Related Soil Properties Research Articles

The effect of soil heterogeneity on the spatial distribution of Heterodera schachtii within sugar beet fields

The beet cyst nematode, Heterodera schachtii, causes severe yield losses in sugar beet production worldwide. It tends to occur in heterogeneously distributed patches within fields. Soil texture is often regarded as the dominant soil property affecting the population density of H. schachtii. This study was based on the hypothesis that a relationship between soil texture and related soil properties and the population density of H. schachtii can be quantified with measurements of the soil's apparent electrical conductivity (EC a). The EC a, which is known to be strongly related to soil texture, was measured in four agricultural fields using the non-invasive EM38 sensor. Two of the fields showed little spatial variation in soil texture, whereas the other two were more spatially heterogeneous. Soil samples to determine the nematode population were taken either along transects or following a nested sampling design. Geostatistical methods were used to analyse the spatial distribution of EC a and nematodes. Correlations between EC a and nematode population density were moderate ( R 2 = 0.47) and strong ( R 2 = 0.74) in heterogeneous fields, indicating that H. schachtii prefers deep soil with medium to light textures and non-stagnic water conditions. Management maps based on EC a and soil taxation maps indicate areas with different soil-related living conditions for H. schachtii. These maps could enable farmers to improve site-specific management strategies on nematode-infested fields.

Influence of Soil Characteristics and As, Cd, and Pb Contamination on their Accumulation Levels in Rice and Human Health Risk Through Intake of Rice Grown Nearby Abandoned Mines

Transfer ability of arsenic (As), cadmium (Cd), and lead (Pb) from soil to polished rice, the influence of soil characteristics, and contamination on As, Cd, and Pb contents in rice and potential health risk were investigated through intake of polished rice grown in nearby abandoned mines. Transfer factors (TFs) of As, Cd, and Pb from soil to polished rice were evaluated based on the total and HCl-extractable concentration of As, Cd, and Pb in soil. Regression analysis was used to predict the relationship of soil properties, and total and HCl-extractable As, Cd, and Pb concentrations in rice and human health risk through the rice consumption. The results showed that As, Cd, and Pb contents in polished rice and human health risk through rice intake were more influenced by HCl-extractable concentrations of As, Cd, and Pb in soil than by total concentration. The contents of As, Cd, and Pb in polished rice showed the negative relationship with soil pH and positive relationship with soil organic matter and cation exchangeable capacity (CEC). As content in polished rice was significantly and positively correlated with total and HCl-extractable As concentration in soil. Same results were observed for the relationship between total and HClextractable As concentration in soil and cancer risk probability (R) as well as hazard quotient (HQ) from As exposure. This demonstrates that human health risk from As exposure could be well predicted by both of total and HCl-extractable As concentrations in soil.

Soil carbon and related soil properties along a soil type and land‐use intensity gradient, New South Wales, Australia

AbstractThe aim of this study was to systematically quantify differences in soil carbon and key related soil properties along a replicated land‐use intensity gradient on three soil landscapes in northwest New South Wales, Australia. Our results demonstrate consistent land‐use effects across all soil types where C, N and C:N ratio were in the order woodland > unimproved pasture = improved pasture > cultivation while bulk density broadly showed the reverse pattern. These land‐use effects were largely restricted to the near surface soil layers. Improved pasture was associated with a significant soil acidification, indicating that strategies to increase soil carbon through pasture improvement in these environments might also have associated soil degradation issues. Total soil carbon stocks were significantly larger in woodland soils, across all soil types, compared with the other land‐uses studied. Non‐wooded systems, however, had statistically similar carbon stocks and this pattern persisted whether or not carbon quantity was corrected for equivalent mass. Our results suggest that conversion from cultivation to pasture in this environment would yield between 0.06 and 0.15 t C/ha/yr which is at the lower end of predicted ranges in Australia and well below values measured in other cooler, wetter environments. We estimate that a 10% conversion rate (cultivation to pasture) across NSW would yield around 0.36 Mt CO2‐e/yr which would contribute little to emission reductions in NSW. We conclude that carbon accumulation in agricultural soils in this environment might be more modest than current predictions suggest and that systematically collected, regionally specific data are required for the vegetation communities and full range of land‐uses before accurate and reliable predictions of soil carbon change can be made across these extensive landscapes.

