Soil CaCO3 Content Research Articles

Variation of trace metal minerals among different soil orders under different land use systems falling in Malwa region of Punjab in North-western India

BackgroundTrace metal deficiency has become a major constraint on the productivity and sustainability of soils. Agriculture becomes more complex, advanced and intensive farming systems develop, however, the deficiency of trace metal are more frequent and extensive in different systems. MethodsThis study investigated the variation of trace metal minerals in soil profiles of diverse land use systems (LUSs), i.e. agriculture, horticulture and forestry, falling under three dominant soil orders (Entisol, Inceptisol and Aridisol) in Malwa region of Punjab. Through comprehensive analyses, we explore the intricate relationships between soil characteristics, land use practices, and the distribution of key trace metals—namely zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn). ResultsThe mean values of DTPA-extractable trace metal from soil profiles of different land uses varied from 1.75 to 2.09, 1.64–2.32, 1.18–1.69 mg kg−1 for Zn; 0.59–1.02, 0.59–0.99, 0.64–0.92 mg kg−1 for Cu; 12.12–16.49, 9.84–16.05, 7.94–11.56 mg kg−1 for Fe; 7.82–9.99, 4.66–9.39, 6.51–7.46 mg kg−1for Mn in soil orders Entisol, Inceptisol and Aridisol, respectively. The concentration of trace metals in different soil orders follows the pattern of ntisol>Inceptisol>Aridisol. In contrast, there is a considerable amount of variation and no discernible pattern in the distribution of trace metals under various LUSs in each soil order. Several LUSs were examined, and agriculture land use system (ALUS) had the greatest Fe and Mn content, while the horticulture land use system (HLUS) had the highest Zn and Cu content. The Irrespective of soil orders and LUSs, the concentration of trace metals decreased as soil depth increased. Diverse LUSs and management practices have a substantial impact on the physico-chemical characteristics of soils, which in turn influence the availability of trace metals. According to the Pearson correlation studies, trace metals were positively associated with soil OC and negatively associated with soil pH, electrical conductivity (EC), and calcium carbonate (CaCO3) and there was also a positive correlation between DTPA-Zn, Cu, Fe, and Mn in the investigated soils. The results of the principal component analysis (PCA) revealed that soil CaCO3 and organic carbon (OC) content were the most variable soil parameters influencing crop trace metal availability in different soil orders and land use systems. ConclusionThe findings contribute to a nuanced understanding of the dynamic interplay between soil properties and land use, providing valuable insights for sustainable agricultural practices and environmental management in the region.

Comparison of Land Suitability Methods for Estimating Quantity of Maize Yield in Calcareous Soils

ABSTRACT The modeling and assessment of land suitability is a prerequisite for land development and is one of the necessary needs to prevent land degradation. Maize is considered to be the most important crop, covering significant areas of agricultural lands in widely different regions across the world. However, not all available lands are equally suitable for maize cultivation. The main objective of this study was focused on identifying the potentials as well as the limitations of studied calcareous soils for maize cultivation in north Khuzestan province, Iran. Furthermore, some parametric models and multi-criteria land suitability evaluation methods for physical, chemical, fertility, and climatic factors (MC-LSE) were compared in estimating the maize yield. The required samples were taken from 23 land units by excavating control pedons. The necessary physicochemical parameters were then measured in the laboratory. The land indices were calculated by using different methods. The maize potential production of the investigated area was then obtained based on the climatic conditions. Finally, using land indices and the potential production, the estimated yield for each land unit was calculated and compared with the actual yield data. The obtained results indicated that the main limiting factors for maize yield in the region are high soil CaCO3 content, high salinity, high alkalinity and low organic matter. A comparison of predicted and actual yield indicated that the corrected square root method is accurate enough to assess land suitability and to estimate the maize yield with a high coefficient of determination (0.91) and a low RMSE value.

