25 years of tillage effects on wheat production in a continuous cropping system

Non-Peer ReviewedHeat stress occurs often in wheat on the Canadian Prairies especially during grain growth (from anthesis to maturity), which has a markedly negative impact on yield (McCaig 1997). Under no-till management (NT), surface residue and stubble act as insulation and impede the exchange rate of thermal energy between the soil and the atmosphere, and the superior soil moisture of NT compared to conventional tillage (CT) can buffer the extremes in daily soil temperatures. It is, therefore, possible that the cooling effect of NT could alleviate the root heat stress of wheat. Under a continuous wheat cropping system on a Thin Black Chernozemic clay loam in central Alberta, Wang et al (2007) found that the near-surface soil temperature of NT was lower than that of CT throughout the growing season, which reduced the risk of root heat stress and benefited grain yield and biomass. The objective of this study was to investigate whether a similar effect of NT is present in southwestern Saskatchewan

Influence of pulse crops on abundance of arbuscular mycorrhizal fungi in a durum-based cropping system

Non-Peer ReviewedPulses are an important component in crop rotations in southern Saskatchewan. Besides their capability to fix nitrogen, pulse crops establish a strong symbiotic relationship with arbuscular mycorrhizal (AM) fungi, which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. Incorporating strongly mycorrhizal crops in a rotation may increase inoculum levels in the soil and benefit the growth of a subsequent crop. The objective of this study was to determine if AMF colonization of a durum crop is significantly affected by cropping history and to assess the impact of pulses in crop rotations on the abundance of AMF communities in the soil. In 2004 and 2005, soil and root samples were taken on durum with preceding crops of chickpea, pea, lentil, canola, and durum. Arbuscular mycorrhizal colonization was significantly lower in durum roots following canola in both years. Phospholipid fatty acid analysis (PLFA) was completed to analyze the relative abundance of AMF, saprophytic fungi, and bacteria in the soil. These results demonstrated that although previous crop may play a role in microbial community structure, it is not the only influencing factor

Estimation of daily soil CO2 emission using instantaneous measurements

Non-Peer Reviewe

Economics of crop diversification opportunities for the Brown and Dark Brown Soil Zones of Saskatchewan

Non-Peer ReviewedProducers, particularly in the Brown and drier parts of the Dark Brown soil zones, have begun to extend and diversify their crop rotations, becoming less reliant on summerfallow and monoculture cereal cropping. The areas planted to crops such as canola, mustard, flax, field pea, chickpea and lentil expanded dramatically in recent years, often into new or non-traditional production areas. These changes in land use practices are expected to continue, and perhaps grow in future years. This study determines and compares the economic merits and relative riskiness (both production and market) of producing chickpea, field pea, lentil, mustard, canola, and flax with spring wheat, durum wheat or barley when grown on chemical fallow and zero-till stubble for various plausible product price scenarios. Field data collected at Swift Current, Scott and Congress were extended with use of a STELLA® model, to elucidate the short-term and the longer-term economic and environmental impacts of these newer cropping systems. Our findings indicate that under current market conditions, risk averse producers in the Brown soil zone would typically choose either a 4-year Fallow-Chickpea-Wheat-Wheat rotation or a 5-year Durum-Chickpea-Mustard-Wheat-Lentil rotation. In the Dark Brown soil zone, risk averse producers would choose a 4-year Canola-Wheat-Lentil- Wheat rotation

Seasonal variation in the soil microbial community in wheat-growing soil and influence of C, N, and P inputs

Non-Peer ReviewedIt has long been know that N and P fertilization increases plant growth and yield, but the impact of fertilization on soil microorganisms has rarely been considered. Long-term plots (36-year old) under fallow-wheat-wheat (F-W-W) rotations with no P or no N fertilization, or normally fertilized, and plots receiving low C inputs due to frequent fallow (F-W rotation) were used to define the impact of C, N and P on the seasonal variation of the soil microbial communities in the fallow-after-wheat or the wheat-after-fallow phases of the rotations. The soil was sampled on June 8, July 4, August 5 and September 16, in 2003. There was no significant (P≤ 0.05) time by treatment interactions. Populations of bacteria, arbuscular mycorrhizal (AM) fungi and saprophytic fungi, as estimated by phospholipids fatty acid (PLFA) indicators, were strongly reduced on July 4th, a date corresponding to rapid plant growth. Sporulation of fungal saprobes was enhanced at that date, as indicated by the neutral lipid fatty acid (NLFA) to PLFA fraction ratio of the fatty acid C18:2. It appears that a competition for resources exists between soil microorganisms and wheat, at least in July at the time of active crop growth. While P availability had little effect on soil microorganisms, absence of N fertilization increased sporulation in AM and saprophytic fungi. In spite of the biotrophic1 nature of AM fungi, C input in the form of infrequent fallow or presence of living wheat plant favoured the partitioning of fatty acids into reserve lipid i.e., NLFA

