14 research outputs found
Grapevine root growth in relation to water uptake from soil
No full textThesis (M.Ag.Sci) -- University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 199
Long-term annual climate trends around the Breton Plots area, Alberta: is there any evidence of local climate change?
No full textThe objective of this research was to investigate the long-term trends in historical climate variables using the data collected near the classical Breton Plots (Alberta, Canada) and to determine if the data show any evidence of local climate change. The climate data used for the study were obtained from the Alberta Climate Information Service (ACIS) for the years 1901 to 2020. Various parametric statistical analyses were conducted to determine if monotonic trends occurred in the climate variables over time, and the analyses were conducted on the annual data as well as the 30-year climate normals. Large fluctuations in annual climate variables occurred, but a positive linear trend was observed in the average annual and growing season minimum air temperatures over time. Between 1901 and 2020 the annual minimum air temperature average increased at a rate of 0.3The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Xylem anatomy and hydraulic architecture of roots of field-grown grapevines (Vitus vinifera L. cv Shiraz) under two systems of irrigation management
No full textHistoric climate change trends and impacts on crop yields in key agricultural areas of the prairie provinces in Canada: a literature review
No full textThe objective of this literature review was to compile research findings on climate change and its impacts on crop production in Prairie Provinces of Canada. Our search strategy included finding primary literature articles from various databases. Seven articles reported increases in average and minimum air temperature over time in the Prairie Provinces of Canada. Increases in maximum air temperature were smaller than that for minimum air temperature. Growing degree days (GDD) and corn heat units (CHU) also increased over time, which has allowed for potential expansion of corn growth northwards. While overall increases in average annual precipitation and growing season precipitation have occurred in Canada between1900 and 2021, western Canada showed increases in some regions but decreases in others. Off-season precipitation and snow cover duration in Canada have decreased since 1950. The number of frost-free days has increased across Canada, on the Prairies and southern Saskatchewan since 1900. Annual snowfall has decreased since 1950 and across Canada the annual maximum snow depth has also decreased. Overall, studies focusing on the Prairie Provinces in Canada have shown accelerated changes in several climate parameters over time, affecting cropping areas and crop yields.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Water Quality of Surface Runoff from Grazed Fescue Grassland Watersheds in Alberta
No full textAbstract
A study was conducted at Stavely Research Station, Alberta, to determine the quantity and quality of surface runoff from small grassland watersheds under three grazing intensities, viz. ungrazed, heavy grazing (2.4 animal unit months per hectare, AUM ha-1) and very heavy grazing (4.8 AUM ha-1). The volume of surface runoff varied each year (1998, 1999 and 2000) and also differed across watersheds, with lower runoff in the ungrazed compared with the heavy and very heavy grazed watersheds. Total dissolved solids in surface runoff water ranged between 34 to 360 mg L-1, and that for runoff from the very heavy grazed watershed was greater than that from other watersheds. Electrical conductivity increased with increased grazing intensity on the watershed. In two of three years the very heavy grazed watershed had greater nitrate concentrations than the other two watersheds. In all three years the levels of nitrate were lower than the maximum acceptable level for drinking water (10 mg L-1 as nitrogen). Levels of orthophosphate (PO43-) in surface runoff from all three watersheds and the three years of study were less than 1 mg L-1, and mostly within the range considered typical for rivers and streams. Total carbon (up to 500 mg L-1) was greater than the amounts considered typical for streams and rivers, and most of it was organic carbon. Nuisance organisms such as algae, nematodes, Giardia spp., Cryptosporidium spp. and rotifers were detected in some surface runoff samples. However, no crustaceans were detected. The results of a canonical correlation analysis indicated that the dominant external forcing factors (meteorological and management) in influencing water quality were year of study, water