Evaluation of Extractants for Determination of Micronutrients in Soils of South Gujarat, India

An experiment was conducted at Department of Soil Science and Agricultural Chemistry, Navsari Agricultural University during the year 2018-19. The methods of micronutrients determination were (i) extracted through diethylene triamine penta acetic acid (DTPA) (ii) extracted through ammonium bicarbonate- diethylene triamine penta acetic acid (AB-DTPA) (iii) extracted through Neubauer. The methods of micronutrients were evaluated through method validation parameters like linearity, sensitivity of instruments, precision and predictability. The available micronutrients determined from the sample soils were correlated with soil physico-chemical properties to know the relationship of these properties with available micronutrients. The linearity study of the series of micronutrients standard were measured through different methods of micronutrient determination. These measured values showed linear relationship with reference values. The coefficient of determination (R2) for all the methods was > 0.90. The precision was determined by relative standard deviation (RSD) (%) of different micronutrient methods which were in the range of 1.834 to 19.11 %. All the studied methods of copper, iron, zinc and manganese determination, AB-DTPA extractant method has highly significant and positive correlation with nutrient uptake by wheat on Microwave Plasma Atomic Emission Spectroscopy (MP-AES) instrument. Organic C and sand content of soil have positive correlation with micronutrients availability. While pH, EC, CEC, CaCO3, silt and clay content of soil have negative correlation with available micronutrients.

Performance of halophytes in soil desalinization and its influencing factors: a meta-analysis

Soil salinization threatening natural and agricultural production challenges global food security. Halophytes are of great interest in soil desalinization in recent years; yet, there is a lack of a comprehensive quantitative overview of biotic and abiotic factors for halophytes’ desalinization performance across global scales. Here, a meta-analysis was conducted using 400 observations from 53 peer-reviewed studies to assess desalinization by halophytes in relation to 27 variables. Results showed that soil salinity was significantly decreased in halophytes field on average by 37.7% compared to control on a global scale (p < 0.05). Desalinization performance was better in cold and hot regions than in temperate regions, in dry regions than in wet regions, in alkaline saline soils than in neutral saline soils, and in conditions with low sand content than high sand content. Under aboveground harvest treatment, desalinization increased with the years of cultivation, while no trends were detected under no harvest treatment, indicating the importance of aboveground accumulation. Desalinization was not related to soil CaCO3 content but was accompanied by soil structure improvement, nutrition enrichment, and microbe propagation, implying other root-microbe-soil interactions rather than CaCO3 dissolution play important roles. Shoot biomass could be used as an indicator of the desalinization performance, and the performance would not be decreased due to the high uptake selectivity for K+ over Na+. Notably, desalinization was similar in the pot experiments and field experiments, but pot experiments would magnify the contribution of aboveground salt accumulation to desalinization. Our findings can help to expand the applicability and efficiency of halophytes for sustainable agricultural development in saline soils.

Variation of Physico-Chemical Properties among Different Soil Orders under Different Land Use Systems of the Majha Region in North-Western India

