Agriculture and Agri-Food Canada 1Brandon Research Centre, Brandon, MB, Canada R7A 5Y3; 2Swift Current Research Centre, Swift Current, SK, Canada S9H 3X2
Cadmium is a heavy metal present in soils from natural and anthropogenic sources. Plant uptake of Cd at levels present in the soil solution is dependent on a system that is largely metabolically mediated and competitive with the uptake system for Zn and possibly other metals. Much of the Cd taken up by plants is retained in the root, but a portion is translocated to the aerial portions of the plant and into the seed. The amount of Cd accumulated and translocated in plants varies with species and with cultivars within species. Soil, environmental and management factors impact on the amount of Cd accumulated in plants. Potential methods of reducing the accumulation of Cd in crops include reduction of Cd input to the soil system, site selection, management practices which decrease the concentration of Cd in the soil solution and its uptake and translocation by plants, and development and production of plant cultivars with the genetic tendency for low Cd uptake.
Key words: Cadmium, fertilizers, genetics, uptake, tillage, rotation
Agriculture and Agri-food Canada,1Brandon Research Centre, PO Box 1000A, RR#3, Brandon, MB, Canada R7A 5Y3; 2Semi-arid Prairie Agriculture Research Centre, Agriculture and Agri-Food Canada, PO Box 1030, Swift Current, SK, Canada S9H 3X2
Root-zone salinization presents a challenge to plant productivity that is effectively countered by salt- tolerant halophytic plants, but unfortunately, much less successfully by major crop plants. The way in which salt affects plant metabolism is reviewed. Cellular events triggered by salinity, namely salt compartmentation, osmotic adjustment, cell wall hardening are connected to the whole plant responses, namely leaf necrosis, altered phenology and ultimately plant death. The roles of ion exclusion and K/Na discrimination in mediating crop response to salt appear to be central to the tolerance response, but they are by no means essential. The processes involved in regulating ion uptake at the membrane level are considered. Recent work elucidating the interaction between calcium and salinity tolerance is reviewed
Key Words: Calcium, cell growth, cell turgor, gene expression, ion regulation, K+/Na+ discrimination, membrane, osmotic adjustment, salinity, salt tolerance, vacuole
1Crop Science Department and 2Land Resource Science Department, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Field studies were conducted to determine the nitrogen (N) fertilizer replacement value (NFRV) when soybean (Glycine max [L.] Merrill) preceded corn (Zea mays L.) in the rotation (S-C), compared to corn preceding corn (C-C). Large, replicated blocks of soybean and corn were established in 1993 and 1994 near Elora, ON. In the following yr, each large block was subdivided into smaller plots. Fertilizer N was applied at six rates from 0 to 200 kg N ha-1 to the second-year corn crop. Corn grain yield responses to fertilizer N were fitted by quadratic regression. Maximum economic rate of N was calculated for each crop sequence and NFRV's were determined. Corn yields were consistently higher when grown after soybean (S-C) than after corn (C-C). Maximum corn yields were 10.4 and 12.3 Mg ha-1 in 1994 and 1995, respectively. NFRV's for S-C, compared to C-C, were 41 and 59 kg N ha-1 in the 2 yr. As a result of these studies and numerous other experiments, recommended fertilizer N rates have been changed to 30 kg N ha-1 less for S-C than for C-C in central Ontario.
Key words: Nitrogen credit, corn, soybean, fertilizer N, replacement value, crop rotation
Department of Agricultural Economics and Department of Agronomy, Division of Agricultural Sciences and Natural Resources, Oklahoma State University, Stillwater, OK 74078, U.S.A.
The five year moving average (5YRMA) wheat (Triticum aestivum L.) grain yield per harvested hectare has declined by more than 18% over the last decade in Oklahoma. By contrast, world wheat yields have increased steadily over the same time period. The Oklahoma wheat yield trend during the last decade is inconsistent with expectations. The objective of the research was to determine why the 5YRMA wheat grain yield per harvested hectare did not increase in Oklahoma during the last decade. Five types of potential explanatory variables were investigated: structural change (including government programs); fertilizer use; proportion grazed; planting date; and environment. Regression analysis was used to determine that the consequences of improvements in technology, research, and education programs, as measured by a linear trend variable, were positive. However, during the last decade, these advancements were overwhelmed by changes in planting date and environmental factors.
