Sulfur nutrition of canola

Non-Peer Reviewe

Fertilizer-use efficiency of point injected N in winter wheat

Non-Peer Reviewe

Canola yield responses to several sulphur sources – a one year's experience

Non-Peer Reviewe

Volatile N loss from decomposing green manure

Non-Peer Reviewe

Residual impact of topsoil removal and soil amendments on crop productivity over sixteen years

Non-Peer ReviewedSoil erosion remains a threat to our global soil resource. This study was conducted to ascertain the effects of simulated erosion on soil productivity and methods for its amendment. Incremental depths (0, 5, 10, 15 and 20 cm) of surface soil or cuts were mechanically removed to simulate erosion at two sites (one dryland, one irrigated) in southern Alberta in 1990. Three amendment treatments (nitrogen + phosphorus fertilizer, 5 cm of topsoil, or 75 Mg ha-1 of feedlot manure) and a check were superimposed on each of the cuts. The sites were cropped annually until 2006. On average, sixteen year yield reductions were 10.0 % for 5 cm, 19.5 % for 10 cm, 29.0 % for 15 cm and 38.5 % for 20 cm of topsoil removal. Average grain yield loss was 50 kg ha-1 cm-1 yr-1 at the Dryland site and 59 kg ha-1 cm-1 yr-1 at the Irrigated site. Amendments ranked manure > topsoil > fertilizer in terms of restoring productivity to the desurfaced soils. The study reinforces the need to prevent erosion and indicates that application of livestock manure is an option for restoring soil productivity in the short term

A simple model for quantifying change in soil organic C as influenced by tillage and crop rotations on the Canadian prairies

Non-Peer ReviewedSimulation models are required for quantifying the impact of crop rotations and tillage on soil organic C dynamics, and for aggregating C sequestration over a relatively large area. However, most current models of soil organic C have been built based on kinetically defined discrete pools with different turnover times. Those pools of soil organic C only exist conceptually. They have not been determined experimentally, thus validation of kinetic models describing soil organic C turnover is usually difficult or not independent from actual measurements. Thus, there is a need to develop a simulation model that can be easily validated and used for estimating future projection of C sequestration under specified management practices. A simple model has been developed to quantify the impact of crop rotations and tillage on soil organic C and validated using long-term field experiments conducted on the Canadian prairies. This simple model required a few input parameters and accurately predicted the change of soil organic C with a relative error of 5% or better. Crop rotation in cereal-dominant cropping systems, affected the amount of soil organic C due to differences in the amount of crop residue inputs. Clay content of soil played a vital role in determining the soil organic C sequestered under conservation tillage compared to tilled systems. This study also showed that the rate constant of soil organic C turnover was about the same for all systems in the drier region of the Canadian prairies, regardless of soil texture and the cropping system

Effect of cropping frequency on C storage in Canadian prairie soils

Non-Peer ReviewedAvailable water is the main constraint to crop production on the Canadian prairies. Summerfallow has been used to counter this problem, but frequent summerfallowing promotes soil organic matter (SOC) loss. Although summerfallow use has decreased substantially over the past 20 years, there is still considerable land devoted to this practice each year. This paper reviews research literature and assesses the influence of cropping frequency on SOC and discusses how this is influenced by ecoregion, tillage, fertility, and crop type. Results from 17 studies in the Canadian prairies were analyzed. In most soils, SOC increased with cropping frequency, but this relationship was not linear. In semiarid regions, SOC gains under no-till management were about 250 kg ha-1 yr-1 greater than for tilled systems at any specified cropping frequency; in subhumid environments, this advantage ranged from 50 kg ha-1 yr-1 for fallowcrop- crop rotations to 250 kg ha-1 yr-1 for continuously cropped rotations. In tilled systems, SOC gains were unaffected by soil zone. SOC gains in wheat-lentil rotations were similar to those in continuous wheat, but when low yielding flax replaced wheat in the rotation, SOC gains were substantially lower. Replacing wheat with fall rye increased SOC gains significantly, because of greater N efficiency and erosion control with the latter. Cropping frequency had no effect on SOC gains in unfertilized systems, but in systems fertilized according to soil tests, SOC gains were directly proportional to cropping frequency (except in the high SOC thick Black Chernozems such as at Melfort)

The influence of simulated erosion on crop growth and the value of topsoil in soil productivity

Non-Peer ReviewedWind erosion is a major soil degradation phenomenon on the Canadian prairies but its effects on soil productivity are not well quantified. In the spring of 1990, incremental depths of soil (0, 5, 10, 15 and 20 cm) were removed with an excavator, to simulate wind erosion at four sites (three dryland and one irrigated) in southern Alberta. Highly significant non-linear relationships were found between the depth of de-surfacing and subsequent spring wheat grain yields showing that simulated erosion drastically reduced soil productivity. Treatment effects at the irrigated site followed the same trend as the dryland site illustrating that topsoil loss cannot be compensated by adequate soil moisture. The 0-1 cm increment of topsoil was worth more (in terms of magnitude of yield loss when it was removed) on the irrigated site followed by the Black, Dark Brown, and Brown dryland soils

Soil microbial community response to buried crop residues is site-specific and depends on depth of burial

Non-Peer Reviewe

Sustainable agriculture – some complicating interactions

Non-Peer ReviewedThere have been numerous definitions of 'Sustainable Agriculture' put forth, but we address the official one adopted by Agriculture Canada: "Sustainable agricultural systems are those that are economically viable, and meet society's needs for safe and nutritious food while conserving or enhancing Canada's natural resources and the quality of the environment for future generations". Speeches and discussions of this topic appear to be the order of the day. Depending on the source and definition, conflicting viewpoints are often expressed. Within Agriculture Canada this concept is being given top priority. In the long-run, one of our main goals is to "ensure that all government policies and programs are in harmony with the concept of sustainable agriculture" (G.A. Neish, address to Canada Grains Commission, October 24, 1989) . This paper will discuss, from a research perspective, some of the inherent complexities and interactions that might make such laudable goals difficult to resolve and suggest some possible mechanisms by which their achievement may be facilitated