The impact of different soil orders and land use systems on the distribution of physico-chemical properties is the most critical matter to address in order to maintain sustainable agricultural production. Hence, the present investigation was carried out to study the variation in the physico-chemical characteristics of soil in diverse land use systems (LUSs), i.e., agriculture, horticulture, and forestry, under major soil orders (entisol, inceptisol, and alfisol) in the Majha region of Punjab. A total of 225 depth-wise (at 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm and 80–100 cm) soil samples were collected from three land-use systems under different soil orders. The mean values of the physico-chemical properties ranged from 6.80–7.50, 7.64–8.34 and 6.94–7.87 for pH; 0.13–0.42, 0.19–0.54 and 0.19–0.46 dS m−1 for EC; 0.14–0.99, 0.21–0.69 and 0.15–0.72% for OC; 0.75–2.07, 1.07–3.32 and 0.93–2.29% for CaCO3; 7.77–41.84, 10.56–40.23 and 7.24–39.51 kg ha−1 for P; and 98.37–334.68, 94.51–230.18 and 93.01–367.39 kg ha−1 for K under different land uses in soil orders entisols, inceptisols and alfisols, respectively. Soil parameters including pH, CaCO3, and phosphorus (P) distribution differed significantly among soil orders; however, soil EC, organic carbon (OC) and available potassium (K) did not. The inceptisols under the agricultural land use system (ALUS) had the highest soil pH, EC, and CaCO3 values. The highest soil OC content was found in entisols under forest land use systems (FLUS), followed by horticultural land use systems (HLUS). The highest values of soil-available phosphorous (P) were found in FLUS under inceptisols, while the highest amounts of soil-available potassium (K) were found in entisols and alfisols under ALUS and FLUS, respectively. Thus, the distribution of physico-chemical properties under different LUSs in each soil order is highly variable and does not follow any particular trend. In general, soil properties such as OC, P, and K content decreased with an increase in soil depth, while pH and CaCO3 values increased with depth in all land uses and soil orders. There was a positive correlation between soil OC and EC, as well as available P and K in the soils investigated. The available P and K are negatively correlated with soil pH and CaCO3 content in the soil. The principal component analysis (PCA) revealed that soil pH and OC were the most variable soil parameters, which influence the availability of other physico-chemical properties under different soil orders and land use systems. Therefore, it is suggested that the land use systems play an important role in the distribution of physico-chemical properties of soil in different soil orders. The results of the study will help students, researchers, and agricultural management staff in managing different land uses for maintaining soil fertility and productivity in alluvial soils of North-western India.

Modelling Soil Color and Soil Fertility Relations on Cultivated Semi-Arid Sloping Landscapes

Soil color is a critical property, providing important information on soil properties. Soil color highly spatially varies on cultivated semi-arid sloping landscapes, indicating differences in soil properties that affect soil fertility. This study evaluated the relationships between color variables (L*: soil brightness, a*: redness, and b*: yellowness) and some basic soil properties on air dry and wet (around field capacity) soil samples, in a semi-arid sloping landscape having been under wheat cultivation for a long time. The values of color variables and soil properties were graphed and relationships between them were modeled using most proper regression models. The soil properties were poorly related to values of a* and b*, while CaCO3, sand, clay, and K contents and EC were highly significantly correlated with values of L*-wet (L*-values obtained on moist soil samples). Soil EC and CaCO3 content can be safely predicted by L*-wet in the study area. Also, the L*-wet should be preferred over L*-dry in predicting soil properties from soil color components in the study area and similar soils.

Increased Production of Tara (Caesalpinia spinosa) by Edaphoclimatic Variation in the Altitudinal Gradient of the Peruvian Andes

Tara production occurs mainly in the altitude gradient, where the edaphoclimatic conditions that affect the production of pods still need to be understood. The goal was to determine the altitudinal and edaphoclimatic effect on the production of tara pods in agroforestry and natural remnants in Cajamarca, Peru. Data analyses performed were the following: principal component analysis (PCA), regression analysis, the bootstrap method, and Pearson correlation analysis. For each 1 °C increase in temperature, the length and width of the pod decreased by 2.1 and 0.62 mm, and of the seed by 0.17 and 0.12 mm in the agroforestry environment; likewise, pod, valve, seed and gum weights were reduced by 23.9, 10.9, 13 and 2.3 g in the agroforestry environment, and 22.3, 13, 9.3 and 2.1 g in the natural environment. Activities such as association with annual crops and perennial pasture possibly favor the length and width of the pod and seed and the weight of the pod, valve, seed and gum in the agroforestry environment when compared to the natural environment. Larger pod and seed dimensions and higher pod, valve, seed and gum weights are related to higher soil CaCO3 contents in the natural environment and higher soil P and B contents in the agroforestry environment at higher altitudes. Higher Fe contents in the soil suggest an improvement in tara’s tannin weight (valve) in the natural and agroforestry environment. The effective response of tara, reflected in its weight and size of pods, was higher in an agroforestry environment than in a natural environment. Further studies on the production of tara pods are necessary for a better understanding of the interaction between altitude and soil fertility to expand the revenue and employment of Peruvian tara farmers.

