Surface Soil Physical Properties Research Articles

Estimation of soil organic carbon by combining hyperspectral and radar remote sensing to reduce coupling effects of soil surface moisture and roughness

Soil organic carbon (SOC) is important in the global carbon cycle. Accurate estimation of SOC content in cultivated land is a prerequisite for evaluating the carbon sequestration potential and quality of soils. However, existing SOC prediction studies based on hyperspectral remote sensing neglect the spectral response of the physical properties of surface soil, leading to inadequate model generalization. With the exponential growth of remote sensing data, the development of pixel-level soil spectral correction methods based on multi-source remote sensing data has become an interesting and challenging topic. This method aims to minimize the effect of soil physical properties on spectra, thus addressing the poor spatiotemporal transferability of SOC prediction models due to uncertain variations in surface soil physical properties. In this study, a soil spectral correction strategy is constructed using satellite hyperspectral image (HSI) and synthetic aperture radar (SAR) images through multi-order polynomial regression and convolutional neural networks. This strategy considers soil physical variables such as soil moisture (SM) content and root mean square height (RMSH) of soil surface roughness. The soil spectral correction model and SOC content prediction model were established using 80 soil samples collected from Site 1. Afterward, the performance and transferability of both models were verified using the remaining 25 samples from Site 1 and 50 samples from Site 2. The results showed that: 1) The effect of SM and RMSH on the soil pixel spectrum can be significantly reduced after correcting HSI using soil spectral correction strategy. The correlation coefficients between the corrected pixel spectrum and the ground-based spectrum increase by over 60 % compared with those between the original spectrum and the ground-based spectrum. 2) Soil spectral correction improves the prediction accuracy and mapping capability of HSI for SOC content, with the highest RP2 of 0.743 and RMSEP of 3.455 g/kg at Site 1. 3) Compared with the original HSI-based SOC prediction model, the soil spectral correction strategy based on multi-order polynomial and convolutional neural network reduced the RMSEP of SOC prediction results at Site 2 by 5.082 g/kg and 5.454 g/kg, and the RP2 increased by 0.390 and 0.409, respectively. 4) When predicting SOC content from raw HIS, SM and RMSH contribute to more than 60 % of the bias, with SM having a larger bias than RMSH. The findings of this study emphasize the influence of soil physical properties on SOC prediction and contribute to the existing research on SOC mapping using HSI and SAR data.

Vegetation, ground cover, soil, rainfall simulation, and overland-flow experiments before and after tree removal in woodland-encroached sagebrush steppe: the hydrology component of the Sagebrush Steppe Treatment Evaluation Project (SageSTEP)

Abstract. Rainfall simulation and overland-flow experiments enhance understanding of surface hydrology and erosion processes, quantify runoff and erosion rates, and provide valuable data for developing and testing predictive models. We present a unique dataset (1021 experimental plots) of rainfall simulation (1300 plot runs) and overland-flow (838 plot runs) experimental plot data paired with measures of vegetation, ground cover, and surface soil physical properties spanning point to hillslope scales. The experimental data were collected at three sloping sagebrush (Artemisia spp.) sites in the Great Basin, USA, each subjected to woodland encroachment and with conditions representative of intact wooded shrublands and 1–9 years following wildfire, prescribed fire, and/or tree cutting and shredding tree-removal treatments. The methodologies applied in data collection and the cross-scale experimental design uniquely provide scale-dependent, separate measures of interrill (rain splash and sheet flow processes, 0.5 m2 plots) and concentrated overland-flow runoff and erosion rates (∼9 m2 plots), along with collective rates for these same processes combined over the patch scale (13 m2 plots). The dataset provides a valuable source for developing, assessing, and calibrating/validating runoff and erosion models applicable to diverse plant community dynamics with varying vegetation, ground cover, and surface soil conditions. The experimental data advance understanding and quantification of surface hydrologic and erosion processes for the research domain and potentially for other patchy-vegetated rangeland landscapes elsewhere. Lastly, the unique nature of repeated measures spanning numerous treatments and timescales delivers a valuable dataset for examining long-term landscape vegetation, soil, hydrology, and erosion responses to various management actions, land use, and natural disturbances. The dataset is available from the US Department of Agriculture National Agricultural Library at https://data.nal.usda.gov/search/type/dataset (last access: 7 May 2020) (doi: https://doi.org/10.15482/USDA.ADC/1504518; Pierson et al., 2019).

