Soil Calcium Carbonate Content Research Articles

An Approach to the Key Soil Physical Properties for Assessing Soil Compaction Due to Livestock Grazing in Mediterranean Mountain Areas

The selection of key soil physical properties (SPPs) for studying the impact of livestock treading is an unexplored research topic, especially in studies that analyze the influence of livestock management on the degradation process. The objective of this work was to demonstrate that the key SPPs for studying the impact of livestock treading depend on the objectives of the research and the environmental characteristics of the study site. This work used discriminant analysis to establish the most significant SPPs among the following: bulk density (BD), total porosity (P), field capacity (FC), infiltration capacity (IC), and aggregate stability (AS). Results showed that (1) IC and BD are the key properties for identifying the areas affected (bare patch) and unaffected (vegetated patch) by livestock treading, (2) none of the SPPs are significant under increasing stocking rates, and (3) BD is the key property for analyzing livestock impact with increasing stocking rate, using soil calcium carbonate content, slope exposure, and grass cover. We concluded that the relationship between physical soil degradation and stocking rate is not linear because it depends on environmental factors; therefore, to establish the key SPPs, it is necessary to take this fact into account.

An Examination of the Effect of Chemically Induced Damage on the Monotonic and Cyclic Shearing Behavior of Biocemented Sands

Abstract Microbially induced calcite precipitation is a biomediated soil improvement method that can improve the engineering properties of granular soils. Although improvements in soil engineering behaviors afforded by biocementation have been extensively characterized, there remains limited understanding of the anticipated long-term engineering behavior of biocemented soils following progressive chemical damage that may be experienced following initial applications. In this study, 10 direct simple shear tests were performed to investigate the effect of chemically induced damage on the drained monotonic and undrained cyclic shearing behaviors of biocemented loose Ottawa F-65 sand. All specimens were either uncemented, biocemented to different cementation levels corresponding to shear wave velocity increases (ΔVs) between 150 and 500 m/s, or biocemented to a ΔVs near 250 or 500 m/s and then subjected to degradation injections, which induced chemical damage and achieved ΔVs reductions of either 100 or 200 m/s. For all specimens, Vs and soil calcium carbonate content measurements were performed to assess improvement magnitudes, cementation uniformity, and evaluate magnitudes of chemically induced damage. As expected, increases in biocementation levels as captured by Vs increases were shown to progressively improve drained monotonic and undrained cyclic shearing behaviors. Following chemically induced damage, however, behavioral improvements were largely retained and were found to be consistent with the nondegraded biocemented specimens on the basis of similar Vs values. The performed tests provide the first examination of the expected long-term engineering behaviors of biocemented sands and yield new understandings regarding the anticipated impacts of chemical damage on behaviors relevant to subsurface liquefaction mitigation applications and other geotechnical use cases.

Synergistic soil, land use, and climate influences on wind erosion on the Colorado Plateau: Implications for management

Two decades of drought in the southwestern USA are spurring concerns about increases in wind erosion, dust emissions, and associated impacts on ecosystems, agriculture, human health, and water supply. Different avenues of investigation into primary drivers of wind erosion and dust have yielded mixed results depending on the spatial and temporal sensitivity of the evidence. We monitored passive aeolian sediment traps from 2017 to 2020 across eighty-one sites near Moab, Utah to understand patterns of sediment flux. At measurement sites, we collated climate, soil, topography and vegetation spatial layers to better understand the context of wind erosion and then combined these data with field observations of land use in models to characterize the influence of cattle grazing, oil and gas well pads, and vehicle/heavy equipment disturbance that potentially drive both exposure of bare soil and increases in erodible sediment supply that increase vulnerability to erosion. Disturbed areas with low soil calcium carbonate content yielded high sediment transport in dry years, but notably areas with little disturbance and low bare soil exposure had much less activity. Cattle grazing had the largest land use association with erosional activity with analyses suggesting that both herbivory and trampling from cattle could be drivers. The amount and distribution of bare soil exposure from new sub-annual fractional cover remote sensing products proved very helpful in mapping erosion, and new predictive maps informed by field data are presented to help depict spatial patterns of wind erosion activity. Our results suggest that despite the magnitude of current droughts, minimizing surface disturbance in vulnerable soils can mitigate a large portion of dust emissions. Results can help land managers identify eroding areas where disturbance reduction and soil surface protection measures can be prioritized.

Relationships between saturated paste and 1:1 or 1:5 soil/water extract sodium adsorption ratios

Relationships between saturated paste and 1:1 or 1:5 soil/water extract sodium adsorption ratios

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.

