ALBERT

Description: Our previous work has demonstrated a relationship between polarity index and organic carbon referenced partition coefficients (Koc) of organic chemicals. Here we compare sorption of benzene, toluene, or o-xylene by protein with non-protein organic sorbents. Koc for benzene, toluene, or o-xylene sorption by collagen was much higher than by lignins, humic acid, chitin, or cellulose. Sorption of benzene, toluene, or o-xylene was not only influenced by organic sorbent polarity and functionality (e.g., aromaticity), but also by additional properties which we inferred related to physical conformation of the organic sorbents. In this respect, collagen exhibits unique sorptive behavior toward removal of nonpolar organic chemicals in the aqueous phase, which was not shared by humic acids of similar C, O or N content. Key words: Sorption, collagen, lignin, polarity, hydrophobic domains

Description: A study was carried out to quantify the diurnal variation of soil respiration in fallow and barley fields and to assess the impact of atmospheric CO2 concentration (C) and crop photosynthesis on soil respiration rates under field conditions. Soil respiration rate was measured twice a day (06:00 and 13:00 h EST) for 69 consecutive days at Ottawa, Ontario, Canada, during the 1990 growing season. Measurements were taken on fallow and under a barley (Hordeum vulgare L. ’Léger’) crop using a dynamic closed chamber system. Crop net photosynthesis was obtained by substracting soil respiration from the vertical CO2 fluxes above the crop which was obtained using the eddy correlation technique. Afternoon soil respiration averaged 22 and 17% more than that in the morning on fallow and barley soils, respectively. No correlation was found between atmospheric CO2 concentration and morning respiration rates. The two daily respiration measurements on fallow soil could be fit to the same function of soil temperature despite important differences in C at the time of measurement. These results indicate that soil temperature might account for the differences in R between morning and afternoon, and that the effect of C need not be considered for the modelling of the soil respiration diurnal cycle. Respiration in soil under barley was 25% lower than in fallow soil. Soil under barley was estimated to have at least 199 g C m−2 more than fallow soil at the time of harvest due to the lower soil respiration and to the input of carbon by barley root residues. High correlations were obtained between crop photosynthesis and soil respiration rates during vegetative and reproductive periods, confirming that the biotic plant component is an important factor controlling soil respiration rates in cropped fields. Key words: Root respiration, chamber measurements, CO2 flux, crop net photosynthesis, greenhouse gas, soil organic matter.

Description: An in-situ constant head well permeameter (CHWP) method employing three or more ponded heads per well was used to establish relationships between field-saturated hydraulic conductivity (Kfs), matric flux potential [Formula: see text], the alpha parameter (α*), soil texture, and soil structure. The relationships were then used to evaluate a single-head CHWP technique which employs representative mean α* values in the determination of Kfs and [Formula: see text]. The measurements were made at several depths on four soils which ranged in texture from loamy sand to silty clay, and in structure from single grain to strong, fine subangular blocky. The Kfs and [Formula: see text] results obtained from the multiple-head CHWP measurements were found to be highly variable within and between soils, yielding within-soil ranges as high as 3.5 orders of magnitude and standard deviation factors (SDF) as high as 5.1. The geometric mean (GM) Kfs and [Formula: see text] values were also highly variable between soils, but they were controlled primarily by soil structure rather than by soil texture or other factors. The α* values, on the other hand, were relatively consistent both within and between soils, yielding an overall SDF of only 1.2 and an overall GM of 11 m−1. Use of α* = 11 m−1 in the single-head CHWP technique yielded Kfs and [Formula: see text] values which were usually accurate to within a factor of 2, and often accurate to within ±25%. These levels of accuracy are within acceptable limits for a field method, considering the many potential sources of error and the extreme range and variability of Kfs and [Formula: see text] normally encountered in the field. Key words: Constant head well permeameter, hydraulic conductivity, matric flux potential, alpha parameter, soil texture, soil structure, single-head analysis

