ALBERT

Description: Cereals grown under irrigation in the Canadian prairies produce large amounts of residues. An experiment initiated at the Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta, in the fall of 1986, to investigate five straw management treatments (1, chopped straw/fall tillage [straw incorporated]; 2, chopped straw/spring tillage [straw incorporated]; 3, straw baled/fall tillage; 4, straw baled/spring tillage; 5, straw baled/direct seeding) and three fertilizer N rates (0, 100, and 200 kg N ha−1) on crop yields under irrigation, was sampled in April 1995 to examine the effect of straw management and fertilizer additions on selected soil chemical characteristics as potential soil quality indicators. If yield is not used, can we evaluate soil quality from a soil genesis baseline or is it crop growth driven? Differences among straw management and fertility treatments have already supplied information on the effects of these treatments after 8 yr. The treatment in which the straw was baled and the land not tilled had the highest soil bulk density. Total soil organic C and N were highest for the straw baled/no tillage treatment and the 200 kg N ha−1 application. Total C was higher for the fall than spring tillage treatments, while total N was lower for the spring than for the fall tillage treatments when straw was incorporated. Light fraction (mg kg−1 C) was highest for the chopped straw and zero fertilizer additions. For several biologically related characteristics, e.g., mineralizable N, biomass C, biological index N, and hydrolysable N, there were significant interactions between straw management treatments and fertility levels. Monosaccharides at the zero fertility level were generally of microbial origin, while plant-origin monosaccharides were more prevalent as the fertility level increased. It is concluded that the present use does not lead to soil erosion, does not pollute groundwater, and does grow plants; with the help of outside resources, any one straw management treatment can be considered as valid in the anthropocentric sense of soil quality. Since the interpretation of significant effects of treatment on soil properties must be carefully considered depending on the crop selected, the concept of soil quality is thus open to question and debate. Key words: Soil quality, straw management, intrinsic value, tillage, labile organic matter

Description: Complete loss of topsoil resulting from erosion or other causes generally results in reduced crop yield. To determine, under dryland conditions, the effect of loss of various amounts of soil and of various amendment practices suitable for use under a cereal production program on soil properties and crop yields, a field was artificially eroded during cut and fill of land-levelling in 1957. Continuous cropping to barley for 7 yr was followed by a wheat-fallow rotation for 22 yr. A continuous wheat experiment was conducted from 1987 to 1991 to determine the effects of five fertility amendments on restoring the productivity to soil from which 10–20 cm and 46+ cm of soil had been removed. In 1990, a below-average precipitation year, after 33 yr and 23 crops, yields from the unfertilized 46+ cm eroded field were only 44% of the yields from the uneroded field. However, with the increased precipitation in 1991 this value was 66%. A one-time topsoil amendment was beneficial in the earlier stages of the experiment, but lost its effect as cultivation mixed it into the "subsoil" over time. Plot treatments with annual applications of manure and high rates of fertilizer generally out-yielded the yields of the check plots of the uneroded treatment. Amendment with straw + fertilizer was not very effective. Soil, once lost, is non-renewable without amendments within the working lifetime of the producer. Key words: Soil erosion, manure, commercial fertilizer, topsoil soil, productivity

Description: Short-term root processes can influence chemical and biochemical conditions at the soil–plant–root interface. In this study, soil phosphorus forms, pH and biochemical properties within and adjacent to the rhizosphere of hard red spring wheat (Triticum aestivum L. ’Katepwa’) and canola (Brassica napus L. ’Westar’) seedlings were studied over a 5-wk period. Soils were from the Ap horizon of a Calcareous Dark Brown Chernozemic soil (Lethbridge, Alta) and an Orthic Gray Luvisolic soil (Breton, Alta) obtained from fertilized and unfertilized long-term continuous-cropped and wheat–fallow rotation plots. Wheat and canola both absorbed more total phosphorus (P), produced more aboveground material and had higher dehydrogenase and alkaline phosphatase activities when grown in Lethbridge soils than when grown in Breton soils. Canola took up more P from both the resin-extractable inorganic P (resin-Pi) and hydrochloric acid extractable (HCl-Pi) fractions than wheat, indicating a greater ability to extract P from soil. Acid phosphatase levels increased over time in the rhizospheres of both wheat and canola. Dehydrogenase activity was greater in the rhizospheres of wheat than of canola, indicating greater microbial activity. Canola roots frequently lowered pH within their rhizosphere which apparently suppressed microbial activity. Dehydrogenase activity in the relatively acidic Luvisolic soils was lower than in the near-neutral Chernozemic soils. The plant-root chemical and biochemical changes in the rhizosphere varied depending on soil chemical characteristics and past soil management history. Results showed canola and wheat utilize different mechanisms to influence their root rhizospheres and obtain their nutritional requirements. Rhizosphere changes were a function of plant species, soil type and previous soil management history. Key words: Rhizosphere, pH, phosphatase, dehydrogenase, P bioavailability, soil phosphorus transformations, wheat, canola

Description: A number of animal licks, representing dry earth exposures, muck licks, and rock face licks, were sampled and analysed for 12 elements by using a sulphuric acid-hydrogen peroxide method to simulate digesta. The various types of licks may serve different needs. Sodium, magnesium, manganese, iron, and copper may draw animals to specific sites. Key words: Salt licks, ungulates, landscape management, Rocky Mountains

Description: A field was artificially eroded by levelling in 1957. It was continuously cropped to barley for 7 yr. Subsequently, the field was cropped to a wheat-fallow rotation up to but not including 1986. Two major restoring productivity experiments were conducted over that time period. After 30 yr and 19 crops, a third experiment was established to determine the effect of artificial soil erosion and four restorative amendments on 13 wheat quality characteristics. Year, erosion level, and amendment all had significant effects on many wheat quality parameters. Erosion decreased overall quality, mainly by decreasing protein content which in turn affected other quality characteristics. Applications of manure, fertilizer, and straw + fertilizer increased protein content and related characteristics substantially compared to the check. Since high-quality bread wheat is central to its worldwide demand, prevention of soil erosion is essential. Conversely, eroded soil can be ameliorated with amendments but at a cost of the amendment and its application. Keywords: Soil erosion, topsoil loss, wheat quality, soil moisture, fertility amendment

Description: Concentrations were measured of various forms of soil P in the Ap horizon of a Lethbridge loam (Dark Brown Chernozemic) brought about by 20 yr of feedlot manure loading or 14 yr of feedlot manure loading + 6 yr of no further additions under both nonirrigated and irrigated conditions. Depth of cultivation affected the concentrations of the various P fractions. Although total P and phosphatase activity increased with manure additions, these increases diminished at triple the recommended loading rates. Increased phosphatase activities never rose above those of the soil from ungrazed native prairie. Irrigation increased the phosphatase activity of the control treatment. Concentrations of total P remained well above those of the control plots, even after 6 yr without any additional manure loading. New approaches to the estimation of P fractions are needed to understand P in land used for manure disposal. Key words: Phosphatase activity, labile phosphorus, pollution, phosphorus harvesting, cultivation depth