Seeding is the most critical operation of the year (Figure 3.1) and the decisions made at seeding can affect yield, grain quality, time of harvest and harvest management.
Seeding factors are frequently linked. For example, the time of seeding and seed density both affect crop maturity and influence harvest management.
SEED TREATMENTS
Seed treatments may be used to prevent seed and soil borne diseases, especially smut. The practice of applying a seed treatment is a farm decision and should be based on the level of risk associated with seed or soil borne diseases.
Soil borne diseases such as root-rots are likely to pose greater risks under cool, wet growing conditions in the spring. Hulless oat are more susceptible to seed diseases than hulled oat and seed treatments are recommended.
There are several of seed treatments available for disease and wireworm control. There are many seed treatments registered for oat in 2019 (Table 3.3) (Saskatchewan Guide to Crop Protection).
SEED SIZE
The relative importance of seed size of a seeded oat crop has been a topic of conversation for many years. Greenhouse studies indicate that larger seed is more vigorous and more competitive with wild oat (Willenborg et al. 2005).
“Our results clearly demonstrate the importance of initial caryopsis [grain] size to the outcome of wild oat-oat competition, and suggest that the ability of oat to exhibit both an increased competitive response and effect to wild oat competition may be a product of specific crop traits such as caryopsis [grain] size.”
As the experiments on seed size were conducted in a greenhouse, the authors comment that: “further investigation is needed to examine the response of oat-wild oat competition to oat caryopsis [grain] size and genotype under field conditions. “
In research conducted at Yorkton and Indian Head, SK, seed size increased early oat vigor, as expressed in biomass, but did not result in significant differences in yield
TIME OF SEEDING
Early seeding can result in increased yield and test weight (see research paper below). Early harvest may also result in higher quality in regions that are prone to frequent fall moisture.
The time of seeding relative to weed emergence is arguably the most important factor affecting weed competition. In fields where wild oat populations are low (see crop rotation above), early seeding caneffectively reduce wild oat competition. Delaying seeding (often practiced by organic growers), is an alternative strategy for weed control. A delay in seeding can allow for pre-seeding control of weeds by tillage or herbicides. However, for wild oat, the strategy is not as effective as with early emerging weeds like kochia. Wild oat emerges relatively late and continues to emerge over 4 to 6 weeks. A better strategy is to select another field with lower wild oat pressure.
Seed early to increase yield and avoid late harvest.
Research Paper (2004): Canadian Journal of Plant Science (2004) 84: 431-442
“Early seeding dates improve oat yield and quality in the eastern prairies”
Authors:
William E. May1, Ramona M. Mohr2, Guy P. Lafond1, Adrian M. Johnston3, and F. Craig Stevenson4.
1 Agriculture and Agri-Food Canada, Indian Head Research Farm
2 Agriculture and Agri-Food Canada, Brandon Research Centre
3 Potash & Phosphate Institute of Canada
4 Private Consultant
Introduction:
“Traditionally, oat (Avena sativa L.) was the last crop seeded on farms in western Canada. Oat could be planted last and still be harvested or used as fodder depending on needs. The late seeding allowed farmers the opportunity to control wild oat (Avena fatua L.) in tame oat with tillage prior to planting. The harvested oat tended to be consumed locally with little attention paid to quality.”
“There have been many changes in cropping practices on the prairies since the early studies in western Canada, the most significant being the introduction of one-pass seeding and fertilizing conservation tillage systems. These new production systems increase the amount of winter precipitation that is captured by the soil, resulting in higher yield and economic return. This increase in available water may increase the yield and quality of oat since oat requires more water than the other cereals.”
Summary:
In this study, conducted during 1998 to 2000, 3 locations were used: Brandon, Indian Head, and Melfort. AC Medallion, AC Juniper, CDC Boyer, and CDC Pacer were the varieties tested. Four seeding dates were chosen: early May, mid-May, early June and mid-June, and the target dates of these were May 1, May 15, June 01 and June 15.
Results And Discussion:
- Delayed seeding decreased the yield of all four varieties.
- Disease resistance matters as it maintains plant health and the ability to continue using moisture for growth, while susceptible varieties suffer a decline during mid-summer dampness.
- “Two [related (1968 & 1990)] studies found that higher temperatures during development reduced seed yield.”
- “Delayed seeding increased thin seed percentage at most locations;”
- “Results from this study clearly show that oat producers can grow more high-quality oat if seeding is conducted in the first 2 weeks of May.”
SEEDING DEPTH
Seed should be planted deep enough to reach soil moisture and never deeper than 8 cm (3”). In direct seeding and where seedbed moisture is optimum, seed depth should be targeted at 2-3 cm (0.75” – 1.25”).
Emergence generally decreases with increased seeding depth and deeper seeding has been associated with increases of some seedling diseases in other cereal crops.
ROW SPACING
Oat is usually seeded with a row spacing of 18-30 cm (7.5-12 inches). Research over a number of years has demonstrated that there is very little differences in yields within these row spacings. However, wider row spacings may result in an increased problem with wild oat and other weed species in oat.
As there is no chemical control for many grassy weed species, care must be taken when using wider row spacing. In addition, wider row spacing may result in difficulty managing swaths in dry conditions as there may not be enough stubble to hold the swath off the ground.
SEEDING RATE
While a plant population of 20-30 plants/ft2 (215 to 320 plant/m2) is usually recommended, research has consistently shown the benefits of increased seeding rates. Next to early seeding, seeding rate is one of the most powerful strategies available for reducing weeds.
Reasons to increase seeding rate:
- High fertility
- Optimum moisture
- Deep seeding
- Late seeding (to reduce tillers)
- Wild oat present
Li et al. (2018) (Figure 3.3) reported that a seeding rate of approximately 44 plants/ft2 (473 plants/m2) decreased weed biomass by more than 50% and increased oat yield. In addition, a high seeding rate reduces the tillers/plant and decreases the time to maturity (Hall and Holzapfel. 2018. Oat Vigour Improves with Larger Seed Size. Report submitted to Saskatchewan Oat Development Commission). The effect of seeding rate on maturity can be seen visually below.
SEEDING RATE CALCULATOR
Optimal seeding rates vary among varieties and are based on kernel weight. Both germination and seedling survival needs to be considered. A field mortality rate of 20 to 30% should be expected (May et al. 2004).
Seeding rates can be calculated using a phone app, for example Seed Calculator from Beyond Agronomy, or online.
A seeding rate calculator from Alberta Agriculture and Forestry is available to assist oat growers to obtain the desired plant density (Figure 3.4). Enter the plant density required, the 1000 kernel weight of the variety, the germination rate, and row spacing. It is also important to note that the emergence rate of oat is not the same as the germination rate (see below).
Research Paper (2004): Canadian Journal of Plant Science (2004) 84: 431-442
“Early seeding dates improve oat yield and quality in the eastern prairies”
Authors:
W. E. May, R. M. Mohr, G. P. Lafond, A. M. Johnston, and, F. C. Stevenson
Extra Notes:
A field mortality rate of 5% was used to adjust the target plant population to 300 plants per square metre (~28 plants per square foot) of viable seeds (including adjustment for germination).
Interpretation:
While the researchers used a mortality rate of 5%, this was insufficient to provide adequate plant populations.
“However, field mortality for the experiment ranged from 18 to 33% …. Our results Indicate that oat seeding rate recommendations should factor a field mortality rate of 20 to 30% in order to achieve a target plant population.”
