Canola Seed Bulking Equals Improved Seeding Rate Accuracy

Mixing seed and fertilizer is a practice which can work successfully as a way of "bulking up" canola seed to more precisely control seeding rates. This can overcome the problem that some drills have, which cannot be accurately set to the low 3.5 - 4.5 lb per acre seeding rate recommended for canola. In addition, metering of seed through individual seed cups can differ, resulting in uneven seed distribution, even if the correct seeding rate is achieved. Some growers have reported that flow through the drill can be affected by humid weather. Under higher humidity, flow is restricted resulting in 'grinding' of seed.

Bulking of seed using fertilizer can overcome these obstacles and provide some 'starter' benefit to canola seedlings. There are a few precautions to make this practice work.

Phosphorus & Nitrogen Banded With Seed

Seed-placed fertilizer can substantially reduce germination and emergence of canola if applied above recommended safe rates. This is because of the 'salt ' effect of fertilizer when placed close to the seed. Injury is most likely on light textured soils, soils low in organic matter or during dry weather.

In Ontario, the recommendation for canola is for a maximum rate of 20 kg/ha (18 lb./ac) of phosphate fertilizer drilled with the seed. Nitrogen, except as monoammonium phosphate (MAP), and potash should not be applied with the seed. MAP has an analysis of 11-52-0. Generally, it is recommended that the rate of nitrogen not exceed 11 kg/ha (10 lb/ac). Some growers report using other fertilizers or higher rates with no apparent problems. Canola is able to tolerate higher rates of fertilizer with adequate moisture, but it is unknown before planting when adverse conditions for germination will occur.

Selecting the Right Bulking Agent

Monoammonium phosphate (MAP) and pelletized sulphur have shown the most promise as fertilizer bulking agents. The Canola Council of Canada is conducting research trials to evaluate pelletized elemental sulphur (10 to 30 lb/ac) as a seed-bulking agent. The council is testing whether by blending seed-sized sulphur and canola seed if seeding rates can be reduced enough to offset the cost of the sulphur.

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Current canola production recommendations set target plant populations between 80 and 110 plants/m^2. (7 - 10 plants/sq ft). However, canola can aggressively compensate for lower populations without any yield loss. Trials have demonstrated that a uniform stand of 10 plants/ m ² will have a yield that is 90% of a full stand. At today's higher seed costs, shaving seeding rates could represent a significant saving. Pelletized sulphur is similar in density and size to canola, reducing the risk of separation in the drill. Elemental sulphur has a low amount of available sulphur (5%) and low salt toxicity. Canola has a relatively high requirement for sulphur, but Ontario research has not demonstrated a benefit to sulphur fertilization.

MAP (11-52-0) fertilizer is more dense than canola but similar in size. Crop safety is excellent when applied below the safe rates noted earlier. However, MAP like other fertilizers can be inconsistent in particle size. Some sources of MAP provide more consistent particle size. Growers have also reported few concerns with separation of MAP and seed. Hybrid canola has a larger seed size than open pollinated types and is more similar in size to MAP. Another form of MAP, called mini-map, which is often used as a starter fertilizer in corn, is much smaller than canola seed, making it not suitable as a bulking agent.

Don't delay planting of canola - fertilizer blends

The salting out effect of fertilizer draws moisture, which can cause desiccation of seed. This can substantially lower germination or vigour. To be safe, only mix the amount of seed and fertilizer together that will be planted in a day. It is unclear as to how long a seed - fertilizer blend can be stored. Humidity conditions and the type of fertilizer will greatly affect this storage time. High humidity will cause some fertilizer types to absorb moisture quickly.

Calibration

It will be important to check the actual output of the drill using the bulked canola blend. Check the output from a number of runs across the drill to ensure similar seeding rate is achieved.

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