Whether you’re a custom chopper or harvesting forage for yourself, there are several adjustments you can make to your self-propelled forage harvester to meet the quality forage needs set by your customers’ (or your own) nutritionist. 

Unfortunately, nutritionists have no universal set of guidelines for what’s needed in forage to produce the best results. Every nutritionist has their own idea of what the farms they deal with need to make milk production better. Having that in mind, you need to understand what the nutritionist is asking for out of the material. Then you need to know how to set your machine to make it work, either by using the operator's manual of the machine or consulting your equipment dealer representative to help with the adjustments.

The first place to start is with the plate on the bottom of the cutterhead. Having the plate set correctly will help move the crop through the crop channel and help with the initial blowing of the material. This can usually be adjusted up or down mechanically. It needs to be adjusted to the crop you are working with.

A good example is alfalfa, which can be a stickier crop. Depending on its moisture at chopping, alfalfa can drag more and slow down in the crop channel, causing a gummy condition in the crop channel. With the bottom plate being closer, the crop has less opportunity to slow down because it will stay in the pocket that is created by the knives and the air flow inside the chopper body. With the plate set too far away, in alfalfa the crop can rub around the knife, which slows down the crop. In corn, you don't need to have the plate as close because corn isn’t as sticky. You can open it up and maybe gain a little horsepower.

The nutritionist will usually recommend a theoretical length of cut (TLOC) for the various crops. We know that feedroll speed determines the actual TLOC you will be putting out, but having sharp knives and a correctly adjusted shear bar will ensure a quality cut and doesn’t waste power trying to do it. 

The knives and the shear bar act like a pair of scissors to take the incoming crop from the feedrolls and cut it to the desired size. So, like scissors, you will get a better cut when the knives and the shear bar are very close. Improper setting of the shear bar can cause the cut to become ragged and uneven, and you’ll need more power to cut the crop. Although having sharp knives is important, I’ve seen dull knives do a decent job of cutting when the shearbar is set tightly, where the knife barely misses the shear bar. 

The need for knife sharpening will change depending on the type of crop. When you're doing pickup work, you can get more debris coming through the cutting system. This can dull your knives faster, which will require you to sharpen them more often. With corn, you're not as worried about debris because of how the crop is cut and the whole plant is immediately taken into the feedrolls. It doesn't matter if you're cutting grasses, alfalfa, corn or sorghum – your shear bar needs to be set as tight as possible, no matter what. That's my recommendation.

When you are chopping corn, the nutritionists will recommend how they would like the corn kernel processed. In years past, they used to say the kernel needed to be split in half. Now, there are some nutritionists who want the kernel completely obliterated; they don't want to see any chunks. 

To achieve the processing the nutritionist wants, you might need to put different rolls in your unit – for example, a spiral cut roll that has spirals all the way across the teeth of the roll. This type of roll can effectively shred the corn crop for farmers who demand more intensive processing of corn kernels and stover when harvesting at mid- to long lengths of cut.

Another thing that goes along with processing is the roll differential speed. You might need to run the rolls at a certain differential speed to get the material your nutritionist likes coming out of the machine. Each manufacturer will have a recommended speed they would like you to use on their unit, but most of them also have ways of changing that speed by swapping pulleys to increase the differential speed. By changing the differential speed, you can alter how aggressively you process the material – not just the kernel – to break up the stalk so it's more digestible. 

So how you adjust your self-propelled forage harvester all comes down to what material you, your customer or a nutritionist you are working with wants. Keep in mind that many manufacturers have suggestions about settings, adjustments or operations in their operator's manuals that can be very helpful. Also, work with your equipment dealer to help you understand what you need to do to get the desired end product.