Integration of cultural weed control enhances weed control in organic cropping systems

Non-Peer Reviewe

Optimum seeding rates for three annual green manure crops: the effect of weed competition

Non-Peer ReviewedGreen manure crops are critical to maintaining soil fertility in organic cropping systems. However, little research has been conducted to address their contribution to weed control. Indian Head black lentil (Lens culinaris), AC Green Fix chickling vetch (Lathyrus sativus), and Trapper field pea (Pisum sativum) are legumes developed for use as annual green manure crops in Saskatchewan. Currently, the recommended seeding rates for these crops are based on those developed for seed production of similar genotypes under weed-free conditions. Thus, our objective was to determine the optimal seeding rates for these three annual green manure crops under weedy and weed free conditions. The competitive ability of the green manure crops was assessed based on their ability to maintain crop biomass and reduce weed biomass. Each green manure crop was grown at five plant population densities (10, 26, 64, 160, and 400 plants m2) with weedy and weed free treatments. Wild oat (Avena fatua) and wild mustard (Brassica kaber) were planted in the weedy treatment to supplement the natural weed community. Biomass samples were taken at early bud and full bloom stages to simulate when these crops would be terminated. Trapper field pea produced the most crop biomass while Indian Head black lentil and AC Green Fix chickling vetch produced comparable amounts of crop biomass under both weedy and weed-free conditions. While Trapper field pea produced more crop biomass than AC Green Fix chickling vetch, weed biomass was similar for both species. Weed biomass was highest for Indian Head black lentil. Total biomass increased between the early bud and full bloom biomass dates for all species. However, weed biomass as a proportion of total biomass increased more than crop biomass between early bud and full bloom in weedy treatments. Recommended seeding rates developed from this experiment will help organic producers take advantage of the weed control offered by a competitive annual green manure while still achieving their objectives of improved soil nutrient status and soil quality

Crop–weed interactions under diverse cropping systems in the Canadian prairies

Non-Peer ReviewedDiverse cropping systems with different input levels and crop diversities can alter weed community dynamics (abundance and crop-weed competition). Organic systems believed to have greater heterogeneity in soil resources which can sustain more competition form weeds compared to conventional systems. However, direct evaluation of competitiveness among the two systems under wide range of crop diversities has not being tested. Therefore, a study was carried out within a long-term cropping systems study at Scott, Saskatchewan to compare weed dynamics. The main experiment consists of three input levels; high, reduced, and organic and three diversity levels; low, diversified annuals, diversified annual perennials. A micro-plot study was carried out within the main experiment with four weed control treatments applied in the wheat phase of reduced and organic systems. The treatments were 1.weed free treatment, 2. weedy treatment, 3. standard weed control and 4. pseudo weed established at 1:1 ratio with the crop. Within organic crop rotations weed density was high in diversified annual perennial system while in reduced systems it was high in diversified annual grain rotations. Overall, diversified annual perennial system had low weed biomass compared to low diversity rotation. There was no difference in weed biomass between organic and reduced systems. There was no difference between organic and reduced systems for yield loss. Grain yield was greater in reduced compared to organic systems. Even under weed-free conditions grain yield was low in organic systems indicating weeds are not the major yield limiting factor in Saskatchewan organic cropping systems

Use of genotypic variation of oat (Aven sativa. L) cultivars to suppress wild oat (Avena fatua. L) competition

Non-Peer ReviewedWild oat (Avena fatua L.) is considered to be one of the most troublesome weed in oat cultivation due to its difficulty to control using herbicides. Genotypic variation in oat cultivars can be used as a potential strategy to suppress the wild oat competition. Seven oat lines generated from a cross of the forage oat CDC Baler and the semi-dwarf oat Ronald were evaluated for the competitive ability with wild oat. The lines were grown with and without wild oat at 250plants m-2 at two locations in 2008.Plant height, light interception, shoot biomass, and grain yield data were recorded. According to the preliminary data analysis the selected cop genotypes shows a significant (P <0.05) difference in plant height among the genotypes. The grain yield, wild oat biomass and test weight was not significantly different among the oat genotypes. Therefore from these preliminary data the variation for the competitive ability was not identified among the oat genotypes used in this experiment

