Lowland Soils Research Articles

Lowland Integrated Crop–Livestock Systems with Grass Crops Increases Pore Connectivity and Permeability, Without Requiring Soil Tillage

Enhancing integrated crop–livestock systems (ICLSs) to improve land-use efficiency is a critical goal. Understanding the ICLS impacts on lowland soils is key to sustainable agricultural practices. Our objective was to test whether adopting ICLSs in lowlands improves soil structure, pore connectivity, and water and air permeability. This study was conducted in a long-term field trial, consisting of the following production systems with flood-irrigation rice: rice–fallow–rice, under conventional tillage and absence of grazing (RFR-ct); rice-grazed ryegrass–rice, under no-tillage and grazing (RGrR-nt); rice-grazed ryegrass–soybean-grazed ryegrass–rice, under no-tillage and grazing (RGrS/RGrR-nt); and a grazed pasture-consortium (winter) and succession field (summer), with no-till rice every 4 years (P4R-nt). Core samples were collected after grazing (October 2018), harvesting (March 2019), and grazing (October 2019). We analyzed soil air permeability, saturated hydraulic conductivity, pore connectivity by computed tomography. Soil tillage in a semi-direct system generated discontinuous porosity. Systems with intense trampling or less surface protection are affected by shearing on topsoil, reducing pore continuity. ICLSs are mainly composed of ryegrass–rice mitigated the harmful effects of trampling, and improved soil structure and functioning. Systems without soil tillage exhibited higher pore connectivity and pores with vertical orientation. Finally, soil tillage is not required to improve structural quality in ICLSs.

How do reactive aluminum and iron phases control soil organic carbon and phosphate adsorption capacity in agricultural topsoils across Japan?

ABSTRACT The growing number of studies suggests that the prediction of soil organic carbon (SOC) storage and persistence can be improved by accounting for variations in soil reactive metal phases. Nevertheless, the dataset on reactive metals is often limited at a national scale. In Japan, the phosphate adsorption coefficient (PAC) has been measured for agricultural soils nationwide. PAC is known to be strongly controlled by reactive metals, and hence, it can be used as a surrogate for reactive metal content. However, the relationships between SOC, reactive metals and PAC across a wide range of agricultural soils remain unclear. We thus examined these relationships using agricultural topsoils taken from 115 sites across Japan, covering two major soil great groups, Andosols and Lowland soils, as well as various land uses and soil temperature regimes (7.2–19.1°C). For the whole dataset, PAC was strongly correlated with oxalate-extractable metals (Alox + 0.5Feox: Metalox, r = 0.83) and moderately with pyrophosphate-extractable metals (Alp + 0.5Fep: Metalp, r = 0.68). These results suggest a stronger contribution of short-range-order (SRO) minerals to PAC as the former parameter reflects the content of both SRO minerals and organically complexed metals, while the latter reflects only that of organo-metal complexes. Moreover, Metalp was the best predictor of SOC contents in both Andosols (r = 0.79) and Lowland soils (r = 0.65). When only soils at near neutral soil pH range were considered, the exchangeable Ca content also co-varied with SOC in Lowland soils (n = 17). Of the two metallic elements, reactive Al phases better explained the variation of SOC and PAC in Andosols, whereas reactive Fe phases also showed similar explanatory power for PAC in Lowland soils. Our analyses also suggested that soil group (esp. erosion intensity) and land use likely impacted the SOC-Metalox relationship in Andosols, whereas environmental factors such as soil temperature and soil redox regime affected those relationships in Lowland soils. Overall, we showed that PAC is a useful surrogate for SRO minerals and organo-metal complexes and, with careful considerations of the environmental and pedogenic factors, it is potentially useful to estimate the amounts of SOC stabilized by reactive metal phases in agricultural soils across Japan.

