ALBERT

Description: Identification of nutritional disorders in crops growing on saline soils may facilitate the development of breeding or agronomic practices that improve yields in saline areas. An investigation was conducted under controlled environment conditions to identify possible cation deficiencies in barley (Hordeum vulgare 'Gait') grown under sulfate-dominated salinity stress. Soil was artificially salinized to produce a factorial of five salinity levels (ranging from approximately 6.5 to 17.5 dS m−1) and five salt types containing various ratios of Na:Mg:Ca. A control treatment (3.1 dS m−1) was also included. Barley was grown for 75 d and harvested for analysis of dry matter yield and tissue composition. Yield response of barley to salinity stress was not differentially affected by the type of salt used in salinization. Concentrations of sodium and magnesium in the plant tissue were generally increased by salinity stress, but these accumulations did not restrict yield since no consistent relationship was found between the concentrations of these cations and barley yield. Potassium concentration in the plants was inversely related to level of soil salinity, apparently because of an antagonistic effect of sodium, but was not consistently related to barley dry matter yield. Calcium uptake was also suppressed by soil salinity. In contrast to the results observed for other cations, a very strong relationship indicative of a yield response curve was observed between yield and calcium concentration in the plant tissue, particularly when the latter was expressed as a ratio of total cation concentration (R2 = 0.94). Furthermore, calcium concentration in the plant tissue and estimated calcium activity in the soil solution in highly salinized treatments were well below those considered adequate. These results suggest that calcium deficiency may have played an important role in restricting yield under salinity stress. The apparent calcium deficiency induced by salinity stress was attributed to reduced activity of calcium in the soil solution because of precipitation with sulfate and high ionic strength. Key words: Calcium, magnesium, potassium, sodium, salinity

Description: Sulfur deficiency has become a widespread limitation to crop production in western Canada. A variety of S sources are commercially available to alleviate these deficiencies but not all are equally effective. Three elemental S products (a finely-divided suspension and two elemental S + bentonite) and ammonium sulfate were compared over a 3-yr period in central Alberta. These products were applied to barley and canola at various rates (0–120 kg S ha−1) in a factorial arrangement with various supplemental rates of sulfate-S (0–40 kg ha−1) in two experiments Fertilizers affording effective and reliable alleviation of S deficiency in the year of application included sulfate forms and finely-divided elemental S products that can be readily mixed into the soil. The residual benefits of the various fertilizer products examined appeared to be comparable despite large differences in short-term availability. The absence of appreciable residual advantage of slow-release elemental S products was attributed to the short duration of S assimilation by canola and barley and the susceptibility to leaching of S oxidized after that period. Key words: Barley, canola, residual, rotation, S fertilizer, uptake, yield

Description: In pursuit of identifying sustainable agricultural production practices, there is an urgent need to develop or identify parameters that effectively describe and differentiate changes in the quality and quantity of soil organic matter resulting from crop management or cultural practices. The effectiveness of the potentially mineralizable nitrogen (No) concept for this purpose was examined using data from a 30-yr crop rotation study, carried out on a Rego thin Black Chernozem at Indian Head, Saskatchewan. Although Kjeldahl N and hydrolyzable soil amino-N are effective for demonstrating the beneficial influence of fertilizers, legumes and continuous cropping on total soil organic N content, they are less effective in identifying changes in organic matter quality. We have shown that a parameter which we called the "initial potential rate of N mineralization" [potentially mineralizable N (No) × rate constant (k) at time = 0] was effective in distinguishing both the absolute and qualitative changes in soil organic N due to various cultural and management practices. The results showed that fertilizers can be as effective as legumes, used either for green manure or for hay, in increasing the quantity and improving the quality of soil organic matter. A 6-yr rotation including 1 yr of fallow, 2 yr of spring wheat (Triticum aestivum L.) and 3 yr of bromegrass (Bromus inermis Leyss) and alfalfa (Medicago sativa L.) hay had a greater quantity and improved quality of soil organic N relative to that of unfertilized continuous wheat (Cont W), but they were equivalent to that of fertilized Cont W. Key words: Soil quality, potential mineralizable N, crop rotations, legumes, fertilizer effects

Description: There are several reasons why the measurement of ammonia emissions is important in agriculture. The emission of ammonia from stored and land-applied manure to the atmosphere can result in a significant loss of nitrogen for crop production. It is necessary to quantify this loss to evaluate manure handling practices for maintaining the nutritive value of the manure. Minimizing the emissions of ammonia from manure also reduces agriculture's impact on the environment. A high atmospheric concentration of ammonia can result in acidification of land and water surfaces, cause plant damage and reduce plant biodiversity in natural systems. Ammonia emissions from manure coincide with odors, which are a nuisance in areas of intensive livestock operations. Reducing ammonia emissions by altering manure management will also reduce odor problems. The purpose of this paper is to review agricultural sources of ammonia and describe techniques used in determining the loss of ammonia from manure-amended soils. Micrometeorological techniques are used to estimate field scale emissions whereas, for small plots where treatment (effects) is used, chambers and mass balance techniques are more suitable methods. A simple method is described, which, when combined with a denuder sampler mounted on a wind vane, permits flexibility in experimental design and requires fewer ammonia samples than the traditional mass balance approach. A chamber method making use of diffusion samplers that can measure the ammonia concentration in the air at the soil surface is also described. Key words: Ammonia, nitrogen loss, agriculture, manure, micrometeorology, chamber

