Variability Of Soil Physico-chemical Properties Research Articles

Altitudinal variations in soil physico-chemical properties at cold desert high altitude

Extreme nature of climate and topographical conditions may affect soil properties at cold desert high altitude. Hence, the present investigation was undertaken to know altitudinal variations in soil physico-chemical properties at cold desert high altitude region. For this, agriculture soils were collected from different altitude viz. site I (1000011000 ft), site II (11000-12000 ft) and site III (>12000 ft amsl) at Leh-Ladakh (cold desert high altitude region), India. Interestingly, sand percentage in soil was significantly high at site III and decreased gradually with the altitude. In contrast to sand level, silt concentration was high at site I and decreased significantly (p<0.05) with increasing altitude. There was no significant (p<0.05) difference in bulk density (BD) and electrical conductivity (EC) among all study sites. However, the highest pH, total dissolved solid (TDS), and CaCO 3 value was recorded at site I while higher soil organic matter (SOM) was at site III. Pearson correlation coefficient analysis showed the negative correlation (p<0.01, p<0.05) of clay, silt, and pH, whereas positive correlation of sand and SOM (p<0.01) with altitude. Hence, our findings suggest the altitudinal variations in soil physico-chemical properties at cold desert high altitude.

Spatial heterogeneity of soil physico-chemical properties in contrasting wetland soils in two agro-ecological zones of Lesotho

Wetlands are complex ecosystems, often exhibiting considerable spatial variability, making the understanding of soil spatial relationships within them difficult. A study was conducted to evaluate spatial variability of soil physico-chemical properties in two contrasting wetlands in two agro-ecological zones (AEZs) of Lesotho. Soil samples were collected along two transects in mini-pits dug at different depths at 50-m intervals. The collected samples were analysed for particle size, pH, soil organic carbon (SOC), SOC pool, available phosphorus (Av-P), cation exchange capacity (CEC), and base cations. Results showed that within-site variability was very low for sand particles and pH (coefficient of variation &lt;15% for both properties). Soil physical properties generally showed less spatial heterogeneity than chemical properties, which differed widely within and between the study sites. There was generally low correlation between soil properties, and SOC accounted for most of the variation observed at both sites, especially T’sakholo with partial R2 = 94%; at Thaba-Putsoa, partial R2 = 44%. Geostatistical analysis showed that all of the nugget to sill ratios (NSR) showed strong spatial dependence (i.e. NSR of 54–94%) except SOC (T’sakholo stream-bank) with no spatial dependence, with the nugget accounting for 23.43%. We therefore conclude that further wetland studies in Lesotho should attempt to quantify not only the soil properties or processes under investigation but also their spatial variability, because this spatial variability can provide insight into underlying ecosystem processes and may itself indicate wetland condition. In addition, results of stepwise multiple regression showed that SOC and texture could be used across these sites for the sustainable management of these wetlands.

Spatial Variability of Soil Physico-chemical Properties in Kadawa Irrigation Project in Sudan Savanna Agroecology of Nigeria

Spatial Variability of Soil Physico-chemical Properties in Kadawa Irrigation Project in Sudan Savanna Agroecology of Nigeria

Coal fly ash and farmyard manure amendments in dry-land paddy agriculture field: Effect on N-dynamics and paddy productivity

A field study was conducted at a dry-land agricultural farm during paddy crop season to assess the effect of fly ash (FA) and farmyard manure (FYM) amendments on the dynamics of inorganic-N (NH 4 + and NO 3 −), N-mineralization and nitrification rates and paddy yields. Four treatments, each consisted of three replicates, were established in completely randomized block design. The treatments were: control, 50 t ha −1 FA, 50 t ha −1 FYM, and FA + FYM (each 50 t ha −1). The variations in soil physico-chemical properties due to treatments were statistically significant. Across different treatments, FA + FYM treated plot had significantly higher organic-C, total-N, total-P, water-holding capacity, but lower bulk density compared to control plot. The effect of various amendments and months was significant for soil inorganic-N (NH 4 + and NO 3 −) concentrations, soil moisture (SM) content, N-mineralization and nitrification rates. Across various amendments and sampling months, inorganic-N, SM, N-mineralization and nitrification rates were greatest in FA + FYM treated plot in August month. An exponential positive relationship existed between gravimetric SM content and N-mineralization ( R 2 = 0.865) and nitrification ( R 2 = 0.633) rates. The SM content was negatively correlated with NH 4 + ( R 2 = 0.841) and NO 3 − ( R 2 = 0.920). The various selected paddy agronomic parameters and yields differed significantly due to treatments. The most effective treatment noted for paddy grain yield was the combination of FA + FYM (92% increase over control) followed by FYM and FA. Significant correlation was noted among soil physico-chemical properties (except soil pH) and paddy productivity. The results suggested that FA and FYM amendments enhance the rates of N-transformation processes, plant available-N and paddy productivity. Thus, FA and FYM can be used as potential amendments to enrich soil productivity and crop yields for dry tropical nutrient poor soils.