Enhanced health risk of soil heavy metal exposure following an extreme rainstorm under climate change

Widespread concerns raised in changes in the health risk of soil heavy metals exposure due to extreme rainstorm under climate change. However, the impacts of extreme rainstorm on human exposure risk and the underlying mechanisms are still unclear. In this study, soil properties, speciation distribution and bioaccessibility of Ni, Cu, Zn, Cd and Pb in soil samples, which were collected before and after extreme rainstorm, were measured, subsequently the soil oral exposure risk of heavy metals was assessed based on bioaccessibility. Results indicate that extreme rainstorm can significantly enhance the accumulated non-carcinogenic and carcinogenic exposure risk by 10.1–188.3 %, with lowland soil posing 1.3–1.7 times higher risk than highland soil. The increase in exposure risk varies among elements in highland and lowland soil. Specifically, the exposure risk for Cd and Pb increased by 2.5–9.7 times, whereas that for Cu decreased by 43.2 % - 60.6 %. The risk of Zn and Ni exposure exhibits complex trends, with an increase of 37.2 %–104.8 % in lowland soil but a decrease of 9.4 %–46.5 % in highland soil. Bioaccessibility variations are the primary risk factors for soil heavy metal exposure during extreme rainstorms, not total concentration. Mechanistically, the extreme rainstorm directly increases soil moisture content and reduce organic matter concentration, leading to an increment in the proportion of bio-utilization speciation and decrement in the speciation bounding to Fe/Mn oxides of soil heavy metals. Furthermore, the bioaccessibility of soil heavy metal positively correlates with their bio-utilization speciation and negatively correlates with their speciation bounding to Fe/Mn oxides, which ultimately increasing exposure risk. Our study suggests the necessity that attentions should be paid to the enhanced health risk associated with soil heavy metal exposure following extreme rainstorm, particularly for population residing in lowland areas.

Fe toxicity tolerance is advantageous in rice growth recovery after Fe stress alleviation

AbstractBackgroundFe toxicity often inhibits rice growth on acid sulfate soils in tropical coastal lowlands. Previous studies in plant physiology and breeding have focused on high‐Fe stress, but not on growth recovery after stress alleviation.AimsThe objective of this study was to elucidate the morphophysiological characteristics in rice growth recovery from high‐Fe stress.MethodsWe evaluated the seedling growths of Taichung65 (T65) (Fe toxicity‐tolerant) and Ciherang (susceptible) in hydroponic culture, during the period of high‐Fe stress (250 mg Fe2+ L−1 for 12 or 18 days) and after stress alleviation.ResultsThe plant growth rate during recovery was negatively correlated with the leaf bronzing score (damage symptoms due to Fe toxicity) at the end of high‐Fe stress, which in turn was negatively correlated with the shoot Fe concentration. After 18‐day stress, T65 showed greater growth recovery than Ciherang, attributable to its higher net assimilation rate, higher transpiration rate (water uptake/green leaf area), and greater increase in total root length during recovery. In particular, T65 showed vigorous lateral root development in nodal roots that emerged during the stress period and vigorous growth of nodal roots that emerged during recovery.ConclusionsOur results suggest that tolerance to high‐Fe stress confers an advantage in growth recovery. It is likely that tolerance to Fe toxicity contributes not only to the maintenance of green leaf area at the end of stress but also to quick root growth recovery, leading to vigorous water uptake and high photoassimilation capacity after stress alleviation.

