Soil Surface Area Research Articles

A model for soil surface roughness influence on the spectral response of bare soils in the visible and near-infrared range

A mathematical model dealing with the influence of soil surface roughness on soil reflectance in the visible and near-infrared range is discussed. The model is based on the assumption that the reflectance from anisotropic rough soil surfaces is strongly correlated with the area of shadowed soil fragments, and therefore depends on the degree of soil roughness as well as on the illumination and the viewing geometry. A rough soil surface is simulated by equal-sized spheres arranged such that their centers form a square grid on a freely sloping plane. This model converts the bare soil reflectance data obtained for smooth samples into data relating to any natural rough surface states under conditions of unlimited illumination, which are defined by the solar altitude, the angle of a slope, and the sloping of the soil surface relating to the sunbeams direction. A simple parameter of the state of soil roughness expressing a proportion of the aggregates' and clods' area in top view in a given soil surface area is used here. The correctness of this model was evaluated on spectral data from 12 air-dried undisturbed soil samples obtained by means of a field spectrophotometer in outdoor conditions at solar altitudes from 31° to 59°. The measurements were taken for soil surfaces sloping at angles of 0°, 10°, 20°, and 30° forward and backward to the direction of sunbeams. Linear regression analysis indicates that for the studied spectral range the correlation coefficient of the relationship between all the 368 data point measured and calculated using this model reaches values of approximately 0.99. It has been found that relation between measured and predicted reflectance coefficient is similar for all the tested soils.

Determination of soil specific surface area by water vapor adsorption: II Dependence of soil specific surface area on clay and organic carbon content

The specific surface area of 60 mineral soil samples estimated by water vapor adsorption at 20 % relative humidity ranged from 12.1 ± 3.6 to 225.1 ±18.4 m2/g. Clay (range 1—72 %) and organic carbon content (0.7—14.6 %) together explained 84 % of the variation in the surface area. The regression equation predicting the specific surface area of soil was surface area (m2/g) =2.69+ 1.23clay-% +8.69org.C-%.

ECTOMYCORRHIZA FORMATION IN EUCALYPTUS: III. SUPERFICIAL ECTOMYCORRHIZAS INITIATED BY HYSTERANGIUM AND CORTINARIUS SPECIES.

Cortinarius and Hysterangium species are a dominant component of the macrofungi in eucalypt forests of Western Australia, and their hyphae occupy 10 % of the soil surface area. Anatomical studies of jarrah (Eucalyptus marginata Donn ex Sm.) and karri (E. diversicolor F. Muell) roots collected in association with hyphae of Cortinarius globuliformis Boug., C. ochraceus Clel. and Hysterangium inflatum Rodway showed mycorrhizal structures with mantles one to five cells thick and Hartig nets penetrating to the hypodermis. These superficial ectomycorrhizas were similar in size to those of non-colonized feeder roots and lacked the expanded cortex and broad mantle of pyramidal ectomycorrhizas formed by Laccaria laccata (Scop, ex Fr.) Berk. & Br. Colonized host roots responded with polyphenol accumulation in the epidermis/hypodermis and lignification of the outer cortex for both the superficial and pyramidal types.

Effects of soil texture on respiration and metal solubility in heating oil-amended soils

A comparison of oil transformations in soils of varying texture but similar fertility could reveal the effects of soil texture on oil decomposition. Differences in soil surface area may also cause differential responses to added metals in soils of diverse textures. The purpose of this experiment was to determine the effect of three different soil textures on rates of soil respiration and soil metal availability and content, following amendment with two types of heating oils.