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.

Prediction of soil calcium carbonate with soil visible-near-infrared reflection (Vis-NIR) spectral in Shaanxi province, China: soil groups vs. spectral groups

ABSTRACT Soil visible-near-infrared reflection (Vis-NIR; 350 to 2500 nm) spectra is a comprehensive reflection of various soil physical and chemical properties, resulting in significant differences of hyperspectral characteristics and diversity of soil property prediction models. Calcium carbonate regulates several soil properties that were widely used to describe soil types and to quantify vulnerability to erosion. Therefore, spectral-based determination of soil calcium carbonate content is essential for agricultural management and environmental evaluation. Based on their reflectance similarity, the soil Vis-NIR spectra data itself can be classified into different spectral groups to predict soil calcium carbonate. To obtain the best hyperspectral quantitative prediction model for soil calcium carbonate based on soil group spectral data and spectral group data, a total of 246 soil samples were collected from seven soil types in Shaanxi province, China, and the soil Vis-NIR spectra were measured. All the soil spectral data were smoothed using Savitzky-Golay and continuum removal method. In this paper, we combined spectral angle cosine (SAC) algorithm with spectral correlation coefficient (SCC) algorithm to classify soil spectra. The results indicated that the coefficient of correlations between measured and predicted soil properties for seven prediction models based on random regression forest (RFR) were low (Ratio of performance to deviation, RPD < 2.00). When soil spectra were classified into three types based on the SAC-SCC spectral similarity measurement method, accuracy of all the prediction models increased significantly (R 2 ≥ 0.96; RPD > 2.00) compared with the individual soil type models. These results provide a novel method for soil spectral classification and soil attribute estimation.

Influence of clogging substances on pore characteristics and permeability of geotextile envelopes of subsurface drainage pipes in arid areas

This study investigates the influence of clogging substances on pore characteristics and permeability of geotextile envelopes that were used for 3, 7 and 15 years in irrigated farmlands in Xinjiang region, which is arid and suffers from the soil salinity problem. Results show that the macropores (above 125 μm) of envelopes are evidently clogged, whereas the smaller pores less than 100 μm are still unblocked after operation. The permeability coefficients of geotextile envelopes after serving for 3 and 15 years are smaller than the minimum required permeability coefficients after clogging. The main chemical components of clogging substances in the geotextile envelope are silicon dioxide and calcium carbonate. Calcium carbonate content of the geotextile envelope is consistent with calcium carbonate content of soil. Chemical clogging susceptibility increases with the operation time of the subsurface drainage pipes. The ratio of O90 size of envelope material over d90 of soils (O90/d90) and saturation index (SI) can be used to assess the susceptibility of physical and chemical clogging respectively. This study provides a preliminary reference for estimating the clogging susceptibility of geotextile envelopes in arid areas.

GPS-GIS based soil fertility maps of Chandgad tehsil of Kolhapur district (M.S.)

The study was carried out to know the fertility status of soils of Chandgad tehsil, of Kolhapur district by using GPS-GIS technology and to correlate soil properties with the available nutrient status and also to evaluate the fertility index of Chandgad tehsil during the year 2015-2016.The pH of soils of Chandgad tehsil varied from 5.01to 7.21, most of the soils were found to be moderately acidic (57.15%) while EC varied from 0.04 to 0.70 dS m-1, the soilswere found to be normal (100 %) in salinity. The Calcium Carbonate content of soils of Chandgad tehsil varied from 0.51 to 3.07 per cent, the area was barely calcareous (33.77%), slightly calcareous (50%) and moderately calcareous (16.23%). Organic Carbon content varied from 0.31 to 1.12 per cent and categorized as low (24.02%), moderate (24.03%), moderately high (21.42%), high (19.50%) and very high (11.03%).The soil available Nitrogen, Phosphorus and Potassium in Chandgad tehsil ranged from 143.21 to 420.26, 1.03 to 20.6 and 102.8 to 293.6 Kg ha-1, respectively. The soils were low (35.71%) and moderate (64.29%) in available Nitrogen. In respect of available Phosphorus very low (40.26%) low (46.75%) and moderate (12.99%). In case of available Potassium low (24.68%), moderate (9.74%), moderately high (36.36%) and high (29.22%). The exchangeable Calcium and Magnesium ranged from 10.00 to 25.00 and 2.25 to 12.50 cmol (p+) Kg-1, respectively. The soils were sufficient (25.32%), deficient (74.68%) and sufficient (13.63%), deficient (86.37%) in exchangeable Calcium and Magnesium, respectively. The exchangeable sodium ranged from 0.13 to 0.97 cmol (p+) Kg-1.The available sulphur varied from 5.12 to 35.93 mg Kg-1. The soils were low (26.62%), moderate (22.73%), moderately high (23.38%) and high (27.27%) in available Sulphur content.The pH was significantly and positively correlated with exchangeable Calcium and Magnesium. EC was non-significant and positively correlated with Nitrogen, Phosphorus, Calcium, Magnesium, Sodium and Manganese. The organic carbon was significantly and positively correlated with Nitrogen, Phosphorus, Potassium and Sulphur. Calcium carbonate was significantly correlated with calcium, magnesium and Sulphur.The fertility index of Chandgad tehsil for Organic Carbon, available Nitrogen, Phosphorus and Potassium was medium (2.02), low (1.32), low (0.86) and medium (1.85), respectively.

