52 research outputs found
Climate change in the semiarid prairie of southwestern Saskatchewan: Temperature, precipitation, wind, and incoming solar energy
No full text Long-term weather data were analyzed to study annual as well as seasonal climate change within an approximately 15 000-km2 area in the semiarid prairie near Swift Current, SK. The climate of the study region has changed over the past 50 yr. Annually, average maximum (Tmx) and minimum (Tmn) air temperatures have increased – rainfall amounts and the number of rainfall events (≥0.5 mm) have increased since the late 1960s-early 1970s; incoming solar energy has decreased, and wind speed has decreased since the early 1970s. Seasonally, for January through April (JFMA), both Tmx and Tmn have increased, the number of rainfall events has increased since the early 1970s, snowfall amounts and the number of snowfall events (≥0.5 cm) have decreased; the number of precipitation events (≥0.5 mm) has decreased, incoming solar energy has decreased, and wind speed has decreased since the early 1970s. For May through August (MJJA), Tmn has increased, incoming solar energy has decreased, and wind speed has decreased since the mid-1970s. For September through December (SOND), the number of rainfall events has increased since the early 1970s and wind speed has decreased. Since 1950, JFMA has become drier and, relative to JFMA, SOND has become wetter. Generally, JFMA has experienced the largest change in climate, whereas SOND has experienced the least climate change. Precipitation amounts and events were negatively correlated with increasing Tmx, suggesting a future decrease in precipitation amounts for southwestern Saskatchewan if global warming continues. Key words: Climate change, semiarid prairie, temperature, precipitation, wind, solar energy </jats:p
Yield and water use of paired-row versus equidistant-row seeded spring wheat in a semiarid environment
No full text A field study was carried out to determine the effects of seed row configuration on days to maturity, water use and grain yield of spring wheat (Triticum aestivum L. ’Leader’) grown in a semiarid environment. From 1986 to 1989, Leader spring wheat was seeded at Swift Current, Saskatchewan in north-south equidistant-rows (25-cm row spacing) and paired-rows (two rows 10 cm apart with 50 cm between the centre of each paired row). Seed and fertilizer were applied at recommended rates for the Brown soil zone. There were no significant differences (P > 0.10) in grain yield, water use or days to maturity between equidistant-row and paired-row seeding. The data suggest that under the environmental conditions of the Brown soil zone paired-row seeding may have no agronomic advantage over equidistant-row seeding.Key words: Paired-row seeding, water use, grain yield, spring wheat </jats:p
Crop growth models for decision support systems
No full text Studies on crop production are traditionally carried out by using conventional experience-based agronomic research, in which crop production functions were derived from statistical analysis without referring to the underlying biological or physical principles involved. The weaknesses and disadvantages of this approach and the need for greater in-depth analysis have long been recognized. Recently, application of the knowledge-based systems approach to agricultural management has been gaining popularity because of our expanding knowledge of processes that are involved in the growth of plants, coupled with the availability of inexpensive and powerful computers. The systems approach makes use of dynamic simulation models of crop growth and of cropping systems. In the most satisfactory crop growth models, current knowledge of plant growth and development from various disciplines, such as crop physiology, agrometeorology, soil science and agronomy, is integrated in a consistent, quantitative and process-oriented manner. After proper validation, the models are used to predict crop responses to different environments that are either the result of global change or induced by agricultural management and to test alternative crop management options.Computerized decision support systems for field-level crop management are now available. The decision support systems for agrotechnology transfer (DSSAT) allows users to combine the technical knowledge contained in crop growth models with economic considerations and environmental impact evaluations to facilitate economic analysis and risk assessment of farming enterprises. Thus, DSSAT is a valuable tool to aid the development of a viable and sustainable agricultural industry. The development and validation of crop models can improve our understanding of the underlying processes, pinpoint where our understanding is inadequate, and, hence, support strategic agricultural research. The knowledge-based systems approach offers great potential to expand our ability to make good agricultural management decisions, not only for the current climatic variability, but for the anticipated climatic changes of the future. Key words: Simulation, crop growth, development, management strategy </jats:p
Determination of the water use and water use response of canola to solar radiation and temperature by using heat balance stem flow gauges
