ALBERT

Beschreibung: Organic carbon depletion as a result of intensive potato production is a serious concern in northwestern New Brunswick, Canada. Underseeding of rotational grain crops with selected grasses and legumes is being used by farmers to increase crop residues in order to maintain soil organic carbon levels. The objectives of this study were to quantify changes in selected soil propertiesm, effects on grain yield, and increases in total biomass production resulting from different underseeding treatments on a Caribou fine-loamy Brunisolic Gray Luvisol. Clovers, ryegrasses and a mixture of timothy, Alsike and red clover were underseeded in Chapais barley plots. Underseeding did little to improve soil bulk density, macroporosity and saturated hydraulic conductivity of the upper plow layer (4–12 cm depth) over one growing season. Averaged over a 3-yr period, underseeding did not significantly affect barley grain yields; however, annual reductions of up to 17% were experienced with some of the more aggressive companion crops, such as Lemtal Italian ryegrass. Underseeding significantly increased total biomass contributions (residues) to the upper 20 cm of the soil by 40 to 90%, making the year in grain production a potential net organic carbon supplier rather than an organic carbon depletor. Key words: Companion crop, roots, soil organic carbon, soil bulk density, soil permeability, crop residue

Beschreibung: Surface area (SA) is an important property of soils, but different methods can give widely different estimates of SA, and of the contribution of organic matter to SA. This study was undertaken to compare two common methods of measuring SA (EGME [ethylene glycol monoethyl ether] and N2 sorption) with SA estimates using H2O sorption on selected Saskatchewan soils; some soils from Kenya were included to show the impact of clay mineralogy. For the Saskatchewan soils, the three estimates of SA were highly correlated to each other and to clay content, but SA EGME was 2 to 3 times SA H2O and 7 to 52 times SA N2. Organic matter did not appear to contribute to SA EGME, increased SA H2O and decreased SA N2. Clearly the three methods differ in their access to internal and external surface area and this should affect their utility as indices of the sorptive capacity of field soils. Key words: Surface area, EGME, N2 sorption, water sorption

Beschreibung: An estimate of the gypsum requirement (GR) of soils affected by Na salts has practical value. The estimated GR can indicate both the quantity of any Ca amendment needed and the progress of site remediation. Four published methods to estimate GR use analytical results that do not directly include any Na in excess of the soil's cation exchange capacity (CEC). GR values thus obtained, for a 15-cm soil layer, are at most 20 to 50 t ha−1. We used these four methods to calculate the GR for various soils with known, differing salt contents. The values obtained were often inconsistent with the sodium adsorption ratio (SAR) and electrical conductivity (EC), parameters that indicate the severity of site-contamination. We also used an unpublished method to estimate GR from the amount of Ca required to bring each soil's SAR down to a threshold value of 7, on the basis of concentrations of soluble ions in a saturated paste filtrate. Estimates of GR made in this way often exceeded 50 t ha−1, but were consistent with SAR and EC levels at the various sites. This method may be more appropriate for estimating GR after brine spills on soils where Na is not readily leached and the quantity of Na exceeds the CEC. This situation often applies on the Canadian prairies. Estimating GR from the quantity of Ca required to replace exchangeable Na may be appropriate for sodic, free-draining soils in areas with high rainfall, or on irrigated land. Key words: Gypsum requirement, salt contamination, sodium adsorbtion ratio, electrical conductivity, formation water

