Report on the east central Saskatchewan Soil Conservation Project

Non-Peer Reviewe

Physical oceanographic investigations in the Eastern Bering and Chukchi Seas during the summer of 1947

New information on the physical properties of the waters in the eastern Bering and Chukchi seas is discussed. It shows that, in summer, the water masses of this area are complicated by the circulation and advective processes. In general, the southern Bering Sea water flows northward and is modified by warm low-salinity water from rivers along the Alaskan coast and from intrusions of cold high-salinity water from the western Bering Sea. This mixture of water funn els through the Bering Strait principally at the surface on the eastern side...

Managing wild oat in tame oat through the seeding date and seeding rate of tame oat

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The response of weed communities to changing management practices

Non-Peer ReviewedThe response of weed communities to changing management practices was assessed as part of the Crop Management Study at the Indian Head Experimental Farm from 1988 to 1990. A split plot design with four reps (144 plots), zero, minimum, and conventional tillage as the main plots, two continuous crop rotations and one crop-fallow rotation as the sub-plots, and spring wheat, winter wheat, flax, and field pea as the crops. Each crop in a rotation was present each year. Weeds were sampled during July each year, after the application of post-emergent herbicides, in order to assess the density and composition of the residual weed flora. In each plot (except the 12 fallow plots) the weeds were counted in 20 quadrats, each 0.25 m^2. Multivariate statistical methods were used to determine if weed communities differed among years, tillages, rotations, and crops. Weed densities were generally low for all years (< 10 plants m-2). From 1988 to 1990, the proportional abundance of different weed types changed. Annual broad-leaved weeds accounted for 40% of the total weed abundance during 1988 and 70% during 1990. Redroot pigweed, kochia, Russian thistle, and thyme-leaved spurge were the major weeds in this group and all increased in frequency of occurrence. Winter annuals decreased from 35% of the total abundance to 19% during the same period. Stinkweed and flixweed were the major weeds in this group. The annual grasses, wild oats and green foxtail, accounted for 5% or less of the abundance in all three years. The perennial group, Canada thistle, perennial sow-thistle, and foxtail barley and the volunteer crop group, spring wheat, winter wheat, and flax were less than 11% of the total abundance in each of the three years. The year to year variation in weed abundance was greater than any variation due to tillage system. The highest weed densities were associated with the rotation that included field pea

Nitrogen response and nitrogen use efficiency of high yielding canola cultivars

Non-Peer ReviewedSeveral new canola varieties have much higher yield potential than those grown in the past. For example, the yield potential of highest yielding varieties listed in the Varieties of Grain Crops booklet for 2001, published by Saskatchewan Agriculture and Food are as much as 35% greater than for the check variety AC Excel. One question that arises is whether such varieties require greater inputs of fertilizer nutrients, particularly nitrogen (N), to realize optimum economic returns

Management for optimum yield of open pollinated and hybrid canola

Non-Peer ReviewedNewer open pollinated (O.P.) and hybrid canola varieties provide higher yield potential but the management strategies necessary to achieve optimum yield are not well understood. To better understand the levels of inputs required to optimize yield and to enhance producers ability to optimize return on their investment a three year study was conducted at Melfort, Indian Head, and Scott during 1999, 2000 and 2001 with the following objective. Objective: To evaluate the effect of seeding rate, fertilizer addition and fungicides on the optimum yield potential of hybrid and open pollinated canola in the Thick Black, Thin Black and Dark Brown Soil Zones

Communique: Reponse de la Haute Autorite a la question ecrite No. 51 de Mme Erisia Gennai Tonietti et M. Pedini. European Coal and Steel Community High Authority Information Service. 24 July 1962

Experience curves are widely used to predict the cost benefits of increasing the deployment of a technology. But how good are such forecasts? Can one predict their accuracy a priori? In this paper we answer these questions by developing a method to make distributional forecasts for experience curves. We test our method using a dataset with proxies for cost and experience for 51 products and technologies and show that it works reasonably well. The framework that we develop helps clarify why the experience curve method often gives similar results to simply assuming that costs decrease exponentially. To illustrate our method we make a distributional forecast for prices of solar photovoltaic modules

