Field Conditions In Soil Research Articles

An experimental investigation of the characteristics of and conditions for brittle fracture in two-dimensional soil cutting

Although the occurrence of different soil failure mechanisms during soil cutting operations is well attested to in the literature, not all have been successfully characterised and modelled. Such quantitative and qualitative models are essential for improving the design, selection and use of soil cutting implements, in different field soils under different field soil conditions. This paper describes an experimental investigation of the failure characteristics of, and conditions for brittle fracture in two-dimensional soil cutting. Comprehensive tests were carried out on sandy loam, clay loam and cemented sand soils using a glass-sided box apparatus and five model plane blades of rake angles 25°, 40°, 55°, 70° and 90°, respectively. Cutting forces were measured and soil deformation patterns were studied using a bead tracer technique. The failure characteristics of brittle fracture are shown to be quite different from those of shear failure. Whilst shear failure is characterised by extensive shear distortion, compaction and the regular formation of distinct slip planes, brittle fracture is characterised by crack propagation and negligible deformation within separated soil clods. This indicates the possibility of using fracture mechanics methods to model the mechanism of brittle fracture. The results further show that transitions between these two modes of failure do occur and are governed by certain soil and implement factors, namely blade rake angle, soil strength and soil–blade interface condition. For example, for three different levels of soil strength of the sandy loam at 176.0 g kg −1 soil moisture content, the mean transition rake angle from brittle fracture to shear failure increased from 32.5° in S1 (c=11.20 kN m −2,φ=29°) to 47.5° in S2 (c=16.00 kN m −2,φ=35°) and to 62.5° in S3 (c=23.93 kN m −2,φ=49°) . These factors should provide a basis for the reliable prediction of the failure type, and hence the quality of soil tilth expected in two-dimensional soil cutting operations.

Effects of forage plant and field legume species on soil selenium redistribution, leaching, and bioextraction in soils contaminated by agricultural drain water sediment

A study was undertaken to assess the potential of two plant species, tall fescue (Festuca arundinacea Schreb., a forage plant) and yellow sour clover (Melilotus indica L., a naturally occuring legume species) for bioremediation of selenium laden soils. Using soil columns under simulated field soil conditions, the effects of these two species were studied on soil selenium (Se) redistribution, leaching, and Se bioextraction. Both leachate volume and Se concentration in the leachate were greatly influenced by presence of vegetation. The volume of leachate was considerably lower for columns having either tall fescue or yellow sour clover plantings. Tall fescue had a higher water use rate and greater rooting density than did in yellow sour clover, indicating the tall fescue will be more practical for bioremediation of Se laden soils. Soil Se distribution analysis yielded the following patterns: (1) contamination of the lower soil profile of uncontaminated soil occurred at the first harvest, but Se concentrations at these depths were not at high levels; (2) except for selenite, all forms of water-extractable soil Se concentrations showed a clear reduction over time of vegetation harvest; and (3) the reductions of total soil Se were significant, but the difference was relatively small between the forage planting and bare soil treatments. This is due to the fact that only a relatively small fraction of total Se inventory was water soluble and available to plants at any one time. A large reduction may become apparent after a longer period of forage plant management.

Pesticide leaching into field soils: sensitivity analysis of four mathematical models

In this study, four mathematical models were evaluated for their sensitivity with respect to both general and specific input parameters. The models compared were MOUSE, GLEAMS, TETRANS, and HYDRUS, which were also employed in a prior analysis of long-term atrazine leaching potential towards groundwater. MOUSE showed only high sensitivity to sorption parameter, but simulations dependend excessively on the soil depth. GLEAMS model sensitivity was moderate with respect to hydraulic conductivity and potential evapotranspiration, whereas it was high for the input parameters related to runoff, sorption, and degradation submodels, besides to the soil water content at the field capacity. TETRANS was sensitive to Kd's inputs whereas it was less to the bypass flow parameter. HYDRUS was sensitive to both Kd and μ parameter inputs, too. Comparisons of measured and simulated alachlor leaching data showed that the analyzed models differently predicted the pesticide transport and that, under some field soil conditions, their calibrations may improve simulations only partially. A general analysis on some pesticide leaching showed the models to give more differentiated performances for highly sorptive soils.

