Exchangeable Bases Research Articles

Dynamics of soil properties as impacted by contrasting lithology, slope class, and land use types: a case study in semi-arid highlands of northern Ethiopia.

Soil characterization is crucial in creating sustainable platforms for land users to identify areas vulnerable to anthropogenic activities. This study was conducted to investigate the impacts of lithology, slope, and land use on soil properties of a semi-arid highland in northern Ethiopia. Disturbed and undisturbed soil samples collected from 0 to 30 cm depth were analyzed. Most of the assessed physical and biochemical soil properties varied significantly (p < 0.05) with lithology, slope class, and land use type. Shale-originated soils were richer in nutrients than soils of other lithologies. A decrease in slope gradient accounted for an increase in most soil properties, while a reverse trend was observed for sand content, bulk density (BD), water stable aggregates (WSA), mean weight diameter (MWD), structural stability index (SSI), soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP). Silt and clay fractions, total porosity, moisture content at field capacity and wilting point, visual evaluation of soil structure, pH, electrical conductivity, calcium carbonate, exchangeable bases, cation exchange capacity, and percent base saturation were found to be higher for cultivated land soils compared to grass land and shrub land soils. Shrub land soils, in contrast, had higher WSA, MWD, SSI, SOC, TN, and AP relative to grass land and cultivated land soils. In summary, slope class and land use type stood out as the major drivers influencing the dynamics and distribution of soil properties other than lithology and their interactions in semi-arid highlands of northern Ethiopia. Thus, from sustainability point of view and in the light of their nutrient retention capability and limitation, more attention should be paid toward ensuring periodic assessment and sustainable management of soils in steep cultivated lands.

Impacts of Extensive Sheep Grazing on Soil Physical and Chemical Quality in Open Mountain Forests, NE Portugal

Grazing and mechanical clearing are common techniques for vegetation management in open Mediterranean forests. Despite its recognized benefits in the prevention of high-intensity and severity forest fires, it is essential to consider its impacts on the physical and chemical soil properties. In an open mountain forest located in the NE of Portugal, soil samples were analyzed at depths 0–5, 5–10, and 10–20 cm collected at two moments: before mechanical clearing, (Control) and after 18 months of extensive sheep grazing, in areas without grazing, only mechanical clearing (MC) and in areas with both mechanical clearing and grazing (MCG). The results indicate that vegetation cutting has induced a significant decrease in extractable potassium, and an increase in the soil organic matter and total nitrogen. The exchangeable bases and the exchangeable acidity did not undergo expressive changes, as indicated by the pH values and the cation exchangeable capacity. After grazing, extractable phosphorus and potassium, organic matter, total nitrogen, exchangeable bases, and cation exchangeable capacity have increased significantly in the topsoil (0–5 cm), reducing soil acidity. Regarding physical properties, only soil permeability has been negatively affected by grazing. Mediterranean mountain open forests management with the combination of vegetation clearing and extensive sheep grazing proved to be effective in reducing vegetable fuel availability and improving soil quality.

The Impact of traditional cocoa-based agroforestry systems on chemical soil fertility in southwest of Côte d'Ivoire

The sustainability of cocoa farming is a major concern for Côte d'Ivoire. Extensive and "full sun" cropping systems need to be reviewed. Against this backdrop, a study was carried out in the south-west of the country (Soubré and Méagui), a major production zone, with the aim of assessing the impact of traditional agroforestry systems on soil fertility. Twenty-seven cocoa farms in the three sectors were visited. To assess the impact of cocoa-based agroforestry systems on soil chemical parameters, four criteria guided the choice of plots. These were mid-slope plots, 25 to 35 years old, unfertilized and denser in associated trees. Soil samples were taken from the 0-20 cm horizon. Organic carbon, total nitrogen, assimilable phosphorus, exchangeable bases (Ca, Mg, K and Na), cation exchange capacity and saturation rate were measured. The results show that traditional cocoa-based agroforestry systems have not impoverished the soil. In fact, chemical fertility in these plots respects the needs of cocoa trees. However, the study did not show an increase in soil organic matter due to the fall of leaves from associated trees. These results will enable the use of traditional agroforestry systems without fear of soil impoverishment due to any competition between cocoa trees and associated trees.

