Range Of Soil Textures Research Articles

EFFECTS OF IRRIGATION CUT-OFF ON PROCESSING TOMATO FRUIT QUALITY

Water management was monitored in 10 commercial processing tomato fields during the 2001 season to evaluate strategies for improving fruit quality. Fields were selected to represent a range of soil types, irrigation systems (drip, furrow, and sprinkler), and water table depths in Sutter County, CA. Soil textures of fields ranged from clay to sandy clay loam and early season water table depths ranged from 70 cm to > 150 cm below the soil surface. Irrigation trials were conducted to evaluate the effects of early irrigation cut-off on fruit quality at each field site. All trials included a grower (normal cut-off) and an early cut-off treatment. Trials that were located in drip-irrigated fields included deficit (cutback) irrigation treatments. Soil moisture was monitored to a 110-cm depth using a neutron probe at each field site. Fruit yield and quality were evaluated from hand-harvested and machine harvested plots. Early irrigation cut-off was found to increase soluble solids of fruits when treatments were sufficiently severe to reduce soil moisture in the upper 70 cm of the soil profile during fruit ripening. Fruit weight was reduced in the early cut-off treatments at field sites where fruit had increased brix levels. Results were consistent in crops grown under sprinkler, furrow, and drip irrigation and a range of soil textures.

Refined PCR protocol for detection of plant pathogens in soil

A polymerase chain reaction method to detect soil-borne plant pathogens such as Pythium ultimum, Plasmodiophora brassicae, and Verticillium dahliae in soil was developed and used with a range of soil textures. DNA extraction was based on lyses with alkali buffer (pH 9.0) containing sodium dodecyl sulfate, extraction with benzyl chloride, and collection by ethanol precipitation. Four modified protocols – purification of extracted DNA from soil, independent addition of glass beads or skim milk to the extraction buffer, and addition of bovine serum albumin (BSA) to the PCR reaction mixture – were evaluated to enhance the sensitivity of detection. The effectiveness varied for three tested pathogens, but none of the four protocols negatively affected PCR detection. DNA purification was essential for detecting the three tested pathogens. Physical disruption with glass beads and the addition of BSA to the PCR reaction mixture were necessary for detecting V. dahliae, and the addition of skim milk was needed for Pl. brassicae. Additions of BSA and skim milk enhanced the detection of P. ultimum. The developed protocol seems applicable to the range of soil textures that are naturally inhabited by these three pathogens. By integrating multiple protocols to enhance sensitivity, PCR can be used to detect various soil microorganisms.

Prediction of hydraulic conductivity for some Australian soils

Pedotransfer functions and their use in simulation modelling have attracted much attention during recent years. In the absence of measured hydraulic conductivity data, prediction from other soil properties would be most useful. A functional form relating near-saturated hydraulic conductivity to the soil water retention curve based on the Kozeny–Carman equation was investigated on Australian soils. For a dataset comprising a range of soil textures and structural conditions (107 samples with bulk density >1.2 Mg/m3) a power-law relationship between near-saturated hydraulic conductivity, effective porosity, and pore size distribution index was obtained. The function was tested on 2 different datasets for independent evaluation. The results showed poor predictions for most soils in this study. While the reasons for poor predictions might be the difference in the measurement techniques or potentials, it is thought that the proposed function mostly fails predictions on soils with high organic matter and management practices affecting macropores and soil structure (e.g. crust). The proposed function did not show much improvement over the more general form of the Kozeny–Carman equation with empirical coefficients. In the absence of other data, the modified Kozeny–Carman equation (with or without water retention parameters) can be used, with caution, on similar soils and larger scale applications. More data are needed to test the reliabilty of these functions for use in specific locations.