Regression-kriging for characterizing soils with remotesensing data

In precision agriculture regression has been used widely to quantify the relationship between soil attributes and other environmental variables. However, spatial correlation existing in soil samples usually violates a basic assumption of regression: sample independence. In this study, a regression-kriging method was attempted in relating soil properties to the remote sensing image of a cotton field near Vance, Mississippi, USA. The regression-kriging model was developed and tested by using 273 soil samples collected from the field. The result showed that by properly incorporating the spatial correlation information of regression residuals, the regression-kriging model generally achieved higher prediction accuracy than the stepwise multiple linear regression model. Most strikingly, a 50% increase in prediction accuracy was shown in soil sodium concentration. Potential usages of regression-kriging in future precision agriculture applications include real-time soil sensor development and digital soil mapping.

Long term nitrogen fertilization: Soil property changes in an Argentinean Pampas soil under no tillage

The main objective of nitrogen (N) fertilization is to achieve high yields and/or to increase grain quality. However, nutrient application may affect soil processes and cycles. These could involve increases in crop residues return to soil, changes in soil organic matter dynamic, NO 3 −-N content and pH decrease. The aim of this study was to determine the effect of N application on: crop residue input, soil organic carbon (SOC) and N (SON), their particulate (POC and PON) and mineral associated (AOC and AON) fractions, mineralizable N (anaerobic incubations, AN), and pH on a Molisoll of the southern Buenos Aires Province under no tillage (NT). A long-term crop rotation experiment has been conducted between 2001 and 2008 on a complex of Typic Argiudoll and Petrocalcic Paleudoll soils at Balcarce, Argentina (37°45′S, 58°18′W). Three N rates (N0, N1 and N2) were evaluated, with an average N input of 0, 57 and 105 kg ha −1 year −1, respectively. Crop sequence was integrated by maize ( Zea mays L.), soybean ( Glycine max (L.) Merr.) and wheat ( Triticum aestivum L.)/soybean double crop. Soil sampling was done in 2008, previous to maize planting. Nitrogen fertilization increased carbon (C) return to soil during 2001–2008 (11.1 and 18.7% for N1 and N2 respect to N0) but no differences in SOC, SON, AOC, and AON were observed among N rates in 0–5 and 0–20 cm depth. It was only found more PON in N1 and a slight tendency to increased POC (3% and 13% for N1 and N2 respect to N0) in 0–5 cm depth. At the same time, NO 3 −-N content in 0–60 cm depth was similar among N rates (89.6 ± 8.4, 88.6 ± 6.4, and 81.6 ± 10.3 kg N ha −1 for N0, N1, and N2, respectively). By contrast, it was determined soil acidification (5.8 ± 0.3, 5.5 ± 0.2, and 5.3 ± 0.2 for N0, N1, and N2, respectively) and AN reductions in 0–5 cm depth as N rate increased, (76.1 ± 3.2; 74.9 ± 6.3 and 57.9 ± 3.5 for N0, N1 and N2 respectively). The high frequency of soybean in the rotation could have prevented higher increases in C return to soil and, as a consequence, mitigated the changes in related soil properties. In addition, the absence of N application to soybean also could have prevented enhances in soil acidification and AN depletion.

Physiochemical Properties of Soil in Relation to Varying Rates of Crude Oil Pollution

Physiochemical Properties of Soil in Relation to Varying Rates of Crude Oil Pollution

Homegardens on Amazonian Dark Earths, Non-anthropogenic Upland, and Floodplain Soils along the Brazilian Middle Madeira River Exhibit Diverging Agrobiodiversity1

Homegardens on Amazonian Dark Earths, Non-anthropogenic Upland, and Floodplain Soils along the Brazilian Middle Madeira River Exhibit Diverging Agrobiodiversity. We test the hypothesis that the agrobiodiversity associated with homegardens on three different soils—upland Amazonian Dark Earths (ADE) and Oxisols (OX), and Fluvent Entisols (FL)—commonly found along the middle Madeira River in the municipality of Manicore, Amazonas State, Brazil, is different due to the contrasting biotic, abiotic, and cultural settings specific to each of these soils. Using data from interviews with 63 farmers about food and utility species, we compare structural and floristic characteristics of homegarden agrobiodiversity. The density of individuals is higher on ADE than on the other soils (mean ± standard deviation: 715 ± 363 on ADE, 474 ± 283 on OX, 642 ± 399 on FL). ADE and OX have higher species richness (28.2 ± 5.6 on ADE, 25 ± 3.7on OX, 23.6 ± 5 on FL), while ADE and FL have a greater degree of domestication (2 ± 0.6 on ADE, 1.3 ± 0.5 on OX, 2.3 ± 0.6 on FL). ADE and OX have greater proportions of richness, density, and coverage composed of South American species, while FL has greater proportions of richness and density composed of Old World species. ADE has higher proportions of density and coverage of Mesoamerican species. Floristic composition is also different between soils: ADE occupies an intermediate position, composed of species associated with each of the other soil types and species that are most common on ADE. These differences in agrobiodiversity emerge through the interaction of human agency, plant responses, and the unique properties of soils in relation to socioeconomic and historical trajectories over time.