Manganese losses induced by severe soil acidification in the extensive Lei bamboo (Phyllostachys violascens) plantation stands in Eastern China

Manganese (Mn) is a critical element in soils, essential to plant growth. Long-term and intensively managed Lei bamboo (Phyllostachys violascens) stands are usually subjected to severe soil acidification and Mn activation. However, Mn migration from topsoil to deep soil induced by severe soil acidification was poorly recognized and studied. The distribution and changes of the total and the operationally defined Mn forms in soil profiles and its potential stress and environmental effect were investigated in a chronosequence of Lei bamboo stands (0, 2, 6, 11, and 16 years of stand age). The results showed that the Mn amount was significantly decreased in topsoil and accumulated in subsoil with the long-term and intensive fertilizer application. Soil exchangeable Mn and superphosphate extractable Mn demonstrated large different variation to total Mn, whereas their sum was largely higher than and highly correlated with 8-hydroxyquinoline (HQN) extractable Mn. Soil organic carbon, pH value, exchangeable bases, and soil redox simultaneously controlled soil Mn depletion. In conclusion, long-term and intensive fertilizer application leads to soil acidification and accelerated soil Mn depletion in bamboo stand soil, promoting Mn accumulation in bamboo shoots.

Definition and Validation of Vineyard Management Zones Based on Soil Apparent Electrical Conductivity and Altimetric Survey

In the current context of increasing costs of production factors, it is essential to optimize the management of available resources, seeking to incorporate technologies that improve knowledge of the variables involved in the agronomic production process. The aim of this study is to define and validate management zones (MZ) in a 3.3 ha vineyard located near Évora, in the South of Portugal. A contact sensor (“Veris 2000 XA”) was used to map soil apparent electrical conductivity (ECa) and a precision altimetric survey of the field was carried out with a global navigation satellite system receiver (GNSS). The results of these surveys were submitted to geostatistical treatments that allowed the definition of three MZ (less, intermediate, and more productive potential). The validation of such MZ was carried out by laboratory analysis of soil samples (texture, pH, organic matter—OM, moisture content, phosphorous, potassium, exchange bases, and cation exchange capacity—CEC), measurements of soil compaction (cone index—CI) with an electronic cone penetrometer, and through indices (Normalized Difference Vegetation Index—NDVI, and Normalized Difference Water Index—NDWI) obtained by remote sensing (RS) using Sentinel-2 satellite images. All these parameters (soil parameters and RS indices) proved the validity of the MZ (of less, intermediate, and more productive potential) defined from the ECa and altimetric survey. This validation attests to the interest of expeditious technological tools for monitoring ECa as a fundamental step in implementing smart agronomic decision-making processes.

Dynamics of land cover changes and condition of soil and surface water quality in a Mining–Altered landscape, Ghana

This study investigated the dynamics of mining effects on land use land cover changes and the chemical and physical characteristics of soil and surface water in the Ahafo mining area in Ghana. Landsat imagery was used to analyze land use-land cover changes (LULC) using a supervised classification technique. Soil samples were collected within 600 m from active mining operations and at depths of up to 75 cm, as well as surface water samples from upstream and downstream of the mine. Atomic Absorption Spectrometry was used to determine the concentration of heavy metals in the soil and water samples. The results demonstrated a significant loss of forest and other vegetation covers, which decreased from 44% to 31% to 8% and 20%, respectively, with corresponding increases in the mining site, mine water, settlement/bare surface, cropland and plantation. Organic matter, organic carbon, exchangeable bases, cation exchange capacity, available phosphorus, and pH were all moderate in the soil surrounding the mine. Except for As (4.027 mg/kg) and Hg (1 mg/kg), all heavy metals found in the soil were within FAO/WHO guidelines. Total Dissolved Solids (TDS) (416.18 mg/L), Total Suspended Solids (55.08 mg/L), Turbidity (54.49 NTU), Ca (84.49 mg/L), Mg (31.97 mg/L), nitrate (10.23 mg/L), and sulphate (606.83 mg/L) in the downstream water were higher than those in the upstream and USEPA/WHO limits for drinking water except for TDS. Because of the geology of the area, there were high concentrations of iron, manganese, and aluminum in the surface water. The results show that mining induced severe land cover changes and impaired surface water and soil quality in the mine's vicinity. The findings have implications for stakeholder education, appropriate community water interventions, and company-community-regulator participatory monitoring to avoid health risk exposure and further water and soil quality and vegetation degradation.