Experimental verification of solubilization effect of soil bromine by waterlogging reduction

ABSTRACT Although the concentration of bromine in the Earth’s crust is only approximately 2 µg g−1, it is one of the most crucial elements in daily human life. On the Earth’s surface, bromine is thought to be widely transported and circulated in the hydrosphere, atmosphere, lithosphere, and biosphere. However, little is known regarding the dynamics of bromine in the terrestrial environments. In this study, waterlogging incubation tests were conducted on two soil types, Lowland soil and Andosol, to verify the solubilization effect of waterlogging on soil bromine. The amount of bromine in the soil extracts increased considerably with incubation time in Lowland soil and Andosol, proving that the soil reduction caused by waterlogging enhanced the solubilization of soil bromine. The amount of bromine solubilized by soil reduction tended to be higher in Andosols, which had a higher total bromine concentration than Lowland soil. The amount by soil reduction during the 28 days period ranged from 0.18 to 1.14 µg g−1 for the Lowland soil group and from 0.20 to 30.2 µg g−1 for the Andosol group. Solubilized bromine could not remain in the soil, and most of it leached out with the percolation water, as shown by the soil-filled column tests. To estimate the amount of bromine leached from a rice paddy field under waterlogged conditions, a percolation test was conducted using Wagner pot-cropped paddy rice plants. The results showed that 531 to 544 mg of bromine per square meter of soil surface leached during one growing season. The amount of bromine leached from the soil was much higher than the previously reported annual amount of bromine addition to land from atmospheric deposition.

Acid Modification and Characterization of Rice Straw Biochar and its Potential as Ameliorant for Saline-Sodic Lowland Soil

Acid Modification and Characterization of Rice Straw Biochar and its Potential as Ameliorant for Saline-Sodic Lowland Soil

Nutrient use efficiency of rice genotypes under iron-toxic lowland soil influenced by high potassic fertilizer and foliar application of kinetin

Nutrient use efficiency of rice genotypes under iron-toxic lowland soil influenced by high potassic fertilizer and foliar application of kinetin

Soil development and ancient Maya land use in the tropical karst landscape: Case of Busiljá, Chiapas, México

AbstractThe soil mantle of the tropical karstic landscapes of Southern Mexico was shaped by specific processes of pedogenesis and long‐term human impacts of ancient Maya agriculture. To understand the interaction between natural and human‐induced soil‐forming processes in the calcareous mountains of Chiapas state, we studied soil toposequences around the Classic Maya site of Budsilhá and related them to the archaeological evidence of settlement and land‐use distribution. Soil chemical analysis, micromorphological observations, and clay mineral identification were carried out in key soil profiles at the main geoforms. Limestone hills are occupied by shallow Rendolls which are usually perceived as incipient soils. However, high content of silicate clay composed of kaolinite and vermiculite and ferruginous clayey soil material observed at macro‐ and microscale backed the hypothesis that these soils were formed from the residues of thick Terra Rossa after their erosion. Swampy lowlands are occupied by thick clayey gleyic soils with clay mineral assemblages similar to those in the upland Rendolls. We suppose that the mineral matrix of the lowland soils is largely derived from the pedosediments of eroded upland Terra Rossa, which lost original ferruginous pigmentation and aggregation due to redoximorphic processes. Some wetland soils contain neoformed gypsum that is atypical for humid tropics; sulfide‐sulfate transformation under fluctuating redox conditions could promote gypsum synthesis. Ancient Maya land use was closely related to soil‐geomorphic conditions: settlements with homegardens occupied calcareous hills, whereas the primary agricultural domain was developed on lowland soils after their drainage by artificial canals.

Severity of topsoil compaction controls the impact of skid trails on soil ecological processes