Growth, Root Characteristics, and Leaf Nutrients Accumulation of Four Faba Bean (Vicia faba L.) Cultivars Differing in Their Broomrape Tolerance and the Soil Properties in Relation to Salinity

The effects of salinity on four faba bean (Vicia faba L) cultivars [Giza 429, Giza 843, Misr 1 (Orobanche-tolerant), and Giza 3 (Orobanche-susceptible)] and soil properties were investigated in a pot experiment with addition of 0, 50, and 100 mM sodium chloride (NaCl) for 9 weeks. Salinity significantly decreased calcium (Ca2+), magnesium (Mg2+), potassium (K+), bicarbonate (HCO3 −), and sulfate (SO4 2−) while significantly increasing sodium (Na+), chloride (Cl−), pH, and electrical conductivity (EC; dS m−1). Root length density (cm cm−3), root mass density (mg cm−3), total dry weight, and salt-tolerance indexes were significantly reduced as a result of application of salinity. The results presented support evidence on the positive relationship between Orobance tolerance and salt tolerance in the three cultivars (Giza 429, Giza 843, and Misr 1). This adaptation was mainly due to a high degree of accumulation of inorganic nitrogen (N), phosphorus (P), K+, Ca2+, and Mg2+ and lesser quantities of Na+ and Cl−, as well as greater K+/Na+ and Ca2+/Na+ ratios.

A cross‐ecosystem assessment of the effects of land cover and land use on soil emission of selected greenhouse gases and related soil properties in Zimbabwe

Land used for agricultural production can contribute significantly to greenhouse gas (GHG) emissions; however, there is very little information on the role of management and land use change in influencing these emissions in Africa. Thus, exploring GHG emissions that occur at the soil‐atmosphere interface is an essential part of the effort to integrate land management strategies with climate change mitigation and adaptation in southern Africa. We measured soil emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from rain‐fed perennial tropical grassland, wastewater‐irrigated perennial tropical pastureland, recently cleared woodland, miombo woodland, a Eucalyptus plantation, regular cropland and recently cleared‐and‐cropped land, on two contrasting soils at five sites in one cropping season in Zimbabwe. Gas samples were collected using static chambers and analysed by gas chromatography. Considerably high GHG emissions were found on sewage effluent‐irrigated pastureland (means, 190 mg CO2‐C m−2 hour−1, 102 µg CH4‐C m−2 hour−1 and 6 µg N2O‐N m−2 hour−1 from sandy soil) and altered woodlands (mean ranges, 38–70 CO2‐C m−2 hour−1, 12–43 µg CH4‐C m−2 hour−1 and 20–31 µg N2O‐N m−2 hour−1 from deforested and cultivated woodland on clay and sandy soils). Relatively low and less variable emissions were found among the rain‐fed perennial tropical grasslands, regular croplands and Eucalyptus plantations (mean ranges, 19–39 mg CO2‐C m−2 hour−1, −9.4–2.6 µg CH4‐C m−2 hour−1 and 1.0–4.7 µg N2O‐N m−2 hour−1). Variability in CO2, CH4 and N2O emissions from soils was to the greatest extent influenced by soil temperature, but soil moisture, mineral‐N and pH were also important. The increased N2O emissions from cleared woodland on clay soil were attributed to increased mineralization and N availability when no tree could take up that N, while the N mineralized on the sandy soil could have been largely leached due to the soil's poor nutrient holding capacity, resulting in a relatively lower N2O emission response to clearing. We concluded that the alteration of woodlands by deforestation and cultivation increased soil temperature, resulting in increased soil respiration, while the establishment of Eucalyptus plantations may provide an option for reduction in soil emissions of CO2 and N2O and a sink for CH4.

