density (1.74 g/cm³) was observed for soil crop land at the upper slope where as the lowest (0.94 g/cm³) was for woodlot at the lower slope. Sand, silt and clay fractions were significantly affected by interaction effects of slope and land uses (P≤0.01). Soil pH, electrical conductivity, organic carbon, cation exchange capacity, total nitrogen, available phosphorus, base saturation percentage and exchangeable basic cations for all land uses were increased down slope while they were affected significantly by slope steepness, land use and soil depth (P≤0.01). Therefore, electrical conductivity at middle and upper slope in grazing land and woodlot; total nitrogen, available phosphorus in crop land at lower slope was significantly different (P≤0.05) due to interaction effect. Furthermore, above ground biomass and grain yields of sorghum, maize and teff were also calculated on farm fields using split plots arrangements. Thus both yields were significantly affected by interaction effect of slope and crop type. Finally, based on the results woodlot, grazing and crop land were recommended for upper, middle and lower slopes respectively.

Forest restoration with Betula ssp. and Populus ssp. nurse crops increases productivity and soil fertility

The rapid re-establishment of forests following large disturbances is being seen as one option to increase the contribution of forests to climate change mitigation. The temporary inclusion of pioneer trees as nurse crops on disturbed sites can facilitate the establishment of target tree species and may additionally benefit productivity and soil fertility. In this study we compared productivity and nutrient cycling between stands of oak target species (Quercus robur and Quercus petraea) that were established with and without widely spaced Betula ssp. or Populus ssp. nurse crops. Simulation results for a full rotation of oaks (180years) indicated that both types of forests, with and without nurse crops, have a comparable total productivity. However, stands with nurse crops supplied 59–96Mgha−1 harvestable biomass after 20years, whereas the first harvest of biomass from stands without nurse crops would occur at least 30years later. Nutrient element costs associated with the removal of Betula ssp. wood were low compared to Populus ssp. Also, nurse crop stands had up to 2.5 times larger pools of exchangeable base cations in top mineral soils (0–30cm) compared to mono-specific oak stands. The high soil cation pools may have resulted from reduced leaching under nurse crops or the increased recycling of cations, also from deeper soil depth, via litter fall and fine-root turnover. Our results show that forest reestablishment with pioneer tree species may be a suitable tool for the rapid recovery of forest productivity and mitigation potential following disturbances while simultaneously helping to maintain or increase soil fertility.

Effect of Carbonates and Bivalent Cations and Their Relationships with Soil Organic Matter from the View Point of Aggregate Formation

Abstract The effect of carbonates on soil structure has not been sufficiently studied yet, despite the fact that in the literature their positive impact is mentioned mostly. Carbonates are the source of bivalent cations in soil solution and may be involved in stabilization of the aggregates, because negatively charged organic materials can be adsorbed onto the surface of clay by bivalent or polyvalent cations. We studied the effect of carbonates and bivalent cations and their relationships with soil organic matter (SOM) from the point of view of aggregate formation. The studies were carried out in several fields located on loamy Calcaric Chernozem, loamy Haplic and Mollic Fluvisols. The results showed that between exchangeable Mg2+ and water-stable macro-aggregates (WSAma) in size fractions &gt;2 mm, positive correlations were found; however, the content of Mg2+ negative correlated with the contents of WSAma in &lt;1 mm fractions as well as with waterstable micro-aggregates (WSAmi). The threshold limit for Mg2+ content for the formation of water-stable macro-aggregates was at 11.5 cmol/kg if all loamy soils were assessed together. A further increase resulted in a lower content of WSAma. If all investigated soils were assessed separately, these results did not enable us to distinguish the maximum formation of WSAma by Mg2+ in individual soils. We observed a positive correlation between the sum of basic exchangeable cations (SBC) as well as between cation exchange capacity (CEC) and larger size fractions of WSAma &gt;2 mm; however, between SBC as well as CEC and smaller size fractions of WSAma &gt;1 mm and WSAmi negative correlations were observed. Statistically significant negative correlations were observed between SOM content in WSA and carbonate content, and this effect was stronger in relation to the labile carbon. There were also positive correlations between SOM in WSA and SBC and CEC found if all loamy soils were assessed together.