Abstract Skid trails are a major management‐induced disturbance in temperate forest ecosystems with considerable impact on soil ecological processes that are so far poorly understood. In German forests, skid trails comprise 10%–20% of the forest area that is potentially affected by soil compaction through heavy machinery. We systematically investigated the influence of skid trails on physical, chemical and microbiological soil parameters at 84 paired plots across four Central European forest types. In low mountain forests with steeper topography, skid trails had more drastic effects than in lowland forests. Skid trails in low mountain areas showed a decrease in the C to N ratio of microbial biomass (MBC/MBN), as well as increased microbial (MBC/SOC) and enzyme activities leading to faster carbon turnover (lower C/N, EOC/EN) and increased CO2 losses (CO2/SOC) from the soil. The overall effects of the skid trails in lowland forests were small. On base‐poor soils, we found an increase in the MBC/MBN ratio, while skid trails in base‐rich lowland soils showed a reduction in CO2/SOC, suggesting a proportional increase in soil carbon storage. Regardless of region‐specific effects, the relative increase in the bulk density of the fine soil was identified as a ‘golden trait’ that determined the effects of skid trails on many soil parameters, as shown by negative correlations with SOC, N, MBC, MBN, MBP, MBC/SOC and CO2/SOC and positive ones with the activities of certain hydrolytic enzymes. Synthesis and applications: Our data clearly showed that carbon conversion processes and soil respiration leading to significant carbon and nutrient losses increased significantly on skid trails in low mountain regions with relatively steep slopes, which was in sharp contrast to lowland sites. The strong context dependence of our findings suggests that the mapping of soil conditions in terms of slope, substrate and moisture with high spatial resolution is mandatory to assess the vulnerability of sites to soil compaction by heavy machinery. Based on such vulnerability analysis, negative impacts can be minimised through the designation of permanently fixed skid trails, technical adaptation of vehicles (e.g. wide base tyres) as well as careful planning and timing of management operations that should be restricted to dry weather and soil moisture conditions or periods of frost.

Impacts of soil, water source, and agro-climatic conditions on exchangeable sodium in rice-cultivated lowland soils of Sri Lanka

Rice is sensitive to salt stress, commonly caused by high concentrations of sodium (Na) in soils. However, the concentration and spatial variability of exchangeable Na in lowland paddy fields of Sri Lanka are not known. This study examined the interactive effects of the agro-climatic zones (ACZs), soil orders, and water sources on exchangeable Na in lowland paddy fields in Sri Lanka using 8566 soil samples. Exchangeable Na was extracted using 0.01 mol/L CaCl2 solution and detected using inductively coupled plasma-mass spectrophotometry. Exchangeable-Na concentration ranged from 0.05 to 4814 mg kg−1 with a mean concentration of 140.7 mg kg−1, and these values were within the optimal range reported for tropical paddy soils. The distribution of exchangeable Na was right skewed with 44%, 35%, and 9.3% of samples falling into 0–100, 100–200, and 200–300 mg kg−1, respectively. Samples from the Low country Dry zone had the highest (157 mg kg−1) Na concentration while that in the Upcountry Intermediate zone was the lowest (13 mg kg−1) ( p < 0.05). Vertisols recorded the highest (255 mg kg−1) and Ultisols recorded the lowest (81 ± 5.0 mg kg−1) among soil orders. Soils receiving supplementary irrigation in Low country Dry zone had lower Na than that in rainfed systems. Exchangeable-Na concentration was positively correlated with soil pH ( p < 0.05). Even though the concentrations of Na in soil samples were within the optimal range, agronomic decisions based on ACZ, soil order, and water source need to be made to minimize the potential development of saline–sodic soils in the study areas.

A Systematic Review on Digital Soil Mapping Approaches in Lowland Areas

Digital soil mapping (DSM) around the world is mostly conducted in areas with a certain relief characterized by significant heterogeneities in soil-forming factors. However, lowland areas (e.g., plains, low-relief areas), prevalently used for agricultural purposes, might also show a certain variability in soil characteristics. To assess the spatial distribution of soil properties and classes, accurate soil datasets are a prerequisite to facilitate the effective management of agricultural areas. This systematic review explores the DSM approaches in lowland areas by compiling and analysing published articles from 2008 to mid-2023. A total of 67 relevant articles were identified from Web of Science and Scopus. The study reveals a rising trend in publications, particularly in recent years, indicative of the growing recognition of DSM’s pivotal role in comprehending soil properties in lowland ecosystems. Noteworthy knowledge gaps are identified, emphasizing the need for nuanced exploration of specific environmental variables influencing soil heterogeneity. This review underscores the dominance of agricultural cropland as a focus, reflecting the intricate relationship between soil attributes and agricultural productivity in lowlands. Vegetation-related covariates, relief-related factors, and statistical machine learning models, with random forest at the forefront, emerge prominently. The study concludes by outlining future research directions, highlighting the urgency of understanding the intricacies of lowland soil mapping for improved land management, heightened agricultural productivity, and effective environmental conservation strategies.