Changes in soil organic carbon, nitrogen, phosphorus, and bulk density after afforestation of the “Beijing–Tianjin Sandstorm Source Control” program in China

Under the “Beijing–Tianjin Sandstorm Source Control” (BTSSC) program in China, approximately 2.6millionha of cropland have been converted into tree plantations during 2000–2010. Although a large amount of biomass carbon has been accumulated, less is known about the variations in soil organic carbon (SOC) and nutrients. This has hampered accurate prediction of SOC sequestration potential and sustainable soil development in the afforested region. This study used a space-for-time substitution method to evaluate four typical afforestation sites (Populus tomentosa, Armeniaca sibirica, 8a Pinus tabulaeformis, and 24a P. tabulaeformis sites) along with the corresponding control sites. The identified sites were used to assess the effects of plant species and afforestation time on soil carbon sequestration and physicochemical characteristics. While a significant SOC accumulation was noted in the 0–20cm layer at the P. tomentosa and 24a P. tabulaeformis sites, SOC depletion occurred in the same soil layer at the A. sibirica and 8a P. tabulaeformis sites. Carbon sequestration at the 24a P. tabulaeformis site was 38.33gCm−2yr−1 in the 0–100cm soil layer, but the other relatively younger tree sites showed carbon depletion in the range of 31.84–109.76gCm−2yr−1. The bulk density of the 0–20cm layer significantly decreased at all the four sites. The largest decrease was at the P. tomentosa site, whereas no significant changes occurred in the 20–100cm soil layers. Nitrogen and phosphorus depletion rate was higher in A. sibirica than in 8a P. tabulaeformis, which was in turn higher than that in P. tomentosa. The results suggested that afforestation hindered soil carbon storage and soil nutrient content but enhanced surface soil physical properties at the early stage of afforestation. The effects of afforestation varied with plant species and afforestation time. Soil carbon, nitrogen, and phosphorus depletion rates were higher in economic forests than in protective forests and were higher in evergreen coniferous forests than in broadleaved deciduous forests.

Soil sorptivity enhancement with crop residue accumulation in semiarid dryland no-till agroecosystems

Water capture and precipitation use efficiency are of great importance in dryland cropping systems because the world's dependence on food produced in dryland areas continues to increase. Growing season evapotranspiration potential greatly exceeds growing season precipitation rates in dryland areas, creating a water deficit for crops. Management practices that positively impact soil physical properties increase the potential for soils to capture water. One way to assess the ability of soils to capture water is through the measurement of sorptivity. Sorptivity is defined as the cumulative infiltration proportionality constant and is governed by surface soil physical properties such as texture, degree of aggregation and aggregate stability. A study was conducted to determine how crop residue accumulation after 12years of no-till management affects surface soil sorptivity under semi-arid dryland conditions and how sorptivity is related to surface soil physical properties known to be related to crop residue accumulation. Surface soil sorptivity, bulk density, porosity (total and effective) and aggregation measurements were made across cropping systems and soil positions representing a wide gradient of crop residue accumulation at 3 sites in eastern Colorado. Results show that increasing crop residue accumulation will have the indirect effect of increased sorptivity via improvements in soil aggregation, bulk density, and porosity that are conducive to water infiltration. Management practices that result in greater amounts of crop residue returned to the soil system lead to beneficial soil physical properties that increase water sorptivity, greatly reducing the potential for runoff and erosion, and thereby increase the precipitation use efficiency of the system.

Soil salinization and sodication from alternate irrigations with saline-sodic water and simulated rain

We conducted a greenhouse study on large, semi-disturbed soil cores excavated from the vicinity of Verdigris Lake in southern Alberta to assess the suitability of different saline-sodic waters for irrigation. Soil salinization and sodication, surface soil physical properties, and yield of five soft white spring wheat crops (Triticum aestivum L. var. AC Reed) were examined under alternate applications of simulated rain with saline-sodic irrigation waters ranging from "safe" to "potentially hazardous" for irrigation. Increased salinity and sodicity of irrigation waters alternated with simulated rain resulted in increased salinity and sodicity in the upper 0.60 to 0.90 m of the soil. Salt accumulation in the root zone decreased as the leaching fraction increased. Aggregate stability and infiltration properties of the soil were generally adversely affected by the more saline and sodic irrigation waters. Infiltration properties were significantly greater with irrigation water (IW) than with distilled water (DW). The soil infiltration rate at 2 h, with DW as the infiltrating water, was the most sensitive soil physical property for assessment of irrigation water suitability. The infiltration test after five crop cycles gave a better indication of the effects of excess sodicity of irrigation water on soil structural stability than the aggregate stability test. The cumulative effects of long-term supplemental irrigation with saline-sodic waters on soil chemical and physical properties need to be considered when assessing irrigation water suitability. Irrigation waters with electrical conductivity (EC) less than or equal to 1 dS m-1 and a sodium adsorption ratio (SAR) less than or equal to 5 did not result in deterioration of soil physical properties and were considered "safe" for supplemental irrigation of the Masinasin soil. Alternate applications of irrigation and distilled water should be used to evaluate soil infiltration rates and the structural stability of soils to which saline-sodic waters are to be applied. Key words: Saline-sodic irrigation water, soil salinity, soil sodicity, aggregate stability, infiltration, water quali