Key words: Wheat, yield, trend, planting date, environment
Crop Science Department, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Specific leaf area (SLA), the ratio of leaf area to leaf weight, is
an important plant characteristic that affects the rate of dry matter production
of crop canopies. It is affected by the conditions of growth of both isolated
plants and crop communities, but the extent to which various environmental
factors impact on SLA under field conditions is not clearly understood.
This study was conducted to study the variability in SLA of leaves on the
main culm, and in the leaf canopy as an entity, under different conditions
of photoperiod, nitrogen and temperature for a number of wheat genotypes
grown under field conditions. Five plantings at approximately bimonthly
intervals on 12 May, 5 July and 22 September, 1993; and on 9 June and 10
August, 1994 were made under both natural photoperiod and an extended photoperiod
of 20 h. A split plot design with two levels of nitrogen (0 kg N ha-1
and 150 kg N ha-1) as main plots and four genotypes of wheat
comprising two spring types (Norseman and Roblin) and two winter types
(Ruby and Harus) as subplots was used.
SLA of individual leaves varied among leaf positions, but the pattern
of variation was dependent on sowing date and genotype. For May and June
sowing dates, SLA increased with leaf number up to leaf 5 and then declined
with subsequent leaf numbers for the spring genotypes, but increased to
leaf 5 and changed little thereafter for the winter types. For July or
August sowing, and for both spring and winter genotypes, the change in
SLA with leaf position was less clear. The results further showed that
some of this variability in SLA with leaf position could be accounted for
by the mean air temperatures over which the leaves developed. As temperatures
increased from 8oC to 26oC, SLA increased to a maximum
value achieved at 18-20oC and then declined. However, there
was a large scatter of SLA values around 18 to 20oC due partly
to some lower SLA values for the July and August sowing dates. This suggests
the impact of other factors such as radiation and the degree of mutual
shading within the canopy on SLA. Mean canopy SLA reflected the individual
leaf values during the period of leaf production, and varied with sowing
date and genotype, although the pattern of genotypic variability was inconsistent
over sowing dates; it decreased rapidly after spike emergence presumably
reflecting leaf ageing. Neither nitrogen nor photoperiod had significant
effects on SLA on both individual leaf and canopy bases. The results suggest
that temperature is one factor affecting SLA under field conditions, but
that further work to identify other factors impacting on SLA in the field
will be necessary. For application of simulation models to situations in
which temperatures are likely to vary, an accounting for the impact of
temperature on the SLA of individual leaves would be desirable.
Key words: Specific leaf area (SLA), sowing date, temperature, simulation, wheat.
Crop Science Department, University of Guelph, Guelph, Ontario, Canada N1G 2W1
In some cereal simulation models, canopy leaf area development is calculated using relationships that summarize how leaf size changes with position. The nature and extent to which various environmental factors interact with ontogenetic variations in leaf size, however, is not clearly understood. This study was undertaken, therefore, to evaluate how temperature, photoperiod and nitrogen impact on leaf to leaf relationships in wheat grown under field conditions. Four contrasting genotypes of wheat comprising two spring and two unvernalized winter types were sown on five dates, supplied with one of two levels of nitrogen (150 kg N ha-1 and 0 kg N ha-1), and grown under natural and extended photoperiod conditions. For the spring wheats, individual mature leaf area increased along with leaf number up to leaf 5 (a stage that coincided with rapid stem elongation) but varied for subsequent leaves in a manner that was dependent on genotype and environment. In the period prior to the expansion of the fifth leaf, neither nitrogen nor photoperiod significantly influenced the pattern of change in leaf size. Thereafter, leaves under low nitrogen and extended photoperiod progressively became smaller, an effect which was due primarily to changes in length rather than in width. For the winter genotypes, which did not reach the stage of rapid stem elongation, mature leaf dimensions increased along with leaf number during the whole period of study and were not markedly affected by photoperiod but, after leaf 5, were smaller for the low nitrogen level. For all genotypes, the size of the first leaf and the coefficients derived by regressing the area of successive leaves on the area of the previous leaf during the vegetative phase varied among sowing dates due partly to the temperature environment under which the leaves at each node developed. The results however indicated that the potential leaf size at any of the lowermost leaf positions can be obtained by using a logarithmic function that relates the potential size of one leaf to its predecessor. Such relationship can be used to calculate actual leaf size if account is taken of environmental and assimilate supply factors that operate during leaf expansion.
