Browsing by Author "Wang, H."
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Item 25 years of tillage effects on wheat production in a continuous cropping system(2007-03-01) Wang, H.; McConkey, B.G.; Peru, M.; Brandt, K.Heat 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.Item Annual crop rooting depth: what do we really know?(2011-03-15) Brandt, K.; Wang, H.; Johnson, E.; Ulrich, D.; Brandt, S.A.Item Can we predict the time of seedling emergence of spring wheat?(2008-02-28) Wang, H.; Cutforth, H.; McCaig, T.; Brandt, T.; Lemke, R.; Goddard, T.; Sprout, C.Item Changes in soil biological and physical properties under reduced tillage systems(1996-02-22) Curtin, D.; McConkey, B.; Biederbeck, V.; Campbell, C.; Schoenau, J.J.; Wang, H.; Lafond, G.; Moulin, A.; Zentner, R.; Brandt, S.Interest in reduced tillage systems has increased in recent years, though important questions remain as to the impacts of such systems on soil quality and nutrient cycling. We examined the effects of tillage on soil biochemical (N and C mineralization, microbial biomass, and light fraction of organic matter) and physical (aggregate stability and size distribution) attributes at seven long-term sites in Saskatchewan, representing a range of soil types and crop rotations. Reduction in tillage increased mineralizable N at most sites, though the effect of tillage was usually not as strong as that of crop rotation (continuous cropping vs. wheat-fallow). Other indicators (microbial biomass N, light fraction N) also provided evidence of improved N fertility under reduced tillage. These findings are in apparent conflict with recent reports that adoption of reduced tillage can reduce N uptake and protein content of wheat. This anomaly remains to be resolved. Wet aggregate stability was improved by reduction in tillage and by elimination of summer fallow on a sandy loam and a silt loam, but treatment effects were small or absent in the heavy textured soils. Aggregate stability increased between spring and fall and decreased during winter. On a sandy loam, where wind erosion was a perennial threat, cropping intensity did not affect the wind-erodible fraction (aggregates < 0.84 mm) but reducing tillage did decrease erodibility of the fallow phase. Data collected between 1982 and 1994 showed that wind erodibility varied considerably from year to year, but there was no discernible relationship with weather or residue amounts from the previous crop.Item A comparison study of geostatistical simulation for predicting soil texture(2011-03-15) He, Y.; Wang, H.; Hu, K.L.; Huang, Y.F.; Li, B.G.; Si, B.; Brandt, K.Item Comparsion of agronomic performance of N fertilizer placement and formulation on wheat, canola, and flax at four sites in Saskatchewan(2006-03-02) Malhi, S.S.; Brandt, S.A.; Hultgreen, G.; Lafond, G.; Lemke, R.; Schoenau, J.J.; Wang, H.Item Cultivar difference in within-spike N remobilization in CWRS wheat(2003-02-18) Wang, H.; McCaig, T.N.; DePauw, R.M.; Clarke, J.M.The objective of the present study was to compare four new CWRS wheat cultivars with two older cultivars, Neepawa and Marquis, in terms of spike dry matter and nitrogen accumulation and within-spike partitioning. Results showed that new cultivars had significantly higher kernel mass and N content per spike than old cultivars, which were mainly attributed to their higher accumulation rates, instead of accumulation duration. N remobilization from glumes occurred during the linear phase of grain filling and new cultivars started remobilizing N earlier and had a higher rates than old cultivars. N remobilization of rachis started later and the rate was smaller than glumes. New cultivars had higher total N remobilization and maximum remobilization rate from rachis than old ones. It seems that cultivars with large sink size had a high rate of accumulation and were able to remobilize more carbohydrates and N into the grains before maturity. Cultivars with small sink size had both relatively low accumulation rate and remobilization rate. Although visual observations showed that Marquis and Neepawa had 1-3 days longer maturity than new cultivars, grain accumulation of carbohydrates and N was minimal during these days because of the severe water stress and/or heat stress.Item Do high-yield and high-protein wheat cultivars use more water?