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Finding optimum seeding rates for winter cereals

Winter cereals benefit from higher rates.

Establishing a good plant stand in the fall is critical to overwinter survival and to maximize crop competitiveness and yield potential the following spring. Skimp on seeding rates and a grower just might not have enough plants per square foot to maximize yield. That is the finding of several research studies conducted during the last few years.

Target high plant stands using 1000 kernel weight calculations for optimum winter cereal establishment. Photo courtesy of Rick Taillieu, RTL

“Seeding rate is part of an integrated approach to crop production. For winter wheat, seeding depth, cultivar selection and fall weed control are also key components in establishing a good plant stand in the fall and following spring to achieve optimum yield,” says Brian Beres, an Agriculture and Agri-Food Canada research agronomist at Lethbridge, Alberta.

Looking at winter wheat and winter triticale, Beres cites two studies, one of his own and one by Ross McKenzie with Alberta Agriculture and Food (AAF), that
support higher seeding rates. Beres’ study, which was a collaboration with Dr. Bob Blackshaw and Lacombe scientists Drs. George Clayton and Neil Harker, looked at four different winter wheat varieties, and compared seeding rates of 30, 45, and 60 seeds per square foot (300, 450, and 600 seeds per square metre) at Lacombe and Lethbridge.

A seeding rate of 450 seeds per square metre would equate to approximately 2.3 bushels per acre for CDC Falcon winter wheat, but this fluctuates with every seed lot due to variation in 1000 kernel weight.

Comparing the effect of seeding rate on stand establishment and spring emergence, the 300 seeds per square metre seeding rate did not always hit the targeted spring stand establishment of 200 to 275 plants per square metre.

“In this study, we had very good spring emergence conditions, yet at the 300 seeds per square metre rate, we still only had about 200 plants per square meter in the spring,” explains Beres. “Two hundred plants per square metre is the minimum stand I would want and we were only able to achieve that in one year at Lacombe with the 300 seeds per square metre, so I think that you gain a lot of insurance against poor stand establishment if you move up to a 450 seeds per square meter seeding rate.”

Table 1. Effect of seeding rate on spring plant density, yield and quality of winter wheat. Source: McKenzie et al. 2007

Beres did not observe a difference in yield between the 300 and 450 seeding rate, but grain yield dropped off at the 60 seeds per square foot at Lacombe. He says this may be due to a lack of fertility at the highest seeding rate, since fertilizer rates were not adjusted as seeding rates were increased. However, crop competitiveness significantly increased with higher seeding rates, which also resulted in lower dockage.

Rick Taillieu, Reduced Tillage Linkages agronomist in Camrose, Alberta, says many growers are adopting higher seeding rates with winter cereals, and that with high grain and input prices, it is important that growers target a good plant stand.

“There is a lot on the line, so establishing a healthy, competitive crop will help ensure winter wheat growers get the best yield possible,” says Taillieu. “There is a very strong correlation between higher plant stand and yield, so it is definitely worth the effort to calculate seeding rate based on seed size and combined germination percentage and seed vigour.”

In McKenzie’s study at three locations in southern Alberta, a positive response to increasing seeding rates from 150 to 350 plants per square metre was also seen for both winter wheat and triticale. Spring stand establishment was the highest for the highest seeding rate of 35 plants per square foot (350 plants per square metre), as was yield.

Dale Soetaert, a Ducks Unlimited agronomist in Edmonton, says that deep seeding can also produce a wreck and winter wheat growers should resist the notion to seed down into moisture. Soetaert explains that winter wheat needs very little moisture to germinate, and the seed is better off placed in dry soil near the soil surface than deeper into moisture. “Physically, the plant has a very difficult time emerging if it is planted more than one inch deep. It has a very short coleoptile, so deep seeding will result in a poor plant stand,” explains Soetaert.

In addition, Soetaert says that research has shown that winter wheat sown shallow into dry dirt emerges just as quickly as when it is sown deeper into moisture. He cautions growers to avoid waiting until rainfall occurs in the fall because that could compromise the stand establishment as well.

Regarding seeding rates, Soetaert has seen the benefits of higher rates first-hand in the field. He says a general recommendation is to seed around two bushels per acre in the south, and in the Parkland, to push rates up to 21⁄4 to 21⁄2 bushels per acre, ideally targeting 300 seeds per square metre to achieve a spring plant stand of 200 to 275 plants per square metre.

Beres also conducted a winter wheat seeding demonstration at the Southern Applied Research Association diagnostic field school. He compared three seeding rates of 100, 300 and 500 seeds per square metre, two winter wheat varieties (AC Bellatrix and AC Radiant) and a 1:1 blend of both, and two seeding depths. In the demonstration, he observed similar trends, with the medium to high seeding rates producing the highest yields.

The importance of seeding depth was also highlighted, with low seeding rates and deep seeding producing low yields.

“We basically wanted to show what can happen, even when the best genetics are used, with poor agronomic practices,” explains Beres. “The best yields come from higher seeding rates and shallow seeding.”