Microbial community structure under various wheat-based cropping systems

Non-Peer ReviewedThe effects of cropping systems on soil biological quality are slow to develop. We sampled the soil of a 36-year old long-term experiment established on an Orthic Brown Chernozem, at Swift Current SK, in the fall of 2003, to define the long-term impact of 10 cropping systems on soil biological quality. Numerous variables related to soil function - soil pH, organic C (SOC), moisture, enzymatic activities, available N, P, and S - and soil community structure - phospholipid fatty acids (PLFA) indicators of fungal saprobes, arbuscular mycorrhizal fungi and bacterial groups - were used to describe soil quality. Soils under different cropping systems had become distinct, as revealed by discriminant analyses. Variations in SOC, and pH were most influential in discriminating the soils. SOC varied from 2.38% under continuous wheat to 1.81% under a fallow-wheat rotation. pH went from 6.55 under fallow-wheat-wheat receiving no P-fertilizer, to 4.89, under chemical fallow – fall rye – wheat. Absence of fallow under normal fertilization increased SOC and decreased soil pH. Variations in SOC and pH were concurrent with variations in microbial community structure. Enhanced AM fungi abundance under low soil P, could compensate for the large soil P depletion created by 36 years without P fertilizer, in a fallow-wheat-wheat rotation, and P-fertilized and non-P-fertilized plots produced similar yields. The season of 2003 was dryer than normal and it remains to be seen if AM fungi can compensate for low soil available P when soil moisture is abundant

Response of cereals to fertilizer N on pulse and other stubbles

Non-Peer ReviewedTo optimize cropping systems requires knowledge of effects of the preceding crop on the grain yield and protein and the response to N of a following cereal crop. To gain this knowledge, we grew hard red spring (HRS) wheat, durum wheat, Canadian Prairie Spring (CPS)-class wheat, Canadian Western Extra Strong (CWES)-class wheat, and barley on barley, bean, coriander, fenugreek, kabuli chickpea, lentil, mustard, and pea stubble at different N fertilizer rates over 9 site-yr: Swift Current (1998-2002), Redvers (2001-02), and Canora (1999 and 2002). N rates were medium (recommended rate based on fall soil nitrate in cereal stubble), low (15-30 kg ha-1 less than medium) and high (15-30 kg ha-1). There was a significant effect of stubble on subsequent cereal grain yield. Cereal on cereal stubble was consistently lowest or second lowest yielding (typically 100 – 800 kg ha-1 lower than other stubbles) with the exception of 2001 at Swift Current when it was the highest yielding. This latter effect was attributed to the superior moisture conserving benefits of cereal stubble during this year with extreme early drought. No single cereal crop was consistently highest or lowest yielding. The trend was for greatest grain protein on pulse stubbles although stubble effects on protein were not as great as on yield owing to confounding yield dilution effects. Within this narrow range of fertilizer N rates, yield or protein response to N was weak. Generally, there were no significant interactions between stubble and cereal crop or stubble and fertilizer indicating the effect of stubble was consistent across cereal type and N rates. The cereal yield and protein response to N on the non-cereal stubbles was not significantly different than that on cereal stubble with the exception that barley protein responded more positively to N on lentil stubble than on cereal stubble. Cereals grown on pulse stubbles tended to have higher yields and protein than on other stubbles. For HRS wheat and durum, the chance of achieving high protein grain was greatest with high fertilizer N on pea stubble (>75% of years). Applying a high fertilizer N rate on cereal stubbles did not markedly increase the chance of attaining high protein wheat or durum. For barley, where low protein is desired for malting, the best chance for low protein barley was on cereal and mustard stubble although barley protein appeared less affected by stubble and fertilizer N than wheat or durum

Long-term response of spring wheat to N and P fertilization in southwestern Saskatchewan

Non-Peer Reviewe

The art of being human : a project for general philosophy of science

Throughout the medieval and modern periods, in various sacred and secular guises, the unification of all forms of knowledge under the rubric of ‘science’ has been taken as the prerogative of humanity as a species. However, as our sense of species privilege has been called increasingly into question, so too has the very salience of ‘humanity’ and ‘science’ as general categories, let alone ones that might bear some essential relationship to each other. After showing how the ascendant Stanford School in the philosophy of science has contributed to this joint demystification of ‘humanity’ and ‘science’, I proceed on a more positive note to a conceptual framework for making sense of science as the art of being human. My understanding of ‘science’ is indebted to the red thread that runs from Christian theology through the Scientific Revolution and Enlightenment to the Humboldtian revival of the university as the site for the synthesis of knowledge as the culmination of self-development. Especially salient to this idea is science‘s epistemic capacity to manage modality (i.e. to determine the conditions under which possibilities can be actualised) and its political capacity to organize humanity into projects of universal concern. However, the challenge facing such an ideal in the twentyfirst century is that the predicate ‘human’ may be projected in three quite distinct ways, governed by what I call ‘ecological’, ‘biomedical’ and ‘cybernetic’ interests. Which one of these future humanities would claim today’s humans as proper ancestors and could these futures co-habit the same world thus become two important questions that general philosophy of science will need to address in the coming years

Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range