ALBERT

Notes: Plants of three cultivars of lucerne (Medicago sativa L.) and of red clover (Trifolium pratense L.) were grown at four levels each of water availability and temperature in all combinations to evaluate these factors as determinants of plant growth. Plants grew in conventional plant growth chambers from age 2 to 4 weeks with the roots held between layers of polyester cloths that held a volume of nutrient solution which was adjusted at 24-h intervals by flushing and blotting the cloths. The experimental design consisted of two growth chamber runs at each of four temperatures. Within each run, water treatments and the species-cultivar combination were arranged In four replicates of a split-plot design with water treatment as whole plot and species-cultivars as subplots.Plant response variables over all treatments were significant (P 〈 0·05) for temperature and water for shoot weights, root weights, shoot/root ratios and number of roots. Cultivars within species had no significant difference in response lo the treatments, but species differences were significant for alt response variables except shoot/root ratio.

Notes: Lucerne populations that had previously been divergently selected for acid detergent lignin (ADL) concentrations of whole herbage were additionally divergently selected for in vitro dry-matter disappearance (IVDMD) of basal stems. Parental plants of the four selected populations were intercrossed and the half-sib progeny evaluated in a replicated field trial in 1988 over two harvests. Cell wall composition of basal stems was determined for detergent fibre components and neutral sugars, uronic acids, Klason lignin and esterified and etherified phenolic acids of the total fibre fraction. Lignin polymer composition was measured by nitrobenzene oxidation. Degradability of cell wall polysaccharide components was determined by a 48-h in vitro ruminal fermentation. Cell wall composition was changed by both selection criteria. Klason lignin proportion of the total fibre did not differ as a result of selection, whereas the ADL concentration of neutral detergent fibre was different among selection groups. The cell wall polysaccharides of lucerne basal stems shifted towards more cellulose (glucose residues) and less hemicellulose (xylose residues) with selection for either low ADL or high IVDMD. While degradability of the cell wall polysaccharides was correlated with various measures of lignin composition and concentration, the results were variable and inconclusive. Surprisingly, Kiason lignin and ADL were positively correlated with cell wall polysaccharide degradability, and esterified ferulic acid was negatively correlated with degradation of the cell wall. Selection for herbage ADL and basal stem IVDMD of lucerne did alter cell wall degradation, but the associated changes in cell wall lignification were not consistently correlated with cell wall degradability.

Notes: A parameter estimation procedure which determines the coefficients of soil hydraulic equations (soil-water characteristic and hydraulic conductivity curves) is developed. The parameters are determined by nonlinear least-squares regression of steady-state water potential measured at several points along an unsaturated horizontal soil column to an equation, herein derived, which describes water potential continuously along the column. To estimate parameter values, total mass of water in the soil column at steady-state, saturated water content, and steady-state flow rate must also be measured.The parameter estimation procedure is verified using synthetic data and is applied in the laboratory. The coefficients appearing in the van Genuchten and Campbell soil hydraulic equations are estimated by the procedure. Alternative methodologies are proposed to augment this procedure and to provide user flexibility. The coefficients in the difficult-to- measure wet range can be determined from measurements taken at steady-state without independently measuring water retention.

Notes: Two nuclear methods were used to quantify hydrogeologic parameters in the unsaturated zone of a reclaimed and revegetated coal strip mine in Clarion, Pennsylvania. Am-Be (neutron) and Cs-137 (gamma-gamma) geophysical logging tools were used to quantify volumetric moisture content, bulk density, total porosity, and unsaturated hydraulic conductivity. An additional study at the same site used postsampling neutron activation analysis to determine concentrations of a bromide tracer in unsaturated zone water samples. Those additional data were used to independently calculate unsaturated hydraulic conductivity.Geophysical logging of six boreholes at the site was conducted on seven different dates. Temporal variations in volumetric moisture content versus depth were observed to be short-lived, with the general shape of the volumetric moisture content profiles remaining spatially stable over the eight month period of investigation. Bulk density values ranged from less than 1.14 to 1.86 g/cm3, corresponding to total porosities of greater than 57% to 30.1%. Large void spaces were encountered during past and present drilling and observed at a measurement point. Unsaturated hydraulic conductivities were calculated using draining profile volumetric moisture content data as input to an explicit numerical solution of the unsaturated flow equation. Calculated values ranged from 2.4 × 10−7 to 1.5 × 10 −3 cm/s. Examination of all of the geophysical log data together showed sharp increases in volumetric moisture content spatially coincident with zones where bulk density increases (and porosity decreases). The bulk density contrast appears to be of more influence than the magnitude of the material property. Increased unsaturated hydraulic conductivity associated with increased volumetric moisture content was seen in several boreholes.Bromide tracer-labeled waters were collected from pressure-suction lysimeters installed at depths of up to 18.1 m for a period of 16 months. Unsaturated hydraulic conductivities, calculated by interpreting concentration peaks as average arrival times of steadily infiltrating water through a uniformly porous media, ranged from 2.8 × 10−6 to 7.2 × 10−5 cm/s. However, a dual-permeability mechanism is suggested by the observed behavior of the tracer. Analysis of the data suggests that fluid flow in this hydrogeologic setting is dominantly transient. Ground-water recharge occurs in short-lived pulses. The periodicity of acid mine drainage formation and flushing to the water table is expected to correspond to infiltration and recharge events.