Key words: Wheat, sowing date, leaf area, temperature, photoperiod
Agriculture and Agri-Food Canada, Brandon Research Centre, Box 1000A R.R.#3, Brandon, MB, Canada R7A 5Y3
Cadmium concentration in durum (Triticum turgidum) grain may be influenced by fertilizer management. A three-year field study conducted on two Orthic Black Chernozemic soils investigated the effects of banded and broadcast applications of N and P, and applications of Zn fertilizer on the yield and Cd concentration of the grain of two cultivars of durum wheat. Applications of N and P fertilizer increased grain yield of durum wheat when soil nutrient supply was low or yield potential was high, while Zn application generally had little effect on grain yield. Cadmium concentration of durum increased with applications of N and P and was generally unaffected by Zn application. Method of application of N or P did not consistently influence either grain yield or Cd concentration of the grain under the conditions of this study. Where differences due to placement occurred, banded P produced higher grain yield and Cd concentration than application of the same level of P as a broadcast treatment. Cadmium accumulation increased substantially with N and P applications, since both Cd concentration in the grain and grain yield increased with N and P application. Year to year variation in Cd concentration in the grain was large, indicating a strong effect of environment on Cd phytoavailability.
Key words: Management, banding, nutrient, accumulation
Department of Entomology, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
Nectar sugar composition and temporal patterns of nectar sugar production were examined in oilseed summer rape (Brassica napus L. ssp. oleifera (Metzg.)) from 6 open-pollinated, 8 pol cytoplasmic male sterile (CMS) hybrid and 7 dominant self-incompatible (SI) hybrid cultivars at three field plot sites in Manitoba. The total sugar content of nectar samples was measured by the Dreywood anthrone reaction for total carbohydrate, and simple sugar composition was determined using an enzymatic bioanalysis for D-glucose, D-fructose and sucrose. Hybrid and open-pollinated cultivar flowers had similar sugar content. Mean total sugar content per flower also did not vary among hybrid breeding systems when compared within individual weeks of the bloom period or within daily sampling periods. However, for all cultivars, total nectar sugar content per flower was lower during the 08:00 and 11:00 h sampling periods and increased to maximum levels during the 14:00 and 16:00 h sampling periods. Significant differences in nectar sugar content were also found in relation to the bloom phenology of the cultivars. Cultivars produced the greatest amount of sugar per flower during the first two weeks of the bloom period, then sugar production decreased in the third and fourth weeks. Nectar sugar ratios from all cultivars averaged approximately 1: 1 glucose: fructose. Nectar glucose content among cultivars was similar, but among breeding systems, CMS cultivars tended to have lower amounts of glucose than SI or open-pollinated cultivars. Selecting for higher total sugar content may produce nectars more attractive to foraging honey bees (Apis mellifera L.), thereby ensuring adequate pollination of hybrid parental lines and F1 hybrid plants. Selecting for lower nectar glucose will produce honeys with more desirable granulation characteristics. Overall, the production and quality of nectar sugar in oilseed rape hybrids are similar to those of open-pollinated cultivars, and are not likely to adversely affect the pollinating activities of honey bees or their potential for honey production.
Key words: Oilseed summer rape, Brassica napus, honey bees, Apis mellifera, nectar, simple sugars
1Research Farm, Agriculture and Agri-Food Canada, Box 29, Beaverlodge, Alberta, Canada T0H 0C0; 2Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, Saskatchewan, Canada S7N 0X2
A dominant gene for white flower colour, derived from B. albogabra is shown to be closely linked to a gene for seed erucic acid in Brassica napus. This observation coonflicts with a previous report on material of the same origin, where independent inheritance of these characters was reported.