Zeoponic formula for plant growth media for ornamental plants Aglaonema siam aurora and Anthurium crystallinum

Plant growth media (PGM) play a crucial role in producing healthy and valuable ornamental plants. A good PGM has the suitable physical, chemical, and biological properties that can help realize the total growth and development potential of the plants. One PGM developed that meets these requirements is a zeoponic, made from zeolite, compost, and cocopeat as raw materials, and formulated specifically for ornamental plants. Ornamental plants are horticultural commodities with high economic value driven by fast-growing demand. However, a common problem in the cultivation of ornamental plants is the unwanted degradation in the appearance of the leaves, e.g., turning into pale and faded color. Hence, the application of an accurate dosage of macro and micro fertilizers on zeoponic ornamental plants can boost growth and enhance the aesthetic value of the plants. With this in mind, this study aimed to find the precise fertilizer formula, specially or even exclusively, for ornamental plants. The experiment was arranged in a factorial completely randomized design (CRD) with two factors, namely (1) plant species consisting of Aglaonema siam aurora and Anthurium crystallinum, and (2) fertilizer dosage consisting of different combinations of N, P, and K fertilizers as well as micro fertilizers. Test parameters observed were plant height, number of leaves, leaf length, leaf width, leaf chlorophyll, and plant beauty. PGM analysis was carried out by measuring pH, EC, available-N, available-P, cation exchange capacity, exchangeable bases, organic-C, and micronutrients. This study showed that zeoponic with a dosage of 0.375 g/l NPK fertilizer was the best for Aglaonema siam aurora, while zeoponic with a dosage of 0.75 g/l of NPK fertilizer was the best for Anthurium crystallinum plants. The use of zeoponic media is highly recommended owing to its suitable chemical properties (e. g, neutral pH, favorable EC and CEC).

SERAPAN N, P, DAN K PADA JAGUNG MADURA-3 DI TANAH LEMPUNG LIAT BERPASIR DIAMELIORASI BIOCHAR DAN BENTONIT-TERAKTIVASI ASAM

Sandy clay loam soil in Bangkalan is a soil with a low content of nutrients, organic matter, bases, and cation exchange capacity (CEC), which inhibits the growth of maize plants. In addition, the nature of the soil causes the fertilizer to become more soluble, and the absorption of nutrients, especially potassium, is low. One of the efforts to increase potassium uptake in sandy loam soils is applying biochar and acid-activated bentonite. This study aimed to examine the effect of adding biochar and acid-activated bentonite to the nutrient uptake of maize plants in the sandy soil of Bangkalan. Biochar was prepared from maize cobs by the Kon-Tiki method; bentonite was activated by physical (200 oC) and chemical (1N H2SO4) methods. The greenhouse experiment was carried out using a completely randomized design with biochar (B) and acid-activated bentonite (T) as treatments, each with three levels, namely 0, 5, 10 t ha-1 and three replications. Soil analysis performed included pH, organic carbon, CEC and exchangeable bases, while plant tissue analysis included leaf height and area. The results showed that the combination of biochar and acid-activated bentonite significantly increased soil pH, soil exchangeable K, soil exchangeable Na, and leaf area of maize plants. A single application of biochar significantly increased soil organic C and maize plant height. The application of acid-activated bentonite significantly increased the CEC of sandy loam soils.

