When seeding into dry soil conditions from March until mid-May, the recommendation to seed canola no deeper than 1” still applies. Here’s why:
- There is still time to wait for a rain to provide the moisture needed for germination and emergence. Growers gain nothing from seeding deep in this time period.
- Going deeper to reach moisture also means cooler soil. Cool conditions combined with the extended distance seedlings must grow to reach the soil surface will mean higher seed and seedling mortality. Higher seeding rates will be needed to compensate.
- Deep seeding allows weeds emerging at the same time to get ahead of the crop. Shallow seeding is a good integrated weed management technique.
Things to consider
Field topography. Shallow seeding into dry hilly land may result in uneven emergence if seeds in low spots have enough moisture to germinate even without a rain event. However, in these fields, deep seeding to reach moisture may not necessarily be an improvement. Uneven emergence is still a strong possibility. The good news is that seeds emerging first in these lower areas may mature later due to better moisture and fertility, so in the end, differences in emergence date between low spots and hill tops may even out later in the season.
Soil type. Growers may get away with deeper seeding – at 1” instead of 1/2” – in lighter soils. Sandier soil tends to dry out faster on top, so moisture and seedbed conditions would be better at this slightly deeper depth.
The tillage effect. In tilled fields, the top layer will be dusty in dry conditions, so seeding at 1” instead of 1/2” could be a benefit. No till is ideally suited to areas that tend to be dry.
Seeding rate. Seeding deeper than recommended will often require a higher seeding rate to meet target plant stands, given that seedling mortality will be higher in deep soils – especially with the added stress of dry conditions.
Seed-placed fertilizer. Dry conditions increase the risks from fertilizer damage to seed and seedlings. Take extra care in dry conditions to limit seed-placed fertilizer to no more than 20 lb./ac. of phosphate. Turn off seed-placed fertilizer for 50 to 100 feet to leave a couple of checks. Evaluate strips to see how seed-placed fertilizer influenced the stand.
Clubroot. Seeding in dry conditions and waiting for moisture will reduce the risk of spreading clubroot versus seeding into moist soils because less soil will cling to implements.
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