(2000-02-22) Wang, H.; McCaig, T.N.; DePauw, R.M.; Clarke, J.M.Some recently developed wheat cultivars have significantly increased yields, while maintaining or even increasing protein content, relative to earlier cultivars. Such cultivars, which meet the demands of the lucrative quality-conscious world markets, have made a substantial contribution to the value of wheat production in western Canada. In order to understand the physiological basis for these genetic improvements we are conducting a multiyear study. Results of this study could be used by breeders to select new cultivars more efficiently and by producers to improve their soil and crop management. In this report we describe cultivar differences in evapotranspiration (ET) and water use efficiency (WUE) from the experiment in 1998 and 1999 at Swift Current, Saskatchewan.Item Durum – mechanisms of yield and grain protein improvements(2009-02-25) Wang, H.; Clarke, J.M.; McCraig, T.N.; DePauw, R.M.; Brandt, K.Item Dynamics of carbon dioxide evolution from decomposing wheat straw(1997-02-20) Curtin, D.; Selles, F.; Campbell, C.A.; Wang, H.; Biederbeck, V.O.Increasing concentration of CO2 in the atmosphere is a concern because of the potential for global warming. Carbon exchange between soil and the atmosphere has an important role in the global C cycle, but partitioning soil CO2 emissions by source (soil organic matter mineralization, crop residue decomposition, root respiration) is difficult. Our objective was to determine the contribution of decomposing wheat straw to CO2 emissions from a Swinton silt loan under controlled conditions (constant 20°C). Two types of straw (i.e., fresh straw collected shortly after harvest and standing stubble that had ‘weathered’ in the field for a year) were either incorporated or placed on the surface of soil (contained in polythene-lined, wooden boxes 10 cm deep with area of 1363 cm2) at a rate equivalent to 2,800 kg ha-‘. One set of soils was watered every two or three days to 90% of field capacity and a second set was allowed to dry (from 90% field capacity) to permanent wilting point before watering. Emissions of CO2 were measured every two or three days using a vented chamber connected to a portable CO2 analyzer. Within 2 d, incorporation of straw increased CO2 flux from 0.3 to about 1.5 umol CO2 mm2 s-1. Surface straw significantly (P < 0.05) increased fluxes, but the effect was small compared with incorporated straw. Straw type had little effect on emissions. Total CO2-C emitted from continuously moist soil in 77 d was 3.3 g box-’ (no straw added), 5.5 g box-’ when straw was placed on soil surface and 9.6 g box-’ when straw was incorporated. In all, 37% of incorporated straw C and 13% of surface straw C was emitted as CO2. Moisture limitation in soil subjected to moist/dry cycles reduced emissions to 34-59% of those observed under continuously moist conditions. Fluxes from soil with incorporated straw were least sensitive to moisture availability. In the absence of straw, CO2-C emitted during the experiment was about equal to the amount by which light fraction C decreased, suggesting that this labile fraction of organic matter was the main source of respired C.Item Ecosystem modeling: supermodel or coupling approach?(2009-02-25) Wang, H.; Flerchinger, G.N.; Lemke, R.; Brandt, K.; Goddard, T.; Sprout, C.Item The effect of leaf spots on yield and quality of wheat in southern Saskatchewan(2001-02-22) Wang, H.; Fernandez, M.R.; Clarke, F.R.; DePauw, R.M.; Clarke, J.M.Although leaf spots have been reported to have a negative effect on yield and quality, the magnitude of the effect of leaf spots on grain yield and quality of wheat cultivars grown on dryland in southern Saskatchewan is not known. Experiments were conducted at Swift Current (Brown soil) and Indian Head (Black soil) for three years to determine effects of leaf spots on grain yield, kernel weight, test weight and protein concentration of wheat. Two fungicides, Folicur 3.6F and Bravo 500 were applied at different growth stages in order to diversify the severity of leaf spots. Three common wheat (T. aestivum L.) cultivars - AC Domain, Laura and AC Elsa and three durum wheat (T. turgidum L. var durum) cultivars with different levels of leaf spot susceptibility were used in this study. The control of leaf spots by fungicides often did not cause an increase of yield, kernel weight, test weight or grain protein concentration in the drier Prairies where yield potential is relatively low. Fungicide treatments significantly increased yield in only two of six location-years (Folicur applied at head emergence in 1997 (0.07-0.13 t ha-1) (P < 0.05) and Folicur applied at flag emergence and/or head emergence in 1998 (0.41-0.47 t ha-1) (P < 0.001) at Indian