Key words: Brassica napus, flower colour, erucic acid, linkage, summer rape
1Agriculture and Agri-Food Canada Research Centre, 107 Science Place, Saskatoon, Saskatchewan Canada, S7N OX2; 2Philom Bios Inc., 318-111 Research Drive, Saskatoon, Saskatchewan Canada, S7N 3R2; 3Agriculture and Agri-Food Canada Research Centre, Box 1000A R. R. #3, Brandon, Manitoba Canada, R7A 5Y3; and 4Alfalfa Dyhydrators Research Laboratory, Tisdale, Saskatchewan Canada, SOE 1TO
Yield and phosphorus (P) uptake response of alfalfa (Medicago sativa L.) to inoculation with Penicillium bilaii (Provide) at varying rates of P fertilizer, was determined in small- and large-plot experiments located in the Dark Brown, Black or Gray soil climatic zones of Saskatchewan and Alberta from 1994 to 1996. Soil at the sites contained low to medium levels of available P. In the establishment year of the small-plot experiments, inoculation of alfalfa with P. bilaii increased yields and P uptake by 3 to 18%, when averaged across P fertilizer rates. The largest response to inoculation occurred early in the growing season. In the year following establishment, yield and P uptake of inoculated alfalfa averaged 3% greater than uninoculated plants. In the establishment year of the large-plot experiment in 1994 and 1995, yields and P uptake of inoculated alfalfa at 10% bloom were 7 and 26% greater than uninoculated plants, when grown without and with a wheat (Triticum aestivum L.) companion crop, respectively. Unlike the small-plot experiment, alfalfa in the year following establishment did not respond to inoculation performed the previous year. The P credit (P fertilizer replacement value) of P. bilaii inoculation, based on yield response in the establishment year and in the year following establishment, averaged 4.6 kg P ha-1 in the small-plot experiments and 5.3 kg P ha-1 in the large-plot experiments. Tillage cropping practices that conserve water near the soil surface, and inclusion of a companion crop, may increase the probability of alfalfa response to P. bilaii inoculation as well as the efficacy of that response.
Key words: Medicago sativa, Penicillium bilaii, Rhizobium meliloti, Triticum aestivum, phosphorus
Centre de recherche et de développement sur les sols et les grandes cultures, Agriculture et Agroalimentaire Canada, 2560 Boul. Hochelaga, Sainte-Foy, Québec, Canada G1V 2J3
The leaf area development of grasses and subsequently radiation interception depends on morphogenetic processes such as leaf extension and appearance. Leaf extension and appearance of timothy (Phleum pratense L.) grown with varying rates of N nutrition and their impact on sward structural characteristics were studied during primary growth in spring and during a summer regrowth. With no N applied in spring and summer, the leaf extension rate (LER) and the leaf appearance rate (LAR) of timothy were approximately 40% and 65% of that obtained under non-limiting N conditions (140 kg N ha-1 in spring and 120 kg N ha-1 in summer). Nitrogen deficiency reduced tiller density in spring but increased it in summer. The differential effect of the N deficiency on LER and LAR modified the sward structural characteristics. Nitrogen deficiency decreased the length of mature leaves, their width and the total leaf length per tiller. The reduced LER associated with N deficiency explained for the most part the N effect on leaf area expansion and radiation interception.
Key words: Phleum pratense L., timothy, leaf extension, leaf appearance, tillering, nitrogen
1Agriculture and Agri-Food Canada, Crop and Livestock Research Centre, PO Box 1210, Charlottetown, Prince Edward Island, Canada C1A 7M8; 2Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Ottawa, Ontario, Canada K1A 0C6; 3Agriculture and Agri-Food Canada, Experimental Farm, Nappan, Nova Scotia, Canada B0L 1C0; 4Plant Science Department, Nova Scotia Agricultural College, Truro, Nova SCotia, Canada B2N 5E3; 5Agriculture and Agri-Food Canada, Crops and Soils Research and Development Centre, Ste-Foy, Quebec, Canada G1V 2J3
AC Endure red clover (Trifolium pratense L.) is a diploid cultivar of the double-cut type developed by mass selection at the Crop and Livestock Research Centre, Agriculture and Agri-Food Canada, Charlottetown, PEI. It is earlier flowering than Florex or Marino, and higher in forage yield, especially in the second and third harvest years.