Dampak Pertanian Organik dan Konvenional pada Biodiversitas dan Sifat Kimia Tanah pada Budi Daya Tanaman Padi Sawah

The phenomenon of leveling off and environmental degradation that occurs as a negative impact of the excessive use of chemical fertilizers and pesticides encourages the development of organic farming systems that can produce crop yields that are not contaminated and free from synthetic chemicals and maintain a healthier environment. The research was conducted from October to December 2022 by taking soil samples from farmers' paddy fields in Tegal Regency using an organic (Cawitali Village) and conventional or non-organic (Jembayat Village) farming system. Composite soil samples were taken from a soil depth of 0 to 20 cm from the soil surface using a soil drill on lowland rice fields with organic farming systems and conventional farming after harvest. The analysis of the chemical properties of the soil carried out was C-organic (Walkley and Black), N-total (Kjeldahl), CEC and soil bases (exch-Ca, exch-Mg, exch-K, and exch-Na), total P (25% HCl) and available P (Bray I), while the observed soil biological properties were the total number of microbial and fungal populations. The results showed that organic paddy soil's chemical and biological properties were relatively higher than conventional paddy soil's. Total fungi in organic lowland soils were lower than in conventional paddy fields. The nutrient status of C-organic and N-total in organic rice fields tended to increase compared to conventional rice fields, namely from very low to low and low to moderate, respectively. In contrast, the other nutrient statuses observed tended to remain relatively unchanged. Generally, soil biological and chemical properties were better in organic farming than in conventional farming systems. Keywords: leveling off, organic farming, conventional farming, nutrient status

Reduction of the mangosteen tree (Garcinia mangostana L.) production cycle: effect of soil type and fertilisers

BackgroundShortening the vegetative cycle of slow-growing crops is a significant challenge for breeders, agronomists, and growers. This reduction is particularly crucial for the mangosteen (Garcinia mangostana) as it would make it easier for farmers to adopt this crop. The mangosteen tree is notoriously slow-growing, taking between 8 and 15 years to produce its first fruits. The plant's slow growth and late fruiting pose a significant obstacle to its adoption and spread in rural areas. In Côte d'Ivoire, these constraints have limited its cultivation to small farms owned by a few producers. However, it could be an alternative for diversifying agricultural income and contributing to poverty reduction in rural areas. This study aims to evaluate the effects of soil type and fertiliser on the agronomic parameters of mangosteen tree growth. The goal is to contribute to shortening its vegetative phase.ResultsThe study results indicate that soil type and fertiliser have a significant effect on mangosteen growth parameters. Evaluating the agronomic performance of mangosteen, it was found that lowland soil promotes better plant growth. Growth rate and height growth were found to be significantly influenced (p = 0.03). After 36 months of monitoring, the growth rates for mangosteen trees grown on lowland soil were 53.08 ± 7.30%, while those grown on forest soil were 41.51 ± 13.43%. Additionally, the use of foliar and granular N-P-K fertilisers resulted in earlier fruiting, starting from the 5th year of cultivation.ConclusionsThe results showed that fertilisers play a crucial role in managing and shortening the juvenile phase of the mangosteen tree. Foliar and NPK fertilisers performed exceptionally well, resulting in earlier fruiting of mangosteen trees, starting from the 5th year of cultivation.