Characterization and suitability assessment of the soils of Iwo series for cocoa production in rainforest area Southwestern, Nigeria

Characterization and soil suitability assessment is a vital tool for understanding the nature and status of soils. It is one of the strategies for achieving food security as well as sustainable environment. This study was conducted to assess the suitability of the soils of Iwo series for sustainable production of cocoa. The study was carried out in 2022, in an area located approximately between 7°32' N and 7°33' N and longitudes 4°32' E and 4°40' E within the Teaching and Research Farm (T&amp;R-F) of Obafemi Awolowo University (OAU), Kajola, Ile-Ife, Nigeria. Three profile pits were established, described and sampled with one at different physiographical units following the guideline for soil profile description according to FAO/UNESCO guideline. The soil samples collected were analyzed for particle size distribution, pH, total nitrogen, available phosphorus, exchangeable bases, and organic matter using standard method. Land characteristics obtained were matched with the crop requirements for cocoa to obtain the soils’ suitability classes using parametric method. The results showed that all the soils are well drained and deep. The texture of the soils ranged from sandy loam to sandy clay loam at the surface and sandy clay loam to clay at subsurface. Soil reaction ranged from highly acidic to slightly acidic (4.2-5.8 water and 3.9- 5.7 pHCaCl2) with low to moderate amounts of organic matter (0.4 to 1.74%) and available nitrogen (0.02-0.14%). Available phosphorus varied from 0.52-24.77 mg/kg in all the horizons in the profiles with the highest values at the surface soil horizons, an indication that soil organic matter contributes significantly to the available P in these soils. The exchangeable bases were low and the relative abundance of the exchangeable bases followed the order: Ca&gt; Mg &gt; Na&gt;K at the exchangeable site. Suitability evaluation of the soils was carried out using parametric approach and the result showed that the soils of mapping units A and B are presently not suitable (N1) while mapping unit C is marginally suitable for cocoa production. With the appropriate fertility management, the soils of mapping unit A were classified as marginally suitable (S3) while soils of mapping unit B and C were classified as moderately (S2) for cocoa production. The limiting factors were mainly low soil fertility (low level of available phosphorus, macro-nutrients, nitrogen and organic matter). Therefore, combined application of organic fertilizer with inorganic fertilizers should be encouraged for optimum productivity.

Characteristics and utilization of black soils in Indonesia

Black soils store a high amount of soil organic carbon (SOC) and play a crucial role in climate change, food security, and land degradation neutrality. However, data and information regarding black soils in tropical regions, including Indonesia, are limited. This study aimed to characterize and identify the utilization of black soils in Indonesia based on legacy soil survey data. We collated 142 soil pedon samples of Mollisols from articles, technical reports, and existing datasets. The site information (site position, elevation, land use type, parent material) and selected physicochemical properties were stored in a spreadsheet, from which exploratory data analysis was conducted. The result showed that the median SOC content was 1.53%, ranging from 0.6 to 8.2 %; cation exchange capacity was 30 cmol kg&lt;sup&gt;-1&lt;/sup&gt;, ranging from 9 to 95 cmol kg&lt;sup&gt;-1&lt;/sup&gt;; base saturation was 87%, ranging from 11 to 100 %; and bulk density was 1.21 g cm&lt;sup&gt;-3&lt;/sup&gt;, ranging from 1.13 to 1.36 g cm&lt;sup&gt;-3&lt;/sup&gt;. Other soil characteristics (particle size distribution, exchangeable bases, pH, pore, and water retention) varied with horizon type and land use/land cover. The black soils have been used for paddy fields, dryland farming, and gardens with low management intensity. Main cultivated crops include rice (&lt;em&gt;Oryza sativa&lt;/em&gt;), corn (&lt;em&gt;Zea mays&lt;/em&gt;), cassava (&lt;em&gt;Manihot esculenta&lt;/em&gt;), sweet potato (&lt;em&gt;Ipomoea batatas&lt;/em&gt;), and nutmeg (&lt;em&gt;Myristica fragrans&lt;/em&gt;), clove (&lt;em&gt;Syzygium aromaticum&lt;/em&gt;), coconut (&lt;em&gt;Cocos nucifera&lt;/em&gt;), and cocoa (&lt;em&gt;Theobroma cocoa)&lt;/em&gt;. Threats to black soil functions include soil erosion, carbon loss, and nutrient imbalance. Soil and water conservation measures, integrated soil nutrient management, and agroforestry are among the best land management practices for black soils.