Study of Potentially Toxic Metal Adsorption in a Polluted Acid and Alkaline Soil: Influence of Soil Properties and Levels of Metal Concentration

In the present study, the adsorption of zinc (Zn), lead (Pb), copper (Cu), and cadmium (Cd) was studied in two already polluted urban soil samples with different pH values, an acidic and an alkaline one. The Langmuir and Freundlich adsorption isotherm equations were used to thoroughly study the adsorption of the metallic elements on the solid surface of the soils. Langmuir equation described the adsorption of each metal satisfactorily, with a slight predominance over Freundlich, in both soils, as the R2 value approached almost unity. Even though Zn and Cu were adsorbed on the soil phase, their adsorption was minimal compared to the adsorption of more harmful metals such as Pb and Cd. Using the values of the coefficients obtained from the equations of the mathematical models, we concluded that in alkaline soils, the retention of metals was much greater than in acidic soils. The simultaneous presence of metals during the addition of the single-element solutions of the metals to the already metal-contaminated soils caused competitive adsorption increasing the retention of the more toxic metals on the solid surface of the alkaline soil. Factors affecting soil sorption (such as soil pH and CaCO3 content) were studied to provide theoretical support for understanding the laws and causes of metal sorption in the soils of the survey.

The influence of micronized sulfur amendments on the chemical properties of the calcareous soil and wheat growth

High soil pH constrains the availability of many plant nutrients including phosphorus (P). Sulfur (S) application to soil is a commonly used method to reduce the soil pH in the plant root zone, increase the availability of nutrients and thus obtain a higher yield. However, the particle size of the S is the most important factor in decreasing the soil pH. This study aimed to investigate the effect of different doses of micronized S application (0, 125, 250, and 375 kg ha−1) on the chemical properties of calcareous soil and the yield and nutrient contents of two wheat cultivars (Burgos and Zhivago). The results indicated that soil pH and CaCO3 content of soil decreased with increasing doses of S application. Soil organic carbon content slightly increased with all S applications in Burgos wheat variety. The highest increase was recorded in the 375 kg ha−1 S application, but no significant difference was determined in the Zhivago variety. The available Cu content in soil varied between 3.43 and 3.55 mg kg−1, Fe content was between 13.86 and 14.93 mg kg−1, Mn content was between 22.73 and 25.65 mg kg−1, and Zn content was between 0.53 and 0.62 mg kg−1. The results revealed that soil pH and CaCO3 content decreased with liquid micronized S applications, however, the effect of S applications on exchangeable cations and heavy metal content was not significant.

Vegetation assessments under the influence of environmental variables from the Yakhtangay Hill of the Hindu-Himalayan range, North Western Pakistan

Vegetation structures and dynamics are the result of interactions between abiotic and biotic factors in an ecosystem. The present study was designed to investigate vegetation structure and species diversity along various environmental variables in the Yakhtangay Hills of the Hindu-Himalayan Mountain Pakistan, by using multivariate statistical analysis. Quadrat quantitative method was used for the sampling of vegetation. PC-ORD version 5 software was used to classify the vegetation into different plants communities using cluster analysis. The results of regression analysis among various edaphic variables shows that soil organic matter, total dissolved solids, electrical conductivity, CaCO3 and moisture contents shows a significant positive correlation with species abundance, while the soil pH has inverse relationship with plant species abundance. Similarly, species richness increases with increase in soil organic matter, CaCO3 and moisture contents, while decrease with increase in soil pH, total dissolved solids and electrical conductivity (p < 0.05). The vegetation was classified into four major plant communities and their respective indicators were identified using indicator species analysis. Indicator species analysis reflects the indicators of the study area are mostly the indicators to the Himalayan or moist temperate ecosystem. These indicators could be considered for micro-habitat conservation and respective ecosystem management plans not only in the study area but also in other region with similar sort of environmental conditions.

