Concerns with Broadcast Seeding Methods

MASC data from 2005 to 2010, indicates, on average over 1.2 million acres of spring wheat and canola are seeded in the third week of May. The MASC dataset also indicates farmers have planted 60% of the province’s wheat crop, and 42% of the canola crop, in a single week given good working conditions. Essentially, when conditions are good, a lot of crop can get into the ground in short order.

Thoughts Turn to Alternative Seeding Methods
Even though it is only the second week of May, talk in the coffee shops has turned to considering broadcast seeding by floater or aerial application. This is not the time to consider seeding crops by broadcasting, as most crops grown in Manitoba maintain yield potential until the beginning of June. For example, in the 4th week of May, sunflower, canola, soybean and edible beans have lost negligible yield, while spring seeded cereals, peas and corn yields have only been reduced15% of normal yield potential.

In general, broadcast seeding is not recommended. In any seeding operation, you need good seed-to-soil contact and a uniform seed placement to optimize germination and emergence. Broadcast seeding results have been variable because of the inability to get the necessary seed-to-soil contact and uniform seed placement.

In a 3-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 seeded 2 to 3 weeks later. Cereals sown by air did not penetrate the soil, resulting in poor germination and had reduction of seed numbers due to predation and exposure. Final results were reduced stands, grain yields, increased weed competition, and maturity variability.

In the same study, seed broadcasted by fertilizer spreader, followed immediately by light harrowing improved populations and yields compared to aerial seeding. However, results were not as consistent as seeding by conventional drill. Results from broadcast seeding will often be dictated by whether the seed can be covered. Therefore, date of seeding by broadcasting will still be influenced by the date when the soil is dry enough to allow harrowing. This includes seeding canola by aircraft onto very wet fields – if it’s too wet to drive across, it’s too wet too 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 Insured’s coverage as determined by the corporation. For canola, if you are still set on this seeding option, the following may help you achieve a stand that Manitoba Agricultural Service Corporation (MASC) will cover.

• Increase the seeding rate by 1 lb/ac acre to account for increased losses due to poor seed placement and non-uniform seed depth.
• Harrow-packing, vibra-shanking with harrows and packers, or light discing with harrows and packers to cover the seed as soon as possible after broadcasting. 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 phosphorus broadcasted is only about half as efficient as that 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?
There has been discussion in previous years about broadcast seeding of soybean and sunflower crops and more recently cereals. This is not recommended. These crop types need to be placed deep enough into 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 important in these crops – a shallower rooted sunflower with a heavy head will fall over as it does not have the rooting support. Cereals attached to the soil by a limited root system can twist with the wind, resulting in dislodged plants and death. Another added concern with soybean – seed inoculant on soybeans are 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 must be given to using conventional seeding methods in order to optimize germination and emergence, the first step in setting maximum yield potential. For some crop types, broadcast seeding should not be considered at any time.

Sources:

• Optimizing Stand Establishment in less than Optimal Conditions. A.Kubinec & P. de Rocquigny, Crops Knowledge Centre, MAFRD
• Seeding Cereals by Air and Ground. G.M. Barnett & J.E. Comeau. Canadian Journal of Plant Science, 1980, 60:1147-1155, 10.4141/cjps80-167
• OMAFRA Spring and Winter Canola: Planting and Crop Development