On Symbolic Ultrametrics, Cotree Representations, and Cograph Edge Decompositions and Partitions

Symbolic ultrametrics define edge-colored complete graphs K_n and yield a simple tree representation of K_n. We discuss, under which conditions this idea can be generalized to find a symbolic ultrametric that, in addition, distinguishes between edges and non-edges of arbitrary graphs G=(V,E) and thus, yielding a simple tree representation of G. We prove that such a symbolic ultrametric can only be defined for G if and only if G is a so-called cograph. A cograph is uniquely determined by a so-called cotree. As not all graphs are cographs, we ask, furthermore, what is the minimum number of cotrees needed to represent the topology of G. The latter problem is equivalent to find an optimal cograph edge k-decomposition {E_1,...,E_k} of E so that each subgraph (V,E_i) of G is a cograph. An upper bound for the integer k is derived and it is shown that determining whether a graph has a cograph 2-decomposition, resp., 2-partition is NP-complete

AtPME17 is a functional arabidopsis thaliana pectin methylesterase regulated by its PRO region that triggers PME activity in the resistance to botrytis cinerea

Pectin is synthesized in a highly methylesterified form in the Golgi cisternae and partially de-methylesterified in muro by pectin methylesterases (PMEs). Arabidopsis thaliana produces a local and strong induction of PME activity during the infection of the necrotrophic fungus Botrytis cinerea. AtPME17 is a putative A.&nbsp;thaliana PME highly induced in response to B.&nbsp;cinerea. Here, a fine tuning of AtPME17 expression by different defence hormones was identified. Our genetic evidence demonstrates that AtPME17 strongly contributes to the pathogen-induced PME activity and resistance against B.&nbsp;cinerea by triggering jasmonic acid–ethylene-dependent PDF1.2 expression. AtPME17 belongs to group 2 isoforms of PMEs characterized by a PME domain preceded by an N-terminal PRO region. However, the biochemical evidence for AtPME17 as a functional PME is still lacking and the role played by its PRO region is not known. Using the Pichia pastoris expression system, we demonstrate that AtPME17 is a functional PME with activity favoured by an increase in pH. AtPME17 performs a blockwise pattern of pectin de-methylesterification that favours the formation of egg-box structures between homogalacturonans. Recombinant AtPME17 expression in Escherichia coli reveals that the PRO region acts as an intramolecular inhibitor of AtPME17 activity

Fertilizer application and deep leaching of nitrate under long term crop rotation

Non-Peer ReviewedIt is commonly believed that the use of nitrogen fertilizers in agriculture will lead eventually to the loss of nitrate via leaching. The nitrate leached below the root zone has the potential to contaminate underground water. The results obtained from various long term crop rotation studies in Saskatchewan suggest that this common belief may not hold in general. This is especially true where nitrogen fertilizers were applied based on soil test recommendation and the land was continuously cropped. Under long term crop rotation studies in the Black Soil Zone at Melfort, the application of nitrogen fertilizer in recent years were based on the general recommendation for wheat. The deep core sample revealed that more nitrate was present in the soil profile under fertilized continuous wheat compared to the unfertilized plots. However, in the Black Soil at Indian Head, where fertilizer application was based on soil test values, similar amounts of nitrate were found below the root zone of fertilized and unfertilized plots after 34 years of continuous wheat. This was in spite of applying 1584 kg of N ha-1 to the fertilized plot over 34 years. A result similar to that at Indian Head was obtained from the crop rotation experiment in the Brown Soil Zone at Swift Current. In the Brown Soil Zone, the inclusion of a fallow phase in the rotation, increased the amount of nitrate found below the root zone although this system had received less fertilizer over the years than the continuously cropped plots. The fallow phase appeared to provide a window for the leakage of nitrate accumulated within the root zone. This was attributed to a better moisture (antecedent moisture) regime and higher amount of mineralized nitrate during the fallow phase. On the other hand, frequent summerfallow can deplete the soil of its N supplying power and this may eventually result in less nitrate leached as was found for the 2-yr rotation at Indian Head after 34 yr