Key words: Red clover, Trifolium pratense L., cultivar description
1Agriculture and Agri-Food Canada, Crops and Livestock Research Centre, Box 1210, Charlottetown, Prince Edward Island, Canada C1A 7M8; 2Nova Scotia Agricultural College, Box 550, Truro, Nova Scotia, Canada B2N 5E3; 3Nova Scotia Department of Agriculture and Marketing, Box 550, Truro, Nova Scotia, Canada B2N 5E3; 4New Brunswick Department of Agriculture and Rural Development, Box 6000, Fredericton, New Brunswick, Canada E3B 4Z7
AC Norboro is a spring feed wheat (Triticum aestivum L. em. Thell.) with high grain yield and early maturity. It is moderately resistant to powdery mildew, and susceptible to leaf blotch. AC Norboro is slightly more susceptible to fusarium head blight than AC Wilmot, Belvedere, and AC Baltic. AC Norboro was developed by Agriculture and Agri-Food Canada.
Key words: Triticum aestivum, wheat (spring), cultivar, description
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, British Columbia, Canada V0H 1Z0
Apples cv. 'Spartan' from the same orchard block in Kelowna, British Columbia were stored in a controlled atmosphere storage facility for 7 - 8 months each year for a period of 4 years from 1989 to 1993 to study the effect of nitrogen fertilization rate and orchard cover crop on the incidence of low-temperature-basidiomycete (LTB) rot. The effect of adding orchard floor litter from the cover crop was studied during the last two years of the study. Rate of nitrogen fertilization did not affect disease incidence but cover crop influenced LTB rot in apples stored with and without orchard floor litter. White clover litter placed in apple bags from the treatment of white clover with a clean strip on the tree row resulted in 12.8% LTB rot and was significantly higher than the mixed grass treatments. The effect was not as clear for apples stored without the addition of litter although apples from the white clover cover had a higher incidence of LTB rot than apples from the clean orchard cover. Sterilizing the orchard litter by autoclaving reduced the incidence of LTB rot compared to nonautoclaved litter, and apples stored without litter had an even lower incidence of LTB rot. Isolations from symptomatic fruit in 1992 showed that 86% of the isolates were pathogenic and caused LTB rot. 'Spartan' apples were infected early during fruit development because 17.2% of the apples were infected by 23 June in 1993. In the orchard, 'Spartlett' pear was more susceptible to LTB infection than Spartan apple. The use of cover crop management for reducing the incidence of LTB rot is discussed.
Key words: Coprinus rot, postharvest, storage, control, pest management
Crop Protection Division, Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Central Experimental Farm, Ottawa K1A 0C6, Canada
In order to enhance the utilization and protection of wild Fragaria germplasm from coastal British Columbia, patterns of morphological variation were assessed in plants from the Pacific coastal region of Canada. Twenty-five characters were evaluated in 87 plants grown in the uniform garden at the Canadian clonal genebank. Seven characters including the number of veins, length of the terminal tooth, roundness of tooth, tooth distribution, leaf thickness, leaf colour and leaf surface were significant at the 5% level in distinguishing ecoregional groupings and a discriminant analysis was also significant. The major pattern of variation involved plants from southern Vancouver Island to the upper Strait of Georgia, ecoregions 192 and 194, which have thinner, paler, more glaucous leaves with less broadly rounded teeth, suggesting hybridization of F. chiloensis with F. virginiana. A clustering of ecoregional group centroids using the unweighted pair group method with arithmetic averages indicated that in order to optimally protect genetic variation, 28.35% of the protected accessions should be selected from each of ecoregions 192 and 194 with ecoregion 191 accounting for 15.98% and the remaining ecoregions contributing 13.66% of accessions.
