James R. Moyer

Yellow sweetclover, green manure, and its residues effectively suppress weeds during fallow

Abstract Improved fallow systems are needed to reduce the negative effects of increased soil erosion and reduced soil quality. Field experiments were conducted to determine weed suppression attained with yellow sweetclover grown as a green manure fallow replacement crop. Yellow sweetclover was undersown in field pea, flax, or Indian mustard and then killed in June of the following fallow year. Living yellow sweetclover competed strongly with weeds during the first fall and spring of fallow. Weed biomass accounted for <1 to 12% of the total plant biomass when yellow sweetclover was terminated in June. Yellow sweetclover residues remaining after termination of growth continued to provide excellent weed suppression. Weed densities in April before planting the succeeding wheat crop were 75 to 97% lower in yellow sweetclover than in untreated fallow treatments. Yellow sweetclover controlled the perennial weeds dandelion and perennial sowthistle, as well as the annuals kochia, flixweed, Russian thistle, and downy brome. Weed suppression was similar whether yellow sweetclover was harvested as hay or its residues were incorporated or left on the soil surface, suggesting that a portion of the weed suppression effect may be due to allelopathic compounds being released from decomposing yellow sweetclover. Results will be used to develop more sustainable agronomic practices in regions where fallow is still widely employed. Nomenclature:Dandelion, Taraxacum officinale Weber in Wiggers TAROF; downy brome, Bromus tectorum L. BROTE; field pea, Pisum sativum L. ‘Trapper’; field pennycress, Thlaspi arvense L. THLAR; flax, Linum usitatissimum L. ‘McGregor’; flixweed, Descurainia sophia (L.) Webb. ex Prantl DESSO; indian mustard = oriental mustard, Brassica juncea (L.) Czern. and Coss. ‘Lethbridge 221’ BRSJU; kochia, Kochia scoparia (L.) Schrad. KCHSC; perennial sowthistle, Sonchus arvensis L. SONAR; Russian thistle, Salsola iberica Sennen and Pau SASKR; spring wheat, Triticum aestivum L. ‘Katepwa’; yellow sweetclover, Melilotus officinalis (L.) Lam ‘Norgold’ MEUOF.

Combining agronomic practices and herbicides improves weed management in wheat–canola rotations within zero-tillage production systems

Abstract Development of more comprehensive and cost-effective integrated weed management systems is required to facilitate greater integrated weed management adoption by farmers. A field experiment was conducted at two locations to determine the combined effects of seed date (April or May), seed rate (recommended or 150% of recommended), fertilizer timing (applied in fall or spring), and in-crop herbicide dose (50% or 100% of recommended) on weed growth and crop yield. This factorial set of treatments was applied in four consecutive years within a spring wheat–spring canola–spring wheat–spring canola rotation in a zero-till production system. Both wheat and canola phases of the rotation were grown each year. Weed biomass was often lower with May than with April seeding because more weeds were controlled with preplant glyphosate. However, despite fewer weeds being present with May seeding, wheat yield was only greater in 1 of 7 site-years, and canola yield was never greater with May compared with April seeding. Higher crop seed rates had a consistently positive effect on reducing weed growth and the weed seedbank. Crop yield was sometimes greater, and never lower, with higher seed rates. Fertilizer timing did not have a large effect on crop yield, but applying N in the spring compared with fall was less favorable for weeds as indicated by lower weed biomass and a 20% decrease in the weed seedbank. In-crop herbicides applied at 50% compared with 100% doses often resulted in similar weed biomass and crop yield, especially when higher crop seed rates were used. Indeed, the weed seedbank at the conclusion of the 4-yr experiment was not greater with the 50% compared with 100% herbicide dose at one of two locations. This study demonstrates the combined merits of early seeding (April), higher crop seed rates, and spring-applied fertilizer in conjunction with timely but limited herbicide use to manage weeds and maintain high crop yields in rotations containing wheat and canola. Nomenclature: Glyphosate; canola, Brassica napus L.; wheat, Triticum aestivum L.

Cereal cover crops for weed suppression in a summer fallow-wheat cropping sequence.

