Tillage systems for summerfallow preparation in north-central Saskatchewan

Non-Peer ReviewedThis paper examines the agronomic and economic performance of seven summerfallow - spring wheat tillage systems studied over a 18 year period on a highly fertile silty clay loam soil at Melfort, Saskatchewan. During 1969-76, areas planted to wheat had the seedbed prepared with a cultivator and harrow; since 1977 one-half of each plot area received conventional seedbed preparation, the other half was sprayed with herbicide and zero till seeded. Overall, wheat yields averaged 3239 kg ha-1 for tillage alone, 3280 kg ha-1 for reduced tillage (combinations of tillage and herbicides), and 3347 kg ha-1 for herbicides only. On an annual basis, method of summerfallow preparation significantly influenced grain yields in only 6 of 18 years. In 3 of these years yields were lowest for tillage alone and highest for herbicides only; in 2 years yields were lowest for reduced tillage, and in 1 year yields were lowest for herbicides only. During 1977-86, preparation of the seedbed by tillage significantly increased yields (compared to zero till seeding) in 6 of 10 years, but it resulted in significantly lower yields in 4 of 10 years. Volume weight, protein content, and % P concentration in the grain were unaffected by the method used for fallow or seedbed preparation. Results of the economic analysis showed that total costs for the complete rotation systems were lowest for the all tillage treatment (average: $109 ha-1), intermediate for reduced tillage (average:$129 to $158 ha-1), and highest for herbicides only (average:$179 ha-1). Although the substitution of herbicides for mechanical tillage provided resource savings in the range of $2 to$10 ha-1, this was more than offset by the increased expenditures for herbicides. Net returns (income above all costs) were highest for tillage alone (average: $129 ha-1) and lowest for the herbicide only treatment in which paraquat or glyphosate was used in combination with dicamba (average:$54 ha-1) . The reduced tillage systems generally produced a net return that averaged $18 to$44 ha-1 lower than the traditional system. The maximum expenditure that could be made for herbicides to break even with the traditional system ranged from $22 to$29 ha-1 for the reduced tillage systems, and from $31 to$37 ha-1 for the herbicides only treatments. The study concluded that although the substitution of herbicides for some or all of the mechanical tillage is attractive to producers from an agronomic and soil conservation perspective, the present economic conditions and in particular, the high cost of herbicides, remains a major deterrent to widespread adoption

Economics of alternative input use and crop diversity strategies in the Dark Brown Soil Zone of Saskatchewan

Non-Peer Reviewe

Effects of input level and crop diversity on energy use efficiency of cropping systems in the Dark Brown Soil Zone

Non-Peer Reviewe

Adding natural disturbances to a large-scale forest scenario model and a case study for Switzerland

In this study we assessed the impact of climate change and the role of natural disturbances on the development of forest resources. A module dealing with natural disturbances was developed for the European forest information scenario model (EFISCEN), based on the observed distribution of damages in the past and the dependency of disturbances on forest characteristics. To put the model to the proof, the development of Swiss forest resources was projected until 2048 under three alternative scenarios. The first scenario consisted of a run without the new module (the base run), in the second scenario the model was run with the new module under current climate (natural disturbance run) and the third scenario was a run with the new module under a changed climate (natural disturbance and climate change run), where outcomes of the process-based model TREEDYN3 were used to simulate the influence of a changing climate on the volume increment and where the frequency of disturbances was increased to simulate the effect of climate change on natural disturbances. Incorporating natural disturbance dynamics in the EFISCEN model resulted in a more realistic simulation of the total fellings and natural mortality, due to the fact that killed, but unrecovered, timberis also taken into account, resulting in a better simulation of volume and increment development. When the natural disturbances module was used in the simulation, the growing stock increased from 366 m3/ha in 1984 to 460 m3/ha in 2048, while without disturbances it increased up to 592 m3ha. The simulation under current climate showed an increase in damage due to natural disturbances of 40% over the period 2004-2048, due to an increase of growing stock and a higher proportion of older stands. Under a simulated climate change scenario, the frequency of disturbances was assumed to increase, which resulted in 25% higher damages. However, the increment increased more than the damage done by disturbances, which resulted in a simulated growing stock volume of530 m3/ha in 2048. The increase in damage must be attributed to an increasing average standing volume. Because of uncertainties caused by the assumptions made in the model and the stochastic character of the disturbances, the results of this study must be seen as merely indicative

The benefits of a wheat-lentil rotation for the Brown Soil Zone

Non-Peer Reviewe

An approach towards an estimate of the impact of forest management and climate change on the European forest sector carbon budget: Germany as a case study

The increasing concentration of greenhouse gases in the atmosphere and the consequent warming of the Earth's surface presents a threat to the environment and economic development. This paper discusses how regional level impacts of transient climate change on forest growth are assessed with process-based models and how these responses are then scaled up to country and European level using national forest inventory data in combination with the European forest information scenario (EFISCEN) model. Stem wood volume and increment in the EFISCEN model is converted to whole tree biomass based on information from process-based models. Calculation of carbon in soil and in wood products is included in this approach. A preliminary carbon budget under current and changing climatic conditions, with current management regime for Germany, is presented and discussed. Although carbon stocks in trees, soil and products are increasing, we found that the German forest sector can sustain a carbon sink until 2050, but the sink gradually becomes smaller, declining from 1.7 Mg C/ha per year in 1995 to 0.7 Mg C/ha per year in 2050. This is due to ageing of forests, as sink activity in older forests is smaller than in younger forests. The sink activity in the soil increased slightly, but rate of storage in trees decreased more. Under changing climatic conditions, both carbon stock and sink activity in trees and soil were larger than under current climatic conditions. International processes, such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol require integrated assessments of the role of forests and forestry on mitigation of climate change, but there is also a need for assessments of the impacts of climate change on forests. Research can provide information for decision-makers regarding the functioning of the system, potential risks and uncertainties. The upscaling approach described in this paper will be used later to investigate the impacts of selected forest management scenarios, under current and changing climatic conditions, on the forestry carbon budgets of 27 European countries

Integrated impedance bridge for absolute capacitance measurements at cryogenic temperatures and finite magnetic fields

We developed an impedance bridge that operates at cryogenic temperatures (down to 60 mK) and in perpendicular magnetic fields up to at least 12 T. This is achieved by mounting a GaAs HEMT amplifier perpendicular to a printed circuit board containing the device under test and thereby parallel to the magnetic field. The measured amplitude and phase of the output signal allows for the separation of the total impedance into an absolute capacitance and a resistance. Through a detailed noise characterization, we find that the best resolution is obtained when operating the HEMT amplifier at the highest gain. We obtained a resolution in the absolute capacitance of 6.4 aF/Hz at 77 K on a comb-drive actuator while maintaining a small excitation amplitude of 15 kBT/e. We show the magnetic field functionality of our impedance bridge by measuring the quantum Hall plateaus of a top-gated hBN/graphene/hBN heterostructure at 60 mK with a probe signal of 12.8 kBT/e.QRD/Kouwenhoven LabQuTec