Beschreibung: There is no information on the effect, in northeastern Saskatchewan, of N and P fertilizers on forage seed production as influenced by these nutrients in the soil. Therefore, experiments were conducted at eight sites from 1988 to 1991 to determine the effect of N and P fertilizers and soil nutrients on seed yields of alfalfa (Medicago media Pers.), smooth bromegrass (Bromus inermis Leyss.), crested wheatgrass (Agropyron cristatum L.), intermediate wheatgrass (Agropyron intermedium [Host.] Beauv.) and timothy (Phleum pratense L.). Nitrogen fertilizer (urea) was applied on grasses annually at 0, 50, 100 and 150 kg N ha−1 in factorial combination with 0, 9 and 18 kg P ha−1 (monoammonium phosphate and triple superphosphate) and on alfalfa at 0 and 50 kg N ha−1 in combination with 0, 9, 18, 26 and 53 kg P ha−1. Nitrogen significantly increased forage seed yields of all species except alfalfa. Phosphorus increased yields of forage seed for all crops except intermediate wheatgrass. The site, N, P and year and their interactions influenced seed yields. Seed yields ranged from a low of 0.29 t ha−1 for smooth bromegrass in 1990, a dry year, to a high of 1.24 t ha−1 in 1989 a cool, moist year. The yield response to N and P fertilizers was affected by available soil N and P. Relative to control, the percentage increase in grass seed yield from applied N and P fertilizers was highly related to the available soil N and P (R2 = 0.93). The estimated smooth bromegrass seed yield response to 50N–9P kg ha−1 was 0.54 t ha−1 when the soil had intermediate amounts of available N and P (2 mg N ha−1 and 8 mg P ha−1, 0- to 60-cm and 0- to 15-cm depths, respectively). On a soil that tested high in available N and P, there was no response to fertilizer. Regression equations were developed that can be used to estimate forage seed yield response of different species in relation to available soil nutrients. These results are useful for estimating the most economical return on fertilizer investment for forage seed production in Saskatchewan. Key words: Forage, seed, N, P, fertilizer, soil tests, correlation

Beschreibung: The in situ use of anion exchange membranes (AEMs) as a soil-testing procedure may provide a more precise evaluation of N availability to forages than standard methods. The main objective of this study was to evaluate the potential of AEMs to predict soil NO3–N availability for forage production in the western part of the province of Quebec, Canada. In 1995 and 1996, AEMs were buried (0–15 cm) in soils at four sites. The fertilizer treatments consisted of five NH4NO3 rates (0, 60, 120, 180, and 240 kg N ha–1). At all sites, NO3−sorbed on the AEMs (NO3AEMs) increased with increasing N fertilizer rates. The NO3AEMs fluxes were significantly related to water soluble NO3–N (NO3w) concentration in soil (R2 varied from 0.35 to 0.98) in the two growing seasons. Forage N uptake was better related with NO3AEMs fluxes (R2 = 0.88 and 0.92 in spring 1996 and 1995, respectively) than with NO3w concentration (R2 = 0.39 and 0.97 in spring 1996 and 1995, respectively). Based on their simplicity, rapidity, and low cost, AEMs have many practical advantages over water NO3–N extraction for assessing grass forage soil N availability in cool continental climates. Key words: Resin, nitrogen, N uptake, grass forage, N mineralization

Beschreibung: The response of soil quality attributes to management practices across a diverse range of farming systems is key to identifying a robust minimum data set (MDS). The objectives of this study were to compare the response and consistency of different soil organic matter (SOM) attributes to changes in soil management practices in eastern Canadian agroecosystems. Soil samples (0–10 cm) were obtained at sites of several replicated experiments throughout eastern Canada, and 16 paired comparisons were selected to determine the effect of conservation (no-tillage, rotations, organic amendments) versus conventional (fall moldboard plowing, continuous cropping, no organic amendments) management practices. A sensitivity index was calculated for each of the attributes by dividing the values for conservation treatments with their conventionally managed counterparts (i.e., Conservation/Conventional). The index showed that light fraction (LF) N (1.58) and macro-organic matter-N (MOM-N) (1.54) were the most sensitive SOM attributes to conservation management practices. Light fraction-C (LF-C), macro-organic matter-C (MOM-C) and microbial biomass-C (MB-C) also showed high sensitivity to conservation management (1.48, 1.34 and 1.44, respectively). The sensitivity index for carbohydrates, whole soil C and total N were 1.23, 1.16 and 1.17, respectively. However, the Friedman two-way analysis of variance test indicated that the sensitivity of the different attributes to conservation management was site specific. For example, although LF-N was highly ranked, it did not respond as frequently as most of the other attributes. A non-parametric sign test showed that whole soil C and N provided the most consistent response to conservation management. The average sensitivity index was highest for the amendment (1.82) followed by the tillage (1.26) and rotational (1.14) conservation management practices, suggesting that organic amendments had the greatest impact on most of the attributes. These results suggest that for eastern Canadian soils, use of MOM-C and MOM-N, MB-C and whole soil C would provide a useful, easy to measure and robust MDS. Key words: Soil quality indicators, response, conservation management