Cropping systems in western Canada that include summer fallow can leave the soil exposed to erosion and require frequent weed control treatments. Cover crops have been used for soil conservation and to suppress weed growth. Experiments were conducted under rain-fed conditions at Lethbridge, Alberta to determine the effect of short-term fall rye (Secale cereale L.), winter wheat (Triticum aestivum L.) and annual rye cover crops in the fallow year on weed growth and subsequent wheat yield. Under favorable weather conditions fall rye was as effective as post-harvest plus early spring tillage or herbicides in spring weed control. Winter wheat and fall rye residues, after growth was terminated in June, reduced weed biomass in September by 50% compared to no cover crop in 1993 but had little effect on weeds in 1995. Fall-seeded cover crops reduced the density of dandelion (Taraxacum officinale Weber in Wiggers) and Canada thistle [Cirsium arvense (L.) Scop.] but increased the density of downy brome (Bromus tect...

Integration of Agronomic Practices and Herbicides for Sustainable Weed Management in a Zero-Till Barley Field Pea Rotation1

Research is needed to develop more comprehensive integrated weed management systems that would facilitate greater adoption by farmers. A field study was conducted to determine the combined effects of seed date (April or May), seed rate (recommended or 150% of recommended), fertilizer timing (fall or spring applied), and in-crop herbicide rate (50 or 100% of recommended) on weed growth and crop yield. This factorial set of treatments was applied in four consecutive years within a barley-field pea–barley-field pea rotation in a zero-till production system. Both barley and field pea phases of the rotation were grown each year to account for variable environmental conditions over years. Weed biomass was often lower with May than with April seeding because of more weeds being controlled with preplant glyphosate. However, despite fewer weeds being present with May seeding, barley yield was only greater in 1 of 4 yr and field pea yield was actually lower with May than with April seeding in 3 of 4 yr, indicating that optimum seed date is highly dependent on crop species and environmental conditions. Higher crop seed rates reduced weed biomass and increased crop yield in 2 of 4 yr in each of barley and field pea. Fertilizer timing had little effect on weed competition in barley, but spring- compared with fall-applied fertilizer reduced weed biomass and increased field pea yield in 2 of 4 yr. In-crop herbicides applied at 50% compared with 100% rates sometimes resulted in greater weed biomass and lower crop yields with recommended crop seed rates, but few differences were noted at high crop seed rates. Indeed, the weed seed bank at the conclusion of the 4-yr study was not greater with the 50% compared with 100% herbicide rate when high crop seed rates were used. This study demonstrates the combined merits of early seeding (April), higher crop seed rates, and spring-applied fertilizer in conjunction with timely but limited herbicide use to manage weeds and maintain high yields in rotations containing barley and field pea. Nomenclature: Glyphosate; barley, Hordeum vulgare L. ‘AC Harper’; field pea, Pisum sativum L. ‘Swing’. Additional index words: Fertilizer timing, integrated weed management, reduced herbicide rate, seed date, seed rate, weed competition. Abbreviation: IWM, integrated weed management.

Suitability of legume cover crop-winter wheat intercrops on the semi-arid Canadian prairies.

Farmers on the Canadian prairies are interested in including legume cover crops in their cropping systems to reduce fertilizer inputs and improve farm sustainability. A field study was conducted to determine the merits of establishing alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) or Austrian winter pea (Pisum sativum L.) cover crops in fall or in spring with winter wheat (Triticum aestivum L.). Spring-planted legumes emerged well within the winter wheat crop, but their growth was limited under these semi-arid conditions. Fall-planted red clover had low plant densities following winter in two of three experiments and fall-planted winter pea reduced winter wheat yield by 23 to 37% compared with the no cover crop control. In contrast, fall-planted alfalfa exhibited good winterhardiness, provided some weed suppression without reducing winter wheat yield, caused only a slight reduction in soil water content, and contributed an extra 18 to 20 kg ha-1 of available soil N at the time of seeding...

Weed management in irrigated fenugreek grown for forage in rotation with other annual crops

Fenugreek (Trigonella foenum-graecom L.) is an annual legume that has potential as a forage crop on the Canadian Prairies. Experiments were established to determine the tolerance of fenugreek to several herbicides and their efficacy on various weeds. Potentially, fenugreek could be grown in conservation tillage systems in rotation with other annual crops. Therefore, additional multi-factor experiments were conducted to determine the effect of herbicides, seeding method, and 11 previous crops on fenugreek yield. Without herbicide application, weeds contributed 37 to 86% to total dry matter production. When imazamox/imazethapyr, or combinations of imazamoz/imazethapyr or imazethapyr with ethalfluralin was applied, weed contents were about 5% of the total dry matter and the herbicides did not reduce fenugreek yield compared to the hand-weeded check. Total forage samples with a low weed content had lower fibre content and higher protein and digestible dry matter content than forages with a high weed content. ...