Methane flux from transplanted soil monoliths depends on moisture, but not origin

Soils both produce and consume methane (CH4), a potent greenhouse gas that contributes to climate change. In coastal forests, upland soils are shifting from being CH4 sinks to sources as sea levels rise, increasingly flooding soils with little prior inundation history. Ecosystem CH4 budgets are highly uncertain due in part to the difficulty in separating fluxes measured at the soil surface into individual production and consumption processes which are likely to have different responses to future environmental conditions. We measured growing season CH4 fluxes from soil monoliths transplanted four years prior along an inundation and salinity gradient to determine how changes in abiotic conditions control CH4 flux rates. To parse net fluxes measured at the soil surface into their component gross rates, we paired field measurements with a stable isotope pool dilution incubation of surface soils. Throughout the growing season, net soil surface CH4 flux was positively correlated with soil moisture (p < 0.01), with lowland-located soils tending towards CH4 sources (mean 0.349 ± 1.11 mg CH4–C m−2 h−1, error is standard deviation) and upland-located soils tending towards CH4 sinks (−0.003 ± 0.003 mg CH4–C m−2 h−1). Transplanted soils’ fluxes were statistically identical to their native neighbors once microtopography-driven differences in soil moisture were controlled for. The pool dilution experiment revealed that production and consumption rates were similar in upland and lowland surface soils (2.82 ± 3.29 μmol CH4 g−1 dry soil d−1 production, 3.47 ± 2.03 μmol CH4 g−1 dry soil d−1 consumption), indicating the majority of production likely occurs at depth in lowland soils. Both gross and net fluxes from transplanted soils showed no effect of soil origin after four years, suggesting low resistance of CH4 cycling to global change drivers. Our results indicate the strength of the coastal forest CH4 sink is likely to decrease in proportion to sea-level rise.

Microbial and thermal indices of organic matter stability in lowland soils with variable texture

Soil organic carbon (SOC) stabilization and turnover are important processes of global carbon cycle. This study evaluates microbial activity and thermal stability of soil organic matter (SOM) in lowland soils of central Europe during relatively dry summer period. We observed that the intensity of soil respiration and substrate availability are positively affected by soil moisture. Soil water availability was correlated with clay content that supported water retention and capillary elevation from the subsurface. Besides moisture, soil respiration was partially controlled also by nutrient availability (Ca, Mg, K, P). Microbial C content was not correlated with any of the properties that were measured. To assess SOM stability, we used thermogravimetry combined with differential scanning calorimetry (TG-DSC). Correlations between TG-DSC data and soil respiration indicate that heterotrophic microorganisms degrade SOM without significant preference for either labile, intermediate, or stable organic fraction. The heat released per mass unit of labile SOM correlated positively with the ratio of microbial vs. total organic C in the sample. This suggests that the energy density of labile OM affects positively the C amount that is converted to microbial biomass. More heat was released per mass of labile OM from the samples that showed higher SOC/SOM ratio and organic C/O value. This indicates that higher portion of C bound in SOM affects positively the energy density of labile fraction. The samples with higher clay content released relatively more heat at higher temperatures in comparison to more coarse-textured soils. Considering the effect of clay on SOC stabilization, the findings of this study pointed on the two contradicting aspects. Although the results suggest that interaction of OM with inorganic clay components results in formation of stable C fraction, fine-textured soils showed higher respiration rate, during the drier period, due to the higher water availability.

The Effect of K-Fertilization and Irrigation on the Composition of Cultivated Soils: Examples from Israel

Evaluation of soil sustainability should take into account chemical and mineralogical changes due to cultivation. Potassium (K) application is a key farming practice that may potentially affect phyllosilicate composition and soil properties. Irrigation is another agent that affects soil composition. This study aims to evaluate the imprints of cultivation on the chemical and mineralogical compositions of lowland soils under semi-arid and Mediterranean climate regimes and to assess them with the natural pedogenesis. The sites examined include two permanent plot experiments with crop rotation, and three single-plant plots. Cultivated, control, and fallow soils were analyzed for their chemical and mineralogical composition. The X-ray diffraction patterns of the clay fraction were decomposed to achieve quantitative detection of changes among the illite–smectite (IS) phases and in kaolinite amounts. In loamy and clayey soils dominated by IS phases, cultivation caused minor changes and diverse behavior of the IS phases. Yet, the K balance was negative under high fertilization levels and higher plant mass production. Fertilization enhanced the natural process of transforming IS into kaolinite and illite in the sandy soil, leading to a positive K balance. This study emphasizes the importance of IS minerals as a dynamic K pool that responds to plant needs.