Measurement and simulation of atrazine and alachlor leaching into two field soils

Two small farmland plots were treated with atrazine and alachlor at a rate of 1.4 and 1.6 kg ha −1, respectively. Subsurface drains were placed in each plot to allow sampling of the leachate from February 14 to May 26, 1989. The early leaching phase was high for both herbicides. Simulations were also made with a deterministic, physically-based model (HYDRUS). Different approaches were used to estimate the values of both sorption ( K d) and degradation (μ) parameters, namely, conventional soil-transfer functions, best-fitting to measured field data, and mass-balance and time-step procedures. The K d-values obtained by the best-fitting method were the lowest, those calculated by conventional pedotransfer functions the highest. Measured and simulated leaching data were then compared. Qualitative (graphics) and quantitative (statistics) evaluations indicated that the herbicide leaching predictions depended greatly on the sorption parameter input. Computer simulations using K d-values derived from the best-fitting and time-step approaches gave the best results in predicting the herbicide leaching under field soil conditions.

Simulation and areal interpolation by different methods of atrazine transport

Atrazine behaviour under field soil conditions is simulated by using a physically-based model (HYDRUS). Examined alluvial soils, located in a reclaimed agricultural area in northern Italy, are characterized by having a high potential hydrological vulnerability. As a prediction sample, computer outputs of maximum penetration depth and atrazine concentration in the upper soil layer are used as point data sets. Both isolinear and choropleth maps of related environmental risk of groundwater contamination by atrazine, through leaching or soil erosion, are constructed using different interpolation methods. Local methods (i.e. moving average, weighted moving averages, and ordinary block kriging) perform better than a global, quadratic trend surface method. Kriging provides the best predictor. To evaluate the associated uncertainty of spatial prediction, a simplified approach for mapping a specified conditional probability of the variable of interest is also shown.

Evaluating the Suitability of MSW Compost as a Soil Amendment in Field Grown Tomatoes Part B: Elemental Analysis

Tomato plants were grown under field conditions in soil amended with 0, 25, and 50 tons/acre of source separated composted municipal solid waste (MSW). The leaves and fruit from these plants were sampled following a dual-stage nested design, and analyzed for 17 elements. Statistical analysis of the results showed that the Na and P contents increased and that the Cd and Be contents decreased in the fruits grown in the amended soil. In the leaves of tomato plants grown in amended soil the Na content increased, and the Cd, Cu, and Mn contents decreased compared to those grown in the control soil. The attenuation of the Cd, Cu, and Mn levels in the tomato tissues was attributed to increases in pH and organic matter in the compost amended soil.

Prediction of the immediate effects of traffic on field soil qualities

Based on the comparative prediction method, a prediction function was developed, which relates pertinent soil and traffic characteristics to the immediate effect of traffic on the field soil condition. The effect on the field soil condition is expressed in terms of a number of soil physical and mechanical properties, which are relevant to soil use and which are referred to as soil qualities. The prediction function is based on a limited domain, in order to restrict the number of soil and traffic characteristics that have to be taken into account, and to limit the range of values they can attain. The prediction function is presented graphically by means of composite diagrams.

