Allelopathy is the direct or indirect impact on plant individuals, whether they belong or not to the same species. Established as substances composed of secondary metabolites, allelopathy can a) affect growth and yield of another plant and b) develop autotoxicity, where plant individuals’ secrete chemicals that prevent propagation and development of seedlings of same species growth.
Allelopathy can be used as a strategic tool to mitigate chemical weed management. Residues of allelopathic cover crops not only provide benefits to the soil but also help to reduce weed populations during their growth and likely for the cash crops seeded in the season thereafter.
There were 14 Camelina varieties that were sown as a new trial at the North Peace Applied Research Farm. Since it is a relatively new crop alternative there is few choices for weed management. In the beginning of the trial weed grasses were promptly reduced with applications of Assure II (Quizalofop-p-ethyl) on June 2 and 15. There is still no registrations for broadleaf weed herbivoryicides, thus it was found that weed pressure in the camelina trial was very high which impacted camelina stand number and yield. Emergent values (P=0.0002) percentage of biomass ground cover (P<0.0001) and visual ratings assessing vigour (P=0.0200) differed across camelina varieties. Variety DH33 had the greatest number of individual stands and the greatest percentage cover compared to DHBC4-1/2 which produced the least amount of stands and similarly occupied less ground cover. Moreover, varieties such as WTCA, DH12, DHBC1 and WT43 stand counts as great as those found in DH33. Percentage cover statistically like DH33 was also found in DHB4-3/4, DHBC8, DHBC1, WT43, WT46-2, and WTCA varieties. None of these parameters translated into yield and instead there was no difference in overall pounds per acre (P=0.7256) and test weight (P=0.4370). In contrast camelina stands exhibiting more vigour were those from DHBC4-1/2 compared to WT46-2 and DH33 which were seen as weaker. Varieties like DH26, DH14, DH12 WTSU WTOM-1 looked as vigorous as DHBC4-1/2.This trial showed that more varieties need to be sown to see their development and consequent yielding to be considered a crop alternative in the Northern Peace region. This crop is in dire need to have approved registrations for broadleaf herbivoryicides, thus once this occurs it is possible camelina could be adopted by growers in the region.
This is the second consecutive year where hemp grew and successfully produced yield at the North Peace Applied Research Station. Biomass (P=0.8217) and yield (P=0.4195) were the same across all varieties. Canda and Joey varieties seemed to produce less yield but more biomass, whereas CFX-1 seemed to be more yielding than fibre producing. Macronutrients were not significant across varieties except Calcium (P=0.0454). There was more calcium content in the X59 variety compared to CRS-1 were less Ca was found. This is our last year in researching if hemp could be an alternative for crop rotation. In Alberta hemp can produce between 750 to 890 lb acre-1 of average seed yield and average fibre production from dual varieties is 2009 to 4018 lb acre-1. In terms of seed yield varieties close to this range are CFX-1 and X59 and in terms of fibre none of the varieties grown are close to the aforementioned range. Thus hemp would be a difficult plant to grow especially for fibre production in this area as varieties have struggled for three years to even get off the ground. Hope is standing for new varieties able to withstand the weather conditions here in the North Peace.
There was more biomass in the Ultimate mix compared to the other cover crop mixes. It is important to note that, despite producing 32% more than the other NPARA blends (P=0.0076), its mean biomass value was statistically the same than biomass found in Pinpoint in NPARA blends 5 and 6 (P=0.0151). In contrast, NPARA blends 1 and 4 which were the blends that produced the lightest mean biomass. It can be argued that blends 5 and 6 as they have corn in their cover crop mix, which is a heavy and bulky plant and ryegrass, which is an early emergence high yielding cover crop. Blends 1 and 4, have cereal rye as part of their mix, but biomass produced from these stands is not as copious as that found in annual ryegrass.
Protein values were the highest in ultimate and pinpoint blends (P<0.0001). As such, Ultimate and Pinpoint had 54 and 42% more protein respectively compared to NPARA protein values combined. Protein content in NPARA blend 3 was the same as that found in Pinpoint blend in comparison to the other blends from NPARA, likely due to white clover being part of such blend.
Acid (P=0.0279) and neutral (P=0.0184) detergent fibre were also greater in the ultimate blend. Acid and neutral detergent fibre were 30 (P=0.0153) and 26% (P=0.0452) respectively compared to those found in NPARA blends. From the blends selected at NPARA, blends #2, 5 and 6 showed statistically similar ADF and NDF values to Ultimate and Pinpoint blends. Lowest ADF and NDF values on the other hand were attributed to blends 1 and 4, possibly due to presence of cereal rye in a greater proportion with respect to the other blends. Total digestible nutrients were greater in Ultimate and Pinpoint blends (P=0.0022). Values were 43 (P=0.0002) and 32% (P=0.0087) greater than those found in NPARA blends.