Role of six European tree species and land‐use legacy for nitrogen and water budgets in forests

AbstractWater and nutrient fluxes for single stands of different tree species have been reported in numerous studies, but comparative studies of nutrient and hydrological budgets of common European deciduous tree species are rare. Annual fluxes of water and inorganic nitrogen (N) were established in a 30‐year‐old common garden design with stands of common ash (Fraxinus excelsior), European beech (Fagus sylvatica L.), pedunculate oak (Quercus robur), small‐leaved lime (Tilia cordata Mill.), sycamore maple (Acer pseudoplatanus) and Norway spruce (Picea abies [L.] Karst.) replicated at two sites in Denmark, Mattrup and Vallø during 2 years. Mean annual percolation below the root zone (mm yr−1±SE, n=4) ranked in the following order: maple (351±38)>lime (284±32), oak (271±25), beech (257±30), ash (307±69)≫ spruce (75±24). There were few significant tree species effects on N fluxes. However, the annual mean N throughfall flux (kg N ha−1 yr−1±SE, n=4) for spruce (28±2) was significantly larger than for maple (12±1), beech (11±1) and oak (9±1) stands but not different from that of lime (15±3). Ash had a low mean annual inorganic N throughfall deposition of 9.1 kg ha−1, but was only present at Mattrup. Annual mean of inorganic N leaching (kg ha−1 yr−1±SE, n=4) did not differ significantly between species despite of contrasting tree species mean values; beech (25±9)>oak (16±10), spruce (15±8), lime (14±8)≫ maple (1.9±1), ash (2.0±1). The two sites had similar throughfall N fluxes, whereas the annual leaching of N was significantly higher at Mattrup than at Vallø. Accordingly, the sites differed in soil properties in relation to rates and dynamics of N cycling. We conclude that tree species affect the N cycle differently but the legacy of land use exerted a dominant control on the N cycle within the short‐term perspective (30 years) of these stands.

The impact of kaolinite and oxi-hydroxides on nitrate adsorption in deep layers of a Costarican Acrisol under coffee cultivation

A nitrogen budget study of a highly fertilized coffee plantation growing on an Acrisol (Ultisol: Ustic Paleohumult) in Southern Costa Rica provided clear evidence of low nitrate (NO 3 −) leaching to groundwater, in spite of a large annual rainfall and fairly high soil permeability. In this study, conducted at the same site, we measured soil properties in relation to nitrate adsorption. The clay content and proportion of kaolinite were high in the 80–200 cm layer and decreased below, whereas the proportion of gibbsite and to a lesser extent of iron oxi-hydroxides increased below 200 cm. Nitrate adsorption isotherms were measured. Nitrate adsorption maxima [coefficient a ( N max ) of the Langmuir equation] ranged from 1.9 to 1.6 cmol c kg − 1 between 80 and 200 cm depth and decreased below to reach a value of 0.9 cmol c kg − 1 at 380 cm depth. Anion exchange capacity and nitrate adsorption maxima were positively correlated with the clay and kaolinite contents, and negatively with gibbsite content and the net charge, assessed from the difference between soil pH in KCl and in distilled water. Nevertheless, the sorption affinity of NO 3 − to mineral surfaces, (coefficient b of the Langmuir equation), was highly correlated with the net charge and with the occurrence of gibbsite and iron oxi-hydroxides. We measured in the field a large NO 3 −–N accumulation in the sub-soil (up to 1570 kg of NO 3 −–N ha − 1 retained between 80 and 380 cm depth). In the layer 80–200 cm, where the clay size fraction was dominated by kaolinite, 55 to 75% of the stored NO 3 − could be extracted by shaking soil in distilled water. In this soil layer, the NO 3 − content was positively related to the net positive charge. In the layer 200–380 cm, where the clay size fraction was dominated by gibbsite, the proportion of NO 3 − extractable in distilled water was lower (45%) than above. Using adsorption coefficients obtained from batch experiments, we computed retardation factors for NO 3 − leaching up to 16 pore volumes in deep layers. Therefore, NO 3 − adsorption has already delayed and may further delay groundwater contamination over decades in these tropical Acrisols. Deep rooting perennial species may take advantage of this subsoil NO 3 −, either after abandoning agriculture, or in agroforestry systems.