Effects of integrated fertilization on soil sustainability and cassava (Manihot esculenta Crantz) yield in an ultisol

The present study aimed to assess the effects of integrated fertilization on soil and cassava yield. A randomized complete block design (RCBD) was used in the 24 x 5 factorial. Factor A comprised 24 cassava genotypes, while Factor B comprised five fertilizer treatment rates (2.5 t/ha poultry manure (PM) + 300 kg/ha NPKMg, 5 t/ha PM + 200 kg/ha NPKMg, and 7.5 t/ha PM + 100 kg/ha NPKMg), 400 kg/ha NPKMg fertilizer, and control. Integrated fertilizer application improved soil fertility compared to 400 kg/ha NPKMg and control treatments. Integrated fertilization of 7.5 t/ha PM and 100 kg/ha NPKMg had a 16–26% and 15–25% significant increase in soil pH compared to other treatments, respectively. Application of 7.5 t/ha PM + 100 kg/ha NPKMg had significant organic matter content at harvest (2.92 and 3.11%) compared to initial values of 1.37 and 1.55%. The treatments of 7.5 t/ha PM and 100 kg/ha NPKMg had (30-88% and 30-87%) and (8-94%, and 11- 91%) higher organic matter and N than other treatments at harvest. Significant differences (P&lt;0.05) were observed in storage root yields. The NR07/0240 produced significant storage root yields of 34.41 and 34.12 t/ha in both cropping seasons. Obubit Okpo had the least yield: 7.34 and 6.55 t/ha. Treatment with 7.5 t/ha PM and 100 kg/ha NPKMg out-yielded other fertilizer treatments, while control had the least storage root yield. The result revealed that treatments with integrated fertilizers had lower soil pH, significantly higher total N, organic matter, and exchangeable bases at harvest.

CHANGES IN PHYSICAL AND CHEMICAL PROPERTIES AND HUMUS CONTENT OF TYPICAL BLACK SOIL IN TREATMENT AND FERTILIZER SYSTEMS

The article presents the results of studies on the effectiveness of various systems of basic soil cultivation and fertilizer systems for growing winter wheat, and their impact on the physicochemical properties of typical black soil and organic matter content. The experiment included plough tillage, tillage with a 10-12 cm disc harrow, 'No-till' technology, and a mineral fertilizer system - source-saving minimized and intensive. The study was conducted in the agrocenosis of winter wheat. The results showed that shallow tillage with a disc harrow and resource-saving minimized mineral fertilizer increased the humus content in the 0-15 cm layer by 0.04% and in the 15-30 cm layer by 0.03% compared to inversion tillage. High rates of hydrolytic acidity (1.61-2.92 mol/m3/100 g of soil) were noted at all doses of mineral fertilizer when using inversion tillage. More optimized indicators of the sum of exchangeable bases of typical chernozem in a layer of 15-30 cm were noted during inversion tillage - 28.0 mol/m3/100 g of soil. The lowest value of the sum of exchangeable bases in the 15-30 cm layer was noted using the No-till technology - 27.6 mol/m3/100 g of soil. High rates of hydrolytic acidity (1.61-2.92 mol/m3/100 g of soil) were observed at all doses of mineral fertilizer using surface tillage. More optimized indicators of the sum of exchangeable alkaline of typical black soil in a layer of 15-30 cm were noted during shelf tillage - 28.0 mol/m3/100 g of soil. The lowest value of the sum of exchangeable alkalines in the soil layer of 15-30 cm according to the No-till technology was 27.6 mol/m3/100 g of soil.

THE IMPACT OF FOREST FIRES ON THE SOIL COVER IN THE CONDITIONS OF THE KUYAR FORESTRY OF THE REPUBLIC OF MARI EL

The influence of forest fires on the physico-chemical properties of sandy soils formed under pine plantations of the southern Taiga subzone in the conditions of the Republic of Mari El is shown. As a result of investigations of 4 soil sections, including 1 control and analysis of about 30 soil samples, soil parameters with the greatest and least variability were revealed. It was found that only the forest floor, which burned completely, with the formation of a specific Opir horizon, was exposed to a low forest fire, the upper mineral horizons have no signs of pyrogenicity. It was found that in the first post-fire year, the acidity in the upper soil horizons slightly increases compared to the control site, along with this, there is an increase in the amount of exchange bases and the degree of saturation with bases, the content of exchangeable potassium and loss indicators during calcination sharply decreases in forest litter. Regression equations are constructed on the basis of the revealed close relationships. It is concluded that, despite the absence of pyrogenic signs in the upper mineral horizons, their properties also change significantly under the influence of the combustion products embedded here together with the soil solution. To detail the data on the functioning of post-pyrogenic ecosystems, a long period of observations and scientific research is necessary.

