Representative sampling size and number of required samples for soil testing in direct seeding fields

Non-Peer ReviewedDirect seeding is widely utilized in the southern Canadian prairies. The associated band application of fertilizers makes conventional soil testing problematic. Strip sampling was suggested in direct seeding fields, but little is known about the optimum strip length. The objective of this study was (1) to identify the representative sampling size (RSS) of a sampling strip and (2) to determine the number of required samples (NRS) in a field in terms of point-based random sampling. Soil samples of 0-10 cm and 10-20 cm were collected from two 10 acre farm fields near Central Butte in the Brown soil zone of Saskatchewan. For strip sampling, five 160 cm long and 10 cm wide sampling strips were selected in these two fields. Different samples with sampling lengths ranging from 5 cm to 155 cm were obtained. For random sampling, 30 and 45 samples using a 4 cm diameter tubular probe were collected in these two fields. The results showed that RSSs differed with fields, nutrient types and soil layers. On average, the RSSs were 60 cm, 65 cm and 35 cm, respectively for testing NO3--N, NH4+-N and extractable P. The NRSs differed with sampling fields but not with nutrient types and soil layers. With a confidence level of 95%, about 30 and 80 random samples are needed in these two fields, respectively, to achieve mean estimate of soil nutrients with a relative error of 10%. This study provided a reference of soil sampling for soil nutrient tests in direct seeding fields

Simulated Productivity Lost by Erosion (SimPLE): model development, validation, and use

Non-Peer ReviewedProductivity lost due to soil erosion can be estimated by existing computer simulation models such as EPIC, NTRM and CENTURY. However, these models require extensive input data and, to date, have had limited success in simulating Western Canadian conditions. The objective of this study was to develop a simple spring wheat model which captured the essential relationships between topsoil erosion and productivity loss in Chemozemic soils. Key relationships in our model describe: (i) how plants create yield from water, N, and P; (ii) how the soil provides these nutrients, and (iii) how erosion impacts on the supply of each nutrient. These relationships were logically connected using the Stella® II modeling environment. Agreement was highly significant (r = 0.55***) between predicted and observed grain yields over 75 site years at Indian Head, Saskatchewan. Also, grain yields from scalped Chemozemic soils in Alberta were closely simulated (r = 0.86****) by SimPLE. Fifty representative soil profiles from the Brown, Dark Brown and Black soil zones were eroded in SimPLE to numerically describe the production lost under wet, normal, and dry scenarios, with and without optimum fertilizer. Yield loss, as a percentage of non-eroded yield, increased with increasing soil erosion following a trend very similar to that reported in field studies. SimPLE is flexible and can be used for analysis of "what if' management scenarios or calculating soil loss tolerance (T) values

An evaluation of soil water use efficiency for different seeding row spacing and stubble height

Non-Peer Reviewe

Post-emergence application of liquid swine manure in east central Saskatchewan

Non-Peer ReviewedIn early 1997, the Prairie Protein Action Committee was established and one of its objectives was to identify ways to meet the increasing demand for wheat with specific protein quality and quantity (Fowler et al. 1998). The main areas of concern were low protein levels in western Canadian wheat and increased competition on the world market for high protein wheat. To address these concerns, one of the objectives was to identify research needs relating to the production and management of wheat protein. Protein quality can be enhanced by genetic improvement or by N fertility management. Among the main objectives in plant breeding programs are the need to increase yield and protein. However, the two traits have generally been found to be negatively related. This negative relationship may be as a result of dilution of the protein concentration as carbohydrates in the endosperm increase with yield. Thus, genetic improvement may have a small contribution toward enhancement of protein content in wheat. Hucl et al. (1998) found that less than 3% of variations in protein concentration in spring wheat was due to genetic variation, whereas over 80% of the variation was due to environmental effects, which include N fertility. Campbell et al. (1997) noted that in the Brown soil zone of Saskatchewan, 18% of the protein variation was due to N fertility. Within a cultivar, up to 99% of the variability in grain protein could be due to soil N variability (Fowler 1986). Hence, N fertility management is key to improving protein quality in wheat. Livestock manure application as a N source to boost yield and protein of wheat offers an alternative to chemical N fertilizers. There is opportunity to enhance protein levels in cereals and achieve protein premiums by delaying manure application and applying it post-emergent to cereals. Delayed manure application also helps widen the window of application and reduce manure application costs. Hence, the objective of this study was to determine the effects of low disturbance, post-emergent liquid swine manure injection on wheat protein and yield in east central Saskatchewan. This paper presents the results of the first two years of this three year study