Effect of sweetclover cultivars and management practices on following weed infestations and wheat yield

There is a renewed interest, especially among organic growers, in using either white sweetclover (Melilotus alba Desr.) or yellow sweetclover [M. officinalis (L.) Lam.] as cover crops. Sweetclover cultivars and tillage practices have changed since these crops were widely used as cover crops in the first half of the 20th century. Experiments were initiated in 1999, 2000, and 2002 to compare the effect of high- and low-coumarin cultivars and crop termination methods on weed suppression, available soil N, moisture conservation and following crop yield. Weed suppression was usually more effective when sweetclover residues were left on the surface than when removed as hay. Sweetclover termination at 70% bloom was often more effective in suppressing weeds than termination at the bud stage. In the summer and fall after termination, surface residues of Yukon, a high-coumarin and drought-tolerant cultivar, reduced lamb’s-quarters (Chenopodium album L.) density by > 80% compared with the no sweetclover check and es...

ACE-1 perennial cereal rye

ACE-1 perennial cereal rye (PC rye) (Secale cereale) was developed by the Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta. This cultivar, tested as LRC 96-1 in western Canada, was developed for silage and greenfeed. ACE-1 is easy to establish, competes well with weeds, grows early in spring, produces more biomass than barley and fall rye under dryland and irrigated conditions, but produces less seed than high yielding fall rye cultivars. Forage quality of ACE-1 was found to be similar to barley. Key words: Cultivar description, rye, perennial, Secale cereale

Effects of Landscape Position, Rainfall, and Tillage on Residual Herbicides

Abstract The effect of soil properties and weather on herbicide persistence and injury to following crops were studied at a site near Lethbridge, Alberta, Canada, with undulating topography that included no-tillage and conventional tillage systems on adjacent fields. Soil pH ranged from 5.2 (lower slope no-tillage) to 7.8 (upper slope conventional tillage) and soil organic matter content ranged from 2.3% (upper slope conventional tillage) to 4.4% (lower slope no-tillage). During the years when the experiments were conducted rainfall ranged from < 50% of normal to > 150% of normal. During dry years atrazine and metsulfuron severely injured wheat and lentil crops, seeded 1 yr after herbicide application, on upper slope locations. The most severe injury occurred on the upper slope conventional tillage location. In years with high rainfall, no crop injury occurred 1 yr after atrazine and metsulfuron application on either upper or lower slope locations in both tillage systems. Imazamox plus imazethapyr caused almost 100% injury in the lower slope position in the no-tillage system (pH 5.2) in the driest year. Following-crop injury due to the imidazolinone herbicides decreased with increasing rainfall and increasing soil pH. The most severe injury to following crops seemed to occur when herbicide dissipation was dependent on microbial activity and rainfall was below normal. Nomenclature: Atrazine; imazamox; imazethapyr; metsulfuron; lentil, Lens culinaris Medic; wheat, Triticum aestivum L.

Effect of previous crop and herbicides on weed growth and wheat yield

Field experiments were established in 1998, 1999 and 2000 at the Lethbridge Research Centre to examine the effect of preceding annual crops and accompanying recommended herbicides on weed infestations in following winter and spring wheat (Triticum aestivum L.). Seven crops and fallow were established in year 1 with and without herbicides for weed control. In year 2, spring and winter wheat were grown without herbicides and with minimal fertilizer inputs to measure the effect of the previous crop and herbicides on weed and crop growth, available N and P, and available soil moisture. Lentil (Lens culinaris Medic) as a previous crop provided an environment that promoted wheat growth but not weed growth. In contrast, mustard (Brassica juncea L.) as a previous crop inhibited spring and winter wheat growth, but did not inhibit total weed biomass production in year 2. The beneficial effects of lentil and the detrimental effects of mustard were partially explained by available soil moisture and soil N for the sec...