Description: Soil water storage (0–1.7 m) was measured every 10 m in a 660-m-long transect using a neutron probe and compared to bulk electrical conductivity, ECA, measurements obtained using noncontacting electomagnetic induction meters. Coherency analysis indicated a lack of correlation at scales less than 40 m. At scales greater than 40 m, ECA explained more than 80% of the variation of soil water storage. Measurement of ECA should be a simple and fast method of determining general field patterns of soil water storage. Key words: Spatial variability, soil water, coherency, electromagnetic induction

Description: The persistence of 14C-fenoxaprop acid, the major degradation product of the herbicide 14C-fenoxaprop-ethyl, was studied at different controlled temperature and moisture conditions in three Saskatchewan soils. At 85% of field capacity, degradation approximated to first-order kinetics at soil temperatures of 10, 20, and 30 °C, with half-life values ranging from 42 to 5 d. In a clay at 20 °C, there was no effect of moisture, between 50% and 100% field capacity, on the rate of 14C-fenoxaprop acid breakdown. There was no loss of radioactivity after 65-d in air dry soils. In all soils incubated at 85% field capacity and 20 °C with 14C-fenoxaprop-ethyl, uniformly labeled in the chlorophenyl ring, there was evolution of 14CO2 indicating ring fission. Over a 56-d incubation period, 10–15% of the applied radioactivity was released from the treated soils as 14CO2. Extraction with ammoniated acetonitrile recovered 14–19% of the original radioactivity; between 3 and 5% of the initial 14C was incorporated into soil microbial biomass; and 17–25% into the fulvic acid, 7–12% into the humic acid, and 30–34% into the humin soil fractions. Key words: Herbicide, biomass, fenoxaprop-ethyl, fenoxaprop, persistence

Description: This study was conducted to evaluate the impact of tillage and fertilization practices on soil organic carbon (organic-C) and the distribution of phosphorus between inorganic (Pi) and organic (Po) pools in a clay and sandy loam soil under a continuous corn (Zea mays L.) production system. Tillage treatments were established in the fall of 1981. The soils for this study were sampled (0- to 10-cm and 10- to 20-cm) in June 1988. Treatments consisted of three types of tillage: (i) conventional (CT): fall moldboard ploughing with two spring diskings; (ii) reduced (RT): with either fall chisel ploughing (1981–1986) or no fall tillage (1987) followed by one spring disking, and (iii) no-till (NT); and two types of fertilization (i) inorganic (I): 170 kg N ha−1. 80 kg P2O5, ha−1, 75 kg K2O ha−1, and (ii) organic fertilizer (O): dairy manure applied to give 170 kg N ha−1 plus 80 kg P2O5, ha−1 from inorganic P fertilizer. Even though a lime application was made in the fall of 1985, soil pH was significantly lower in the I fertilizer treatments. Reduction of tillage intensity resulted in a lower pH in the surface layer of the sandy loam soil. Tillage did not affect soil organic-C, or total soil Po (soil-Po) in either soil. Compared with the I fertilizer treatment, the O fertilizer treatment resulted in increased levels of soil organic-C and soil-Po only in the sandy loam soil. Labile levels of Po in the soil were not affected by treatments. Increased soil-Po levels possibly resulted from an increase in stable Po complexes. Moderately labile Po levels were not affected by treatments in the clay soil. In the sandy loam soil, O fertilization decreased moderately labile Po levels in the surface layer of the NT treatment, and increased this P fraction in the 10- to 20-cm soil layer of the RT and CT treatments. In the surface layer of both soils, labile levels of Pi were greater for the O fertilization treatment (approximately 40 and 47% higher for the clay and sandy loam, respectively), and were lower under CT. Increased labile Pi levels were associated with the O fertilizer treatment in the 10- to 20-cm depth increment in the sandy loam soil only, suggesting a greater downward movement of P with manure applications. Key words: Conventional tillage, zero-tilled, no-till, reduced tillage, manure, P fractionation