Soil chemical attributes under west indian cherry fertigated with nitrogen and humic substances

The use of humic substances (HS) in the soil can increase the efficiency of nitrogen fertilizers and contribute to the increment in soil organic matter and plant nutrient availability. Hence, this study aimed to evaluate, in two production cycles, the effect of applying HS and different nitrogen (N) doses on the chemical attributes and organic matter fractions of a soil cultivated with West Indian cherry in the Brazilian semiarid region. The experiment was set up in split plots, arranged in strips with four replicates. The absence or presence of HS using KS100 as the source was tested in the plots, and N fertilization (50; 75; 100; 125 and 150% of the recommended dose), using urea, was tested in the subplots. Soil pH, H+Al, Al3+, and Na+, K+, P, Ca2+, Mg2+, Fe2+, Mn2+ and Zn2+ contents were determined, and cation exchange capacity and bases saturation (V %) in the 0-0.2 and 0.2-0.4 m layers were calculated. Analyses of stocks of total organic carbon and carbon (C) of the humic acid, fulvic acid and humin fractions, and humic substances were performed. It was possible to observe that, in the second production cycle of West Indian cherry, the soils showed higher contents of nutrients available to plants. Increase in N availability did not enable a clear trend in the behavior of chemical attributes and organic C stocks in the soil. Under the studied conditions, KS100 application allowed a reduction in the C stocks of the HS of the soil.

Агроэкологическая оценка степени деградации лугово-чернозёмной почвы в яблоневых садах на примере ФГУП «Мичуринское» Тамбовской области

In the monoculture of a weakly growing apple tree, the fatigue of meadow-chernozem soils manifests itself at the age of 16-18 years of trees. A methodology for assessing the degree of soil degradation in apple orchards has been developed. Its approbation on the example of meadow-chernozem soil showed that the rate of capillary rise of water in aggregates of 0.25-5 mm, the amount of exchange bases, mobile phosphorus, exchangeable potassium, the number of bacteria, the intensity of cellulose destruction and the total nitrogen content in barley leaves in the tillering phase when grown as a test culture degraded to the greatest extent. The weakest degree of degradation of meadow-chernozem soil was noted by total porosity, maximum hygroscopic, capillary moisture capacity, the content of exchangeable potassium, magnesium, pH of salt extract and the amount of yeast. The soil parameters that have changed the least are the components of the buffering of meadow-chernozem soil: total porosity, maximum hygroscopic and capillary moisture capacity, the content of exchangeable potassium, magnesium, pH of salt extract and the amount of yeast. The degree of degradation of meadow-chernozem soil in 26-year-old low-growing apple orchards of the Federal State Unitary Enterprise "Michurinskoye" of the Tambov region on rootstock 62-396 with row spacing under black steam is low or medium. Assessment of the degree of soil degradation can also be used as a characteristic of the level of agricultural technology in a given farm. Keywords: APPLE ORCHARDS, SOIL TRANSFORMATION, SOIL DEGRADATION, SOIL FERTILITY ASSESSMENT

Changes in soil organic carbon and nutrient pools in aggregate‐sized fractions along a chronosequence of wolfberry (Lycium barbarum L.) plantations in arid areas of Northwest China