Adsorption and Efficacy of Trifluralin and Butralin as Influenced by Soil Properties

Significantly higher rates of butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] were required to produce the same level of weed control as trifluralin [2,6-dinitro -N,N-dipropyl-4-(trifluoromethyl) benzenamine] when applied to soybeans [Glycine max(L.) Merr.] on seven different soils in the field. Higher rates of butralin were also required to control barnyardgrass [Echinochloa crus-galli(L.) Beauv. ♯ ECHCG] in growth chamber studies. No differences in the extent of soil adsorption of trifluralin and butralin were apparent; therefore, differences in efficacy could not be attributed to differences in soil adsorption. Herbicide rates required for 80% weed control and Freundlich K-values (adsorption capacity indices) were mostly highly correlated with soil organic-matter content and soil surface area as measured by benzyl ethyl ether (BEE) and ethylene glycol monoethyl ether (EGME) on nine soils. Analysis of the organic-matter content of the nine soils by 10 soil testing laboratories resulted in highly significant differences among laboratories.

Adsorption, Mobility, and Efficacy of Alachlor and Metolachlor as Influenced by Soil Properties

Alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] adsorption was positively correlated with soil organic-matter content, clay content, and surface area as measured by ethylene glycol monoethyl ether (EGME) or benzyl ethyl ether (BEE) and inversely correlated with herbicidal activity. Alachlor was adsorbed in slightly greater amounts by soil than metolachlor. Metolachlor had slightly greater bioactivity than alachlor on grass weeds, but the herbicides had similar activity on broadleaf weeds. Slightly greater amounts of metolachlor than alachlor were leached through a Norfolk soil and slightly greater amounts of alachlor were retained in the upper soil zones, compared with metolachlor.

Non-destructive measurement of wheat roots in large undisturbed and repacked clay soil cores

Non-destructive observations of root growth and distribution can be obtained from counting root intercepts with observation tubers inserted in the root zone. This paper describes the technique of inserting clear acrylic tubes horizontally into large undisturbed and repacked soil cores. Counts of roots intersecting scribed lines on the sides of the tubes were made with a fibrescope. Comparison was made between observation root tubes of different diameter (25 and 38.5 mm). The r2 values for the relationships between root intercept counts and destructively determined values of root length density (RLD) ranged from 0.78 to 0.96. The larger diameter tubes had higher r2 values. Theoretical calibration of the technique does not appear to be possible since analysis indicated that fewer roots intersected the scribed lines on the observation tube than would have been expected from a non-disturbed, randomly distributed root system. It is not known if this discrepancy is due to non-randomness or to an artifact associated with the insertion of the observation tube. Roots were not more prolific at the edge of the soil cores. Comparison of values of root length per unit soil surface area, rates of downward root growth and water uptake rates were within the ranges previously reported for wheat roots of field crops grown on clay soils. Observed root growth and distribution was found to be sensitive to four soil and water treatments imposed. It is concluded that the technique will allow quantitative analysis of root growth and distribution in undisturbed soil cores.

Water Droplet Impact and its Effect on Infiltration

ABSTRACT THE effect of droplet impact on the infiltration characteristics of a Warden silt loam soil were investigated in the laboratory. The hydraulic resistance of the seal formed on the soil surface by impacting water droplets was found to increase with increasing droplet kinetic energy per unit soil surface area (KEa). Experimental data also showed that the depth of water infiltrated prior to surface ponding decreased with increasing application rate (rainfall intensity), kinetic energy per water droplet (KEd), and water droplet energy flux (DEf). A unique relationship between DEf and the depth infiltrated prior to ponding was noted for the Warden silt loam. A procedure for determining the depth of water that can be applied to the Warden silt loam without the potential for runoff based on this relationship and an equation for computing DEf was presented. It appears that DEt, which is a function of both application rate and KEd, may be more effective in evaluating the runoff potential of irrigation sprinklers and rainstorms than application rate alone on soils prone to surface sealing such as the Warden silt loam.

