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Seeding delays hurt some crops more than others

What is the best seeding date for different crops?


April 8, 2008
By Bruce Barker

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What is the best seeding date for different crops? Most crops grown on the prairies like to be seeded early, all within a 10 day window or so. Unfortunately, getting all the crops into the ground in such a short period of time is not achievable for most farmers due to machinery, weather and time constraints.

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Spring wheat suffered the lowest yield loss with later seeding, while yellow mustard suffered the most. Photo By Bruce Barker.

“Practical considerations dictate a trade-off between optimal yield potential and workload spreading,” says Rob Dunn, land management specialist with Alberta Agriculture and Food (AAF). “Earliest is best. There’s a gradual yield decline when we have a one or two week delay after the optimum time. It really drops off after three weeks.”

Dunn explains that yield declines are attributed to a shortened vegetative and grain filling period as well as lower water use efficiencies. Seeding earlier helps to avoid heat and drought stress at flowering, and provides a longer grain filling period that is especially important for cereals. Yield loss is minimized when growing an early maturing or early planted crop that completes a greater portion of its life cycle before the onset of summer heat or drought.

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Most dryland crops can be planted early on the prairies, since they are able to germinate in relatively cool soils. Seeding can usually begin when average daily temperature reaches five degrees C at a two inch soil depth. The exceptions are warm season crops like chickpeas, corn and sunflowers, which require warmer soil temperatures in the nine to 10 degrees C range to initiate germination. Kabuli chickpeas germinate at 10 degrees C, for example, although desi chickpeas initiate germination at six degrees C.

To put those seeding dates into perspective, the average temperature at Lethbridge from 1997 through 2006 was five degrees on April 8 and 10 degrees C on April 26. Dunn says that comparable Swift Current temperatures would be about one week earlier.

Research at Agriculture and Agri-Food Canada (AAFC) in Swift Current, Saskatchewan, shows the relative performance of crops seeded at 10 days earlier or later than the ‘normal’ May 10 to 15 date. Spring wheat had the least yield decline from the earliest to latest seeding date – an 11 percent decline. Yellow mustard had the greatest with a 39 percent yield decline from the earliest to latest seeding date.

Other research also found similar trends. For yellow mustard, Stewart Brandt at AAFC Scott found yields declined by 32 percent when seeding was delayed for four weeks. Ross McKenzie with AAF found southern Alberta mustard yields declined by 37 percent with seeding delays of three to four weeks.

Similarly, McKenzie found that malt barley yields were reduced by about 20 percent with seeding delays of about three weeks. Losses were greater in years and at sites with more severe drought stress. Other AAF research found that barley yields were reduced by 47 percent in central Alberta with a five to six week seeding delay and declines were more pronounced with later maturing varieties.

Chickpea yields also suffered losses with later seeding. The losses ranged from about 10 percent in southern Alberta to about 30 percent in central Montana. In southern Alberta trials, yields declined by 20 percent in AAF trials.

Table 1. Impact of seeding earlier or later than May 10 to 15 at Swift Current, Saskatchewan.
 –  Yield increase (percentage) Early seeding
Yield decline (percentage) Late seeding
Yield decline (percentage) Early to late seeding
Spring wheat  6 minus 5 minus 11
Field peas 3 minus 16 minus 19
Lentil 4 minus 23 minus 27
Desi chickpeas 5 minus 9 minus 14
Canola – Argentine 13 minus 6 minus 19
Canola – Polish 6 minus 24 minus 30 
Brown mustard 1 minus 20 minus 21
Yellow mustard 22 minus 17 minus 39
 Source: AAFC, Gan et al.

When is too early?
Dunn says that crops have different susceptibilities to post-emergence frost. Broadleaf crops are generally more at risk than cereals. Cereals are more tolerant because their growing point remains below the ground. Peas and lentils are the most tolerant of broadleaf crops and, although they can be injured by frost, they can regrow from a scale node at or near the soil surface.

Balancing early seeding with frost risk is the delicate act which farmers go through every year when deciding which crops to seed first. Dunn suggests that peas and cereals are good choices for early seeding because they have better frost tolerance than oilseeds. If barley and wheat are grown, then barley could be planted before wheat since barley’s earlier maturity will help spread the workload at harvest.

By late April to early May on the southern prairies, oilseeds can be planted to capture good yield potential while reducing the risk of spring frosts. Finally, warm season crops can be sown once the soil temperatures warm up later in May. -end-

What happens with delayed winter cereal seeding?
Research has shown that delayed winter cereal planting beyond the optimal date reduces winter survival, delays maturity and reduces yield. Fall rye is hurt the least and is followed by winter triticale, while winter wheat is impacted the most. Later seeding also results in increased weed competition from winter annuals and early emerging spring weeds.

Ross McKenzie, with Alberta Agriculture and Food, looked at whether increasing seeding rates could help compensate for delayed fall seeding. In the research, winter wheat yields were 18 percent lower and winter triticale 11 percent lower when seeded three weeks after the optimum date. He also found that the higher seeding rates did help increase yields, but did not fully compensate for the delayed seeding.

Generally, the optimum seeding date for winter wheat is September 9 at Lethbridge, September 6 in the Maple Creek and Estevan regions, September 3 for the Kindersley and Swift Current areas, and August 30 for the North Battleford, Saskatoon, Wynyard and Yorkton regions. -end-

The Bottom Line
We have found, unfortunately, that not every crop can be planted by the first Tuesday in May as recommended. Our planting sequence takes into account how we manage the crop after planting such as the order we would apply herbicides, insecticides, the order we would need to desiccate, swath and harvest. By pre-planning our planting, we hope to maximize our operations in regards to time, labour and equipment use. We also take into account the sensitivity of the crop in regards to grade loss. An example would be to harvest the grass seed first before wet weather limits its drying ability, harvest green peas next before they bleach, the rest of our pulses next to ensure maximum aeration during the long, sunny warm days of August, and perhaps leaving our flax and canola towards the end of harvest as they can tolerate periods of wet, cool weather while maturing. Warren Kaeding, Churchbridge, Saskatchewan.

In my area of west central Saskatchewan, early seeding has always proven to be the best
strategy. Late frosts are seldom the issue, often the main problem is getting everything ready to seed early. Ian McPhadden, Milden, Saskatchewan. -end-