Development and production of cowpea inoculated with Bradyrhizobium strains in a traditional cultivation system in Southwestern Amazonia

Traditional cowpea cultivars are conserved in the Juruá Valley (Acre) by farmers who adopt a "beach" production system, in lowland areas on the banks of the Juruá River and tributaries. Cowpea inoculation is a sustainable and low-cost technique that has provided an increase in the growth and productivity of the crop, but that has not yet been tested in this production system. The objective of this work was to evaluate the development and production of cowpea inoculated with Bradyrhizobium strains in a traditional cultivation system in Southwestern Amazonia. A randomized block design with three replications and four treatments was used: seeds inoculated with strains BR 1808, BR 3262, and BR 3267, and a control without inoculation. Inoculation provided an increase in the majority of the studied variables. The productivity obtained in the treatments with BR 3262 and BR 1808 was superior to the other treatments. The strain BR 3262 showed higher levels of total chlorophyll and nitrogen. Inoculation with Bradyrhizobium proved to be a promising technology for the cultivation of cowpea beans in lowland soils of the Juruá River.

Soil Characteristics in Oak Lowland Stand

The behavior of the vehicle-soil interaction and reduction of the possible soil damage to an acceptable level is one of the goals of forest engineering. This study aimed to analyze the impact of a 6-wheeled forwarder on water-physical soil characteristics on lowland soil – pseudogley. The research was conducted using a 17-ton Timberjack 1710B forwarder, which forwarded 694.1 m3 volume of oak (Quercus robur L.) assortments. Soil characteristics were measured after each of the eight passes of the loaded forwarder. Bulk density measured on the surface layer ranged from 1.01–1.23 (Me=1.10) g/cm3 (undisturbed soil); 1.14–1.70 g/cm3 (multiple passes of the loaded forwarder). The highest soil density increase was observed after the first pass of the loaded forwarder (16%). Soil solid phase ranged from 2.49 to 2.73 g/cm3 with no statistically significant difference between undisturbed soil and soil after multiple passes of the vehicle. The highest porosity decrease was observed after the first pass of the loaded forwarder (10%). The highest soil water retention capacity decrease was observed after the first pass of the loaded forwarder (3%). The highest soil air capacity decrease was observed after the first pass of the loaded forwarder (30%) compared to the undisturbed soil of the forest stand.

Soil toposequences, soil erosion, and ancient Maya land use adaptations to pedodiversity in the tropical karstic landscapes of southern Mexico