Variations in chemical and physical properties of Amazon forest soils in relation to their genesis

Abstract. Soil samples were collected in six South American countries in a total of 71 different 1 ha forest plots across the Amazon Basin as part of the RAINFOR project. They were analysed for total and exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical quality proposed. A diverse range of soils was found. For the western areas near the Andean cordillera and the southern and northern fringes, soils tend to be distributed among the lower pedogenetic levels, while the central and eastern areas of Amazonia have more intensely weathered soils. This gives rise to a large variation of soil chemical and physical properties across the Basin, with soil properties varying predictably along a gradient of pedogenic development. Nutrient pools generally increased slightly in concentration from the youngest to the intermediate aged soils after which a gradual decline was observed with the lowest values found in the most weathered soils. Soil physical properties were strongly correlated with soil fertility, with favourable physical properties occurring in highly weathered and nutrient depleted soils and with the least weathered, more fertile soils having higher incidence of limiting physical properties. Soil phosphorus concentrations varied markedly in accordance with weathering extent and appear to exert an important influence on the nitrogen cycle of Amazon forest soils.

The Role of Subsurface Flow in Hillslope and Stream Bank Erosion: A Review

Sediment is one of the most common causes of stream impairment. Great progress has been made in understanding the processes of soil erosion due to surface runoff and incorporating these in prediction technologies. In many landscapes, however, the dominant source of sediment is derived from mass wasting of hillslopes and stream banks, potentially driven by subsurface flow. We highlight the mechanisms and importance of subsurface flow processes in erosion associated with hillslopes and stream banks. Subsurface flow affects erosion directly by seepage and pipe flow processes and indirectly by the relationship of soil properties with soil water pressure. Seepage contributes to erosion through interrelated mechanisms: hydraulic gradient forces that reduce the resistance of the particle to dislodging from the soil matrix and particle mobilization when soil particles become entrained in exfiltrating water. Preferential flow through soil pipes results in internal erosion of the pipe, which may produce gullies by tunnel collapse. The eroded material can clog soil pipes, causing pore water pressure buildup inside the pipes that can result in landslides, debris flows, embankment failures, or reestablishment of ephemeral gullies. Research in the past decades has advanced our understanding of these processes, leading to mathematical relationships that can be incorporated into mechanistic, process‐based models. Further research advances are necessary, however, especially on the complexity of the interactive effects of surface flow, seepage, pipe flow, and vegetation on soil erosion properties. More information is needed on the extent that subsurface flow contributes to hillslope and stream bank erosion. We believe that multidisciplinary efforts between soil scientists, geotechnical engineers, hydraulic engineers, and hydrologists are necessary to fully understand and integrate subsurface flow and soil erosion processes in simulation tools.

Spatial structure of microbial biomass and activity in prairie soil ecosystems

Management of soil ecosystems requires assessment of key soil physicochemical and microbial properties and the spatial scale over which they operate. The objectives were to determine the spatial structure of microbial biomass and activity and related soil properties, and to identify spatial relationships of these properties in prairie soils under different management histories. Soil were sampled along a transect at 0.2 m intervals in each of five long-term treatments, namely, undisturbed, cattle grazed at two intensities, and cultivated with either wheat ( Triticum aestivum L.) or cotton ( Gossypium hirsutum L.). Contents of organic carbon (C org), dissolved organic C (DOC), soluble nitrogen (N sol), and microbial biomass C (C mic) and N (N mic) as well as dehydrogenase activity (DH) in 70 samples were evaluated. Results showed that long-term soil management altered the spatial structure and dependence of C org and microbial biomass and activity. Cultivation has contributed to high nugget variance for C org, C mic, N mic and DH which interfered with detection of spatial structure at the sampling scale used. Contents of C org were spatially connected to microbial biomass and activity and to DOC in the uncultivated but not in the cultivated soils, indicating that various factors affected by management may operate at different spatial scales.

Effects of Soil and Topographic Properties on Spatial Variability of Corn Grain Ethanol Yield