Surface Soil Physical Properties After Twelve Years of Dryland No‐Till Management

Water is the principle limiting factor in dryland cropping systems. Surface soil physical properties influence infiltration and cropping systems under no‐till management may affect these properties through residue addition. The objectives of this study were: (i) to determine how cropping intensity and topographic position affect soil bulk density, porosity, sorptivity, and aggregate stability in the surface 2.5 cm of soils at three eastern Colorado sites; and (ii) to relate these properties to crop residue returned to the soil surface. No‐till cropping systems had been in place on three slope positions, at three sites, for 12 yr prior to this study. Wheat (Triticum aestivum L.)‐corn (Zea mays L.)‐fallow (WCF) and continuous cropping (CC) systems were compared with wheat‐fallow (WF) on summit and toeslope positions at two sites (Sterling and Stratton), and at the third site (Walsh) wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow (WSF) replaced WCF. Cropping systems (CC and WCF or WSF) that returned more crop residue decreased bulk density and increased total and effective porosities compared with WF. Site and slope positions that produced more crop residue also improved these properties. However, sorptivity developed no significant differences as a result of cropping system. Macroaggregates made up a higher percentage of total aggregates in CC and WCF or WSF compared with WF in proportion to residue added and were also a function of clay content of the soil at different sites and slope positions. These factors enhance the potential for greater infiltration and hence greater water availability for crops.

Compost Effects on Soil Physical Properties And Field Nursery Production

Field production of ornamental shrubs often results in significant topsoil removal and degradation of surface soil physical properties. Building soil organic matter through compost amendments is one way to ameliorate effects from topsoil removal in woody ornamentals production. We amended field soils with three composts to evaluate their effects on soil physical properties and shrub biomass production. Specifically, we applied either duck manure-sawdust (DM), potato cull-sawdust-dairy manure (PC) or paper mill sludge-bark (PMB) composts to a Plano silt loam soil using two application methods: 2.5 cm of compost incorporated into the top 15 cm of soil (incorporated-only) or 2.5 cm of compost incorporated plus 2.5 cm of compost applied over the soil surface (mulched). We grew three shrub species from liners: Spirea japonicum ‘Gumball’, Juniper chinensis ‘Pfitzeriana’, and Berberis thunbergia ‘Atropurpurea’. Shrub species and soil amendment treatments were established in triplicate in a randomized split plot design. Total soil carbon (TC), bulk density (ρb), aggregate stability, soil moisture retention capacity (MRC), volumetric moisture content (θv), and saturated hydraulic conductivity (Ksat) were measured over three years (1998 to 2000). We measured above and below ground shrub dry matter production at the end of the first (1998) and second (1999) growing seasons. Mulched treatments resulted in 15%-21% higher TC than the incorporated-only and no-amendment control treatments. Bulk density decreased with increasing TC contents. Greater aggregate stability and the formation of larger aggregates were related to increased TC. Field moisture retention capacity tended to be higher in the incorporated treatments compared to the mulched and nonamended control treatments. Compost amended treatments increased saturated hydraulic conductivity (Ksat) sevenfold over the nonamended control. There were no compost effects on shrub biomass until the second year of growth. Barberry was the only species to respond significantly and positively to compost application. Specifically, mulched DM compost produced 39-42% greater total Barberry biomass than the other compost treatments and the nonamended control. Our findings showed that compost effects on soil physical properties differed among composts and their subsequent effects on shrub growth were species specific.