Establishment and growth of white spruce on a boreal forest floodplain: Interactions between microclimate and mammalian herbivory

White spruce ( Picea glauca (Moench) Voss) is a dominant species in late-successional ecosystems along the Tanana River, interior Alaska, and the most important commercial timber species in these boreal floodplain forests. Whereas white spruce commonly seed in on young terraces in early primary succession, the species does not become a conspicuous component of the vegetation until after 60–80 years. To address what abiotic and/or biotic factors may explain the paucity of spruce in earlier stages of succession, we examined germination and growth of planted white spruce seedlings across an environmental gradient that included variation in soil physico-chemical properties in the presence and absence of mammal browsing. The effect of browsing pressure over the first four years after planting was most noticeable on the older terraces. Likewise, direct effects of hare browsing on spruce seedling mortality were only manifested at the oldest sites. Spruce germination and survival was inversely proportional to soil cation concentrations, which was largely controlled by temperature-driven evapotranspiration. High light intensities and high air temperatures significantly reduced seedling growth, whereas variation in soil moisture only explained a significant amount of variation in seedling survival. Temperatures within the needle clusters on terminal shoots reached values that adversely affect photosynthesis (>32 °C) on multiple occasions over the growing season. We conclude that the direct (temperature) and indirect (soil chemistry) effects of high insolation are major factors constraining spruce performance on early successional terraces, and that these effects can be significantly exacerbated by mammal browsing on associated deciduous vegetation.

Patrons spatio-temporels d’émergence et de croissance initiale des semis de deux espèces de chênes semées dans un pâturage abandonné

• Fine-scale spatial and temporal establishment patterns of direct-seeded oaks on abandoned agricultural land have been little studied despite their potential importance for long-term stand structure. • Here we periodically monitored seedling emergence and early growth of bur oak (Quercus macrocarpa Michx.) and red oak (Q. rubra L.) on an abandoned pasture, and tested the effects of herbaceous competition, rodents, and soil physicochemical properties. • Herbaceous competition slightly decreased diameter growth, but rodents had little impact on establishment. Red oak seedlings emerged earlier than bur oak and in a greater proportion (92% vs. 56%). Seedling emergence and early growth of both species showed significant spatial structures that were partly explained by variation in soil physicochemical properties. Bur oak was more responsive to microenvironmental heterogeneity than red oak, yet much of the variation in emergence and growth of both species remained unexplained. • This suggests that other factors, such as acorn size or genetic variability, may exert equal or greater control than microenvironmental heterogeneity over seedling emergence and early growth of these two oak species on abandoned pastureland.

Subsoil constraints to crop production on neutral and alkaline soils in south-eastern Australia: a review of current knowledge and management strategies

Crop yield variability and productivity below potential yield on neutral and alkaline soils in the semiarid Mediterranean-type environments of south-eastern Australia have been attributed, in part, to variable rooting depth and incomplete soil water extraction caused by physical and chemical characteristics of soil horizons below the surface. In this review these characteristics are referred to as subsoil constraints. This document reviews current information concerning subsoil constraints typical of neutral and alkaline soils in south-eastern Australia, principally salinity, sodicity, dense soils with high penetration resistance, waterlogging, nutrient deficiencies and ion toxicities. The review focuses on information from Australia (published and unpublished), using overseas data only where no suitable Australian data is available. An assessment of the effectiveness of current management options to address subsoil constraints is provided. These options are broadly grouped into three categories: (i) amelioration strategies, such as deep ripping, gypsum application or the use of polyacrylamides to reduce sodicity and/or bulk density, deep placement of nutrients or organic matter to overcome subsoil nutrient deficiencies or the growing of ‘primer’ crops to naturally ameliorate the soil; (ii) breeding initiatives for increased crop tolerance to toxicities such as salt and boron; and (iii) avoidance through appropriate agronomic or agro-engineering solutions. The review highlights difficulties associated with identifying the impact of any single subsoil constraint to crop production on neutral and alkaline soils in south-eastern Australia, given that multiple constraints may be present. Difficulty in clearly ranking the relative effect of particular subsoil constraints on crop production (either between constraints or in relation to other edaphic and biological factors) limits current ability to develop targeted solutions designed to overcome these constraints. Furthermore, it is recognised that the task is complicated by spatial and temporal variability of soil physicochemical properties and nutrient availability, as well as other factors such as disease and drought stress. Nevertheless, knowledge of the relative importance of particular subsoil constraints to crop production, and an assessment of impact on crop productivity, are deemed critical to the development of potential management solutions for these neutral to alkaline soils.