Soil organic matter (P=0.9045), Cation Exchange Capacity (P=0.0669), pH (P=0.7063), P (P=0.1634), K (P=0.1623), Mg (P=0.7874), S (P=0.2400), Zn (P=0.9525), Fe (P=0.2619), Cu (P=0.4967), B (P=0.3848), Al (P=0.9629) and Na (P=0.9629) as well as nitrate (P=0.2096) were the same for all treatments. Moreover, insects were monitored every two weeks and data suggests that number of insects did not differ across treatments (P=0.0950).
Overall, NPARA blends 1 and 4 more digestible for the animal to eat compared to the other NPARA blends. However, NPARA blend #3 might also be a good choice of energy as it provides as much protein as that found in the Pinpoint blend.
Soil infiltration measurements are preliminary and do not provide any effect made by the treatments themselves. It is expected that in following seasons, soil analysis and infiltration conducted can be used to compute and further analyse differences among treatments.
Cover crop mixes were crafted to observe how different cover crop roots affect infiltration and fertility across the soil column. Consider treatments as four sets of three treatments. The first set consists of a brassica group (daikon radish, forage radish and forage turnip) which is sown at 1X, 2X and 3X of the recommended seeding rate. With the exception of the fallow treatment, all other sets have a brassica group at either of these seeding rates and field pea and sunflower. Thus, The second set was sown with oat, Japanese millet, sweet clover, chicory, in addition with the brassica group and afore mentioned crops. Third set had a brassica group with only field pea and sunflower and the last set of three was seeded with a brassica group, brown midrib corn, annual ryegrass and hairy vetch. Treatments were harvested for biomass yield and sent for feed analysis. Due to funding constraints, biomass was not collected for fallow plots and no subsequent feed analysis in the plots of this treatment were made. Biomass yield was statistically the same across all treatments (P=0.0582). Likewise, protein (P=0.4873) and acid detergent fibre (P=0.0982) were the same among treatments. Neutral detergent fibre (P=0.0029) on the other hand, was greater in mixes containing oat, Japanese millet, sweet clover, chicory, field pea and sunflower, despite brassica seeding rates. Moreover, mixes with only brown midrib corn, annual ryegrass and hairy vetch and single rates of the brassica group showed NDF as great as those found in previous mentioned mixes. Values of NDF were low in mixes were only the brassica group was present or when it was accompanied with field pea and sunflower. In fact, NDF in treatment sets with sown with brassica group, field pea and sunflower plus oat, Japanese millet, sweet clover and chicory was 113% more than that found in sets sown with only the brassica group. This same set were Japanese millet, oat, chicory and sweet clover were sown had 97% more NDF than sets were a brassica group plus field pea and sunflower were seeded and 69% more NDF than mixes including brown midrib corn, annual ryegrass and hairy vetch.
Allelopathy is the influence, usually detrimental, of one plant on another, where toxic substances are released when a plant dies or produced through decaying tissue. These secondary metabolites may establish direct or indirect impacts on populations of their own or different species. Allelopathy can a) affect the growth and yield of another crop (Batish et al. 2001) or b) develop autotoxicity, meaning chemicals expelled from plant residues of a species can hinder the growth of seedlings of the same species. Thus, if managed properly, allelopathy can be a great alternative in weed management.
Many of the cover crops seeded to protect the ground have allelopathic properties. Crops such as rye (Secale cereale L.), annual ryegrass (Lolium multiflorum L.), hairy vetch (Vicia villosa L.) and sunflower (Helianthus annuus L) have been shown to limit or reduce the growth of other plant species. Therefore, residues of these cover crops not only provide benefits to the soil but also help to reduce weed populations through allelopathy for the cash crops seeded in the season thereafter. In this experiment weeds were surveyed every two weeks after cover crop mix seeding to observe if allelopathic effects changed according to cover crop species or cover crop mixes. At the end of the season, plots were either roller-crimped or incorporated. The following growing season, canola, field pea and wheat will be sown perpendicular to the direction of these plots to observe if weed populations are still suppressed by the allelopathic effects of the cover crops and their mixes. Further, it will be assessed whether roller-crimping and incorporation impact weed suppression along with allelopathy.