Toward Improved Identifiability of Soil Hydraulic Parameters

We present a thorough identifiability analysis of the soil hydraulic parameters in the parametric models of Brooks and Corey (BC; Brooks and Corey, 1964), Mualem–van Genuchten (VG; van Genuchten, 1980), and Kosugi (KC; Kosugi, 1996, 1999) using the recently developed Shuffled Complex Evolution Metropolis (SCEM-UA) algorithm (Vrugt et al., 2002b, and unpublished data). Because the SCEM-UA algorithm globally thoroughly exploits the parameter space and therefore explicitly accounts for parameter interdependence and nonlinearity of the employed parametric models, the algorithm is suited to generate a useful description of parameter uncertainty and its antithesis, parameter identifiability. A set of measured water retention characteristics of the UNSODA database (Leij et al., 1996) spanning a wide range of soil textures and three transient laboratory outflow experiments with decreasing flow rates were used to illustrate that a parameter identifiability analysis facilitates the selection of an adequate parametric model structure and provides useful information about the limitations of a model. Moreover, results suggest that one should be especially careful in establishing pedotransfer functions without knowledge of the underlying posterior uncertainty associated with the soil hydraulic parameters using direct estimation methods.

Soil compaction effects on water status of ponderosa pine assessed through 13C/12C composition.

Soil compaction is a side effect of forest reestablishment practices resulting from use of heavy equipment and site preparation. Soil compaction often alters soil properties resulting in changes in plant-available water. The use of pressure chamber methods to assess plant water stress has two drawbacks: (1) the measurements are not integrative; and (2) the method is difficult to apply extensively to establish seasonal soil water status. We evaluated leaf carbon isotopic composition (delta13C) as a means of assessing effects of soil compaction on water status and growth of young ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws) stands across a range of soil textures. Leaf delta13C in cellulose and whole foliar tissue were highly correlated. Leaf delta13C in both whole tissue and cellulose (holocellulose) was up to 1.0 per thousand lower in trees growing in non-compacted (NC) loam or clay soils than in compacted (SC) loam or clay soils. Soil compaction had the opposite effect on leaf delta13C in trees growing on sandy loam soil, indicating that compaction increased water availability in this soil type. Tree growth response to compaction also varied with soil texture, with no effect, a negative effect and a positive effect as a result of compaction of loam, clay and sandy loam soils, respectively. There was a significant correlation between 13C signature and tree growth along the range of soil textures. Leaf delta13C trends were correlated with midday stem water potentials. We conclude that leaf delta13C can be used to measure retrospective water status and to assess the impact of site preparation on tree growth. The advantage of the leaf delta13C approach is that it provides an integrative assessment of past water status in different aged leaves.

Generalized model for NOx and N2O emissions from soils

We describe a submodel to simulate NOx and N2O emissions from soils and present comparisons of simulated NOx and N2O fluxes from the DAYCENT ecosystem model with observations from different soils. The N gas flux submodel assumes that nitrification and denitrification both contribute to N2O and NOx emissions but that NOx emissions are due mainly to nitrification. N2O emissions from nitrification are calculated as a function of modeled soil NH4+ concentration, water‐filled pore space (WFPS), temperature, pH, and texture. N2O emissions from denitrification are a function of soil NO3− concentration, WFPS, heterotrophic respiration, and texture. NOx emissions are calculated by multiplying total N2O emissions by a NOx:N2O equation which is calculated as a function of soil parameters (bulk density, field capacity, and WFPS) that influence gas diffusivity. The NOx submodel also simulates NOx emission pulses initiated by rain events onto dry soils. The DAYCENT model was tested by comparing observed and simulated parameters in grassland soils across a range of soil textures and fertility levels. Simulated values of soil temperature, WFPS (during the non‐winter months), and NOx gas flux agreed reasonably well with measured values (r2 = 0.79, 0.64, and 0.43, respectively). Winter season WFPS was poorly simulated (r2 = 0.27). Although the correlation between simulated and observed N2O flux was poor on a daily basis (r2 = 0.02), DAYCENT was able to reproduce soil textural and treatment differences and the observed seasonal patterns of gas flux emissions with r2 values of 0.26 and 0.27, for monthly and NOr flux rates, respectively.

