Page 211 - Nutrient Management Planning Guide

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Getting the Most Out of Commercial Fertilizer Applications

sensitive areas. Broadcasting, even with incorporation, mixes fertilizer with crop residue. As a result, microorganisms immobilize nutrients (primarily N) for weeks or months while they decompose the residue. Because of these limitations broadcasting is usually considered the least efficient way to apply most crop nutrients.

Seed-Placed

Seed-placed fertilizer refers to fertilizer placed within the seed row. It can be an effective placement method because the added nutrients are in close proximity to developing roots making them readily accessible to plants. This is especially important for immobile nutrients such as P and Cu.

There is no common nutrient loss process (e.g., volatilization or run-off) for seed-placed fertilizer. The problem with this method, however, is that fertilizer in the seed row can be harmful to seed, delaying or severely reducing crop emergence. This damage is due to ammonia toxicity or a salt effect from the fertilizer. The maximum fertilizer rate that can be safely placed in the seed row depends on the fertilizer used, crop type, soil moisture, and the width of spread of seed and fertilizer in the seed row (SBU). Urea (46-0-0) is the most damaging seed-placed fertilizer due to ammonia toxicity. Potash (KCl) and ammonium sulphate (20-0-0-24) are also problematic since these products induce a salt effect. Usually this is not as damaging as ammonia toxicity.

Band or Side Band

Banding is the application of fertilizer in a narrow row at seeding depth or slightly deeper. Banding can be done weeks or months prior to seeding, or during seeding depending on equipment. Side-banding refers to the

placement of fertilizer in a narrow row slightly to the side and below the seed row during the seeding operation. Banded and side-banded fertilizer applications have similar characteristics, and are both considered “banded” fertilizer. Mid-row banding places a row of fertilizer midway between two rows of seed, during the seeding operation. Side-banding and mid-row banding maintains a consistent distance between fertilizer and the seed, while fall banding or banding in a separate operation creates varying distances between fertilizer granules and the seed row.

Band placement is efficient for most fertilizers since the band is below the seed and roots will grow toward the fertilizer source. Banding creates a greater distance between seed and fertilizer, and this allows the opportunity to apply higher rates of fertilizer during seeding without a risk of ammonia toxicity and salt effect. For N, the narrow band of fertilizer is below crop residues so immobilization is not a factor. For P and K, the band has minimal soil contact and consequently little sorption occurs. There is no common nutrient loss process (e.g., volatilization or run-off) with spring banding.

Banding fertilizer may require an additional field operation and cost more because of additional energy requirements (e.g., fuel). Banding is not an effective placement for elemental sulphur because weathering and redistribution is limited.

Dribble banding refers to the application of liquid fertilizer in narrow strips on the soil surface before or after seeding. The effectiveness of dribble banding is more comparable to broadcasting than to banding fertilizer. Nutrient loss processes common to dribble banding and broadcasting include N volatilization and immobilization and P, K, and Cu stratification.