Description: Concern has been expressed that reduced tillage systems may lead to excess soil compaction, negatively impacting on crop growth. The objectives of this study were to determine the effects of tillage systems zero (ZT), minimum (MT) and conventional tillage (CT) and crop rotations on soil bulk density and penetration resistance after 4 yr on an Indian Head heavy clay soil, in southeastern Saskatchewan. Moisture content was similar among tillage systems, except for slight differences in the lower soil depths with crop rotation. Penetration resistance and bulk density of a heavy clay soil were increased in the surface 10 cm of the soil by ZT as compared to CT management. However, in the deeper soil zones, tillage system did not consistently influence either bulk density or penetration resistance. Inclusion of peas in the crop rotation had a moderating effect on bulk density and penetration resistance, while inclusion of flax in a continuous rotation increased bulk density and penetration resistance in the surface soil profile. At the 30- to 45-cm depth, ZT had a lower bulk density than CT or MT in the rotation which included fallow, possibly because the tillage operations associated with the cultivated fallow led to compaction in the deeper soil zone. Penetration resistance was great enough in the deeper soil zone in all tillage systems to restrict rooting, but difference due to tillage treatment or cropping rotation was not sufficient to markedly influence crop production. Key words: Penetration resistance, bulk density, crop rotation, tillage

Description: Soil contamination is no longer restricted to isolated incidents and locations; it is a general and contentious problem. However, the problem is complex, starting with the very definition of what level and type of contamination is unacceptable. A myriad of regulatory and de facto guidelines have emerged, and they are extremely fragmented, inconsistent and incomplete. This review attempts to summarize the historical development of assessment and remediation guidelines, to highlight the unique difficulties of the problem, and then to discuss the scientific information that exists and that is needed to improve guidelines. There is an unlimited scope for research on this subject. Key words: Contaminant, cleanup, toxicity, pathways, risk, hazard assessment

Description: Twenty-five soil media representing 13 subsoils and organic overlays, and their mixtures, that had been used in pot culture fallow, or for growing root, leafy vegetable and grass crops, were studied to determine if the benefits of organic amendments to crop yields in optimally watered and fertilized soils were due to improvements in soil physical conditions. The soils were subjected to particle and aggregate size fractionation; and the stability of the aggregates was determined. The results suggested that admixing of residual organic overlays improved the structure of all mineral subsoils, except perhaps an alluvial sand. Aggregation and stability of aggregates 〉 2 mm were improved, thus leading to improved aeration, root proliferation and to increases in crop yields. In addition, grass crops were shown to be more effective than root and leafy crops for improvement of the structure of the various soils. Key words: Organic soils, soil aggregation, soil structure stability

Description: Soil water limits plant growth in the Canadian Prairie Provinces. Efficient use of soil water is, therefore, paramount in crop production. Two 2-yr field studies were conducted (i) to determine the effects of crop selection and cropping practice on the temporal and spatial distribution of soil water and (ii) to quantify water use and water-use efficiencies (WUE) of alternative crop/cropping systems for a subhumid region of Alberta. The first study was at the Ellerslie Research Station on an Orthic Black Chernozemic and the second at the University of Alberta Breton Plots on an Orthic Gray Luvisol. At each site three annual crops/cropping systems [barley (Hordeum vulgare L.), barley intercropped with field pea (Pisum sativum L.), and faba bean (Vicia faba L.)] and a perennial forage [creeping red fescue (Festuca rubra)] were grown in 1987 and in 1988. At Ellerslie, tillage methods to grow annual crops were conventional and zero tillage. At Breton, the two tillage methods used were: (i) conventional and (ii) deep tillage (to enrich the surface horizon with clay from the subsoil). The experimental design used was a split plot with four replications. Soil water was measured by neutron attenuation. Evapotranspiration was calculated as the change in soil water to 0.80-m depth plus precipitation. Soil water changes were more closely associated with the kind of crop grown than with the method of tillage used. The barley/field pea intercrop exhibited a pattern of water use similar to barley. Greater water-use efficiency measured in the intercrop system was attributed to differences in canopy structure and plant biomass production. Faba bean and red fescue had lower WUE than barley and the intercrop. The water requirement by faba bean was close to that of red fescue and related to leaf area development. Small tillage effects on soil water were observed during 1988. Soil water under zero tillage was greater than under conventional tillage. Faba bean and red fescue are likely to succeed more in agro-ecological regions such as Breton. Further studies are required to improve our understanding of the effects of these cropping systems on water resources when they are used in rotational-production systems. Key words: Barley, field pea, faba bean, creeping red fescue, conventiional tillage, zero tillage, deep tillage, water-use efficiency