AbstractDifferent land use and management actions can affect soil aggregates (SAs) and nutrient stocks, which are crucial for sustainable agriculture. The impacts of various chrono‐sequences on the soil aggregate structure, soil organic carbon (SOC) and nutrients associated with aggregate fractions in wolfberry (Lycium barbarum L.) plantations are still not fully understood. This study examined the composition and stability of SAs, SOC, total nitrogen (TN), available phosphorus (AP) and exchangeable cations (K+, Na+, Ca2+ and Mg2+) in bulk soil and various aggregate‐size fractions from five wolfberry plantations with varying ages (1, 4, 6, 10 and 13 years) and a corn field (0 years) in the arid region of northwest Ningxia in China. The results indicated that silt–clay (&lt;53 μm) fractions were dominant in the soil, accounting for 51%–66%, under different plantation ages. The proportion of the macro‐aggregates (&gt;250 μm) increased significantly, by 40%–47%, over the 4 years of wolfberry plantation. Likewise, the soil aggregate stability was improved, and total exchangeable bases (TEB) along with numerous cations concentrations (K+, Na+, Ca2+ and Mg2+) in SAs were significantly reduced as the wolfberry plantings became older. Both concentrations of SOC and TN in the soil aggregates peaked in the 13th year. The silt–clay fractions stored a considerable amount of SOC and nutrients. However, short‐term (under 6 years) cultivation of wolfberry reduced the stocks of SOC, TN and AP in the soil, while long‐term (over 10 years) cultivation increased them, particularly in macro‐aggregates. These findings indicated that long‐term wolfberry farming had several advantages, such as enhancing soil structure, accumulating SOC and nutrients and ameliorating alkaline soils, especially after 10 years, in the arid northwest of China.

Physicochemical Properties of Soil Cultivated with Durian (Durio zibethinus Murr.) in Gua Musang, Kelantan

This study was carried out in an area cultivated with durian in Gua Musang, Kelantan with a soil series of Rengam-Jerangau. The objective of this study was to determine the physicochemical properties of soil cultivated with durian at different elevations and samplings. The soil composite sampling was determined at three elevations (top, middle and bottom elevation) marked using GPS coordinate with two different depths (0-15 cm and 15-30 cm). The United States Department of Agriculture (USDA) of the soil texture is clay with bulk density ranging between 0.98 to 1.11 g/cm3. Significant parameters at alpha value of 95% include total carbon content (0.903% until 1.389%), total sulphur content (0.059% to 0.100%), exchangeable bases calcium, potassium and sodium at 3.520 cmolc/kg to 5.582 cmolc/kg, 0.380 to 0.581 cmolc/kg and 0.101 to 0.155 cmolc/kg respectively. From the significant parameters, only exchangeable potassium was affected by the by both elevation and depth of the sampling while the other parameters were only affected by the elevation. As some of the nutrients had been classified as low, extensive measures need to be done for healthy growth performance.

What C:N ratios in soil particle-size fractions really say: N is preferentially sorbed by clays over organic C

Factors affecting soil organic carbon (SOC) retention in the tropics are relatively well known, but this is not the case for N retention and thus C:N ratios, a common proxy for organic matter stability. Recent data suggest that SOC and N concentrations vary with climate, whereas soil C:N ratios depend on particle-size fractions contents. However, such knowledge is still incipient for tropical soils, native vegetations and deeper soil layers, which are critical to understand how land use and climate change affect C and N fluxes. We assessed SOC, N and C:N ratios in bulk soils and sand, silt and clay fractions, and their correlations with other soil properties under native tropical forests in the highlands near Lavras, Brazil. Soil samples were collected to 1-m depth in soils of contrasting texture and mineralogy, formed on quartzite, sericite-schist, gabbro, itabirite, ironstone, meta-limestone, gneiss, and phyllite. Mean SOC and N concentrations were generally high, whereas mean soil C:N ratios varied from 9.5 to 18.7 among parent materials, and only in three soils C:N ratios varied considerably with depth. Enrichment factors (EFs) were generally < 1 in the sand and silt fractions for SOC and especially N. Conversely, EFs for clay were mostly > 1 for SOC and even higher (up to 6.58) for N. Such trend indicates that SOC and N are concentrated in clays, and more importantly, that N sorption is favored compared with SOC, and likely dependent on clay mineralogy. Soil C:N ratios decreased with increasing values of exchangeable bases, due to higher N in the most fertile soils, suggesting that a mechanism of R-NH3+ cationic sorption is likely involved. Our results suggest that soil N is a critical component of the overall stabilization of soil organic matter onto clays of tropical soils, deserving further investigation also under temperate climate and other zones.