Assessment of Soil Properties under Long Term Integrated Nutrient Management Using STCR-based Targeted Yield Equations under Rice-wheat Cropping System

The experiment was carried out to assess the effect of organic and chemical fertilizers on soil chemical properties under a nine year long experiment of AICRP on STCR initiated in Kharif 2008. The field experiment was laid out at research farm of JNKVV, Jabalpur after Rabi season of 2018-19. The study was framed in split plot design with four main treatments of nutrient management viz., T1-control; T2-GRD; T3- Soil test based NPK application for yield of 6.0 t ha-1 for each crop, and T4- Soil test based NPK application for yield of 6.0 t ha-1 for each crop + 10 t ha-1 yr-1 FYM and four soil depths as sub treatment from D1- 0-15 cm; D2- 15-30 cm; D3- 30-45 cm and D4 – 45-60 cm replicated three times. The results shows significant influence of INM on soil organic carbon (SOC), cation exchange capacity (CEC) and CaCO3 content of soil. After nine years of chemical fertilizer applications on general recommended dose bases and soil test bases in combination with FYM reported no profound impact on soil pH, electrical conductivity.

Variations of soil organic carbon fractions in response to conservative vegetation successions on the Loess Plateau of China

Land use changes profoundly affect the equilibrium of soil organic carbon (SOC) sequestration and greenhouse gas emissions. With the current global climatic changes, it is vital to understand the influence of ecological restoration and conservation management on the dynamics of SOC under different land uses, especially in erosion-endangered Loess soils. Therefore, we investigated changes in SOC through a suit of labile fractions, namely: light fraction organic C (LFOC), heavy fraction organic C (HFOC), coarse particulate organic C (CPOC), fine particulate organic C (FPOC), and dissolved organic C (DOC), from two forests i.e., Robinia pseudoacacia (RP) and Platycladus orientalis (PO), with different ages, in comparison with farmland (FL). The SOC and STN contents significantly increased over 42 years in the RP forest where the contents of CPOC and FPOC were significantly higher than in the FL. Moreover, total SOC and its labile fractions, in the studied land use types, significantly correlated with soil CaCO3, pH, and STN contents, indicating their key roles in SOC sequestration. The results reported here from different vegetation with different ages provide a better understanding of SOC and STN alterations at different stages of vegetation restoration. Our findings suggest that long-term natural vegetation restoration could be an effective approach for SOC sequestration and soil conservation on the Loess soil.

The Vegetation of the United Arab Emirates Gulf Coast: Description and Analysis

Leandro, P.; Knuteson, S.L., and Bartholomew, A., 2022. The vegetation of the United Arab Emirates Gulf coast: Description and analysis. Journal of Coastal Research, 38(5), 951–967. Coconut Creek (Florida), ISSN 0749-0208. This geobotanical study describes the United Arab Emirates (UAE) mangrove and coastal halophyte plant communities in the intertidal areas and coastal salt flats along part of the UAE Arabian Gulf coast. Nine coastal vegetation association/community groups have been identified with TWINSPAN: Association 1, Avicennietum marinae Chapman, J. 1970.; Association 2, Salicornietum fruticosi Br. Bl. 1928; Association 3, Arthrocnemo macrostachi–Halocnemetum strobiliaci assoc. nova; Association 4, Suaedetum verae (fruticosae) Br. Bl. ex O. Bolós and Molinier 1958; Association 5, Tetraenetum qatarensis assoc. nova; Community 6, Calotropis procera; Community 7, Heliotropium bacciferum and Cornulaca monacantha; Community 8, Prosopis cineraria, and two new communities associated with anthropogenic disturbance; Community 9a, Avicennia marina with Sesuvium portulacastrum; and Community 9b, Avicennia marina with Salicornia fruticosa. Vegetation profiles of each community are presented. Canonical correspondence analysis revealed that the A. marina communities are associated with: higher salinity of the soil, higher soil CaCO3 content, and higher soil ion concentrations (K+, Mg++, Na+, Cl–). Coastal development has modified the UAE Gulf coast extensively in recent years, and this study describes the coastal plant association/communities, which will be useful for botanists, ecologists, and managers involved in coastal restoration efforts.