The structure of Chariklo's rings from stellar occultations

Two narrow and dense rings (called C1R and C2R) were discovered around the Centaur object (10199) Chariklo during a stellar occultation observed on 2013 June 3. Following this discovery, we planned observations of several occultations by Chariklo's system in order to better characterize the physical properties of the ring and main body. Here, we use 12 successful occulations by Chariklo observed between 2014 and 2016. They provide ring profiles (physical width, opacity, edge structure) and constraints on the radii and pole position. Our new observations are currently consistent with the circular ring solution and pole position, to within the $\pm 3.3$ km formal uncertainty for the ring radii derived by Braga-Ribas et al. The six resolved C1R profiles reveal significant width variations from $\sim 5$ to 7.5 km. The width of the fainter ring C2R is less constrained, and may vary between 0.1 and 1 km. The inner and outer edges of C1R are consistent with infinitely sharp boundaries, with typical upper limits of one kilometer for the transition zone between the ring and empty space. No constraint on the sharpness of C2R's edges is available. A 1$\sigma$ upper limit of $\sim 20$ m is derived for the equivalent width of narrow (physical width <4 km) rings up to distances of 12,000 km, counted in the ring plane

Modifiable risk factors associated with bone deficits in childhood cancer survivors

<p>Abstract</p> <p>Background</p> <p>To determine the prevalence and severity of bone deficits in a cohort of childhood cancer survivors (CCS) compared to a healthy sibling control group, and the modifiable factors associated with bone deficits in CCS.</p> <p>Methods</p> <p>Cross-sectional study of bone health in 319 CCS and 208 healthy sibling controls. Bone mineral density (BMD) was measured by dual-energy x-ray absorptiometry (DXA). Generalized estimating equations were used to compare measures between CCS and controls. Among CCS, multivariable logistic regression was used to evaluate odds ratios for BMD Z-score ≤ -1.</p> <p>Results</p> <p>All subjects were younger than 18 years of age. Average time since treatment was 10.1 years (range 4.3 - 17.8 years). CCS were 3.3 times more likely to have whole body BMD Z-score ≤ -1 than controls (95% CI: 1.4-7.8; p = 0.007) and 1.7 times more likely to have lumbar spine BMD Z-score ≤ -1 than controls (95% CI: 1.0-2.7; p = 0.03). Among CCS, hypogonadism, lower lean body mass, higher daily television/computer screen time, lower physical activity, and higher inflammatory marker IL-6, increased the odds of having a BMD Z-score ≤ -1.</p> <p>Conclusions</p> <p>CCS, less than 18 years of age, have bone deficits compared to a healthy control group. Sedentary lifestyle and inflammation may play a role in bone deficits in CCS. Counseling CCS and their caretakers on decreasing television/computer screen time and increasing activity may improve bone health.</p

Imaging of the Muscle-Bone Relationship

Muscle can be assessed by imaging techniques according to its size (as thickness, area, volume, or alternatively, as a mass) and architecture (fiber length and pennation angle), with values used as an anthropometric measure or a surrogate for force production. Similarly, the size of the bone (as area or volume) can be imaged using MRI or pQCT, although typically bone mineral mass is reported. Bone imaging measures of mineral density, size, and geometry can also be combined to calculate bone’s structural strength—measures being highly predictive of bone’s failure load ex vivo. Imaging of muscle-bone relationships can, hence, be accomplished through a number of approaches by adoption and comparison of these different muscle and bone parameters, dependent on the research question under investigation. These approaches have revealed evidence of direct, mechanical muscle-bone interactions independent of allometric associations. They have led to important information on bone mechanoadaptation and the influence of muscular action on bone, in addition to influences of age, gender, exercise, and disuse on muscle-bone relationships. Such analyses have also produced promising diagnostic tools for clinical use, such as identification of primary, disuse-induced, and secondary osteoporosis and estimation of bone safety factors. Standardization of muscle-bone imaging methods is required to permit more reliable comparisons between studies and differing imaging modes, and in particular to aid adoption of these methods into widespread clinical practice