To maximize biofuel production requires understanding relationships of soil properties and topography with variation of biofuel production within fields. The objective of this study was to determine the potential impacts of terrain attributes and soil properties on the variation of corn (Zea mays L.) grain ethanol yield at different locations within a corn–soybean [Glycine max (L.) Merr.] rotation field located in southwest Michigan. Ethanol yield at 33 geo‐referenced points in the field was obtained for the rotational corn years of 2006 and 2008. In both years, ethanol yield was significantly negatively correlated with elevation and positively correlated with soil total C, N, and organic C probably due to nutrient availability associated with these variables. Partial least square regression (PLSR) analyses were conducted between the ethanol yield and five combinations of terrain attributes, soil properties, and three‐degree polynomial of spatial coordinates, and number of factors for each analysis was selected based on leave‐one‐out cross validation. Two factors from PLSR analyses on the combination of terrain and soil properties explained about 46 and 44% of the ethanol yield variation for 2006 and 2008, respectively. Combining a three‐degree polynomial of spatial coordinates with soil and terrain attributes improved the R2 only from 0.46 to 0.50 for 2006 ethanol yield, while improved the R2 from 0.44 to 0.70 in 2008. The overall result indicates that soil and topographic properties explained most of the spatial variation in ethanol yield in the relatively dryer year of 2006, while only a small fraction of spatial variation was explained in 2008.

Soil macroporosity in relation to subsurface drain location on a sloping clay field in humid climatic conditions

Macroporosity of soil and earthworm abundance in relation to the distance from subsurface drain lines were determined to investigate the effect of subsurface drainage on the spatial variation of clay soil structure. Our hypothesis was that soil macroporosity near a drain line location would be greater than the macroporosity at a midpoint between two drain lines where the groundwater table remains theoretically at a higher level. The experimental site was located on a post-glacial clay soil classified as a very fine Aeric Cryaquept (Vertic Cambisol). The area of the field was 1 ha and the slope varied from 2 to 4%. Measurements of soil properties were carried out along four subsurface drain lines installed 50 years before soil sampling. In each drain line, vertical soil profiles were examined at different distances from the drain: (1) above the drain, (2) 2 m from the drain, and (3) midway between two drains (6–7 m from a drain). In each vertical profile, soil macroporosity, number of earthworm burrows and root channels, and saturated hydraulic conductivity ( K sat) were determined in three soil layers to the depth of 50 cm. In addition, the field saturated hydraulic conductivity ( in situ) and the number and fresh mass of earthworms were determined. The results showed that the number of earthworm burrows was 44% (90 burrows m −2) greater above a drain than at a distance of 6–7 m from the drain. There was also an indication of higher earthworm density above the subsurface drains than between them. The other measures of soil physical properties were not clearly related to distance from the drain. One reason for the small differences in soil properties in relation to drain position was probably the groundwater level that in our clay field varied less in relation to drain location than was expected. Spatial variation of the investigated soil properties was mostly explained by the slope of the field. Even though the groundwater table was shallower at the downslope part compared with the upslope part of the field, the number of biopores, K sat and the number of earthworms clearly increased downslope.

Influence of olive mill waste application on the role of soil as a carbon source or sink

Organic matter (OM) is involved in the enhancement of soil quality since it acts on soil structure, nutrient storage and biological activity. Organic carbon (OC), the dominant element constituent of OM, and related soil properties are probably the most widely acknowledged indicator of soil quality. The typically Mediterranean climate of the South of Spain promotes low yields on crops and low organic carbon in soil. The present work was carried out to evaluate the effect of the application of alperujo, olive oil waste difficult to eliminate, on the fixation or emission of carbon on soil in an olive grove situated in Montoro (Cordoba, Spain). In the study three treatments were considered: 15 kg (A), 7.5 kg (B), 0 kg (C) of alperujo per tree and the implementation of the amendment has been made for three consecutive years. The results confirm the benefits of the amendment on the carbon content organic soil with a fixation with respect to control of 4.8 and 6.1 t ha − 1 for the first year and 8.7 and 6.8 t ha − 1 for the second in treatments A and B, respectively. Of the different climatic agents considered in the study, it was the temperature which had a major influence on the emissions of CO2 into the atmosphere and the flow of gas presented the highest values in soils treated with the highest dose.

On farm assessment of tillage impact on soil carbon and associated soil quality parameters