Tillage effects and specific energy requirements of rotary tillage

Rotary tillage experiments were carried out under laboratory conditions in 3 types of Dutch soil. The moisture contents were set at 6 levels. Two tools were used; a knife blade and a tine. The energy required to work the soil was assessed with a pendulum. The specific energy requirement was expressed in units per volume of loosened soil, EV (kJ m −3) and also in units per surface area of loosened soil, EA (kJ m −2). In silty clay loam EV ranged between 153 and 160 kJ m −3 for the knife blade, and increased from 170 to 280 kJ m −3 for the tine, when the moisture content increased from 17 to 22%. EA increased from 2.5 to 9 kJ m −2 × 10 −1 for the knife blade and from 3.8 to 10.5 kJ m −2 × 10 −1 for the tine, when the moisture content increased from 17 to 22%. In sandy loam EV decreased from 110 to 75 kJ m −3 for the knife blade and from 165 to 130 kJ m −3 for the tine, when the moisture content increased from 9.5 to 17% EA increased from 1 to 2.5 kJ m −2 × 10 −1 for the knife blade and increased from 2.7 to 2 kJ m −2 × 10 −1 for the tine, when the moisture content increased from 9.5 to 17%. In silty loam EV decreased from 117 to 95 kJ m −3 for the knife blade and from 170 to 137 kJ m −3 for the tine, when the moisture content increased from 17 to 22%. EA increased from 3.7 to 5 kJ mm −2 × 10 −1 for the knife blade, and from 3 to 5.5 kJ m −2 × 10 −1 for the tine, when the moisture content increased from 17 to 22%. The energy requirement was related to penetration resistance, shearing resistance and modulus of elasticity. In silty clay loam the penetration resistance decreased from 3.9 to 2.6 MPa × 10 −1, the shear resistance hardly changed and ranged between 0.8 and 0.9 MPa × 10 −1, and the modulus of elasticity decreased from 46 to 23 MPa × 10 −1, when the moisture content increased from 17 to 22%. In sandy loam the penetration resistance decreased from 5.5 to 1.9 MPa × 10 −1, the shear resistance decreased from 0.6 to 0.4 MPa × 10 −1 and the modulus of elasticity decreased from 84 to 15 MPa × 10 −1, when the moisture content increased from 9.5 to 17%. In silty loam, the penetration resistance decreased from 3.6 to 1.7 MPa × 10 −1, the shear resistance decreased from 0.6 to 0.4 MPa × 10 −1 and the modulus of elasticity decreased from 58 to 11 MPa × 10 −1 when the moisture content increased from 17.5 to 22%.

Effect of drip irrigation on the yield and quality of Golden Delicious and Jonathan apples

SummarySix drip irrigation treatments were applied to a six-year-old apple orchard during 1977-1980. Four treatments received the same amount of water (1.0 class A pan evaporation coefficient from June to harvest), but differed with respect to the volume and the surface area of irrigated soil by using emitters with different discharge rates, different numbers of laterals per tree row and continuous v. pulse irrigation. Yields, growth, fruit size and crop load were not significantly affected by these irrigation treatments. Two additional treatments received less water (0.75 class A pan evaporation from June to harvest), one continuously and the other by pulse irrigation. Yields, growth and fruit size were decreased and crop load was increased compared to the other four treatments. Pulse irrigation of 30 min on and off reduced crop load under irrigation with the 0.75 pan coefficient but not with the 1.0 pan coefficient. The pulse irrigation effect was more pronounced in cv Golden Delicious, which had higher...

Rainsplash as a mechanism for soil contamination of plant surfaces.

We characterized the physical transport of soil, and therefore contaminants attached to the soil, onto vegetative surfaces due to rainsplash. Soil accumulation by tomato plants (Lycopersicon esculentum) was investigated as a function of soil particle size, rainstorm characteristics, foliage height, surface area and canopy cover of the plants. No soil particles greater than 105 micron in diameter were detected on the plants. Most of the soil was splashed no higher than 40 cm above the ground surface. Linear relationships were observed for concentrations of less than 53 micron soil on vegetation and certain rainfall characteristics. Data from this study, as well as ancillary calculations, provide evidence that a significant fraction of surficial contamination of foliage may be attributed to the rainsplash mechanism.