temperature and grazing. Surface runoff discharge did not influence water quality measurements. The dominant water quality parameters were found to be total carbon, organic carbon, total dissolved solids and electrical conductivity. Overall, this study indicated that during the three years, the surface runoff volumes from the watersheds were small and grazing of these watersheds posed little risk of nutrient (e.g., nitrate, ammonia and orthophosphate) contamination of adjacent streams, but organic carbon loading and dissolved solids may be of concern. The presence of parasites was detected in two or less runoff water samples each year, and thus pose little risk of contamination of adjacent streams. However, it may be necessary to monitor parasites especially in areas under cow-calf operations.</jats:p
Estimating actual evapotranspiration using water budget and soil water reduction methods
No full text Studies on estimation of actual evapotranspiration on disturbed lands are scarce and yet such data are essential in hydrologic modeling. Our study compared the variability of estimates of actual evapotranspiration (AET) from a reclaimed site in northern Alberta using the simplified water budget (WB) and soil water reduction (SWR) methods. The AET estimates from the simplified water budget equation (AET1) required field soil water content, precipitation and runoff. The AET estimates from the soil water reduction method (AET2) required daily potential evapotranspiration (PET), field capacity (FC) water content, minimum field-measured water content, and field water content. Soil water was measured using neutron moisture gauge every 2 wk during the growing season for a 2-yr period. The average AET1 and AET2 estimates for 2001 were 1.9 and 1.4 mm per day, respectively, where as those for 2002 were 2.1 and 1.2 mm per day, respectively. The paired t-tests to compare AET1 against AET2 indicated significance differences (P ≤ 0.05) in 5 out of 11 measurement dates, especially during high rainfall periods. Overall AET2 estimates were more variable than AET1 estimates. Therefore, the larger variability of AET2 estimates imply less reliability of spatially averaged AET2 estimates for use in regional and global circulation models. Key words: Extractable water, reclaimed land, water budget, soil water reduction, potential evapotranspiration </jats:p
Management impacts on organic carbon under continuous perennial grass, perennial grass-legume mixture, and annual cereals on a thick Black Chernozemic soil
No full textImpacts of annual and perennial pasture management on soil organic carbon (SOC) and equivalent SOC stocks (equal soil mass basis) were investigated in two trials [(CAESA (1994 to 1997) and BMP (2008 to 2012) trials] conducted on the same experimental paddocks at Lacombe, Alberta. The original site was broken from perennial grass in 1992 and the CAESA trial established in 1993. Between 1994 and 1997, half of the paddocks included winter triticale and a mixture of triticale and spring barley; half included smooth and meadow bromegrass; and each paddock was light, medium, or heavily grazed. The BMP trial (2008 to 2012) on the same paddocks included fertilized, direct seeded barley as silage; grazing and haying of unfertilized meadow bromegrass, fertilized meadow bromegrass, and meadow bromegrass and alfalfa mixture; and unfertilized oldgrass that was continuous since 1994. Between trials (1998 to 2007) all paddocks received no fertilizer. In the 0-15 cm depth SOC under oldgrass was constant between 1994 and 2012 and averaged 88 Mg C haThe presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Growth and physiological responses of balansa clover and burr medic to low levels of salinity
No full textThis study investigated a wide range of morphological and physiological responses of burr medic (Medicago polymorpha L. cv. Scimitar) and balansa clover (Trifolium michelianum L. cv. Frontier) to different levels of salinity. Balansa clover and burr medic plants were grown in the greenhouse at 25°C day temperature and 16°C night temperature. Salt treatments were applied 6 weeks after germination, and plants were grown for a further 6 weeks before harvest. The salt treatments included a control, 20 mm, 40 mm, and 80 mm of NaCl. The shoot biomass yield was significantly affected by the species × salt interaction (P = 0.04). For balansa clover, the shoot biomass yield was greatest for the control treatment and lowest for the 20 mm NaCl treatment. For burr medic, the shoot biomass yield did not differ among salt treatments. Sodium (Na+) and potassium (K+) concentrations in leaves and stems increased with salinity. Compared with a non-saline control, sodium concentration in leaves in the 80 mm NaCl treatment was 3-fold higher for balansa clover and 2-fold higher for burr medic. Under various saline treatments, leaf Na+/K+ ratio stayed relatively constant in balansa clover (0.3–0.4) and burr medic (0.4–0.5), whereas stem Na+/K+ ratios for both species increased with salinity. The most sensitive parameters to salinity were Na+/K+ and Na+/Ca2+ ratios, whereas biomass, chlorophyll fluorescence, net photosynthesis, stomatal conductance, transpiration, and δ13C and δ15N discrimination were least sensitive. Therefore, accumulation of sodium in the plant tissues did not reach the threshold for causing reduction in growth
