As spring approaches we are getting more questions on starter fertilizer rates. Many questions revolve around what is the lowest rate of fertilizer that can be applied with the seed and still get a starter effect. These questions are the result of growers wanting to seed as many acres per day as possible. Growers also want to keep fertilizer costs down and take advantage of the efficiency of banding lower rates of P fertilizer compared to broadcast P fertilizer.
To give agronomists and growers a better idea how far apart dry fertilizer particles or liquid fertilizer drops are at various rates of P fertilizer, we put together a few tables. These tables show the distance between fertilizer particles or drops of liquid fertilizer at various rates. We also created a visual display of these tables (see pictures below). You can see all of the pictures like this for corn, soybeans, wheat canola and sugarbeets on our website (Thank you to John Heard from MB Agriculture for helping with this project). These displays show the actual seeds of several crops with a dry or liquid fertilizer rate right alongside the seed. These displays are a great way to show growers a real view of the distance between the seed and fertilizer materials at several rates of dry and liquid fertilizer. University research has shown that to get the full starter affect, a fertilizer drop or particle must be within 1.5 – 2.0” of each seed. If the fertilizer particle or drop is more than 1.5 – 2.0” away from the seed, the starter effect is lost. In the tables, you will see what rates are necessary to get the starter effect at various row spacings.
Some people don’t believe these displays, but you can prove it to yourself pretty easy with liquid fertilizer. Just run the planter/seeder at normal speed (5-8 mph) across a hard surface/tarp and see what you get. Once you get up to full speed of planting, you will see that what looks like a steady stream of liquid fertilizer when the planter is standing still, ends up being individual drops hitting the ground with some space between them. At low rates of fertilizer the spaces will be wide and you will not get the starter effect you are counting on. The solution is to apply higher rates, which will give you the starter effect you need. This higher rate of P2O5 will also help keep up with crop removal which should be a long term goal of any fertility plan.
We encourage you to go to www.agvise.com, click on “New – Starter Fertilizer Distribution Display,” and print out a full set of these displays (an example of the seed placed fertilizer with wheat and corn is shown). Having a full set of these displays and the tables from this article on your desk will make it easier to explain to growers what happens when they try to get by with low starter fertilizer rates. Please give our staff a call if you have any questions.