Head. Fungicide applications significantly increased kernel weight in only three of six location-years (applications at flag leaf emergence at Swift Current (0.8-1.1 mg) (P < 0.05) and Indian Head (1.8-2.0 mg) (P < 0.001) in 1998 and at Indian Head in 1999 (10-1.1 mg) (P < 0.01). An increase of grain protein concentration was only found in treatments of Bravo applications at Indian Head in 1998 (0.3-0.7%) (P < 0.001). It seems that the control of leaf spots tended to have higher effect on yield and quality at Indian Head than Swift Current, it could be attributed to better controls of leaf spots at early milk stage (P < 0.001) and/or higher yield potential at Indian Head (P < 0.001). Although the cultivars used in this study have different leaf spot susceptibility (P < 0.001), there were no consistent cultivar differences in the effectiveness of the fungicides on control of leaf spots and on the yield, kernel weight and other quality characteristics. Leaf spots are a common and potentially severe foliar disease of wheat. Many studies have reported that leaf spots have a negative effect on grain yield (Eyal and Ziv, 1974; King, et al., 1983; McKendry and Henke, 1994), test weight (Milus, 1994) and milling quality (Mckendry et al., 1995), especially under environments favorable for the development of leaf spots or under intensive management such as irrigation (Duczek and Jones-Flory, 1994) and high N fertilizer rates (Howard, et al., 1994). In the past decade there has been an increase in the incidence of leaf spotting diseases of wheat in southern Saskatchewan, Canada. These are attributed mainly to Pyrenophora tritici-repentis (tan spot), Septoria nodorum and S. tritici (septoria leaf blotch complex) and all current spring wheat cultivars are susceptible to this disease complex - 333 - (Fernandez, et al., 1996; Fernandez, et al., 1998). Consequently there is increased pressure on producers to chemically control diseases that might affect yield and quality. The magnitude of the impact of leaf spots on grain yield and quality of wheat cultivars grown on dryland in this area, however, is not known. Research on these issues is therefore necessary to provide informed guidelines for use by producers. The objective of this study was to determine the effect of leaf spots on grain yield, kernel weight, test weight and protein concentration of spring common (T. aestivum L.) and durum (T. turgidum L. var durum) wheat in southern Saskatchewan.Item The effect of leaf spots on yield and quality of wheat in southern Saskatchewan(2001-02-22) Wang, H.; Fernandez, M.R.; Clarke, F.R.; DePauw, R.M.; Clarke, J.M.Although leaf spots have been reported to have a negative effect on yield and quality, the magnitude of the effect of leaf spots on grain yield and quality of wheat cultivars grown on dryland in southern Saskatchewan is not known. Experiments were conducted at Swift Current (Brown soil) and Indian Head (Black soil) for three years to determine effects of leaf spots on grain yield, kernel weight, test weight and protein concentration of wheat. Two fungicides, Folicur 3.6F and Bravo 500 were applied at different growth stages in order to diversify the severity of leaf spots. Three common wheat (T. aestivum L.) cultivars - AC Domain, Laura and AC Elsa and three durum wheat (T. turgidum L. var durum) cultivars with different levels of leaf spot susceptibility were used in this study. The control of leaf spots by fungicides often did not cause an increase of yield, kernel weight, test weight or grain protein concentration in the drier Prairies where yield potential is relatively low. Fungicide treatments significantly increased yield in only two of six location-years (Folicur applied at head emergence in 1997 (0.07-0.13 t ha-1) (P < 0.05) and Folicur applied at flag emergence and/or head emergence in 1998 (0.41-0.47 t ha-1) (P < 0.001) at Indian Head. Fungicide applications significantly increased kernel weight in only three of six location-years (applications at flag leaf emergence at Swift Current (0.8-1.1 mg) (P < 0.05) and Indian Head (1.8-2.0 mg) (P < 0.001) in 1998 and at Indian Head in 1999 (10-1.1 mg) (P < 0.01). An increase of grain protein concentration was only found in treatments of Bravo applications at Indian Head in 1998 (0.3-0.7%) (P < 0.001). It seems that the control of leaf spots tended to have higher effect on yield and quality at Indian Head than Swift Current, it could be attributed to better controls of leaf spots at early milk stage (P < 0.001) and/or higher yield potential at Indian