B. H. Ellert

Nitrous oxide emissions from an irrigated soil as affected by fertilizer and straw management

Nitrous oxide (N2O) emission from farmland is a concern for both environmental quality and agricultural productivity. Field experiments were conducted in 1996–1997 to assess soil N2O emissions as affected by timing of N fertilizer application and straw/tillage practices for crop production under irrigation in southern Alberta. The crops were soft wheat (Triticum aestivumL.) in 1996 and canola (Brassica napusL.) in 1997. Nitrous oxide flux from soil was measured using a vented chamber technique and calculated from the increase in concentration with time. Nitrous oxide fluxes for all treatments varied greatly during the year, with the greatest fluxes occurring in association with freeze-thaw events during March and April. Emissions were greater when N fertilizer (100 kg N ha−1) was applied in the fall compared to spring application. Straw removal at harvest in the fall increased N2O emissions when N fertilizer was applied in the fall, but decreased emissions when no fertilizer was applied. Fall plowing also increased N2O emissions compared to spring plowing or direct seeding. The study showed that N2O emissions may be minimized by applying N fertilizer in spring, retaining straw, and incorporating it in spring. The estimates of regional N2O emissions based on a fixed proportion of applied N may be tenuous since N2O emission varied widely depending on straw and fertilizer management practices.

Carbon, ash and organic matter relationships for feedlot manures and composts

Composting is increasingly recognized as a means of handling livestock manure. Using relationships derived from a dataset of >3000 samples representing the decay spectrum from raw manure to mature compost (from unpaved feedlot pens bedded with straw or wood residuals) we propose that measurement of either total carbon or ash content is sufficient to estimate carbon, organic matter and dry matter mass changes during composting of beef feedlot manure. Key words: Compost, carbon, ash content, feedlot manure

Management-induced Changes in the Quantity and Composition of Organic Matter in Soils of Eastern Canada

Organic matter plays a key role in soil quality and the productivity of agroecosystems: it is a source and sink of plant nutrients, maintains soil tilth, aids the infiltration of air and water, promotes water retention, reduces erosion, and controls the efficacy and fate of applied pesticides.

Nitrogen balance in century-old wheat experiments

Abstract: Managing nitrogen (N) inputs to sustain high yields while minimizing losses to adjacent environments remains among the foremost aims in agroecosystems. We studied the N balance in a study established in 1911 at Lethbridge, AB, Canada. The experiment includes three cropping systems — continuous wheat (W), fallow–wheat–wheat (FWW), and fallow–wheat (FW) — with a factorial of two N rates (0 and 45 kg N ha-1) and two phosphorus (P) rates (0 and 20 kg P ha-1) superimposed beginning in 1967. In unfertilized subplots, grain yields generally increased for the first eight decades, but then declined, perhaps partly because of growing N deficiency. Yield response to N increased over time, especially under continuous cropping and when co-applied with P. Soil N concentration in the surface 15 cm declined in the first few decades, and then approached an apparent steady state. Application of N increased soil N, roughly in proportion to the amount of residue returned. For the first half-century (1911–1967), N removal was approximately equivalent to the loss of soil N in the surface 15 cm. Since then, however, when the soil organic N was near steady state, removals of N in grain exceeded N inputs by approximately 20–30 kg N ha-1 yr-1, suggesting an input from outside sources, perhaps partly from atmospheric NH3. This study demonstrated the importance of long-term experiments in evaluating the N balance of cropping systems, and indicated the potential significance of non-fertilizer N inputs from outside sources in such ecosystems.

Soil organic carbon changes as influenced by carbon inputs and previous cropping system

Abstract: We planted continuous wheat, with and without nitrogen fertilizer, onto a preceding long-term (44 yr) experiment with contrasting cropping systems, and measured soil organic carbon (SOC) after 6 yr. Changes in SOC were driven mostly by cumulative plant C inputs, as influenced by yield response to added nitrogen.

Soil carbon dynamics in wheat plots established on grassland in 1911 as influenced by nitrogen and phosphorus fertilizers

Abstract: Soil organic carbon (SOC) changes slowly, and final management influences can be measured only after decades. Analysis of archived samples from a site established on grassland in 1911 showed that SOC, under wheat systems, approached steady state after several decades, and that its amount reflected the inputs of residue C.

Effect of fertilizer and cropping system on grain nutrient concentrations in spring wheat1

Abstract: Wheat (Triticum aestivum L.) is a major food source supplying nutrients required for adequate human nutrition. Changing fertility and cropping practices could alter the concentration of essential elements in wheat grain. This study utilized two long-term field experiments to determine the effect of nitrogen (N) and phosphorus (P) fertilization and cropping system on the concentration of N, P, potassium (K), sulphur (S), calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), and zinc (Zn) in wheat grain. Fertilizer P increased P (18%), K (6%), Mg (4%), and Mn (7%) concentrations but decreased Zn (26%) and Cu (22%). The grain concentration of P, K, Ca, Mg, Mn, and Zn declined as crop yields increased in response to N fertilization or more favourable growing conditions. A cropping system with alfalfa hay increased the wheat grain concentration of N (10%), S (17%), Cu (20%), Mg (18%), and Zn (50%). Cropping systems with wheat alone had only minor effects on human nutrient concentrations in wheat grain, depending on the frequency of fallow. Changing wheat production systems, especially fertilizer application, could suppress the availability of essential micronutrients Cu and Zn if the concentrations were already low but most other elements were generally adequate.

Woodslee Tile Runoff Experiment: Fertilization Effects on Soil Organic Matter

The original objective of this field experiment was to determine the effects of crop rotation and fertilization on soil and water quality by examining water flow and loss of N, P, and K through tile drains in a clay loam soil (Bolton et al., 1970). From this field study several papers have been published on nutrient and atrazine losses from tile drains (Von Stryk and Bolton, 1970), structural changes resulting from soil and crop management systems (McKeague et al., 1987), effects of distance from the tile drain on maize growth over a 10-yr period (Bolton et al., 1982), and the effects of fertilization and crop rotation on maize root disease (Stone et al., 1987). The cropping history and yield data (Drury and Tan, 1995) from this site provide a unique opportunity to evaluate the effects of fertilization on soil organic matter turnover and storage of maize-residue C (Gregorich et al., 1996).