A species-area curve for buried viable seeds

A species-area curve was constructed for buried viable weed seeds in a 5-year-old subterranean clover-annual ryegrass pasture in south-eastern Australia. A soil surface area of about 200 cm2 (to a depth of 10 cm) was required to obtain a representative individual sample (i.e. a replicate) of the number of taxa in the soil seed bank, whereas a combined area of about 1000 cm2 was required for adequacy within any treatment. The total number of buried viable seeds of all species combined was distributed spatially in a more-or-less uniform manner. This suggests that a sample whose size is sufficient for determination of species diversity of buried seeds is equally adequate for measuring buried seed density.

Herbaceous standing crop in relation to surface and subsurface rockiness

A study, carried out in non-wooded parts of savanna and in desert grassland, demonstrated that herbaceous standing crop can decrease with increasing surface rock cover. However, such decreases corresponded more directly to a soil volumetric decrease than to a decrease in soil surface area per se. The relationship was also found to depend strongly on subsurface rock weathering patterns which may reverse the indicated relationship between standing crop and surface rock cover. The application of surface rock cover data without regard to profile stoniness, is, therefore, likely to be of limited use for comparing plant production across different geological substrates. The role of different rock types in giving rise to soils of different fertility with corresponding plant responses, was also indicated by the data. Sensitivity of plant standing crop to surface rock cover was possibly dependent on mean annual rainfall, but further data are required. The interpretation of aboveground standing crop data in terms of aboveground annual production is briefly discussed.

Atterberg Limits as Indices of External Surface Areas of Soils

AbstractSurface area measurements on soils are usually laborious and require expensive equipment. The relationship between Atterberg limits (plastic and liquid) and surface area is investigated with a view to being able to estimate the latter from the former. The results show that there is a very strong relationship (r2 > 0.9) which permits surface area to be estimated rapidly and cheaply.

Transport of radon through cracks in a concrete slab.

A model involving the use of line sources is developed to describe the transport of radon through the cracks or gaps which appear in concrete slabs used in building foundations. The strength of these sources is determined from the results of the diffusion model proposed by Landman in a previous work. Once the strength of the source is known, additional transport mechanisms can be treated in a simple manner. Pressure differences across the slab and in the underlying soil are discussed. The rate of exhalation through a portion of the cracked slab is determined and compared to the rate of exhalation from the same surface area of bare soil. In typical cases, their ratios vary from 0.25 to 0.50. Therefore, these transport mechanisms account for a larger portion of the levels of radon found in many houses than do previous models.

Contents of natural radioactive nuclides in soil in relation to their surface area

Concentrations of uranium series nuclides (238U, 226Ra, 210Pb), thorium series nuclides (228Ra, 212Bi), and potassium in soil of a granitic belt were examined in relation to their surface area of soil, clay mineral composition, and the SiO2 and Fe contents. In soil which is less weathered and has a surface area of around 10 m2/g, the 238U, 226Ra, 210Pb, 228Ra, and 40K contents increase with an increase the SiO2 content related to the elemental compositions of their parents rocks. In homologous soils resulting from progressive weathering, the 238U, 226Ra, 210Pb, and 228Ra contents are found to increase with increasing surface area. For an homologous soil which is free from the clay consisting of three‐layer units, the 40K content decrease with increasing surface area. However, in an homologous soil which contains a clay consisting of three‐layer units, the 40K content is not surface area dependent.