Head (P < 0.001). Although the cultivars used in this study have different leaf spot susceptibility (P < 0.001), there were no consistent cultivar differences in the effectiveness of the fungicides on control of leaf spots and on the yield, kernel weight and other quality characteristics. Leaf spots are a common and potentially severe foliar disease of wheat. Many studies have reported that leaf spots have a negative effect on grain yield (Eyal and Ziv, 1974; King, et al., 1983; McKendry and Henke, 1994), test weight (Milus, 1994) and milling quality (Mckendry et al., 1995), especially under environments favorable for the development of leaf spots or under intensive management such as irrigation (Duczek and Jones-Flory, 1994) and high N fertilizer rates (Howard, et al., 1994). In the past decade there has been an increase in the incidence of leaf spotting diseases of wheat in southern Saskatchewan, Canada. These are attributed mainly to Pyrenophora tritici-repentis (tan spot), Septoria nodorum and S. tritici (septoria leaf blotch complex) and all current spring wheat cultivars are susceptible to this disease complex - 333 - (Fernandez, et al., 1996; Fernandez, et al., 1998). Consequently there is increased pressure on producers to chemically control diseases that might affect yield and quality. The magnitude of the impact of leaf spots on grain yield and quality of wheat cultivars grown on dryland in this area, however, is not known. Research on these issues is therefore necessary to provide informed guidelines for use by producers. The objective of this study was to determine the effect of leaf spots on grain yield, kernel weight, test weight and protein concentration of spring common (T. aestivum L.) and durum (T. turgidum L. var durum) wheat in southern Saskatchewan.Item The effect of N fertilizer placement, formulation, timing, and rate on the agronomic performance in wheat(2003-02-18) Wang, H.; Lemke, R.; Hahn, D.L.Increasing the efficiency of nitrogen fertilizer uptake by crops improves the agronomic, economic, and environmental value of fertilizer N. Band placement of urea below the soil surface increased recovery of N in plants in both conventional and no-tillage systems. The latter systems require all fertilizers be applied before or during the seeding operation. In order to avoid seedling damage caused by fertilizer, side banding and mid-row banding opener systems have been developed to separate the seed and fertilizer. The objective of this study was to compare the agronomic performance in wheat between side banding and mid-row banding N fertilization and estimate effects of fertilizer formulation, timing and rate in an Orthic Brown Chernozem. A three-year experiment (2000-2002) was conducted near Swift Current in the Brown Soil Zone (Swinton silt loam, Orthic Brown Chernozem) of southern Saskatchewan. Seventeen treatments were arranged in a randomized complete block design in four replications with plot size of 3 m × 9.2 m. A Canada Western Red Spring wheat, AC Barrie, was seeded on a no-tillage management. Results showed that the environment had a major impact on the grain yield and biomass production. In general, the difference in agronomic performance between side banding and mid-row banding treatments was small.Item Estimating the AM fungal resources of wheat fields(2012-03-13) Dai, M.; Sheng, M.; Bremer, E.; He, Y.; Wang, H.; Hamel, C.The arbuscular mycorrhizal (AM) fungi are a taxonomic group of microscopic soil dwellers generally promoting the growth of most plant species, including wheat, by mobilizing soil minerals, in particular soil P. Despite the importance of the AM fungi for plant nutrition, no technology exists to identify the fields in which AM fungi are doing a good job with feeding P to crops and the fields where agronomic interventions are required. We set out to fill this gap and examined 225 commercial fields in 2007, 2009 and 2010. We first found that P yields were limited by P supply rates below 3.5 μg P 10 cm-2 day-1. Fifty seven percent of the organic fields surveyed were below this threshold. A trend for higher P use efficiency in organic than conventional wheat crops at low soil P fertility levels was concurrent with higher levels of AM root colonization. The AM fungal communities of soils were simpler than expected. Some 122 phylotypes were found, but only ten of these accounted for over half of the AM fungal DNA sequences encountered. The main drivers of AM fungal diversity varied with the species of AM fungi. Among all the variables considered, soil