Soil quality and aggregation in runoff water harvesting forestry systems in the semi-arid Israeli Negev

Water availability is a major limiting factor for dryland afforestation. Earthworks that modify natural landforms for the formation of runoff harvesting systems are prevalent in the Israeli drylands, with the aim of establishing afforestation projects. However, serious concerns alarm that such earthworks have detrimental effects on the geo-ecosystem functioning. Therefore, the objective of this study was to examine the impact of the establishment of contour bench terrace (also called shichs/shychs/shikim) runoff harvesting systems on selected soil properties, with particular focus on soil aggregation. Thus, we assessed the effect of the establishment of contour bench terraces in a multi-aged forestry land, comprised of 2-year-old and 9-year-old afforestation areas, and compared them to ‘natural’ hillslopes as a reference treatment. The study was implemented in the Ambassadors' Forest, located in the semi-arid northern Negev of Israel, where we sampled the surface soil (at a depth of 0–5cm) in north- and south-facing hillslopes. Considerable differences were recorded for the afforestation systems between the source (inter-terrace area) and sink (terrace-bottoms) areas. Data normalizing according to the relative cover percentage of the terraces and inter-terrace areas showed that the mean values of mean weight diameter (MWD), stable aggregate content, and particulate organic carbon in the natural hillslopes were 1.4%, 32.4%, and 20%, respectively, greater than in the 9-year-old afforestation systems, and 12.1%, 28.9%, and 31%, respectively, greater than in the 2-year-old systems. Means of clod content, aggregate slaking index, and clay dispersion index in the natural hillslopes were 62.3%, ~twofold, and 35.0%, respectively, smaller than in the 9-year-old systems, and almost threefold, nearly twofold, and 46.2%, respectively, smaller than in the 2-year-old areas. The soil calcium carbonate content was similar in soils of the natural hillslopes and 9-year-old afforestation lands, which was ~17% smaller than in the 2-year-old afforestation systems. Considerable differences among the land-uses were also recorded for the soil texture. Mean coarse root biomass, despite revealing only a marginally-significant effect (p-value=0.0765), was 40.0% greater in the natural hillslopes than in the 9-year-old systems, and more than twofold greater than in the 2-year-old systems. Hillslope aspect affected some of the measured properties, revealing only slightly better soil conditions in the (mesic) north- than in the (xeric) south-aspects. The data revealed that forestry-related earthworks degrade the soil quality and geo-ecosystem functioning in the short term. Yet, despite some discrepancies, the data also showed the occurrence of self-restoration processes of the geo-ecosystem over the long term.

Rapid Removal of Atmospheric CO2 by Urban Soils.

The measured calcium carbonate content of soils to a depth of 100 mm at a large urban development site has increased over 18 months at a rate that corresponds to the sequestration of 85 t of CO2/ha (8.5 kg of CO2 m(-2)) annually. This is a consequence of rapid weathering of calcium silicate and hydroxide minerals derived from the demolition of concrete structures, which releases Ca that combines with CO2 ultimately derived from the atmosphere, precipitating as calcite. Stable isotope data confirm an atmospheric origin for carbonate carbon, and 14C dating indicates the predominance of modern carbon in the pedogenic calcite. Trial pits show that carbonation extends to depths of ≥1 m. Work at other sites shows that the occurrence of pedogenic carbonates is widespread in artificially created urban soils containing Ca and Mg silicate minerals. Appropriate management of fewer than 12000 ha of urban land to maximize calcite precipitation has the potential to remove 1 million t of CO2 from the atmosphere annually. The maximal global potential is estimated to be approximately 700-1200 Mt of CO2 per year (representing 2.0-3.7% of total emissions from fossil fuel combustion) based on current rates of production of industry-derived Ca- and Mg-bearing materials.

