Safe seed-placed fertilizer practices and equipment limits

When it comes to applying seed-placed fertilizer, it is important to find the suitable application rate for each specific soil type and composition. But it is also important to understand that seeding equipment and technology is a factor, and may impact growers’ fertilizer rates.

The seed-safe rate for fertilizers relies on numerous factors. Crop choice, soil composition, pH levels, organic matter, seedbed moisture, and field variability are all necessary components in determining seed-safe rate.

On top of that, the Seedbed Utilization (SBU) is another very important factor in the seed-safe rate. But the SBU is the only component based on the equipment the grower is using, and it is one of the most important elements in safe fertilizer application.

Garth Donald, Manager of Agronomy at Decisive Farming, thinks even modern farming technology can be big limiting factors when it comes to seed placed fertilizer application.

Many drills use a twin-knife seeding system, where the second knife places the fertilizer a safer distance away from the seed than traditional seed-placed fertilizer.

The SBU takes the spread of the seed and fertilizer out of the openers by the spacing between openers to calculate the safe seed rate. The greater the spread and smaller the spacings, the more fertilizer can be applied.

“If you take a nine-inch spacing on a one inch spread on medium soil, that’s 25 pounds of nitrogen you could safely put down,” said Donald. “With a two-inch spread on nine-inch spacing, that’s 35 (pounds). That’s 10 more pounds. It’s the same row spacing, but you’ve added that inch of spread.”

However, any single knife systems place the seed and fertilizer in the ground out of the same opener, which creates problems in comparison. This lowers the safe seed-placed fertilizer rate dramatically, often leading to farmers applying fertilizers in different ways, typically by broadcasting it with a spreader.

This can create a new challenge for growers.

“If you put everything through the (fertilizer spreader), that’s fine, it’s seed-safe,” said Donald. “However, your roots aren’t going to reach non-mobile nutrients in the year of application. It’s a year after.”

This means farmers need to plan ahead with their application of fertilizer, and “build” the nutrients in their soil for the future.

“To get around it is to change your philosophy,” said Donald. “You’ll put the max seed-safe with the seed. But then you’re going to have to look at your forward planning. So, you may put down Phosphate, or you might make a Nitrogen Phosphate blend that goes down the mid-row bander (Fertilizer spreader on a seeding drill). But that’s for next year.”

Different seeding units provide different options for growers, and each provide a different SBU. Knowing the equipment’s limitations on seed-placed fertilizers can help farmers maximize yields, while minimizing risk.

For more information on implementing a soil health strategy on your farm, contact us today.