The effects of osmotic and matric water potential on mycelial growth, production and germination of conidia, and production and maturation of pseudothecia of Pyrenophora triticirepentis (PTR), the cause of tan spot of wheat, were examined on clarified V8 juice agar amended with KCl or polyethylene glycol 8000 (PEG8000). Patterns of the growth responses of three isolates to decreasing osmotic an...

The initial soil water content affects wetting front instability. A series of experiments were conducted where water was infiltrated into a 20/30 sand with initial volumetric water contents of 0, 0.005, 0.01, 0.015, 0.02, 0.03, 0.04 and 0.047 cm/cm. Both water content and matric potential were measured. Water content was measured with Synchrotron X-rays at the Cornell High Energy Synchrotron So...

In slope engineering, soils are commonly at unsaturated state. The question of how to apply unsaturated soil mechanics theory to the slope stability analysis has become a hot spot in today’s geotechnical engineering research. Based on the experimental research of how shear strength of residual soil varies with water content, reasonable computation modules can be created. By using limit equilibr...

To understand the hydraulic properties of soils, accurate prediction of unsaturated hydraulic conductivity is needed which is commonly derived from the soil water release characteristic. In fine-textured soils the modified Mualem-van Genuchten (MMVG) function has been used extensively to predict the change in relative conductivity with changes in matric potential, but this assumes that the soil...

Estimation of soil hydraulic and solute transport parameters is important to provide input parameters for numerical models simulating transient water ̄ow and solute transport in the vadose zone. The Levenberg±Marquardt optimization algorithm in combination with the HYDRUS-1D numerical code was used to inversely estimate unsaturated soil-hydraulic and solute transport parameters from transient m...

where the diagonal elements of DI were denoted by cos qpj + i sin (pi. As is well known, the number of real parameters in R, if (4) is not fulfilled, can be counted as follows: the first column Rji is an n dimensional vector of length 1, giving n1 parameters; the second column Rp is of length 1 and is orthogonal to the first column giving n 2 parameters; the third column of R must be a unit vec...

A soil-water characteristic (SWC) curve describes the amount of water retained in a soil (expressed as mass or volume water content, m or v) under equilibrium at a given matric potential. An SWC is an important hydraulic property, related to size and connectedness of pore spaces, hence strongly affected by soil texture and structure, and by other constituents, including organic matter. Modeling...

The epidemiology of sclerotinia rot of carrot was investigated on carrot ‘Cellobunch’ during 1999 and 2000 in Ontario. Apothecia were first detected in the crop in early August to mid-September, after the carrot canopy closed and after 7–11 days with soil matric potentials between –0.1 and –0.4 bars and soil temperatures between 14 and 23 °C. Ascospores were first detected in mid-July to mid-Au...