Key words: Fragaria chiloensis, Fragaria virginiana, Pacific coast, genetic variation, ecoregions, germplasm protection
Centre de Recherche en Horticulture, Pavillon de l'Envirotron, Département de phytologie, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval, Sainte-Foy, Québec, Canada G1K 7P4
Au cours de l'hiver 1994 et du printemps-été 1994, des impatiens (Impatiens wallerana 'Accent Coral') et des géraniums (Pelargonium X hortorum 'Orbit Hot Pink') multipliés par semis ont été produits dans un substrat commercial (PRO-MIX 'BX') et dans 24 substrats composés de perlite (35% par volume), de tourbe et de six résidus organiques (boues d'épuration des eaux usées compostées, compost forestier, tourbe usée extraite d'un biofiltre traitant des eaux usées municipales fraîche et compostée, boues de désencrage fraîches et compostées). Le but de cette étude était d'identifier la proportion maximale de ces résidus à incorporer à un substrat tourbeux afin de produire des plantes de qualité. Les paramètres de croissance (indice de croissance, masse sèche aérienne et qualité visuelle) ont généralement diminué avec l'augmentation de la proportion d'incorporation (5, 10, 25 ou 40% par volume). Lors de l'expérience de l'hiver, la croissance des plantes témoins était supérieure à celle des plantes produites dans les substrats composés de résidus. Une proportion de 25% de résidus organiques par volume s'est révélé maximale pour la production d'impatiens et de géraniums.
Mots clés: Impatiens wallerana, Pelargonium X hortorum , boue résiduaire, compost, tourbe, subirrigation
Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9
The suitability of Brassica juncea (L.) Czern as a host plant for oviposition for Lygus lineolaris (Palisot de Beauvois) was measured by comparing egg laying on five experimental lines or cultivars of this species with that on B. napus L. (cv. AC Excel, a suitable host) in no-choice or choice tests during a 14-d period in the greenhouse and field. Egg laying was measured indirectly by counting newly hatched nymphs emerging from the plants. The numbers of nymphs emerging from B. juncea (cv. Cutlass) and four experimental lines of B. juncea were about two to ten times lower than from B. napus, indicating that L. lineolaris females lay fewer than half as many eggs on the former species than on the latter species and that B. juncea as a species is a poor host plant for oviposition. The inflorescence was the preferred region of the plant for oviposition on B. napus but not on B. juncea. The numbers of nymphs emerging from the inflorescence of B. juncea (cv. Cutlass) were 8.4 times lower than from the inflorescence of B. napus, indicating that the differences in oviposition on these species were due to the presence of an antixenosis-type of plant resistance factor(s) in the inflorescence of B. juncea.
Key words: Insecta, Miridae, Lygus lineolaris, oviposition, resistance, Brassica juncea, B. napus
Agriculture and Agri-Food Canada, Research Centre, 107 Science Place, Saskatoon, Saskatchewan S7N 0X2; Agriculture and Agri-Food Canada, Indian Head Research Farm, P.O. Box 760, Indian Head, Saskatchewan, SOG 2KO; and Manitoba Zero Tillage Research Association, P.O. Box 1000A, RR #3, Brandon, Manitoba, R7A 5Y3
Changes in tillage and other agronomic practices have shown benefits of increased grain yield for many crops, but these changes may alter the micro-environment resulting in changes to populations of disease causing agents and other micro-organisms. This study examined the effects of row spacing (10, 20, 30 cm), seeding rate (54, 108, 161 kg ha-1 for barley; 67, 134, 202 kg ha-1 for spring wheat) and seed-placed phosphorus (0, 8, 16 kg ha-1) on root diseases in spring wheat and barley using a zero-tillage production system in four environments. Root rot severity was assessed by visual ratings and the causal agents were identified. Analyses of variance indicated significant differences in root rot severity and the incidence of some causal agents for the main treatment effects ( i.e. row spacing, seeding rate, seed-placed phosphorus) and no significant interactions between locations, years, and cultural practices. Contrasts of treatment means showed that higher rates of seeding decreased root rot severity and the incidence of Fusarium in wheat but these effects were small ( less than 6%). The higher rates of mono-ammonium phosphate fertilizer reduced root rot severity in barley by 7% and the incidence of Gaeumannomyces graminis var. tritici in wheat by greater than 40%. Wider row spacings showed a small reduction of 6% in root rot severity in wheat but mostly had no effect on root diseases. Wheat yields were negatively associated with root rot severity in three of four environments. Fertility, root rot severity, and seeding rate had the greatest impact on wheat yield. Root diseases did not affect barley yields. Therefore, the use of wider row spacings and higher seeding rates with zero tillage practices will not lead to adverse effects on root diseases in wheat and barley. Phosphorus fertilizer should be used to reduce losses resulting from take-all disease in wheat.