Risk Assessment Test for Lead Bioaccessibility to Waterfowl in Mine‐Impacted Soils

Due to variations in soil physicochemical properties, species physiology, and contaminant speciation, Pb toxicity is difficult to evaluate without conducting in vivo dose-response studies. Such tests, however, are expensive and time consuming, making them impractical to use in assessment and management of contaminated environments. One possible alternative is to develop a physiologically based extraction test (PBET) that can be used to measure relative bioaccessibility. We developed and correlated a PBET designed to measure the bioaccessibility of Pb to waterfowl (W-PBET) in mine-impacted soils located in the Coeur d'Alene River Basin, Idaho. The W-PBET was also used to evaluate the impact of P amendments on Pb bioavailability. The W-PBET results were correlated to waterfowl-tissue Pb levels from a mallard duck [Anas platyrhynchos (L.)] feeding study. The W-PBET Pb concentrations were significantly less in the P-amended soils than in the unamended soils. Results from this study show that the W-PBET can be used to assess relative changes in Pb bioaccessibility to waterfowl in these mine-impacted soils, and therefore will be a valuable test to help manage and remediate contaminated soils.

Characterizing soil spatial variability with apparent soil electrical conductivity: I. Survey protocols

Spatial characterization of the variability of soil physico-chemical properties is a fundamental element of (i) soil quality assessment, (ii) modeling non-point source pollutants in soil, and (iii) site-specific crop management. Apparent soil electrical conductivity (EC a) is a quick, reliable measurement that is frequently used for the spatio-temporal characterization of edaphic (e.g., salinity, water content, texture, and bulk density) and anthropogenic (e.g., leaching fraction) properties. It is the objective of this paper to provide the protocols for conducting a field-scale EC a survey (Part I) and apply these protocols to a soil quality assessment in central California's San Joaquin Valley (Part II). The protocols are comprised of eight general steps: (i) site description and EC a survey design; (ii) EC a data collection with mobile GPS-based equipment; (iii) soil sampling design; (iv) soil core sampling; (v) laboratory analysis; (vi) calibration of EC a to EC e; (vii) spatial statistical analysis; (viii) GIS database development and graphic display. For each outlined step, detailed discussion and guidelines were presented. The developed protocols provide the guidelines to assure reliability, consistency, and compatibility of EC a survey measurements and their interpretation.

Availability of metals to the nematodeCaenorhabditis elegans: Toxicity based on total concentrations in soil and extracted fractions

Current regulation of metals in soils is based on total metal concentrations rather than on actual exposure concentrations. Considering the extreme variation in soil physicochemical properties, total concentrations are not reflective of the availability and resultant toxicity of metals in different soils. In this study, the availability of Cd, Cu, Ni, Pb, and Zn to the free-living soil nematode Caenorhabditis elegans was assessed after 24-h exposures in three soils using a sequential soil extraction procedure. Albany soil, sampled from southern Georgia, USA, is characterized by a high sand content, whereas Cecil soil from the Piedmont region of Georgia contains higher fractions of clay and organic matter. The final soil was an American Society for Testing and Materials (ASTM) artificial medium composed of peat, kaolin clay, sand, and calcium carbonate. Based on their composition, ASTM medium would sorb metals most strongly and Albany soil the least strongly. In fact, 24-h lethal concentrations to 50% (LC50s) of nematodes for the five metals as determined by the total metal concentration followed this trend. In addition, water-extractable metals were lowest in ASTM medium and highest in Albany soil when spiked at the same concentrations. Our data show the need to consider soil type when performing toxicological tests and establishing site-specific allowable metal concentrations in soil.