Earthworm inoculation and straw return decrease the phosphorus adsorption capacity of soils in the Loess region, China

Loess Plateau is important for maize production in China. Therefore, a good understanding of soil phosphorus (P) behavior in the Loess region is crucial for optimizing fertilization in its agriculture systems. To date, research on factors influencing P adsorption/desorption has mainly focused on fertilization. Widespread application of straw return and increasing soil fauna in agricultural croplands inevitably affect soil P behavior either directly or indirectly in this area. However, less attention has been focused on these effects and their interactions. Here, a field plot experiment was performed based on a completely randomized design to investigate the response of P adsorption–desorption characteristics to the presence/absence of earthworms and straw return. Treatments included: (1) control without earthworms and straw (E0S0); (2) treatment with only earthworms (E1S0); (3) treatment with only straw (E0S1); (4) treatment with both earthworms and straw. The Langmuir model was superior to the Freundlich model in interpreting the P adsorption data and allowed better evaluation of the maximum P adsorption values. The maximal P adsorption, P adsorption affinity constant, and maximum buffer capacity in the earthworm and straw treatments were 2.4–8.3%, 8.3–13.9%, and 2.2–26.3% lower than those in E0S0. The readily desorbable P, standard P requirement, and degree of P saturation increased by 15.6–44.3%, 13.1–23.1%, and 4.4–16.5%, respectively, in earthworm and straw treatments. Additionally, earthworm inoculation and straw return treatments significantly increased total soil P, Olsen P, soil organic carbon, free Fe2O3, and CaCO3 contents and specific surface area of the soil. Redundancy analysis showed that soil organic carbon explained most (14.7%) of the total variation in P adsorption and desorption. These results show that combining earthworm inoculation with straw return can effectively reduce soil P adsorption capacity, increase its P desorption capacity, and thus, increase its available P content. These results provide a scientific basis for improving the utilization efficiency of soil P.

Impacts of Gümüşhane cement dust emissions on soil elemental compositions

The cement dust deposition can cause environmental pollution and heavy metal contamination, which negatively impacts soil nutrient availability and hence crop productivity. Thus, this study evaluates the impact of cement dust emissions on soil elemental compositions in different tillage managements. In this study, composite soil samples were taken from conventional tillage (CT), and notill (NT) managed fields under wheat-sugar beet (potato)-fallow cropping sequence. Soil samples were randomly collected from 0-30 cm depth in three replications and different distances (1, 2, 4, 6, 8, and 10 km) from a cement plant. Soil pH, clay, and CaCO3 contents were higher under CT than those under NT, whereas; sand and K contents were greater under NT management. The CT significantly decreased K content compared to those under NT by 5% in 2014. In addition, soil Mg+2 content decreased (p < 0.002) by increasing the distance. Soil Mg+2 content at 1 km was significantly higher than those at 4 km (by 3%), 2 km (by 4%), 8 km (by 10%), 6 km (by 10%), and 10 km (by 19%). Similarly, distance significantly influence soil Cu (p < 0.001), Zn+2 (p < 0.008), and Mn+2 (p < 0.0002), and K (p < 0.001), however, there were not any clear trend according to increases in distance from cement plant. The moving average of soil bacteria and fungi populations and their ratios have shown that the bacteria and fungi populations increased with distance, where increases in the fungi population under CT were more dramatic than those under NT management. Moreover, the principal component analysis showed that soils under NT were differently influenced by cement dust emission than CT managed soils. In conclusion, cement dust accumulation under both tillage practices negatively influenced soil elemental compositions and related microbial populations.

Global patterns of leaf construction traits and their covariation along climate and soil environmental gradients.