No-tillage (NT) farming offers innumerable benefits to soil and water conservation, however, its potential to sequester soil organic carbon (SOC) and related soil properties varies widely. Thus, the impact of long-term (>4 yr) NT-based cropping systems on SOC sequestration and selected soil physical and chemical parameters were assessed across soils within five Major land Resource Areas (MLRAs: 99 and 111 in Michigan; 124 and 139 in Ohio; and 127 in Pennsylvania) in eastern U.S.A. Soil samples were collected from paired fields of NT and plow tillage (PT) based cropping systems and an adjacent woodlot (WL). The SOC concentration, bulk density (ρ b), texture, pH, electrical conductivity (EC), soil N, coarse particulate organic matter (CPOM) C and N, and nitrate N (NO 3-N) concentrations were determined. Conversion from NT to PT practice increased surface soil pH from 5.97, 6.56 and 6.02 to 6.62, 6.91 and 7.09 under MLRAs 127, 111 and 99, respectively. NT soils had higher SOC concentration soils by 30, 50 and 67% over PT soils at 0–5 cm depth under MLRAs 99, 111 and 127, respectively. Considering the whole soil profile SOC, WL had higher SOC pool than NT and PT practices under MLRAs 99, 111 and 124, however, there was no significant difference ( P < 0.05) between NT and PT practices across five soils. Almost the same trend was observed in the case of depthwise soil N content. NT soil had higher N content than PT soils by 27, 44 and 54% under MLRAs 99, 127 and 111, respectively. However, whole soil profile N content of NT soil was significantly higher by 12% than PT soil under MLRA 99. Concentrations of CPOM associated C and N of NT soil was higher than PT soil under MLRAs 99, 111 and 127 at 0–5 soil depth. These results indicated that impact of tillage on soil C and associated soil quality parameters is confined within specific soil types.

Simplified Relationships for Particle-Size Distribution and Permeation Groutability Limits for Soils

The particle-size distribution of soil with mean particle size and fines content are used not only in soil classifications but also in a number of other soil property relationships. In this study, two simple relationships (hyperbolic [tan h(x)] and S-curve) were investigated to represent the particle size distribution of soils. The parameters of the hyperbolic model were correlated to various soil parameters such as the mean particle size, particle size range, and fines content. There was no direct correlation between Fredlund (four-parameter model) and S-curve model parameters and the soil parameters. The predictions of the two (hyperbolic) and three (S-curve) parameter models were compared to the four-parameter model (unimodal) using limited soil data from the literature and the agreements were good. The hyperbolic model was used to map the Unified Soil Classification System. A recent study had quantified the relationship between the grouting pressure and the fines content in nonplastic soils. Also in the current practice, upper and lower particle-size distribution limits are used in determining the groutability of soils. In this study, the relationship between grouting pressure and fines contents of the soil was generalized using the hyperbolic particle-size distribution model and verified with a groutability study using an acrylamide grout. Based on limited data in the literature, the groutability of soils was defined using a new set of parameters, grouting pressure, fines content, and mean particle size diameter of the soil.

Advances in precision agriculture in south-eastern Australia. IV. Spatial variability in plant-available water capacity of soil and its relationship with yield in site-specific management zones

Spatial variability in grain yield can arise from variation in many different soil and terrain properties. Identification of important sources of variation that bear significant relationship with grain yield can help achieve more effective site-specific management. This study had three aims: (i) a geostatistical description/modelling of the paddock-level spatial structure in variability of plant-available water capacity (PAWC) and related soil properties, (ii) to determine optimal number of management zones in the paddock, and (iii) to assess if the variability in PAWC and related soil properties is significantly associated with the variability in grain yield across the management zones. Particle size distribution, bulk density (BD), field capacity (FC), permanent wilting point (PWP), and soil water content (SWC) at sowing were measured at 4 soil depths (to 0.60 m) at 50 representative spatial sampling locations across a paddock near Birchip (Victoria). PAWC and plant-available water at sowing (PAWs) were derived from these data. Moderate to strong spatial dependence across the paddock was observed. The magnitude of the structural variation and of range varied widely across different soil properties and depths. The south-east edge and the central areas of the paddock had higher clay content, FC, PWP, PAWC, and lower PAWs. The paddock was divided into 6 potential management zones using combined header yield and normalised difference vegetation index (NDVI). The adequacy of zoning was evaluated using relative variability (RV) of header yield and soil properties. The mean RV for 3 zones differed little from that of 6 management zones for header yield and for each measured soil property, indicating division of the paddock into 3 zones to be adequate. The results from residual maximum likelihood (ReML) analysis showed that low yield zones had significantly higher clay content, FC, PWP, SWC, and PAWC and significantly lower PAWs than both medium and high yield zones. The mean FC, PWP, and PAWC in the low yield zones were, respectively, 25%, 26%, and 28% higher, and PAWs 36% lower than their corresponding values in the high yield zones. Linear regression analysis indicated that 59–96% of the observed variation in grain yield across management zones could be explained by variation in PWP. The practical implications of these results are discussed.