Field pea is a poor competitor crop. As a temporal solution to control faster growing weeds and alleviate competition, fields are sprayed with Group 2 herbicides which have shown to cause herbicide weed resistance. It is hypothesized that if the seeding rate is increased, yield will be compensated despite weed competition. In addition, if field pea is intersown with cover crops, there is greater weed suppression. This is an economic advantage as it removes the necessity for herbicide application and inclusion of cover crops supply additional organic matter to the soil. This two-year split block experiment consisted of a Group 2 herbicide (in this case REFINE SG) application to spring wheat. Plots were either sprayed with the herbicide at 12 g ac-1 or left untreated. The following year, field pea was sown at three different seeding rates (90, 180 and 270 lb ac-1). Each of these rates were either sown alone or intersown with either annual rye, barley, oat and rye at 5, 35, 35, and 17 lb ac-1. Weeds were counted using 25 cm quadrats every two weeks and grouped as either broadleaf or grass.
Six of the eight intercrops were shown to yield more as an intercrop than as monocrops sown separately across an equivalent area of land. These mixes included faba bean and wheat, barley and peas, oats and peas, oats and crimson clover, wheat and red clover, and barley and red lentils. As seen from the yield graph below, peas did not emerge in this year’s intercrop trial, nor did canola due to excess moisture. The C.V. value corresponding with the yield analysis is 60.3, thus results should not be considered reliable.
Eight cover crop blends were subject to a nutritive analysis. There were significant differences in many of the nutritive indicators measured including dry matter (P=0.002), crude protein (P=0.001), TDN (P=0.02), and phosphorus content (P=0.03). ADF (P=0.18) and calcium (P=0.06) were statistically similar between treatments. NPARA Blend #6 produced 2.6 tonnes/acre of dry matter, the highest of any treatment. NPARA blends #4 and #1 had the highest level of crude protein at 33.4% and 31.5%, respectively. NPARA Blend #1, 75.1%, and Pinpoint Blend, 74.7%, exhibited the highest TDN. C.V. values were high for all except ADF and TDN.
In the previous year (2020), cover crops were also seeded, but C and N contents obtained through decomposition were not sufficient to show significant differences across cover crop blends. The impact of cover crop seeding on nitrogen and carbon content can take several years for differences to be observed. Furthermore, the use of cover crops for soil quality improvement is a process that requires steady and uninterrupted contributions.
Yield from each crop was different across all intercropping combinations (P≤0.0001). Pulses such as faba bean intersown with wheat and field pea intersown in barley and in canola reported the lowest yields. Barley intersown in both lentil and field pea, respectively, was higher yielding than other cereals such as oat, wheat and other types of main crops such as flax and canola. The North Peace weather is characterized for its long dry periods, where rains could turn out once a month and extensive heat can stress and jeopardize grain quality of main crops. It is also characterized for its soils with heavy clay, where moisture from rain periods can last for days and excess water is unable to filter through. Pulses require plenty of rain and soil moisture in order to produce competent yields. It is possible the dry periods occurring in the summer season compromised pulse yields while cereals were able to manage heat stress.
Number of insects per plot varied across weeks (P≤0.0001) and across intercrop combinations (P=0.0002). The interaction between weeks and intercropping combinations was the same (P=0.3690). The greatest number of insects was reported on the first week of August whereas the lowest was June 24, which coincided with a period of extreme heat and drought. Canola and field pea intercropping combination had the lowest number of insects compared to the rest of the combinations where numbers were statistically the same.
The 2021 growing season was the third attempt to successfully grow hemp varieties at the NPARA farm. In the growing seasons of 2019 and 2020 not a single seedling converted into a mature stand. In this year, there were more emergent plants per square foot from the CFX-1 variety compared to the Joey variety which had less (P≤0.0001). Grandi was one of the most vigourous (P=0.0003) varieties with the greatest number of standing individuals (P≤0.0001) whereas the X-59 hemp variety was the least both in vigour and number of standing individuals per square foot. Along with Grandi, other vigourous varieties were CFX-1, Katani and CRS-1. The least vigourous varieties, on the other hand, were Joey and Canda, aside from X-59. The hemp variety with the highest moisture content was Canda while lowest moisture content was found in the CRS-1 variety. The most productive hemp variety was CFX-1, whereas the least productive was Joey (P=0.0003). Under the right conditions, the CFX-1 hemp variety could be considered apt to be grown as a rotational crop. On a similar note, hemp varieties such as Katani and Grandi could also yield high as they showed to be as productive as CFX-1. Hemp varieties such as Joey or Canda may not be the best choices as yield is below par the aforementioned. It is ambitioned that next year we can grow hemp varieties and compile results for a better approach in yield differences among them.