Leaf functional traits and their covariation underlie plant ecological adaptations along environmental gradients, but there is limited information on the global covariation patterns of key leaf construction traits. To explore how leaf construction traits co-vary across diverse climate and soil environmental conditions, we compiled a global dataset including cell wall mass per unit leaf mass (CWmass ), leaf carbon (C) and calcium (Ca) concentrations, and specific leaf area (SLA) for 2348 angiosperm species from 340 sites world-wide. Our results demonstrated negative correlations between leaf C and Ca concentrations and between leaf C and SLA across diverse nongraminoid angiosperms. Leaf C concentration increased with increasing mean annual temperature (MAT) and mean annual precipitation (MAP) and with decreasing soil pH and calcium carbonate (CaCO3 ) concentration, whereas leaf Ca concentration and SLA exhibited the opposite responses to these environmental variables. The covariations of leaf Ca-C and of leaf SLA-C were stronger in habitats with lower MAT and MAP, and/or higher soil CaCO3 content. This global-scale analysis demonstrates that the leaf C and Ca concentrations and SLA together govern the C and biomass investment strategies in leaves of nongraminoids. We conclude that environmental conditions strongly shape leaf construction traits and their covariation patterns.

Phosphate-Solubilizing Bacteria as a Panacea to Alleviate Stress Effects of High Soil CaCO3 Content in Phaseolus vulgaris with Special Reference to P-Releasing Enzymes

The present study examines the role of leguminous compost (LC), humic acids (HA), and phosphate-solubilizing bacteria (P-SB) in alleviating the stress effects of high soil CaCO3 content in Phaseolus vulgaris. Two pot trials for two consecutive seasons; fall 2019 and summer 2020 were implemented in an open greenhouse. A mixed three-way ANOVA, two independent factors (season and soil treatments) and one within factors (time) were used with four replicates. Residual maximum likelihood (REML) analysis was used for the mixed model of the studied traits. Inoculation of calcareous soil with P-SB (a 1:1 mixture of two Pseudomonas sp.; Ps. mallei and Ps. cepaceae) significantly exceeded LC, HA, or even LC+HA for the positive results obtained. P-SB facilitated nutrient solubility (e.g., N, K, Fe, and Mn), including conversion of insoluble phosphorous into a form available in the tested soil due to increased soil enzymatic activities (e.g., phosphatases and phytases). This mechanism, combined with a decrease in soil calcium carbonate content and an increase in cation exchange capacity (CEC) and organic matter (OM) content, increased the availability of various nutrients to plants, including P, in the soil, which contributed to the increased plant output. Adequate P content in plants led to a marked decrease in plant acid phosphatase activity under high content of CaCO3. The study concluded that the use of P-SB promotes biological activities, nutrient availability, and thus the productivity of calcareous soils, enabling Phaseolus vulgaris plants to withstand stress produced by high CaCO3 content through the development and/or adoption of potentially effective mechanisms. Strong highly significant interactions between the treatments and time were observed using the Wald’s statistics test, which indicates a positive correlation.

Vis-NIR spectroscopy predicts threshold velocity of wind erosion in calcareous soils

Wind erosion potential can be assessed using the Threshold Friction Velocity (TFV) of the soil, which is not always easy to measure, especially on regional and global scales. To overcome this difficulty, the spectroscopy technique can provide a useful approach in estimating the TFV as an alternative for time-consuming wind tunnel studies in the field. In this study, we evaluated the potential of Vis-NIR spectroscopy in predicting the TFV and some TFV-related soil properties using Partial Least Square Regression (PLSR) and the Support Vector Regression (SVR). We also developed a Point Spectrotransfer Function (PSTF) using Multiple Linear Regression (MLR) to predict the TFV based on diagnostic wavelengths and compared it to the derived Pedotransfer Function (PTF). For this purpose, 300 in-situ wind tunnel tests were performed in the Fars Province, Iran and the spectral reflectance of soil samples were analysed using a spectrophotometer apparatus. The 10 best key wavelengths resulting from the correlation analysis between the TFV and the spectral reflectance were 750, 1342, 1446, 1578, 1746, 1939, 2072, 2162, 2217, and 2338 nm which were mostly located in the short-wavelength infrared (SWIR) area. The derived PSTF performed better than the PTF for the TFV estimation (R2 = 0.94, RMSE = 0.71). Results of the predictive models revealed that machine learning using the SVR had a significantly (P < 0.01) higher prediction accuracy for the TFV estimation (R2 = 0.85, RMSE = 0.45, RPD = 2.50, and RPIQ = 4.06) than the PLSR (R2 = 0.68, RMSE = 1.01, RPD = 1.72, and RPIQ = 2.64). The same results were obtained for the soil moisture, clay and CaCO3 content. This study proved that reflectance spectroscopy coupled with the machine learning algorithm is a promising technique for large-scale assessment of wind erosion.