Description: The reclamation success of abandoned wellsites in agricultural areas depends on their capacity to sustain levels of biomass production similar to those which existed prior to soil disturbance. We examined the effect of four (0, 50, 100 and 150%) topsoil replacement depths (TRD) and five amendment treatments [compost, manure, alfalfa (Medicago sativa L.) hay, wheat (Triticum aestivum L.) straw, check) in the reclamation of three wellsites in south-central Alberta. The largest incremental effect of TRD on spring wheat response in the 4 yr (1997-2000) study occurred between the 0 and 50% treatments. Increasing TRD from 100 to 150% had little impact on crop response. Of the 20 treatments (four TRD × five amendments), the reclamation capacity of the 100% TRD-compost treatment ranked highest, being 19% higher than the baseline treatment (100% TRD-check). The lowest-ranking treatment overall , was the 0% TRD-straw treatment, which yielded 64% of the baseline treatment. Crop yield responses to organic amendments were larger when the recipient soil was lower in organic matter. Positive responses to one-time applications of organic amendments in the short-term (4 yr), advocate their use in soil reclamation of abandoned wellsites, despite a lingering question about the longevity of their beneficial effects. Key words: Soil reclamation, topsoil, organic amendments, natural gas wellsite

Description: Modelling soil organic carbon (SOC) stock changes in agroecosystems can be performed with different approaches depending on objectives and available data. Our objective in this paper is to describe a scheme for developing a dynamic SOC algorithm for calculating net greenhouse gas emissions from Canadian farms as a function of management and local conditions. Our approach is flexible and emphasizes ease of use and the integration of available knowledge. Using this approach, we assessed the performance of several SOC models having two or more compartments for some common agroecosystems in Canada. Analysis of long-term data for conventional management practices at different sites (n = 36) in Canada, including recent model applications in the literature on some of those data, indicated that the results obtained with two-compartment models, such as the Introductory Carbon Balance Model (ICBM) and Modified Woodruff Model (MWM), yielded results comparable to those of a multi-compartment model (CENTURY). The analysis also showed that a model such as ICBM need stuning to be applied to management and conditions across Canada. Two-compartment models programmable in a simple spreadsheet format, though they may not supplant more complex models in allapplications, offer advantages of simplicity and transparency in whole-farm analyses of greenhouse gas emissions. Key words: Virtual Farm, soil organic carbon, soil disturbance, C inputs, Introductory Carbon Balance Model (ICBM), CENTURY, Modified Woodruff Model (MWM).

Description: Herbicide application has been proposed as an alternative to tillage for termination of established alfalfa (Medicago sativa L.) stands but it may alter the pattern and amount of N released from alfalfa residues. A controlled environment study was conducted to investigate the effect of termination technique on the availability of N to four barley (Hordeum vulgare L.) crops. Four treatments consisting of a factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (surface, incorporated) were established. Nitrogen uptake by the four consecutive crops of barley was measured during a 125-d period after termination. Termination method, particularly residue placement, strongly affected N release from alfalfa residues. Nitrogen accumulation by the initial barley crop accounted for 〉60% of cumulative N uptake in incorporated treatments compared with 39% and 24% for herbicide and tillage treatments in which alfalfa residue was surface applied. Herbicide application also slightly increased N uptake by the initial barley crop. Nitrogen uptake by subsequent barley crops was not affected by termination method; however, cumulative N uptake remained substantially greater for incorporated treatments throughout the 125 d experiment. Effects of residue particle size on N release from alfalfa residues were small. These results suggest that herbicide termination in which residue is retained on the soil surface may reduce the short-term plant-available N supply. Provided that mineralization is sufficient to meet the N needs of subsequent crops, maintaining a smaller reservoir of soil inorganic N may be beneficial in reducing the potential for leaching or denitrification losses. Key words: Plant-available N, termination method, alfalfa, herbicide, tillage, growth chamber

Description: Surface soil samples taken from two long-term crop rotations at Lethbridge, Alberta were used to assess the influence of fertilizer N and P on total and mineralizable concentrations of organic C and N in a Dark Brown Chernozemic soil. Rotations sampled were continuous wheat and fallow-wheat-wheat initiated in 1912. In 1967 and 1972, N fertilizer and P fertilizer treatments, respectively, were superimposed over the rotation treatments (which had received no previous fertilizer) to produce a factorial of two N rates (0 and 45 kg N ha−1) by two P rates (0 and 20 kg P ha−1). After 18 yr of application, N fertilizers increased organic C content in both rotations by approximately 14% over that observed in soil receiving no N fertilizer. Organic N contents, similarly, were increased by 15 and 11% in the continuous wheat and fallow-wheat-wheat rotations, respectively. As well, N fertilization increased relative N mineralization potential by 22% in the continuous wheat rotation and by 44% in the fallow-wheat-wheat rotation. Phosphorus fertilization had no significant influence on either total or mineralizable C and N concentrations. Soil pH (measured in dilute CaCl2) was reduced, on average, from 7.2 to 6.9 by 18 annual N applications. These results demonstrate that N fertilization can make significant contributions to the replenishment of organic matter in soil and to the maintenance of indigenous soil N fertility. Key words: Organic matter, nitrogen, carbon, mineralizable nitrogen, mineralizable carbon, pH

Description: Now, as a new century begins, may be a good time to reflect on the future of Soil Science on the Canadian prairies. One way to do that is to step back about one hundred years, to the turn of the previous century when our grassland soils were first cultivated. What questions perplexed scientists then? And how did they look for answers? My objective is to listen for our forebears’ thoughts in their writings, now largely buried. From this historical vantage may emerge insights, not only into where our science has been, but also into where it might yet go. Key words: Soil organic matter, crop rotation, grassland soils, history