No full text Sap flow gauges using a heat balance have been reliable for measuring real-time transpiration in a number of crops. However, information on the accuracy of sap flow gauges in canola is lacking. Therefore, a study was conducted to validate the sap flow system in canola and to observe sap flow response to variations in temperature and solar radiation. There were strong relationships between sap flow measured with sap flow gauges and actual transpiration measured by the gravimetric method over short periods of 1 h (r2 = 0.93 and RMSE = 2.34 g h-1), and over longer periods of 1 d (r2 = 0.83 and RMSE = 48 g d-1), although sap flow slightly overestimated transpiration. In both cases the slope was not significantly different from 1. Water use in canola, estimated with sap flow gauges or from actual transpiration measurement, was dependent upon temperature (r2 = 0.94 to 0.96). Water use increased until daytime temperatures reached 36°C, after which water use decreased. Sap flow followed solar radiation trends in the field. Heat is lost or dissipated from the gauges convectively as the sap flows through the stem, conductively through the solid stem material, and radially into the surrounding air. As the convective proportion of the heat loss from the gauge increased, the accuracy of the water use estimation using the sap flow gauges increased. For sunny days, convective heat loss through sap flow accounted for a major portion of the total heat input to the gauges, while on cloudy days radial heat loss from the gauges accounted for a major portion of the heat input. Thus, at low sap flow rates during cloudy days, the possibility of error in the sap flow system was high. Overall, sap flow in canola was strongly related to daily solar radiation (r2 = 0.92). The sensitive response to weather variations and the possibility of improving the accuracy at high flow rates in the field makes the use of sap flow gauges a viable option for measuring real-time transpiration in canola. Key words: Brassica napus, canola, heat balance, sap flow, transpiration, temperature, solar radiation </jats:p
Stubble height effects on microclimate, yield and water use efficiency of spring wheat grown in a semiarid climate on the Canadian prairies
No full text In the semiarid region of the western Canadian prairies, seeding directly into standing cereal stubble is gaining popularity. This four year study was conducted at Swift Current, SK, to determine how seeding into tall (>30 cm high), short (about 15 cm high) and cultivated cereal stubble altered the microclimate thereby affecting the growth and yield of hard red spring wheat (Triticum aestivum L.). The treatments were deployed immediately before seeding on plots that had overwintered with tall stubble. Seeding wheat into tall stubble increased grain yield and water use efficiency by about 12% compared to wheat seeded into cultivated stubble. Yield and water use efficiency for wheat seeded into short stubble were intermediate to the other stubble treatments. As well, wheat seeded into tall stubble grew taller than wheat seeded into the cultivated stubble. Further, there was a tendency for spring wheat grown in tall stubble to produce more dry matter and more leaf area, to have a lower proportion of dry matter as leaves and a higher proportion as stems, and to have a lower harvest index than the other treatments.Growing season evapotranspiration (ET) was not affected by stubble height. When the seedlings were small, compared to cultivated stubble, tall stubble altered the microclimate near the soil surface by reducing the daily average windspeed, soil temperature, and incoming solar radiation, and increasing the reflected solar radiation. Throughout much of the growing season, potential ET at the soil surface, measured with minilysimeters, was significantly lower in the tall stubble. Tall stubble, compared to cultivated stubble, increased the proportion of ET that was transpired by the wheat. As well, reduced windspeeds and increased photosynthetic area may have increased the efficiency of net carbon assimilation. To increase grain yields, producers in the semiarid prairies who direct-seed spring wheat are advised to seed into stubble left standing as tall as practical (at least 30 cm). Key words: Standing stubble, wheat, microclimate, water use, yield </jats:p
Sward age and weather effects on alfalfa yield at a semi-arid location in southwestern Saskatchewan
No full text Alfalfa (Medicago sativa L.) yield in the first and second years after establishment is typically much greater than yield in subsequent years under dryland production systems in semiarid regions. Alfalfa is a deep-rooted perennial that uses soil water stored at soil depths below the reach of shallow-rooted cereals and grasses. Since alfalfa yield is positively related to evapotranspiration, this study was conducted to determine the relationship between historical alfalfa yield data and weather variables as affected by sward age. Rambler alfalfa yields collated by sward age during cultivar yield trials from 1951 to 1994 at Swift Current, Saskatchewan, were statistically related to monthly precipitation (April to August) and monthly pan evaporation (May to September) during the growing season, and to the fall and winter total precipitation (September to March). One-year-old swards yielded more than 3-, 4- or 5-yr-old swards. For 1- and 2-yr-old alfalfa swards, weather accounted for 50% and 47% of the yield variability, respectively. However, weather accounted for 85, 87 and 96%, respectively, for 3-, 4- and 5-yr-old swards. We hypothesize that soil water stored deep in the profile accounted for much of the remaining yield variability in one and two year old swards. Researchers must measure soil water use from soil depths to at least 3 m when assessing dryland alfalfa yields. Key words: Medicago sativa L., weather, modelling, forage yield </jats:p
