Which Fertilizer Attachments Should
I Put On That New Planter?

Many farmers are looking at updating their corn planters, in anticipation of more corn acres. The question that comes up is "what type of fertilizer system to install on the planter", since it is usually more expensive to retro-fit. Before you can answer this question, you need to look at your entire fertilizer system. The fertilizer applied with the planter will need to be integrated into the bigger picture to provide maximum returns. Only after making this assessment can you decide whether liquid or dry systems will suit you better, and whether it should be seed placed, or in a 2x2 band. 

How much fertilizer do I need?

There is a big difference between an intensive livestock farm, where soil tests have been built up to high levels by regular manure applications, and cash cropping on rented land where only the minimum amount of fertilizer has been applied. In the first case, the only goal of planter applied fertilizer may be a starter boost which can be achieved with a small amount of fertilizer or it could be the application of all the fertilizer for the crop in one pass. In the latter case, much more fertilizer will need to be applied at planting to meet the nutrient requirements of the crop.

How much fertilizer do I want to put through the planter?

There are choices between the amount of fertilizer that is broadcast preplant, applied at planting, and side-dressed. In general, the efficiency of phosphorus (P) use will be greatest if it is banded at planting time, while N and K are much less sensitive to placement. A system that uses a high-P starter on the planter, and broadcasts or side-dresses the rest of the fertilizer will give the greatest starter benefit while minimizing the amount of fertilizer that needs to be carried on the planter. On the other hand, where total fertilizer requirements are relatively low (such as where manure is applied), and where there are competing uses for time after planting, it may work better with the total fertilizer requirements applied with the planter.

What is my tillage system?

In no-till systems, there is a consistent yield advantage to applying a greater proportion of the total nitrogen at planting time (30-40 lb/ac). This does not appear to be the case in conventional tillage, so it is probably a response to reduced N mineralization in the cooler soils under no-till. If you are not broadcasting N pre-plant, and are planting no-till corn, your fertilizer system should be able to apply this N at planting.

Of course, the final choice of system on the planter will be a compromise between the optimum fertilizer use, and the weight, cost and complexity of the equipment added to the planter. Remember that the primary role of the planter is to consistently place the seed at the proper depth and spacing, and any fertilizer attachments that interfere with that are counterproductive.