Will charophyte species increase or decrease their distribution in a changing climate?

Most charophyte species are threatened across Europe. Understanding their current and future distribution is a challenge for their conservation. We looked for species distribution models (SDM) and for increasing or decreasing species occurrence under a future climate scenario in Switzerland. Firstly, we modeled the occurrence of charophyte species in 1402 Swiss localities using presence–absence data and environmental variables (waterbody size, mean July temperature, July precipitation, soil calcium carbonate content and proportions of land used by agriculture and forest cover in the catchment area and in the surroundings). We used generalized additive models (GAM) to analyze the data. Secondly, based on the models, we predicted the occurrence of the species in 21,092 localities listed in Switzerland. Thirdly, we applied a climate scenario to our models (2°C mean July temperature increase and 15% reduction in July precipitation) and predicted species occurrence under these new conditions. Twelve charophyte species were modeled successfully. The major driver of species distribution was the waterbody size, followed by climate and land-use variables. We detected predicted impacts of climate changes on the species occurrence and identified the potential winners and losers. About half of the species are predicted to become losers; they colonize the littoral zone of lakes. Other charophytes are potential winners; the majority of them colonize small waterbodies.

Georeferenced Status of Cobalt in Soils of Yavatmal District of Maharashtra

The present study entitled Georeferenced Status of cobalt in soils ofYavatmal district of Maharashtra was conducted during 2012-13 at Department of Soil Science and Agricultural Chemistry, Dr. PDKV, Akola with objective to assess the cobaltstatus in soils of Yavatmal district and to study relationship of cobalt with soil properties and preparation of GIS based soil fertility maps of micronutrients. In the Yavatmal district, the cobalt ranged 0.02-1.80 mg kg -1 . Based on critical limit of cobalt (0.25mg kg -1 ) the deficiency was noticed 61.97 percent. The nutrient indices of DTPA-Co were 1.67 respectively. DTPA-cobalt showed negative and significant correlation with soil pH (-0.142**).The calcium carbonate content of soil showed negative and significant correlation with DPTA-cobalt (r=-0.104*). It could be concluded that, in Yavatmal district the soils were found deficient in cobalt (61.97%).

Investigation of different irrigation systems based on the parametric evaluation approach on the Dasht Bozorg Plain

The main objective of this study was to compare different irrigation systems based on a parametric evaluation system in an area of 3070 ha on the Dasht Bozorg Plain, Khuzestan Province, southwestern Iran. Soil properties in the study area such as texture, depth, electrical conductivity, drainage, calcium carbonate content and slope were derived from a semi-detailed soil study carried out on the Dasht Bozorg Plain on a scale of 1:20 000. Once the soil properties were analysed and evaluated, suitability maps were generated for surface, sprinkle and drip irrigation systems using remote sensing (RS) techniques and GIS (Geographic Information System). The results showed that for 1567.6 ha (51.1%) in the study area sprinkle irrigation was highly recommended, whereas for 1876.6 ha (61.3%) in the study area drip irrigation would be extremely efficient and suitable. However, there were no highly suitable lands for surface irrigation, but for all irrigation systems no unsuitable land exists in the study area. The results showed that by applying sprinkle irrigation instead of drip and surface irrigation, the arability of 1611.6 ha (52.5%) on the Dasht Bozorg Plain will improve. In addition, by applying drip irrigation instead of sprinkle or surface irrigation, the land suitability of 802.4 ha (26.2%) on this plain will improve. A comparison of the different types of irrigation systems revealed that sprinkle and drip irrigation were more effective and efficient than surface irrigation for improving land productivity. It is noteworthy, however, that the main limiting factor in using sprinkle and/or drip irrigation in this area is the soil calcium carbonate content and the main limiting factors in using surface irrigation are soil calcium carbonate content together with drainage.

