Starter fertilizer – How low can you go?

We are receiving more and more questions on starter fertilizer. More growers are discussing optimal starter fertilizer rates and how low starter fertilizer rates can be. These questions are the result of wanting to keep fertilizer costs down, to plant as many acres per day as possible, and to take advantage of more efficient, low-rate banded P fertilizer compared to higher broadcast P fertilizer rates. To illustrate the role of starter fertilizer rates and seed placement, we put together displays showing the distance between fertilizer granules or droplets at various rates and row spacings. On our website, you can find all the displays for corn, soybean, canola, and sugar beet. We greatly thank John Heard with Manitoba Agriculture for helping with these displays.

The displays show the normal seed spacing for several crops with different dry or liquid fertilizer rates alongside the seed. These displays help visualize the distance between the seed and fertilizer at several rates. University research shows that to achieve the full starter effect, a fertilizer granule or droplet must be within 1.5-2.0 inches of each seed. If the fertilizer granule or droplet is more than 1.5-2.0 inches away from the seed, the starter effect is lost.

If you are wondering about the accuracy of these displays, you can prove it to yourself pretty easily. Just run the planter partially down on a hard surface at normal planting speed. What you imagine as a constant stream of liquid fertilizer, ends up being individual droplets at normal speed, especially with narrow row spacings and lower fertilizer rates.

These displays will help you explain to growers how the starter fertilizer rate must be adequate to keep fertilizer within 1.5-2.0 inches of each seed for the full starter effect. In addition to an adequate starter fertilizer rate, additional P and K should be applied to prevent nutrient mining, causing soil test levels to decline in years when minimum fertilizer rates are applied. If very low fertilizer rates are applied, soil test levels will decline and require higher rates of fertilizer in the future to maintain good yields.

Check out all the fertilizer displays by clicking here.