Evaluating the average seedbank addition of canola in producers’ fields

Non-Peer ReviewedSeed shatter in canola leads to a considerable yield loss and the dispersal of canola seed into the seed bank. The volunteer plants can then create a weed problem in the subsequent crops and result in crop yield loss. In 2010 a study was conducted to measure the harvest losses of canola in producers’ fields. A total of 26 fields were surveyed within 150 km radius from Saskatoon, SK. Out of these fields, 3 swathed and 3 direct combined fields from Kernen Crop Research Farm were included to compare the amount and time of seed loss in both harvesting methods. Sampling was done within 3 weeks of harvesting. Transects were laid at three random locations in each field from the center of one swath to the center of the adjacent swath. Six 0.25 m2 quadrats were kept in each transect at 1m interval. Plant counts were taken in each quadrat before sampling and were included in the total seed loss. Then the remaining crop residue, shattered seeds and some surface soil were removed from each quadrat using Ultra Shop Vacuum Cleaner. The bulked sample of each transect was air dried and cleaning was done using Carter Dockage Tester with different Sieve combinations. Finally the weight of pure seed and thousand seed weight were measured to calculate the amount of seed loss per unit area. The average seed loss was found to be 135.5 kg ha-1, which is equivalent to 5.8 % of the total yield and it resulted in seed bank addition of 4400 seeds m-2. Yield loss among producers ranged from 2.2 to 13.6 % (13 to 70 times the normal seeding rate). An average of 379 seeds m-2 were germinated (ranged from 6 to 2224 seeds m-2) within 3 weeks of harvesting. Direct combining resulted in higher seed loss than swathing. Both natural dehiscence of pods and seed loss from combining contributed for the buildup of canola seed bank

Volunteer canola (B. napus) in western Canada

Non-Peer ReviewedIn western Canada, survey and small plot research has shown that volunteer canola persists for at least four years in rotation (Derksen at al. 1999; Thomas et al. 1999). It is not clear whether this is due to persistence of the seedbank additions during harvest or the result of replenishment of the seedbank by subsequent volunteers. We are examining the life cycle of volunteer canola beginning with the seedbank additions incurred during harvest and as well as a focus on the seedbank ecology of this species in western Canada. Research in Europe has shown that B. napus can be readily induced into secondary dormancy by a combination of darkness and moisture stress (Pekrun, 1994). Nonetheless, field studies have revealed that only a small proportion of seeds persist via secondary dormancy in Europe (Pekrun et al. 1998). Canadian B. napus genotypes differ in their potential for induction into secondary dormancy using a laboratory assay. While some genotypes consistently exhibit low potential for the induction into secondary dormancy, others consistently exhibit high potential for the induction into secondary dormancy. High temperatures are perhaps the most important contributing factor to the induction of secondary dormancy, while low temperatures rapidly remove secondary dormancy. These observations suggest the seed ecology of a typical summer-annual weed. Furthermore, observations in a field experiment in 2000 revealed that volunteer canola germination was limited to the early portion of the growing season. Spring seedbank evaluations indicated far greater seed viability than was reflected by field emergence. It is was not clear if the seeds that did not emerge lost viability or were induced into secondary dormancy as our lab results would suggest. A more detailed field experiment examining the persistence of B. napus and induction into secondary dormancy was initiated

Wild oat (Avena fatua L.) time of emergence and density influence tame oat (Avena sativa L.) yield and quality

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Optimizing productivity in organic farming systems through variation of seeding density for field peas and lentils

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2002 soil and weed survey conducted on Saskatchewan organic cropland

Non-Peer ReviewedA soil survey and a weed survey were conducted on 5% of the organic farms in Saskatchewan, in the four major agricultural eco-regions in the 2002. Soil tests were taken in April and May prior to planting. Phosphorus levels were deficient in all regions. Nitrogen and sulphur varied between fields but were lowest over all in the boreal transition eco-region. Potassium was high in all regions. The weed surveys were conducted in July on the same fields as the soil survey. The most abundant species was green foxtail (Setaria virids (L.) Beauv.), wild oats was the fourth most abundant and the seventh most abundant species was Canada thistle (Cirsium arvense (L.) Scop.). Annual broad-leaved weeds were the most common weed group in the survey. Buckwheat (Polygonum convolvulus L.), lamb’s quarters (Chenopodium album L.), stinkweed (Thlaspi arvense L.), and wild mustard (Sinapis arvensis L.) were four of the six most abundant weeds in the organic survey. These results are opposite to the trend seen in conventional production where annual broad-leaves have become less abundant according to the surveys conducted from 1976 to 1995 (Thomas, 1996)

Branching in field pea

Non-Peer Reviewe