The soil mantle of the tropical karst landscapes of southern Mexico was a key resource for ancient Maya agriculture and experienced deep transformation due to long-term human impacts under changing environmental conditions. We conducted a comparative analysis of three compound soil toposequences in mountainous (Sierra de Chiapas/Middle Usumacinta Valley, Busiljá, and Chinikihá archaeological sites) and platform (NE Yucatán Peninsula, Yalahau region) karst landscapes to reconstruct general tendencies and regional variations in pedodiversity development and soil–human interactions since the Early Preclassic Period. Toposequence characterization is based on macro- and micromorphological observations, accompanied by a suite of laboratory data. Calcareous upland geoforms of all toposequences have similar soil combinations consisting of shallow Rendzina and deep red clayey Terra Rossa types of profiles. We argue that Rendzinas, now dominant in the upland soil cover, in most cases, are not a product of incipient pedogenesis on limestone; they have developed from the residues of Terra Rossa soils after their advanced erosion. Pedosediments generated by ancient soil erosion have been found in the piedmont and depression positions in the mountainous landscapes of Chiapas, as a result of lateral downslope soil removal, and in the subsurface karstic cavities in the platform of NE Yucatán, indicating vertical “soil piping.” The soils of the lowland domains show contrasting differences between the toposequences: gleyic clay–rich soils and humic alluvial soils prevail in Chinikihá and Busiljá, whereas hydromorphic carbonate soils have formed in Yalahau karstic depressions. These differences in the lowland soil properties led to divergent ancient Maya land use strategies; in Chinikihá and Busiljá, the major agricultural domain was developed in the lowlands, implying largescale artificial drainage. On the contrary, in Yalahau, mostly upland Rendzinas were cultivated, implying “precision agriculture” and “container gardening.”

CHEMICAL COMPOSITION AND PEDOGENESIS OF SOILS OF AGRICULTURAL COLLEGE FARM, NAIRA, ANDHRA PRADESH

The study on elemental composition and pedogenesis of soils of Agricultural College farm, Naira of Srikakulam district was carried-out during 2021. The soils were developed from granite-gneiss parent material. Total silica (SiO2) content of soils ranged from 50.5 to 74.6 percentage. Silica content in general decreased with soil depth, while sesquioxides (R2O3), alumina (Al2O3), iron oxide (Fe2O3), CaO, K2O, Na2O, MnO were found increasing with depth. High silica/ sesquioxide ratio of soils indicated siliceous nature of soils. The aluminum oxide content of the profiles varied from 15.80% to 26.25%. Highest value was reported in lowland profile, whereas, the lowest value was recorded in rainfed upland profile. Iron oxide content varied from 5.04% to 8.50%. Iron oxide content showed slight variation within profiles. Among the other oxides, CaO &gt; MgO &gt; K2O &gt; Na2O was of the order as the soils were developed under semi-arid climate, wherein, basic cations have accumulated in these soil profiles due to limited leaching. The molar concentration of silica (SiO2) ranged from 0.841 to 1.24 moles, and molar concentration of sesquioxide ranged from 0.191 to 0.313 moles. The molar ratio of SiO2 / R2O3 varied from 2.68 to 6.51 in different soil profiles. The SiO2 / Al2O3 ratio varied from 3.33 to 8.02. These wider molar ratios indicated salacious nature of parent material and due to dominance of silica among chemical fractions. Midland (P3) and lowland (P4) soil profiles showed silt/clay ratio of less than 0.45 and upland profiles showed more than 0.45 indicating relatively advanced weathering in mid and lowland profiles while it was moderate weathering in upland profiles. The Weathering Index of Parker (WIP) values of the soils of study area ranged between 2.8 and 32.4. The lower WIP values (2.8 to 8.1) were associated with rainfed uplands and higher values of 14.7- 32.4 with irrigated low lands. The PIA values ranged from 67 to 97 tend to decrease with the depth in all profiles. The profiles examined have the CIA values varied from 66 to 95 indicating high to intense weathering. The CIA values decreased with depth in all the profiles. The surface horizons of P1 and P2 soil profiles were classified as moderately weathered. On the other hand, all subsurface horizons of these two profiles were highly weathered. However, in profiles P3 and P4 the CIA values ranged between 68 to 90 indicating that these soils were highly weathered. CIW values closely followed the trend of CIA values. The bases/R2O3 values of all profiles ranged from 0.061 to 0.608 and found increased with soil depth in all the profiles. Relatively higher values of bases/R2O3 were found in P4 (low lands) indicating base rich character. Middle land and lowland black soil profiles showed silt/clay ratio of less than 0.45 and upland profiles showed morethan 0.45 indicating relatively advanced weathering in mid and lowland profiles while moderate weathering in upland profiles.