Influence of rotation cropping and sugarcane production on the clay mineral assemblage

The present study examines the influence of unfertilized crop production on Calcic Haplustept soils in southwestern Iran. Soil profiles from about 100 years of rotation cropping (wheat, corn, barley and vegetables) and those from 40 years of irrigated sugarcane production were compared with the adjacent uncultivated soils. Particle size analysis revealed there was an increase in clay contents of soils from the rotation cropping. There was 66.1% clay in the Ap horizon of rotation cropping soil and 56.8% was in the A horizon of uncultivated soil. On the other hand, the sums of sand and silt fractions were 43.2 and 33.9% for uncultivated and rotation cropping soils, respectively. Therefore, differences between clay contents could be attributed to cultivation and subsequent mineral alteration. Organic matter contents were greater under cultivated soils; consequently the cation exchange capacity under sugarcane (19 cmol c kg − 1 ) and rotation cropping (30 cmol c kg − 1 ) were greater than for the uncultivated soils (16 cmol c kg − 1 ). Under cultivation, both the gypsum and calcium carbonate content of soils were lower, especially in the surface horizon. The lower electrical conductivity of soil solutions further reflected enhanced leaching of the cultivated soils. Depletion of K by the sugarcane is due to the release of nonexchangable K from interlayer positions in micaceous minerals. Expandable minerals were abundant in the Ap horizon of the cultivated soils, unlike in the uncultivated soils, while only small amounts were found in C horizons of cultivated soils. This trend agrees with changes in soil physico-chemical properties, especially for fixed K and increased CEC. TEM showed that the subsurface horizons of the cultivated soils contained more palygorskite than the surface. It can be concluded that intensive cropping and strong irrigation over a long time could have brought about changes from micaceous and palygorskite minerals to expandable minerals.

Comparison of Different Irrigation Methods Based on the Parametric Evaluation Approach in Abbas Plain: Iran

The main objective of this research is to compare different irrigation methods based upon a parametric evaluation system in an area of 29,300 ha in the Abbas plain located in the Elam Province, in the west of Iran. The soil properties of the study area such as texture, depth, electrical conductivity, drainage, calcium carbonate content, and slope were derived from a semidetailed soil study carried out on the Abbas Plain on a scale of 1:20,000. Once the soil properties were analyzed and evaluated, suitability maps were generated for surface, sprinkle, and drip irrigation methods using remote sensing techniques and geographic information system. The obtained results showed that for 16,125 ha (55.03%) of the study area surface irrigation method was highly recommended; whereas for 16,600 ha (56.66%) of the study area a sprinkle irrigation method would provide to be extremely efficient and suitable; moreover, it was found that 15,425 ha (52.65%) of the study area was highly suitable for drip irrigation methods; however, one soil series coded 9 and covering an area of 2,150 ha (7.34%) was incompatible for sprinkle and surface irrigation systems. For drip irrigation systems the unsuitable lands did not exist in this zone. The results demonstrated that by applying sprinkle irrigation instead of surface and drip irrigation methods, the arability of 21,250 ha (72.53%) in the Abbas Plain will improve. In addition by applying drip irrigation instead of surface and sprinkle irrigation methods, the land suitability of 6,275 ha (21.42%) of this plain will improve. The comparison of the different types of irrigation techniques revealed that the sprinkle and drip irrigation methods were more effective and efficient than the surface irrigation methods for improving land productivity. It is of note, however, that the main limiting factor in using either surface and/or sprinkle irrigation methods in this area is soil texture and the main limiting factor in using drip irrigation methods were soil calcium carbonate content and soil texture.

Predicting the response of wheat (Triticum aestivum L.) to liquid and granular phosphorus fertilisers in Australian soils

Liquid forms of phosphorus (P) have been shown to be more effective than granular P for promoting cereal growth in alkaline soils with high levels of free calcium carbonate on Eyre Peninsula, South Australia. However, the advantage of liquid over granular P forms of fertiliser has not been fully investigated across the wide range of soils used for grain production in Australia. A glasshouse pot experiment tested if liquid P fertilisers were more effective for growing spring wheat (Triticum aestivum L.) than granular P (monoammonium phosphate) in 28 soils from all over Australia with soil pH (H2O) ranging from 5.2 to 8.9. Application of liquid P resulted in greater shoot biomass, as measured after 4 weeks’ growth (mid to late tillering, Feeks growth stage 2–3), than granular P in 3 of the acidic to neutral soils and in 3 alkaline soils. Shoot dry matter responses of spring wheat to applied liquid or granular P were related to soil properties to determine if any of the properties predicted superior yield responses to liquid P. The calcium carbonate content of soil was the only soil property that significantly contributed to predicting when liquid P was more effective than granular P. Five soil P test procedures (Bray, Colwell, resin, isotopically exchangeable P, and diffusive gradients in thin films (DGT)) were assessed to determine their ability to measure soil test P on subsamples of soil collected before the experiment started. These soil test values were then related to the dry matter shoot yields to assess their ability to predict wheat yield responses to P applied as liquid or granular P. All 5 soil test procedures provided a reasonable prediction of dry matter responses to applied P as either liquid or granular P, with the resin P test having a slightly greater predictive capacity on the range of soils tested. The findings of this investigation suggest that liquid P fertilisers do have some potential applications in non-calcareous soils and confirm current recommendations for use of liquid P fertiliser to grow cereal crops in highly calcareous soils. Soil P testing procedures require local calibration for response to the P source that is going to be used to amend P deficiency.