organic matter level and soil texture were most often significantly correlated with the relative abundance of the different AM fungi. The research results suggest the possibility of using simple regression models to estimate the quality of soil AM fungal communities invisible to the naked eye. It appears that national databases on soils and climate, and soil analyses using PRS™-probe can be used to develop cost effective tools allowing the management of nutrient efficient wheat production systems based on ecological principles.Item Estimation of daily soil CO2 emission using instantaneous measurements(2010-02-25) Wang, H.; McConkey, B.; Curtin, D.; Cutforth, H.; Brandt, K.Item Evaluation of the CENTURY model with laboratory measured soil respiration(2001-02-22) Wang, H.; Curtin, D.; Jame, Y.W.; McConkey, B.G.; Zhou, H.F.The CENTURY model is widely used in assessing the effect of management on soil C dynamics. However, recent testing of the model revealed that it performed unsatisfactorily in simulating soil C changes in southwestern Saskatchewan, suggesting that the model may need further testings and modifications. Evaluations of the model were made with measurements conducted in an laboratory experiment which included different straw placements (incorporated in the soil and applied on the soil surface) and soil water regimes (continuously moist and moist-dry). Results from model testing revealed some weaknesses of the model and modifications were made to improve model performance. The temperature function was modified to slightly increase the relative decomposition rate when temperatures were below the reference temperature. The moisture function was modified to reduce the relative decomposition rate when the soil moisture was very low. The modified model also assumed that soil mineral N is readily available for the use of decomposition of soil C pools, but only about 6.6 mg m-2 d-1 of soil N is available for C pools on the soil surface. When N availability is less than that required for maximum decomposition rates of soil or surface pools, decomposition rates of these pools were reduced until supply met demand. The modified model improved simulations of daily C fluxes, cumulative CO2 emissions and soil mineral N. To use this modified model for estimating soil respiration in the field, further studies on the N availability for soil surface C pools and the dryness of surface-placed residue are needed. The concentration of CO2 in the atmosphere has increased by about 25% since the beginning of the industrial revolution. There are concerns that continuing increases in levels of CO2 and other greenhouse gases will contribute to global warming. Soils contains about three times as much C as the atmosphere, and they have the potential to store additional C (Campbell and Zentner, 1993). Agricultural soils on the Canadian prairies contain about 3 Pg soil organic carbon (SOC) in the top 30 cm layer, which is about 20 times the amount of CO2-C emitted annually by fossil fuel combustion in Canada. Research shows that if properly managed agricultural lands could be an important sink for C. Management options to enhance C storage in Canadian prairie soils include: decreasing summer fallow frequency, reducing tillage, including legumes in crop rotations, proper fertilization, and growing forage and trees on marginal lands (Campbell and Zentner, 1993; Campbell et al., 1995). For example, reduction in tillage intensity, especially no-tillage (NT) cropping, has been shown to increase SOC at various locations (Janzen, et al. 1998). Although changes in SOC occur when soil management practices are altered (Mann, 1986), it is common for these changes to remain undetectable for 10 or 20 years. The reason is that because of the inherent spatial variability of SOC in the field, too many samples are required to be taken to ensure that small differences can be statistically separated (Campbell et al., 1976; Campbell et al., 2000). Thus, we often use a process-based simulation model that describes soil organic matter turnover and nitrogen cycling dynamics in soils to estimate management induced SOC changes. The CENTURY model (Parton et al., 1987) is one of such models that is the most widely used and has been extensively evaluated in various ecosystems (Scholes et al., 1997). However, the recent testing of the CENTURY model revealed that it performed unsatisfactorily in simulating soil C changes in a 30-yr crop rotation experiment in southwestern Saskatchewan (Campbell et al., 1999), suggesting that