Laboratory and Field Evaluations of Sorghum for Response to Aluminum and Acid Soil1

AbstractPlant responses in controlled environments (greenhouse and growth chamber) should relate to field plant responses if laboratory screening methods are to be used effectively for the improvement of plant tolerances to soil stress conditions. Eight acid soil susceptible and tolerant sorghum [Sorghum bicolor (L.) Moench.] genotypes were compared for dry matter production, element uptake, and visual plant stress symptoms under field stress (Georgia) and artificially‐induced Al‐toxic nutrient solutions (Nebraska). Sorghum was grown on three soil types (Typic Rhodudults, Fragiaquic Paleudults, and Typic Hapludults) and at three levels of Al (0, 46, 93 µmol L−1) in nutrient solution. Net seminal root lengths were used to evaluate plants for Al tolerance in the laboratory. The objectives of this study were to compare sorghum genotype responses when plants were grown under both field and laboratory conditions to determine genotypic differences and to better quantify Al and acid soil tolerance screening techniques. Among the genotypes studied, SC0283 was the most tolerant to acid soil field stress conditions and was also the least affected by Al toxicity conditions in nutrient solutions. NB9040 was susceptible to acid soil field conditions, exhibited considerable tolerance to medium levels of solution Al, and was susceptible to high levels of solution Al. Tolerance or susceptibility to Al among the sorghum genotypes was influenced by the level of the acid soil stress condition. Manganese toxicity probably affected plant responses in the field. Genotype responses to Al‐induced stress conducted in the laboratory and to acid soil stress conducted in the field showed similar responses when the screening parameters for each environment were quantified. The susceptibility response of NB9040 was equivalent at 93 µmol L−1 Al (32 µmol L−1P) in solution and pH 4.4 to 4.8 for the three soils used in this study.

Leaf mineral element concentrations and growth of sweet sorghum subjected to acid soil stress

Abstract The nutritional profile of sweet sorghum [Sorghum bicolor (L.) Moench] cultivars grown under acid soil field stress conditions is a critical consideration when developing plants which are adapted to these infertile soils. Uptake and accumulation of macro‐ and micronutrients vary among genotypes and ultimately Influence plant growth and development. This study compared fourteen sweet sorghum germplasm lines and varieties for their Individual patterns of leaf nutrient concentrations and productivity when grown under acid soil field conditions (pH 4.45 to pH 4.85) at three locations over a two‐year period. Significant year x location interactions were found for Fe, K, and Ca concentrations at both Blairsville and Calhoun and for Mn and P levels at Blairsville and Calhoun, respectively. Data from Calhoun on plant height, dry weight, visual stress ratings, and rainfall indicate a possible association between drought tolerance and acid soil tolerance in sorghum. No significant differences in A1 concent...

Response of Cucumber (Cucumis sativus) to Annual Weeds and Herbicides

Weed and cucumber (Cucumis sativusL. ‘Poinsett’) growth was studied where herbicides were soil-applied or applied to emerged weeds in the established crop. Cucumber yields were decreased at least 36% in 2 of 5 yr when weeds interfered for 4 weeks after emergence. Sequential applications of bensulide [O,O-diisopropyl phosphorodithioateS-ester withN-(2-mercaptoethyl)benzenesulfonamide] applied preplant and incorporated (PPI) + trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) applied postemergence and incorporated (POI) were outstanding and controlled Japanese millet (Echinochloa crus-galliLink. var.frumentacea), Texas panicum (Panicum texanumBuckl.), Palmer amaranth (Amaranthus palmeriS. Wats.), and common purslane (Portulaca oleraceaL.) without affecting the growth or yield of cucumber. Compared with bensulide, the selectivity of soil-incorporated butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] with cucumber was limited. Laboratory bioassays showed that under warm field soil conditions, PPI applications of 1.7 kg/ha of butralin persisted more than 2 months, but were dissipated after 4 months. Ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine] reduced cucumber yields only when it was soil-incorporated to the crop-seed depth at planting. Applications to soil of bensulide + DCPA (dimethyl tetrachloroterephthalate) stunted cucumber plants, reduced leaf area, increased leaf thickness, and caused higher near-infrared (0.75 to 1.34 μm) leaf reflectance.