The Effects of Livestock Grazing and Recreation on Irish Machair Grassland Vegetation

Machair grassland uniquely occurs over sandy, calcareous soils of coastal sand-plains in dune systems of north-western Scotland and Ireland. This study assesses the plant species composition of Irish machair grassland at a landscape-scale. Machair sites were sampled with quadrats and multivariate analysis was used to assess relationships between species abundance, soil physical variables, livestock grazing and recreation activity. Grazing by cattle and sheep was recorded at most sites, with recreation activities at nearly half the sites. Detrended and Canonical Correspondence Analysis ordinations showed that the main gradients of community composition were related to the key variables of soil calcium carbonate content, soil organic matter content, livestock grazing intensity and recreation pressure. Partial Canonical Correspondence Analysis showed that livestock grazing intensity and recreation pressure explained about twice as much variation as the key soil variables and that rabbit grazing had a much smaller but significant effect. Livestock grazing and recreation activities were shown to be ecologically damaging in terms of having a larger area of bare sand and a lower species diversity. Bare sand can increase the risk of storm damage and reduce habitat heterogeneity by sand-plain deflation. Controls on livestock density, the length of the grazing season and recreation activities are proposed, which we suggest would facilitate vegetation recovery. We highlight the need for local planning authorities, who control coastal development in Ireland, to include agricultural management prescriptions in their machair site management plans.

Soil landscape evolution due to soil redistribution by tillage: a new conceptual model of soil catena evolution in agricultural landscapes

This paper focuses on analysing tillage as a mechanism for the transformation of soil spatial variability, soil morphology, superficial soil properties and development of soil–landscape relationships in agricultural lands. A new theoretical two-dimensional model of soil catena evolution due to soil redistribution by tillage is presented. Soil profile truncation occurs through loss of soil mass on convexities and in the upper areas of the cultivated hillslopes; while the opposite effect takes place in concavities and the lower areas of the field where the original soil profile becomes buried. At sectors of rectilinear morphology in the hillslope (backslope positions), a null balance of soil translocation takes place, independent of the slope gradient and of the rate of downslope soil translocation. As a result, in those backslope areas, a substitution of soil material in the surface horizon with material coming from upslope areas takes place. This substituted material can produce an inversion of soil horizons in the original soil profile and sometimes, the formation of “false truncated soil”. In the Skogstad agricultural field (Cyrus, MN) spatial patterns of soil properties (soil calcium carbonate content) in the surface soil horizons and soil morphology along several slope transects were analyzed. These spatial patterns are compared with those estimated for soil redistribution (areas of erosion and deposition) due to tillage using the Soil Redistribution by Tillage (SORET) model and water erosion using the models Water Erosion Prediction Project (WEPP) and Universal Soil Loss Equation (Usle2D). Results show that tillage was the predominant process of soil redistribution in the studied agricultural field. Finally, some practical implications of the proposed model of soil landscape modification by tillage are discussed. Nomographs to calculated the intensity of the expansion process of the eroded soil units by tillage are proposed for three different patterns of tillage.

Biotic Soil Crusts of Oregon's Shrub Steppe: Community Composition in Relation to Soil Chemistry, Climate, and Livestock Activity

Abstract We examined biotic soil crust cover and composition at nine shrub-steppe sites in central and eastern Oregon, U.S.A. One pair of livestock-grazed and excluded transects was established at each site. Data were collected on the cover of biotic soil crust and vascular plant species, soil surface pH and electrical conductivity, and other environmental variables. Using gradient analysis, we found that differences in community composition among sites were most strongly related to soil pH, electrical conductivity (EC), and Calcareous Index Value (CIV; a scale representing the relative calcium carbonate content of soils). Other important variables included precipitation, elevation, aspect, and temperature. We found total crust cover to be highest at sites with lower pH, EC, and CIV. Dominant species differed markedly between the more calcareous sites with higher pH, and the less calcareous, lower pH sites. Livestock exclusion was not an important gradient in the ordination of these data, being overshadow...