Quantification and simulation of soil water on grazed fescue watersheds
No full textA 2-year study was conducted at the Agriculture and Agri-Food Canada Stavely Range Substation, Alberta. The objective was to quantify and simulate the soil water status of small grassland watersheds under 3 grazing intensities and 4 topographic positions. The grazing treatments were ungrazed (or control), heavy (2.4 AUM ha-1) and very heavy (4.8 AUM ha-1) grazing and the topographic positions were upperslope, midslope, lowerslope and 5 m away from the collector drain. Moisture readings were taken every 2 weeks between spring and fall using a CPN 503 moisture neutron probe. Readings were taken at the soil surface and at 15-, 25-, 35-, 45- and 55-cm depths. Total annual precipitation in 1998 and 1999 was 648 and 399 mm, respectively. In both years grazing treatments did not affect total soil water in the 0-50 cm (TSW50) depth interval for the upper, middle and lower slope positions, but TSW50 close to the collector drain was significantly (P ≤ 0.05) greater for the heavy grazed compared to the very heavy grazed treatment. Within each grazing treatment, TSW50 differences among slope positions occurred mainly under the heavy grazed treatment. Simulation of soil water at each soil depth and watershed was conducted using the Versatile Soil Moisture Budget Model (VB2000). Statistical and graphical evaluations of the model results were conducted using the volumetric soil water data collected for 1998 and 1999. The statistics determined included average error (AE), root mean square (RMS), coefficient of residual mass (CRM), modeling efficiency (EF) and coefficient of determination (CD). All statistics varied with each soil depth and watershed, indicating the transient nature of the data. This is reflected in the mostly negative CRM values, which ranged between -1.0 and 0.16. Overall model fitting to the whole data for all depths, watersheds and years gave values of CRM = -0.08 and EF = 0.19, indicating a slight over-prediction by the model. Spatial variation due to presence of rocks or cracks and averaging across slopes may have partly contributed to the discrepancies between model results and observed data.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202
Is conservation agriculture a climate-smart option for smallholders in sub-Saharan Africa?
No full textSub-Saharan Africa (SSA) faces the challenge of developing a climate-smart agriculture (CSA) that simultaneously ensures food security, mitigation and adaption to climate change (CC). Conservation agriculture (CA) is widely promoted in SSA and is considered as a way to meet these CSA objectives. The objective of the study was to assess whether CA in SSA contributes to the three pillars of CSA, seeking evidence from the peer-reviewed literature that compares the performances of CA and conventional tillage-based (CT) cropping systems. The positive yield responses to CA compared to CT are widely documented in SSA. The positive effects on soil fertility result in increased yield in the long term. Yield impacts in the shorter term are variable and depend to a great extent on the climatic context. CA responds better under low and/or erratic rainfall conditions, mainly due to the mulching effect on soil water conservation. This suggests the potential of CA as a cropping strategy to adapt to more variable rainfall in the future as predicted in many regions of SSA. However, an increase in yield does not necessarily translate into an increase in farm income. The economic impact of CA is highly dependent on the socioeconomic context. The potential of CA to mitigate CC remains unclear. Retention of crop residues as mulch may not always translate into soil carbon sequestration. Further studies on the impact of CA on soils' greenhouse gases emissions are needed. In conclusion, the ability of CA to contribute to CSA is very site- and farm-specific, and lies to a great extent in its capacity of retaining crop residues as mulch on the soil surface. (Texte intégral