Soil type affects accuracy of dielectric moisture sensors

Several types of dielectric soil moisture sensors were evaluated at various locations in California. The TRASE and ThetaProbe devices were reasonably accurate over a range of soil textures. In silt loam and silty clay soil types, the Enviroscan readings were inaccurate. The Aquaterr meter, which provides a qualitative measurement of soil moisture content, responded to changes in soil moisture content for several different soils, but little response occurred in one sandy soil.

Estimation of annual nitrous oxide emissions from a transitional grassland-forest region in Saskatchewan, Canada

The increasing atmospheric N2O concentration and the imbalance in its global budget have triggered the interest in quantifying N2O fluxes from various ecosystems. This study was conducted to estimate the annual N2O emissions from a transitional grassland-forest region in Saskatchewan, Canada. The study region was stratified according to soil texture and land use types, and we selected seven landscapes (sites) to cover the range of soil texture and land use characteristics in the region. The study sites were, in turn, stratified into distinguishable spatial sampling units (i.e., footslope and shoulder complexes), which reflected the differences in soils and soil moisture regimes within a landscape. N2O emission was measured using a sealed chamber method. Our results showed that water-filled pore space (WFPS) was the variable most correlated to N2O fluxes. With this finding, we estimated the total N2O emissions by using regression equations that relate WFPS to N2O emission, and linking these regression equations with a soil moisture model for predicting WFPS. The average annual fluxes from fertilized cropland, pasture/hay land, and forest areas were 2.00, 0.04, and 0.02 kg N2O-N ha-1 yr-1, respectively. The average annual fluxes for the medium- to fine-textured and sandy-textured areas were 1.40 and 0.04 kg N2O-N ha-1 yr-1, respectively. The weighted-average annual flux for the study region is 0.95 kg N2O-N ha-1 yr-1. The fertilized cropped areas covered only 47% of the regional area but contributed about 98% of the regional flux. We found that in the clay loam, cropped site, 2% and 3% of the applied fertilizer were emitted as N2O on the shoulders and footslopes, respectively.

White Pine Chlorosis in Northern Illinois: Iron Deficiency or Not?

Eastern white pine (Pinus strobus L.) is a prized ornamental. Its natural habitat includes a wide range of soil texture and moisture conditions, leading to the assumption by many that this species can be planted almost anywhere. Its performance in human-altered landscapes demonstrates otherwise. One malady, symptomized by chlorotic foliage, has been dubbed "white pine decline," and because alkaline soil is often associated with this condition, iron deficiency has been postulated. Our studies, conducted over a wide range of soil textures throughout northern Illinois, confirm the negative role of soil alkalinity but lead us to reject the hypothesis of iron deficiency. On the contrary, our data suggest iron efficiency by this species.

A quick test procedure for soil nitrate‐nitrogen

Abstract A procedure for extraction and measurement of nitrate‐nitrogen (NO3‐N) in soil is described. Extracting solution [0.025M Al2(SO4)3] and field‐moist soil are measured volumetrically, with NO3‐N concentration measured by nitrate‐sensitive colorometric test strips or nitrate‐selective electrode. Across a range of soil texture, moisture content, and NO3‐N concentration, the procedure was well correlated with conventional laboratory analysis of 2N KC1 soil extracts (r2 = 0.94). This quick test procedure is proposed as an on‐farm monitoring technique to improve N management.

Development of a competition index for young conifer plantations established on boreal mixedwood sites

A competition index was developed, and then used to examine the relationships between perennial competition and plantation performance. Species included were white spruce, black spruce, and jack pine for both over-wintered containers and bare root stock. A total of fifteen four-year-old plantations were used in this study representing a range of soil textures located on boreal mixedwood sites in northern Ontario.Effective canopy cover, derived from vertical hemispherical photographs taken at the base of seedling leaders, provided an accurate estimate of the perennial woody competition affecting seedling diameter growth. Initial seedling size, defined by the stem volume at time of planting, proved to be an important covariate in the analysis.Using the relationship between effective canopy cover and seedling root collar diameter, the following questions regarding vegetation control decision-making were addressed: 1) jack pine was more sensitive to increased levels of competition, 2) over-wintered container stock were more sensitive than their larger bare root counterparts, 3) minimal differences occurred in the pattern of growth response to competition across the range of soil textures studied, and 4) early tending treatments should be concentrated on jack pine plantations or on spruce plantations with an effective canopy cover in excess of 60. Key Words: competition index, hemispherical photographs, boreal plantations, white spruce, black spruce, jack pine, tending guidelines.

