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The Trouble With Broadcast Seeding

With minimal acres seeded the first week of May 2011, the later-than-normal seeding is the talk of the coffee shop.

But it’s too soon to panic.

Data from the Manitoba Agricultural Services Corporation shows that from 2005 to 2010 more than 1.2 million acres of spring wheat and canola on average are seeded in the third week of May. The MASC data also indicates farmers have planted 60 per cent of the province’s wheat crop, and 42 per cent of the canola crop in a single week given good working conditions.

Most crops grown in Manitoba maintain yield potential until early June.

For example, in the fourth week of May, sunflower, canola, soybean and edible beans have lost negligible yield, while the yield potential of spring-seeded cereals, peas and corn yields have only been reduced 15 per cent.

NOT RECOMMENDED

This is not the time to consider seeding crops by broadcasting by floater or aerial application. In any seeding operation, you need good seed-to-soil contact and a uniform seed placement to optimize germination and emergence. That’s hard to accomplish with broadcast seeding.

In a three-year study by Barnett and Comeau (Canadian Journal of Plant Science,1980), aerial seeding of oats, wheat and barley was inferior to a conventional drill even when seeding took place two to three weeks later. Cereals sown by air did not penetrate the soil, resulting in poor germination. Final results were reduced stands, lower grain yields, increased weed competition, and variability maturity.

The same study found that seed broadcasted by fertilizer spreader, followed immediately by light harrowing improved populations and yields compared to aerial seeding. However, results were less consistent than conventional drill seeding.

Results from broadcast seeding will often be dictated by whether the seed can be covered. So the date of broadcast seeding will still be influenced by the date when the soil is dry enough to allow harrowing. If it’s too wet to drive across, it’s too wet to seed by any method.

CROP INSURANCE CONSIDERATIONS

MASC will not cover crops broadcast seeded by ground rig or aerial applications unless it is shown that the crop germinated and established a sufficient stand to yield at least the farmer’s coverage.

But if you are still set on this seeding option for canola, the following may help you achieve a stand that Manitoba Agricultural Service Corporation (MASC) will cover.

Increase the seeding rate by one lb./ac. to account for increased losses due to poor seed placement and non-uniform seed depth.

Cover the seed as soon as possible after broadcasting by harrow packing, vibra shanking with harrows and packers, or light discing with harrows and packers. Harrowing alone may not pack well enough to ensure germination.

Avoid creating lumps or clods during cultivation or straw piles.

If broadcasting fertilizer as well as seed, be aware that broadcasted phosphorus is only about half as efficient as banded. There is also greater risks of denitrification on saturated soils, reducing N fertilizer efficiency. Adjust fertilizer rates accordingly, keeping in mind a realistic target yield based on the time of year and field conditions.

OTHER CROP TYPES?

The potential for success is even lower with other crops such as soybean, sunflowers and cereals. They need to be placed deep enough in the soil to receive constant moisture to stimulate germination and emergence. If germination starts, but the seed dries out, it’s dead.

Root development is also key – a shallower-rooted sunflower with a heavy head will lodge. Cereals attached to the soil by a limited root system can twist with the wind, resulting in dislodged plants and death. Seed inoculant on soybeans is at risk of drying out and perishing if the seed is placed on the soil surface instead of in moist soil.

FINAL THOUGHTS

During the month of May, priority should remain on using conventional seeding methods in order to optimize germination and emergence.

Sources:

Optimizing Stand Establishment in Less than Optimal Conditions. A. Kubinec &P. de Rocquigny, Crops Knowledge Centre, MAFRI

Seeding Cereals by Air and Ground. G.M. Barnett &J.E. Comeau.Canadian Journal of Plant Science, 1 9 8 0 ,6 0 : 1 1 4 7 -1 1 5 5 , 10.4141/cjps80-167

http://www.omafra. gov.on.ca/english/crops/pub811/4tillage.htm#aerial

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