Differential Impacts of Cropland Expansion on Soil Biological Indicators in Two Ecological Zones

Agricultural expansion in Sub-Saharan Africa is characterized by different farm ages in smallholder communities. This study investigated changes in microbial indices broadly (i) at the reconnaissance survey level in four agro-ecological zones and (ii) in different farms at the forest (Dompem) and forest–savanna transition (Adansam) zones, as influenced by the duration of cultivation. Soils from one-year (first cultivation of cleared forest/fallow), three-year, five-year, and ten-year farms were analyzed for basic soil properties, active or labile carbon (POXC), basal respiration (BR), microbial biomass (Cmic) using permanganate oxidizable C, alkali trap, and chloroform fumigation incubation. In both study levels, POXC content was &lt;1% of soil organic carbon (SOC) in all zones, higher in the wet agro-ecological zones, and positively correlated with SOC (r = 0.70, 0.81; p &lt; 0.01, p &lt; 0.001). Dompem SOC and BR declined by 1–23% and 6–25% (p &lt; 0.001), respectively, in the first three years; Cmic (p = 0.002) and %Cmic/SOC (p = 0.610) decreased from three-year farms onwards. Conversely, the Adansam SOC, BR, Cmic, and %Cmic/SOC rather had irregular trends. The microbial indices were influenced by exchangeable acidity, the sum of exchangeable bases, and effective cation exchangeable capacity negatively or positively, followed by SOC, pedogenic compounds, particularly dithionite-citrate iron (Fed), oxalate iron (Feox), and lastly, soil pH. Therefore, understanding the degree, direction, and changing aspects of these drivers of soil ecosystem services is necessary for sustainable soil management practices in different agro-ecological zones.

ORIGIN AND CORRELATION OF VARIABLES IN SOME BOREHOLES OF BUI DIVISION IN THE NORTH WEST REGION OF CAMEROON

Multivariate data with inherent complexity can be simplified and interpretation eased with application of the Principal Component Analysis (PCA), while retaining trends and patterns. Huge data is reduced to fewer dimensions, maintaining the intrinsic relation between the variables. Sample bottles were cleaned and rinsed with the water sample from the boreholes, and finally filled to the brim to avoid any atmospheric oxidation. The samples were taken immediately to the Laboratory for physico-chemical analysis. The Boreholes were BH1 (Oku subdivision), BH2 (Mbven subdivision), BH3 (Nkum subdivision), BH4 (Jakiri subdivision) and BH5 for Kumbo subdivision. The PCA had application of the Software Package for Social Sciences SPSS), that converted the complex variables obtained from the analysis, at different periods and sites into a correlation matrix. Pearson’s correlation matrix applied in this work, reduced the data in correlation circles that were a range of geometrical projections from higher to lower dimensions. There was no strong correlation between the different variables indicating that they function independently. Most of the correlation values lie between +/- 0.29 and 0.1 which indicated a low degree of correlation. Nonetheless, absence of correlation never existed between the correlated pairs as no value of zero was obtained. Sixty-six variables were correlated, with 31 having a positive correlation, whereas 35 were negative. Consequently, 46.96 % variables had positive correlation and 50.04% with a negative correlation. The positive correlation values indicated a common source with the variables evolving similarly. A negative correlation of -0.185897 was expressed between Ca2+ and HCO3- within the boreholes. A negative correlation of pH with EC (-0.032559) and other anions (NO3- ; -0.137635, Cl-; -0.091810, SO42- ; -0.111072) indicated a decrease in pH (acidification) which can be linked to an increase in the mineralization process that increase anions into the milieu. The pairs of exchangeable bases; Na+- Ca2+; (0.138758) Na+- K+, (0.412315) had positive correlations which indicated that; increasing or decreasing of the concentration of cations was probably a combination of anthropogenic inputs and other processes governed by chemical reactions. An exception was with Na+- Mg2+ pair that gave an anomaly with a negative correlation (-0.090762). The anomaly was ignored because the low correlation coefficient was insignificant. The findings from this work enabled the origins of ions in the boreholes to be identified and related.