Tillage and water content effects on surface soil physical properties

The effects of pre-tillage soil water content (PTSW) and multiple-pass tillage on soil physical condition was investigated on a silt-loam soil susceptible to wind erosion. PTSW was shown to affect the soil condition produced by tillage and an interaction between intensity of tillage and PTSW was identified. The ‘excess’ tillage treatment produced 13.9% of aggregates <0.26 mm diameter when PTSW was 0.58 times the lower plastic limit as compared with 6.0% when PTSW was equal to the lower plastic limit (highly significant). On this soil the avoidance of excessive tillage reduced the likelihood of a significant PTSW effect. Aggregates produced from ‘excessive’ tillage were more stable than those from the ‘intermediate’ and ‘minimum’ tillage treatments when dry aggregate stability was determined soon after tillage. Aggregates formed during tillage with PTSW near the plastic limit were less resistant to mechanical breakdown when compared with those formed at lower PTSW levels. Excessive tillage at the lower plastic limit and at 0.58 times the lower plastic limit resulted in dry aggregate stability indices of 0.835 and 0.923, respectively (significant). More intense tillage produced a smoother soil surface, which increases the susceptibility of the soil to wind erosion. Random soil roughness and soil surface area were not affected by PTSW. Dry bulk density was lower for ‘minimum’ tillage as compared with the other two treatments. Excessive tillage of this soil should be avoided, especially at low PTSW, because of the large quantities of wind-erodable aggregates which can result. In assessing the most appropriate PTSW for desired tillage objectives, the effect on aggregate stability must be considered.

Effect of hedgerow species in alley cropping systems on surface soil physical properties of an Oxic Paleustalf in south-western Nigeria

SUMMARYEffects of hedgerow species on surface soil physical properties were studied in an on-going trial established since 1981 on an Oxic Paleustalf in southwestern Nigeria. The experimental treatments wereLeucaena leucocephala, Gliricidia sepium, Alchornea cordifoliaandAcioa barteriihedgerows planted at 4 m interhedgerow spacings and a control (no hedgerows). Plots were sequentia-ly cropped with maize (Zea mays) and cowpea (Vigna unguiculata). Soil physical properties, i.e. particle size distribution, bulk density, apparent pore size distribution and water infiltration, were monitored during the dry season in January and the main growing season in June 1989. Soil temperature was monitored at approximately monthly intervals from February to June 1989. Soil properties of alleycropped plots were superior to those of the control. Soil compaction was highest in the control and lowest withL. leucocephala. Between the hedgerow species, within-season increases in soil compaction were largest withA. cordifolia. Lowest soil temperatures were observed withL. leucocephalaandA. barterii. Frequency, quantity and quality of prunings produced by the hedgerow species appeared to have a major beneficial effect on soil physical properties.

Physical properties of surface soil in a topsoil removal area and a nearby undisturbed site

Abstract Surface soil physical properties were measured at 3 sites within an area where topsoil had been removed, and a nearby area where no topsoil had been removed. Most physical parameters which affect plant growth were significantly better at the undisturbed site, and worst at the site with the least pasture cover. Penetration resistance was the best physical parameter at distinguishing between the 4 sites. The differences in physical properties at the sites within the topsoil removal area are consistent with compaction of the surface soil during earthmoving operations.

Surface Soil Physical Properties after 36 Years of Cropping to Winter Wheat

AbstractA dryland tillage and cropping system study for winter wheat (Triticum aestivum L.) was conducted on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) from 1941 to 1977, a period much longer than most field studies. In 1977, soil samples were collected from the surface layer to evaluate effects of the long‐term tillage and cropping practices on dry and water‐stable aggregate distribution, organic matter (OM) concentration, modulus of rupture, penetrometer resistance, and bulk density of clods. Oneway disk tillage resulted in significantly fewer small dry aggregates than sweep tillage in the wheat‐fallow system, but had no significant effect in the continuous wheat system. Mean weight diameters (MWD) were similar for all tillage methods. Oneway tillage resulted in more &lt; 0.25‐mm diameter water‐stable aggregates than sweep tillage in both cropping systems, resulting in lower MWD for oneway than for sweep tillage. Organic matter concentration was lower for oneway than for sweep tillage in both systems, while continuous wheat resulted in higher OM concentration than wheat‐fallow for comparable tillage methods. Slight changes from 1966 to 1977 indicated that soil OM concentration was at or nearly in equilibrium with prevailing management and climatic conditions. Modulus of rupture of briquettes and resistance of briquette fragments to fracture with a penetrometer were inversely related to OM concentration, but no tillage method or cropping system had an overriding influence on soil physical properties. Dry aggregate analyses indicated that the soil did not contain enough coarse aggregates to control wind erosion, indicating the need to maintain residues on the soil surface to aid wind erosion control.