Extraction Time Requirements for Determination of Exchangeable Bases with a Mechanical Vacuum Extractor

AbstractDetermination of extractable bases with neutral 1 M NH4OAc is a commonly performed soil analysis. Introduction of a mechanically controlled vacuum extractor permits control of extraction time across the range of soil textures. Comparisons of organic soil materials, montmorillonitic and low cation exchange capacity (CEC) soils revealed that complete base extraction is possible with reduced extraction times. Fourteen‐hour extraction is required for base removal from organic soils, but 8‐ and 4‐h extractions removed bases from montmorillonitic and low CEC soils, respectively. Decreased extraction times permit increased capacity for laboratory soil analyses, increase the effective life of the vacuum extractor, and decrease analysis time.

COMPARAISON DE DIFFERENTES METHODES D’EXTRACTION DU P ASSIMILABLE EN RELATION AVEC LES PROPRIETES CHIMIQUES ET PHYSIQUES DES SOLS DU QUEBEC

The objective of this study was to compare different available-P extracting methods on 83 Québec soils. The alkaline Olsen’s method and five acid chemical extractants (Bray-1, Bray-2, new Mehlich, North Carolina double acid DA-4 and DA-10) were compared with each other and with two anion-exchange resin methods. The ratio of P-HCl/P-DAF of Mehlich was used to identify the group of soils with predominant P-Ca forms [Formula: see text]. Within this soil group, the Bray-2, DA-4 and DA-10 methods extracted more P and they were less correlated with all the other methods (r = 0.01 to 0.48*). The Bray-1 and Mehlich methods showed good relationships with Olsen, F−- and HCO3−-form resin methods (r = 0.80** to 0.89**) for this soil group, with the exception that Bray-1 solution was more affected by the presence of free carbonates. In the soil group containing more than 0.6% oxalate-Al, the Bray-1, Bray-2 and DA-10 methods extracted more P than the Mehlich, DA-4 or Olsen methods. The F−-form exchange resin extracted more P than that in the HCO3− form. The depressing effect of free iron oxides on the DA-4 method was also observed with the soil group containing more than 0.6% oxalate-Fe. The contents of DA-4-P were less correlated with those of other methods (r = 0.74** to 0.88**) in this soil group. On the other hand, the Olsen, F− and HCO3− resins extracted more of the P-Fe forms from these soils. The DA-4 method was further influenced by the soil organic matter (OM) contents. The relationships between P-Olsen, P-HCO3−-resin with the other chemical methods were also improved by taking into account the contribution of OM contents. Soil texture influenced mostly Bray-2, Bray-1, DA-4 and DA-10 extractable P. The Mehlich, Olsen and F−-resin extractable P was less affected by clay contents while the HCO3−-resin was the most consistant over a wide range of soil textures. Key words: Available-P, anion-exchange resins, new Mehlich extractant, P-forms, soil testing

Simplified filter paper method for determining the 15-atmosphere percentage of soils

A simplified filter paper method of determining the 15-atmosphere percentage in soils has been tested over a range of soil textures from sands to heavy clays. The regression of filter paper determinations against pressure membrane determinations of the 15-atmosphere percentage for the 34 soils gave the equation- y = 1.03x + 3.0 (r = 0.99 and P<0.001) where y = 15-atmosphere percentage (filter paper) x = 15-atmosphere percentage (pressure membrane). The results given by this simplified method indicate that it should be acceptable to agronomists and ecologists for field studies where facilities are limited.