Beschreibung: Aeration is a critical factor of substrate performance for container grown plants. In a 14-mo nursery study, although air-filled porosity dropped below optimum values, the gas relative diffusivity was unaffected, as a result of an increase in pore effectiveness. This indicates that, contrary to the general belief, aeration properties of potting substrates may not deteriorate with time. Key words: Potting soils, container substrates, air-filled porosity, gas diffusivity

Beschreibung: not available

Beschreibung: Field experiments were conducted on sandy loam soils in Prince Edward Island (PEI) with two cultivars of soybeans at two locations to determine the relationship between Se concentration in the seed sown and the Se concentration found in the harvested soybean crop. Seeds containing a range of Se from 0.78 to 38.5 mg kg−1 were used. These variable concentrations of seed Se were obtained in field experiments by varying the rates of seed and foliar applied Se. Grain Se concentration increased with increased Se concentration in the planted seed. A high proportion of the variation in Se concentration in the harvested soybean crop was explained by variation in the Se content of the planted seed (R2 = 0.98). The regression was calculated using averages of cultivars for both locations. From the regression equation it could be predicted that planting seed containing 24 mg Se kg−1 would produce a soybean crop containing 0.5 mg Se kg−1. When used at 200 kg soybean per tonne ration this would provide a Se concentration of 0.1 mg kg−1 assuming negligible contributions from other ingredients. Selenium concentration of 0.1 mg kg−1 in animal ration is considered adequate to protect livestock from Se deficiency diseases. Key words: Podzol soils, seed-applied Se, grain Se

Beschreibung: Conservation tillage practices such as no-till (NT) and conventional tillage (CT) with a heavy-duty cultivator can influence the physical properties of soils. This study was conducted to determine the effect of 24 yr of NT versus CT on the physical properties of a clay loam soil in southern Alberta. Physical properties quantified were bulk density (BD), mean weight diameter (MWD), plant-available water-holding capacity (PAWHC), saturated hydraulic conductivity (Ksat), soil water characteristic [θ(ψ)] and unsaturated hydraulic conductivity [K(ψ)] relationships, and pore-size distribution (PSD). Bulk soil samples and small soil cores (5-cm depth increments to 20 cm) were taken from CT and NT fields in 1992, and tension infiltrometer measurements were made in 1994. The results from this study are reported as general trends for the tillage fields. Statistical probability levels are not reported because of the unreplicated nature of the experiment, the limited number of sampling locations within each tillage field, and to a lesser extent, the different sampling times for CT and NT in 1992. Plant-available water-holding capacity was higher for the CT field (14.3%) than the NT field (10.8%), and a greater amount of water was held at a given water potential (−1500 to −1.5 kPa) for the former, indicating a higher potential for soil water conservation under conventional tillage. Geometric mean Ksat values (small soil cores) were higher for the NT field (18.20 × 10−6 m s−1) than the CT field (1.74 × 10−6 m s−1). The K(ψ) values (small soil cores) between −10 and −2 kPa were higher for the CT field than the NT field at the 0- to 5-cm, 10- to 15-cm and 15- to 20-cm depths, but values were higher for the NT field at the 5- to 10-cm depth. Near-saturated K(ψ) values (−1.5 to −0.3 kPa) of the surface soil, as derived from tension infiltration measurements in 1994, were higher for the CT field (2.43 × 10−7 m s−1) than for the NT field (6.09 × 10−8 m s−1). There was a greater percentage volume of larger pores (30–40, 40–67, 67–200, 〉200 µm) for the NT field than for the CT field, and there was a lower percentage volume of smaller pores (0.2–0.6, 0.6–4 µm) for the CT field than for the NT field. Differences in certain soil physical properties between CT and NT fields may be related to the lag time between the most recent tillage event and sampling for the CT field. Key words: Conservation tillage, heavy-duty cultivator, physical attributes, soil water, hydraulic conductivity, porosity