Effects of aged and fresh biochars on soil acidity under different incubation conditions

Biochar has positive effects as a soil acidity amendment which is a global concern. However, few studies have been reported on the effect of aged biochar on soil acidity. Incubation methods with different ventilation conditions may induce different effects on soil acidity amendment using biochar. This study analyzed the effects of fresh and aged biochars on soil acidity amendment with different incubation methods. Samples of typical acidic soil (plinthudults) and fresh Pinus massoniana bark were collected from the hilly red soil region of southern China and used to create biochar (PB) with the oxygen-limited pyrolysis method at 450°C. A 4-month-aged PB (PBa) which was produced by a natural forest fire was collected from the same area as that of biochar PB. A 69 days incubation experiment was conducted using an improved incubation method. The treatments comprised 100g soil+2g PBa (PBA), 100g soil+2g PB (ventilated incubation, PBV), 100g soil+2g PB (sealed incubation, PBS) and 100g soil only incubated under ventilated (CKV) and sealed (CKS) conditions. Soil pH was measured periodically. Soil exchangeable base cations, exchangeable acidity, exchangeable aluminum (Al3+) and cation exchange capacity (CEC) were measured after incubation. Throughout the incubation period, PB and PBa positively enhanced soil pH (P<0.05), with PB exhibiting more remarkable effects. A similar effect was also observed for soil exchangeable Al3+ and exchangeable acidity. After incubation, soil pH values of PBV (5.05±0.02) and PBS (4.99±0.03) were than the value of PBA (4.98±0.03), with nonsignificant differences (P>0.05) between values in PBV and PBS. PB addition improved soil exchangeable base cations and base saturation compared to PBa addition. Soil CEC levels in PBA, PBV, and PBS were not significantly different from those in CKV and CKS, but CEC in PBV and PBS were significantly higher than the CEC in PBA. All parameters in PBV were not significantly different from the parameters in PBS. Biochar PB can be used to amend soil acidity, but the efficiency declines to a certain extent if biochar PB has undergone a short-term aging before being added to soils. The different ventilation conditions had little influence on soil acidity amendment using biochar.

Use of Alkaline Slag and Crop Residue Biochars to Promote Base Saturation and Reduce Acidity of an Acidic Ultisol

This investigation was conducted by using alkaline slag and crop straw biochars to reduce acidity of an acidic Ultisol through incubation and pot experiments with lime as a comparison. The soil was amended with different liming materials: lime (1 g kg−1), alkaline slag (2 and 4 g kg−1), peanut straw biochar (10 and 20 g kg−1), canola straw biochar (10 and 20 g kg−1) and combinations of alkaline slag (2 g kg−1) and biochars (10 g kg−1) in the incubation study. A pot experiment was also conducted to observe the soybean growth responses to the above treatments. The results showed that all the liming materials increased soil pH and decreased soil exchangeable acidity. The higher the rates of alkaline slag, biochars, and alkaline slag combined with biochars, the greater the increase in soil pH and the reduction in soil exchangeable acidity. All the amendments increased the levels of one or more soil exchangeable base cations. The lime treatment increased soil exchangeable Ca2+, the alkaline slag treatment increased exchangeable Ca2+ and Mg2+ levels, and the biochars and combined applications of alkaline slag with biochars increased soil exchangeable Ca2+, Mg2+ and K+ and soil available P. The amendments enhanced the uptake of one or more nutrients of N, P, K, Ca and Mg by soybean in the pot experiment. Of the different amendments, the combined application of alkaline slag with crop straw biochars was the best choice for increasing base saturation and reducing soil acidity of the acidic Ultisol. The combined application of alkaline slag with biochars led to the greatest reduction in soil acidity, increased soil Ca, Mg, K and P levels, and enhanced the uptake of Ca, Mg, K and P by soybean plants.

Acidification processes in soils with different acid buffering capacity in Cryptomeria japonica and Chamaecyparis obtusa forests over two decades