the model may need further testings and modifications for use on the Canadian prairies. Because of the problems associated with SOC measurement and the variability of environmental conditions in the field, it is difficult to rigorously test the mechanism of a process-based soil organic matter model. Alternatively, the model can be readily tested against measurements of CO2 emissions from a controlled laboratory experiment. The objectives of this study were thus: (1) to test the validity of the CENTURY model with the soil respiration measured from laboratory experiments and (2) to address the weaknesses revealed during the model testings by modifying the model.Item Evaluation of the EUROSEM model for predicting water erosion on steeplands in the Three Gorges Reservoir areas, China(2003-02-18) Wang, H.; Cai, Q.; Zhu, Y.Because of the construction of the Three Gorges Dam in China, many farmers in the Three Gorges Reservoir areas will resettle in surrounding mountain areas and have to cultivate deep slopelands. Hence, a tool for assessing the risk of soil erosion, predicting runoff and erosion rates, and designing and evaluating the soil protection strategies in this area is needed. The European Soil Erosion Model (EUROSEM), a process-based model simulating erosion on an event basis for fields and small catchments, was tested using data from an experiment on steeplands in the Three Gorges Reservoir areas. This experiment included treatments of uncultivated slope, cultivated slope, hedgerows and fertilized-hedgerows. Results showed that EUROSEM predicted runoff reasonably well. It could be used to determine soil erosion in steeplands, especially for assessing the impact of land use change.Item Genotype difference in kernel discolorations in CWRS and CWAD wheats(2003-02-18) Wang, H.; Fernandez, M.R.; McCaig, T.N.; Gan, Y.T.; DePauw, R.M.; Clarke, J.M.Kernel discolorations of wheat, such as black point (including smudge and penetrated smudge), red smudge and Fusarium-damaged kernel (FDK), are important downgrading factors in western Canada. This study was undertaken to determine cultivar differences in incidences of these kernel discolorations and their downgrading effects in CWRS and CWAD wheats. Grain samples were taken at maturity from six CWRS and four CWAD cultivars in a four-year (1997-2000) field study at six sites: one in the Grey soil zone, two in the Brown soil zone and three in the Black soil zone in western Canada. For CWRS cultivars, Garnet tended to have lower incidences in black point, smudge and FDK and resulted in the least downgrading compared with other CWRS cultivars. For CWAD cultivars, Kyle tended to have lower incidence of black point, Plenty had less smudge caused downgrading effects, DT 369 had lower penetrated smudge incidence, but higher red smudge incidence, and Plenty tended to have severer FDK-caused downgrading effects compared with other CWAD cultivars. CWAD class had higher frequency of downgrading than CWRS class and it usually had higher incidences of all kernel discolorations (black point, smudge, penetrated smudge, red smudge and FDK) and greater downgrading effects than CWRS class.Item A global sensitivity analysis of DNDC model using a Bayesian based approach(2010-02-24) Qin, X.; Wang, H.; Li, Y.; Brandt, K.This study was aimed at demonstrate the application of the Bayesian based global sensitivity analysis (GSA) approach to denitrification and decomposition (DNDC) model using the tool of Gaussian emulation machine for sensitivity analysis (GEM-SA), in order to provide information on the relative effect of parameters on major model outputs. To execute the GSA study, twenty-eight input parameters were selected and eighty-six years’ DNDC simulation was run on basis of Three Hill’s spring wheat system. Three interested multi-year’s model outputs were chosen, whose sensitivity to inputs has been tested: yield, annual change in soil organic carbon (dSOC) and N2O flux. We found the effect of input parameters on three mentioned DNDC outputs not vary only with different simulated year but also with specific output variable. Moreover, the influence of inputs on variance of outputs varies with the form of sensitivity indices, i.e. main effects (individual contribution of each input to variance of model output) or total effects (when all inputs’ interactions are considered). Consequently, multi year’s SA is necessary for the nonlinear DNDC model and most sensitive parameters to specific output should be focused on further validation and calibration of that variable.