Roland Kröbel

A proposed approach to estimate and reduce the environmental impact from whole farms

Abstract Greenhouse gas (GHG) emissions remain an important field of agricultural research. Apart from measuring, simulations are frequently used to investigate management impacts on GHG emissions. The HOLOS model has been developed (using country specific emission factors) to explore potential mitigation practices with respect to GHG emission reduction or increased carbon storage. However, avoided GHG emissions can create nutrient surpluses, and thus other environmental hazards (e.g. for human and/or ecosystem health). We propose to expand the “Virtual Farm” concept by connecting the budgets carbon, nitrogen, and energy flows, and thus estimate environmental impacts as a function of management choices, environment, and climate influence. Initial tests to combine HOLOS with the carbon model Introductory Carbon Balance Model (ICBM) in Norway have been promising. The approach will be further developed for Canadian farming systems, based on a minimum of required input data, but with the option of using specific inputs if the data are available.

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 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 changes in management practices and animal performance on ammonia emissions from Canadian beef production in 1981 as compared to 2011

Abstract: The present study compared ammonia (NH3) emissions from Canadian beef production in 1981–2011. Temporal and regional differences in cattle categories, feed types and management systems, average daily gains, carcass weights, and manure handling practices were considered. A scenario-based sensitivity analysis in 2011 estimated the impact of substituting corn dried distillers’ grains with solubles (DDGS) for grain in feedlot diets. On average, 22% of the total nitrogen (N) intake was lost as ammoniacal nitrogen (NH3-N) in both years. Manure emission sources were consistent across years, averaging 12%, 40%, 28%, and 21% for grazing, confinement, storage, and land spreading, respectively. Emissions per animal in 1981 and 2011 were 16.0 and 18.4 kg NH3 animal-1 yr-1, respectively. On an intensity basis, kilogram of NH3 emitted per kilogram of beef decreased 20%, from 0.17 in 1981 to 0.14 in 2011. This reduction was attributed to increases in reproductive efficiency, average daily gain and carcass weight, and improved breeding herd productivity. In 2011, substituting DDGS for grain in feedlot diets increased total NH3 emissions and losses per animal. Although addition of by-products from the bioethanol industry can lower diet costs, it will be at the expense of an increase in NH3 emissions.

Yield and profitability of long-term rotations

Smith, E. G., Janzen, H. H. and Krobel, R. 2015. Yield and profitability of fallow and fertilizer inputs in long-term wheat rotation plots at Lethbridge, Alberta. Can. J. Plant Sci. 95: 579–587. A long-term, 42-yr study was used to determine the impacts of crop rotation and fertility management on wheat yield and profitability. Crop rotations included continuous wheat (W), fallow–wheat (FW), and fallow–wheat–wheat (FWW). Original plots were split for nitrogen (N) and phosphorus (P) fertility treatments, a two-factor factorial for N (0 and 45 kg ha−1) and P (0 and 20 kg ha−1). Phosphorus increased yield during the first half of the period, but had little impact during the last half. Nitrogen had no yield impact on fallow crops during the first half of the period, but had a positive impact during the last half, and throughout for wheat after wheat. The soil became incapable of releasing adequate N for wheat after fallow. Simulated distributions of net returns determined the W rotation with N and P fertilize...