Variability among sorghum genotypes for uptake of elements under acid soil field conditions

Abstract The nutritional balance of sorghum [Sorghum bicolor (L.) Moench] plants grown under acid soil stress conditions is one crucial consideration when developing plants which are adapted to these infertile problem soils. Absorption of elements varies with each genotype and ultimately affects plant growth and development. This study compared seventeen different sorghum grain genotypes for their individual patterns of leaf nutrient accumulation when grown under acid soil field conditions (pH ≤ A.8) over a three‐year period. Significant differences among years for leaf concentrations of Ca, Mg, K, Mn, P, Fe, Al, and Zn were detected. Year x genotype interactions occurred for Ca, Mg, and Mn leaf concentrations. All genotypes in this study differed in their ability to absorb elements, but some general patterns of nutrient accumulation were noted. Comparison of SCO283, an acid soil tolerant genotype, and BSD106, a susceptible genotype, revealed differences in mean concentrations of Al, Fe, Mn, and Cu. For breeding purposes, these four elements would definitely need to be monitored when determining the nutritional profile of various genotypes which are grown under acid soil stress conditions.

Effect of species and cultivation on the responses to phosphate of annual pastures and crops

Three crop species, sand-plain lupin, Lupinus cosentinii L. (cv. Chapman), narrow-leaf lupin, L. angustifolius L. (cv. Uniharvest), and wheat, Triticum aestivium (cv. Gamenya), were grown under field conditions in soil fertilized then cultivated to 10 cm depth. Two annual pasture species, subterranean clover, Trifolium subterraneum L. (cv. Daliak), and Wimmera ryegrass, Lolium rigidum Gaud. (cv. Wimmera), were also grown in the field both with and without cultivation. All species were fertilized with seven levels of phosphate broadcast on the soil surface before cultivation. The amount of phosphate which produced 90% of maximum yield depended on species and cultivation practice: wheat required 98 kg phosphorus/ha; L. angustifolius, 65 kg/ha; L. cosentinii, 42 kg/ha; subterranean clover, after cultivation, 49 kg/ha; subterranean clover, not cultivated, 28 kg/ha; Wimmera ryegrass after cultivation, 40 kg/ha; Wimmera ryegrass, not cultivated, 18 kg/ha. All species except wheat required less current phosphate in this experiment than they did 3 years earlier on the same site in virgin soil. Cultivation changed the distribution of soil phosphate, and the roots of the pasture species followed the phosphate distribution.

Changes in Nutritive Value of Siratro Forage with Age1

AbstractNutritive value characteristics are not as well documented for tropical legumes as for temperate legumes and grasses. ‘Siratro’ (Phaseolus atropurpureus D.C.), a tropical legume, was grown under field conditions in soil classified as a udertic haplustoll with adequate moisture, to determine its nutritive value as affected by plant age. Plant samples, harvested at the ground level every 2 weeks, beginning at the 4th week after establishment and continuing to 26 weeks of age, were separated into leaf, petiole, and stem fractions and analyzed for crude protein (CP) and in vitro digestible dry matter (IVDDM). The nutritional value of Siratro was relatively high at all times, averaging 68% IVDDM for whole plants over a 26‐week period. During the first 18 weeks of growth, leaves averaged 75% IVDDM, ranging from 74 to 77%; stems averaged 61%, ranging from 59 to 63%; and petioles averaged 70%, ranging from 67 to 73%. Crude protein averaged 15% for whole plants and was highest during the first 8 weeks of growth. After the 16th week, CP content remained stable at about 13%. Leaves had the highest CP content, averaging 21% with values ranging from 15 to 23%. All three plant portions showed a declining pattern, with time, in percent of both CP and IVDDM, but the change was less than that found in perennial tropical grasses.

Effect of Tillage and Chemical Weed Control Practices on Soil Moisture Losses during the Fallow Period

AbstractMaintaining surface residues with stubble‐mulch tillage or chemical weed control significantly improved moisture conditions in the seed zone and markedly reduced surface crusting. Field and laboratory studies showed the drying rate of the 0‐ to ½‐inch portion of the soil profile was greatly reduced by plant residues on the soil surface. However, under field conditions soil moisture content below 2 inches was not materially increased by surface residues. The value of surface residues to increase moisture storage during the fallow period is discussed.