Keywords: Zero tillage, cultural practices, common root rot, take-all, cereals
Agriculture and Agri-Food Canada, Research Centre, Lethbridge, Alberta; Seconded to - Environmental Sciences Division, National Hydrology Research Institute, 11 Innovation Boulevard, Saskatoon, Saskatchewan Canada S7N 3H5
In a study involving two sites in western Canada, residues of the herbicide metribuzin in lentil were monitored by gas chromatography following postemergence application at 0.28 kg a.i. ha-1. On the day of spraying, initial residues in lentil green foliage were of the order of 1 mg kg-1. Metribuzin residues in the green foliage continually decreased with time to non-detectable levels (< 0.02 mg kg-1) at 42 d after application. No metribuzin residues were detected in the straw or mature seed.
Key words: Metribuzin, 4-amino-6-(1,1-dimethylethyl)-butyl-3-(methylthio-1,2,4-triazin-5(4H)-one; lentil, Lens culinaris Medic., residues, residue analysis, gas chromatography
Increased crop competitiveness may complement existing weed control
methods. The objective of this research was to establish whether spring
wheat Triticum aestivum L. genotypes with contrasting competitive abilities
respond differently to weed control levels. Four sibling genotypes differing
in
competitive ability were grown under simulated weedy conditions and
subjected to four weed control levels. The competitive genotypes were superior
to the less conpetitive genotypes in
grain yield under weedy, partially weedy and non-weedy conditions.
Key words: Triticum aestivum L., competition, weed control, genotype X weed control interaction
Department of Crop Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Evaluation of several herbicides for the control of alfalfa and red clover in a legume-notill corn system showed that spring burn-down of the legumes may be preferred to fall burn-down. Spring application gave similar or greater control of these species than fall applications. Treatments with dicamba (3,6-dichloro-2-methoxybenzoic acid) at 0.6 kg ha-1 were the most effective in controlling red clover and alfalfa.
Key words: Weed control, perennial legumes, spring application, fall application
Horticultural Research Institute of Ontario, University of
Guelph, P.O.Box 587, Simcoe,
Ontario, Canada N3Y 4N5
Sixteen processing sweet corn cultivars were evaluated to characterize cultivar sensitivity to nicosulfuron/rimsulfuron in field studies, conducted over a two-year period. Response to nicosulfuron/rimsulfuron varied widely, depending on cultivar and application rate. Delmonte 2038 was highly sensitive of nicosulfuron/rimsulfuron resulting in the death of all plants. Nine cultivars showed moderate visual injury but this did not always result in a significant yield reduction. Six cultivars were characterized as fully tolerant to field applications at rates of 25 g ai/ ha-1. These cultivars were Reveille, CNS 710, Krispy-King, Reward, More and GH 2628.
Key words: Sensitivity, herbicide injury, cultivars, nicosulfuron, rimsulfuron, Zea mays
1Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, K.W. Neatby Building, Central Experimental Farm, Ottawa, Ontario, Canada K1A OC6; 2Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, Saskatchewan, Canada S7N OX2
A review of biological information is provided for Erucastrum gallicum (Willd.) O.E. Schulz. A European native, it was introduced into Canada and the United States in the early 1900's and spread rapidly along the railroads. The species occurs in all the provinces and the Northwest Territories and is particularly abundant in the Prairie provinces and midwestern United States. It is a summer annual, rarely a winter annual or biennial species, and is characterized by high reproductive output. Plants occur most commonly on waste ground and along roadsides and railroads, followed by agricultural fields. Erucastrum gallicum is of allopolyploid origin (n= 15, 7 + 8 chromosomes), and contains a single multi-locus isozyme genotype. The species is a close relative of Brassica and is capable of limited genetic exchange with the oilseed rape species, B. rapa and B. napus. The possible transfer of genes from transgenic canola varieties to Erucastrum gallicum poses a remote, but potential, environmental risk. Populations of Erucastrum gallicum, including both Old World and North American populations, constitute a valuable germplasm resource as potential sources of beneficial agronomic traits, such as disease resistance for canola crop improvement.
Key words: Dog mustard, Erucastrum gallicum, weed biology, risk assessment, germplasm, canola