The influence of iron oxides on the surface area of soil

SummarySoils from Denmark and Tanzania have been extracted with ammonium acetate (controls), EDTA to dissolve amorphous iron oxides, and dithionite‐EDTA (DE) to dissolve crystalline iron oxides. The surface areas of the extracted soils have been determined by applying the BET equation to nitrogen adsorption and by water adsorption at 19 percent relative humidity. High correlations (P < 0.001) were found (i) between EDTA‐extractable iron (amorphous iron oxides) and the decrease in the surface area following EDTA extraction, and (ii) between the difference between DE‐extractable iron and EDTA‐extractable iron (crystalline iron oxides) and the further decrease in the surface area following DE extraction. The calculated specific surfaces of both the amorphous and the crystalline iron oxides varied from soil to soil but without any definite trend. The means of all the soils investigated may therefore serve as reasonable estimates of the specific surfaces of amorphous and crystalline iron oxides in soil.

Diffusion of radon through cracks in a concrete slab.

A mathematical model is developed to describe diffusion of radon through cracks or gaps in concrete slabs which are used in building foundations. As radon approaches the soil surface from underlying soil, it encounters a concrete slab. The radon will diffuse toward any air-filled cracks. The rate of exhalation through a portion of a cracked slab is determined and compared to the rate of exhalation from the same surface area of bare soil. In a typical case, this ratio is approx. 0.25. This is about a 20-fold increase to the ratio found when the concrete slab has no cracks. Therefore crack pathways are potentially a major source of indoor radon.

Water Vapour Adsorption at 20°C: A Possible Method for Determining Apparent Surface Area of Soil

Water Vapour Adsorption at 20°C: A Possible Method for Determining Apparent Surface Area of Soil

Apparent Photosynthesis, Evapotranspiration, and Light Penetration in Two Contrasting Hard Red Winter Wheat Canopies1

AbstractCrop canopy structure is highly variable in time and space influencing canopy light interception, apparent photosynthesis (AP), and evapotranspiration (ET). Our objectives were to relate AP and ET to light interception, leaf area index (LAI), temperature, and yield in two row‐spacings of winter wheat (Triticum aestivum L.) in a field environment. ‘Wanser’ winter wheat was planted at 20 — (140 kg seeds ha−1) and 40 — cm (70 kg seeds ha−1) row spacings in Ritzville silt loam (Mesic Calciorthidic Haploxerolls). Two aluminum frame chambers covered with mylar and occupying 0.74 m2 of soil surface area were used with infrared gas analyzers to measure AP and ET in each row spacing from the respective differences between chamber intake and exhaust CO2 and H2O concentrations. On clear days from stem extension to the milky ripe developmental stage and when incoming short‐wave solar radiation (SR) was 700 War−2 (± 140 Wm−2), best fit quadratic polynomial regression curves of AP and ET were obtained for each row spacing. Interception of SR across rows in each spacing was measured after anthesis with tube solarimeters 2, 27, and 53 cm above the soil surface.Values of LAI, AP, and ET were generally greater in the 20‐ than hi the 40‐cm spacing. After anthesis, LAI declined sharply in both spacings resulting in decreasing AP values; but ET was not greatly reduced. In contrast to days before anthesis, average air temperatures after anthesis were generally greater than average leaf temperatures. Sensible heat transferred from air to foliage was apparently an energy source promoting ET late in crop development. After anthesis, SR differed significantly between spacings at 2 cm, but not at 27 or 53 cm above the soil. Plant heights in both spacings were about equal averaging 70.3 cm. At 18 days after anthesis (watery ripe stage), the 20‐cm spacing had about 22% less SR 2 cm above the soil than the 40‐cm spacing. At that tune AP and LAI values were about equal between spacings so that the greater SR intercepted by 20‐cm spacing was apparently by tissue of low photosynthetic capability, such as dead or senescing leaves and tillers. Both spacings had statistically equal grain yields (2,102 kg ha−1 average); but the 20‐cm spacing had 67% more heads m−2, resulting hi more kernels nr*, than the 40‐cm spacing. The 40‐cm spacing had greater kernel weights and about 2.5 more kernels/head than the 20‐cm spacing. Increasing winter wheat yields by increasing post‐anthesis light interception appears unlikely unless sufficient water were available to maintain dense stands with high post‐anthesis LAI values.