Although plant–soil interactions play important roles in regulating soil acidity, it remains unclear whether the species influence is changeable across soil acidity gradients. We resampled soils in eight stands of Cryptomeria japonica and seven stands of Chamaecyparis obtusa in which soil chemical properties were documented in the 1990s. Half of the sites for each species had soils with a high acid buffering capacity (ABC), and the remaining sites had soils with a low ABC. ABC was defined by two criteria: the concentration of exchangeable base cations and the concentration of exchangeable Al. The aims of this study were (i) to characterize the accumulation of base cations and exchangeable Al by both tree species in high- or low-ABC soil profiles down to a depth of 40cm and (ii) to clarify the changes of soil ABC in stands of C. japonica or C. obtusa grown in high- or low-ABC soil over the past two decades. In the low-ABC group, Ca depletion and Al accumulation were observed in both species. Potassium depletion also occurred in C. obtusa stands. In contrast, high-ABC soils showed different trends. In C. japonica soils, Ca accumulated during this period and sharp distinctions in exchangeable Ca concentrations were observed between the uppermost soil horizons and deeper horizons; however, in C. obtusa soils such distinctions were not evident and depletions both Ca and K occurred. These results suggest that plant–soil interactions differed in the two soils. We speculate that C. japonica accumulates Ca in soils with high ABC but loses this trait in low-ABC soils, meaning that C. japonica responds to an acidic environment with a positive feedback of soil acid buffering capacity, such that ABC becomes greater in a high-ABC soil and smaller in a low-ABC soil. It appears that C. obtusa promotes depletion of cations such as Ca and K and accumulation of exchangeable Al in soils regardless of ABC. Neither C. japonica nor C. obtusa is suitable for planting in nutrient-poor soils as they promote a shortage of base cations and an increase in Al toxicity.

Impact of Community Conservation Management on Herbaceous Layer and Soil Nutrients in a Kenyan Semi‐Arid Savannah

AbstractThe impact of community conservation management on a semi‐arid savannah herbaceous vegetation and soil nutrient status was studied in the conservation and grazing zones of two community ranches in Laikipia County, Kenya. Land zoning was carried out in 1999 using participatory approaches to demarcate conservation areas excluded from livestock grazing, buffer areas for grazing and high‐intensity use zones for both grazing and settlement. Collected data included cover, grass species composition, standing grass biomass and topsoil chemical characteristics using line transect and quadrant methods. The conservation zones had significantly higher herbaceous diversity, species richness and relative abundance of both annual and perennial grasses, basal cover and herbage and a lower percentage of bare ground compared with the continuously grazed zones. The conservation zones also had higher total organic carbon, organic nitrogen and exchangeable basic cations content, indicating improved soil nutrient status. The grazing zones exhibited loss of vegetation cover and reduction of forage production, with a decline in rangeland condition, whereas the conservation zones showed recovery and improvement of the rangeland condition. Long‐term implementation of Natural resource management programme in community wildlife conservancies seems to drive the semi‐arid savannahs to exist in two steady states and transitions under the influence of grazing. We recommend long‐term monitoring of the impact of the community conservation model on the rangeland and timely incorporation of remedial measures such as shifting bomas (cattle corrals) across the grazing zones, aggressive rangeland rehabilitation of severely degraded areas through reseeding and random grass seed broadcast along stock routes. Copyright © 2014 John Wiley &amp; Sons, Ltd.

The match between microbial community structure and soil properties is modulated by land use types and sample origin within an integrated agroecosystem

It is of global concern to adopt measures to mitigate land degradation caused by agricultural production systems. One of the strategies proposed is to replace degraded pastures with agrosilvopastoral systems which integrate three different land-use types: crop production, livestock pasture and forestry plantation (denoted iCLF). However, little is known about the differences between iCLF and other land use types in terms of soil microbial community structure. Distance matrices based on individual soil chemical properties and individual soil microbial variables were correlated by Procrustes analysis and these relationships yielded vectors of residuals depicting these correlations (matches). These vectors were used as univariate response variables in an ANOVA framework in order to investigate how the match sizes (the strength of correlation/covariance) between individual soil chemical properties and individual soil microbial variables vary across land use types (levels: iCLF; degradated pasture; improved pasture; and a native cerrado fragment) and also across sample origin within iCLF (levels: soil samples under more influence of the exotic tree forest stand; soil samples under influence of the pasture; samples within the transition between the forest stand and the pasture). We were able to obtain insights into the fact that the land use distinction can be driven by more than just individual soil chemical and microbial variables. The integration of crop, livestock and forestry promoted a dominance of fungi in this low fertility and low pH environment. P availability and the composite variable exchangeable base cations (Ca+2, Mg+2, K+) were the soil properties whose strengths of correlation (match sizes) with individual microbial variables were the most affected by land use type and sampling origin within iCLF. While the strength of the correlation between soil microbial structure variables and P availability was typically land use type dependent, the response of the microbial structure to exchangeable base cations was mainly affected by the sample origin within iCLF. Finally our results point towards the conclusion that increases in the heterogeneity of vegetation within integrated crop, pasture and forestry systems are an important driver of microbial community response to environmental changes, and may be one means by which to increase the sustainability of tropical agroecosystems.