PREDICTION OF CROP YIELDS ACROSS FOUR CLIMATE ZONES IN GERMANY: AN ARTIFICIAL NEURAL NETWORK APPROACH
No full textThis paper shows the ability of artificial neural network technology to be used for the approximation and prediction of crop yields at rural district and federal state scales in different climate zones based on reported daily weather data. The method may later be used to construct regional time series of agricultural output under climate change, based on the highly resolved output of the global circulation models and regional models. Three 30-year combined historical data sets of rural district yields (oats, spring barley and silage maize), daily temperatures (mean, maximum, dewpoint) and precipitation were constructed. They were used with artificial neural network technology to investigate, simulate and predict historical time series of crop yields in four climate zones of Germany. Final neural networks, trained with data sets of three climate zones and tested against an independent northern zone, have high predictive power (0.83global change, agriculture, artificial neural networks, yield prediction
Effect of temperature, vernalization and water stress on phyllochron and final main-stem leaf number of HY320 and Neepawa spring wheats
No full text An understanding of the effect of environment on leaf growth is needed to accurately simulate phenological development of a cereal crop. This study was conducted to determine the effect of temperature, cold (vernalization) and water stress on the phyllochron (degree-days leaf−1) prior to the terminal spikelet stage and on the final leaf number produced by the main stem (FLN) of two spring wheat varieties (Triticum aestivum L.), Neepawa and HY320, grown on the Canadian prairies. Within each of five day/night temperature regimes (30/25 °C, 24/19 °C, 21/12 °C, 16/7 °C and 7/2 °C, with means of 28 °C, 22 °C, 18 °C, 13 °C and 5 °C, respectively), the varieties were grown under two cold (not vernalized and vernalized) and two water (wet and dry) treatments. Within a given temperature regime, both varieties responded similarly to the cold treatments. Vernalization reduced phyllochron and FLN in all but the lowest temperature regime, where phyllochron increased and FLN was unaffected. When effective, severe water stress increased phyllochron and decreased FLN. HY320 was relatively more affected by vernalization and less affected by severe water stress than Neepawa. For both varieties, phyllochron was curvilinearly related to temperature and increased as temperature increased. The relationships were noticeably altered by vernalization and severe water stress. When not vernalized, FLN for HY320 increased as temperature increased; FLN for Neepawa reached a maximum at 20 °C. When vernalized, FLN was independent of temperature under optimum water; the reduction of FLN by severe water stress increased as temperature increased. The results of this study suggest that the effect of environmental change on both phyllochron and FLN must be accounted for when accurate and reliable modelling of the early development of spring wheat is required.Key words: Spring wheat, phyllochron, leaf number, temperature, water stress, vernalization </jats:p
Effect of fallow frequency on soil water conservation in the semi-arid region of Saskatchewan
No full textNon-Peer ReviewedThe effects of fallow frequency on soil water conservation were quantified for a 40 yr
(1967-2006) field experiment conducted on a medium textured Orthic Brown Chernozem (Aridic Haploboroll) in semiarid southwestern Saskatchewan, in which soil water contents were measured each year in early spring, shortly after harvest, and again just prior to freeze-up in the fall. The three treatments examined were continuous wheat (Triticum aestivum L.) (Cont W) and fallow-wheat (F-W), each receiving N and P fertilizer and Cont W receiving only P. On average, 36 % of the precipitation received during the fall and winter months for Cont W (N+P) was conserved in the soil. In the summer fallow system (F-W (N+P)) a greater proportion (42 %) of the precipitation was conserved during the first fall and winter. During the second overwinter period, only 6 % of the precipitation received was conserved in the F-W system compared to 44 % in the first overwinter period. Compared to the 36% of fall and wither precipitation conserved in Cont W (N+P), inadequate N fertility (Cont W (+P)) resulted in only 27 % of the precipitation being conserved during this period. We developed equations that will allow estimation of water conserved as a function of precipitation received between harvest and seeding for F-W and Cont W (N+P. Trends in grain yield were fairly closely correlated with growing season precipitation and potential evapotranspiration
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