Differences in oxalate–carbonate pathway of Brosimum alicastrum in karst homegarden and forest soils

AbstractThe oxalate‐carbonate pathway (OCP) allows atmospheric carbon dioxide (CO2atm) sequestration through deposition of CaCO3 in soils. The participation of Brosimum alicastrum Sw. (Moracea) in the OCP has been demonstrated in traditional Maya agroforesty systems (homegardens) in Yucatan, Mexico, but remains unstudied in wild vegetation. To compare the OCP role of B. alicastrum trees associated to homegardens and forest, the calcium oxalate (CaC2O4) content of leaves, bark, roots, and adjacent soil of 40 trees was measured, as well as the abundance of soil and rizospheric oxalothropic bacteria. The highest CaC2O4 contents were present in leaves (45.37 g kg–1) and adjacent soil (576.93 mg kg–1) of wild trees. Oxalotrophic bacteria abundance was higher in the rhizospheric soil associated to wild trees. Soil CaC2O4 content was positively correlated to soil Ca (rs = .911; p &lt; .01) and CaCO3 (rs = .885; p &lt; .01) contents in wild trees and negatively correlated to soil redox potential (rs = –.625; p = .02). The CaC2O4 contents and oxalotrophic bacteria abundance in soils indicate an active participation of B. alicastrum trees in the OCP in both systems, allowing the capture of CO2atm. The lower potential to sequester CO2 in homegardens is mainly due to the use of the B. alicastrum as forage, which prevents the addition of litter to soil. If trees in homegardens were not defoliated, the amount of CO2atm captured by B. alicastrum in these systems would be greater than those in forest because the tree density in homegardens can be up to 18 times greater than in forest.

Spatial prediction of soil calcium carbonate content based on Bayesian maximum entropy using environmental variables

Soil calcium carbonate (CaCO3) content is an important soil property. The prediction of soil CaCO3 content is necessary for the sustainable management of soil fertility. In this work, we attempted to incorporate environmental variables directly and through regression models into the framework of Bayesian maximum entropy (BME) to predict CaCO3 content. Firstly, multiple linear regression (MLR) and geographically weighted regression (GWR) were used to establish a relationship between sampling data and environmental variables, including Digital Elevation Model, pH, temperature, rainfall, and fluvo-aquic soils. Prediction results of MLR and GWR served as soft data and were incorporated into the framework of BME to estimate the CaCO3 content. Secondly, soil samples and environmental variables were combined to generate probability distributions of CaCO3 at unsampled points. These probability distributions were used as soft data for the BME to predict the CaCO3 content. The results showed that the GWR method (r = 0.84, RMSE = 24.0 g kg−1) performed better than the MLR method (r = 0.73, RMSE = 30.1 g kg−1). The BME-GWR method outperformed the BME-EV and BME-MLR methods. The r values of BME-GWR, BME-EV, and BME-MLR methods were 0.87, 0.86, and 0.82, respectively, and the RMSEs of the three methods were 22.2, 23.9, and 25.2 g kg−1, respectively. The spatial distribution of CaCO3 content predicted by the above methods was similar and significantly higher in the southwest than in the northeast.