AGRO 3503, Unit I-5. Combines and grain harvesting.


All cereal crops are harvested with grain combines. The purpose of this unit is to familiarize you with the basic functions of the grain combine, variations of the basic components, factors related to efficient grain harvesting, and some new technology in grain harvesters.


All grain combines have four basic parts:


1) the header collects the grain and cuts it,

2) the threshing unit place where the grain is separated from the plant,

3) sifter/straw separators place where the grain is cleaned,

4) augers/bins stores the grain until it can be transferred.


I. Header units. Around 75% of harvest grain losses occur at the header. There are various kinds of headers on the market today. Here are some



Corn header:


Reel header, batter board type:



Reel header: pick up reel.



Stripper header.



Air reel (uses air to force stalks onto cutter bar)



There are basically three main types of thresher units:

1) rasp-bar separate grain with friction.

2) flail separate grain with force.

3) rotary separate grain with centrifugal force and combinations of the above.


There are several factors that will affect the efficiency of grain harvesting:

1. grain moisture content

2. header reel speed, positioning

3. ground speed

4. weed interference

5. thresher settings

6. operator skill

7. dull cutter bar

8. transfer, transport losses

9. many others


Grain harvesting is more of an art. An operator can get the best combinations of settings and speed in the morning, but it will be different in the afternoon or evening with changes in grain moisture content and climatic conditions. It is best to observe all the manufacturers recommended settings and go from there. An occasional check behind the combine for lost grain is also a good idea. Every bushel counts.


Take the quiz on Unit I-5. There are some links about the use of GPS, GIS yield monitors and a few questions on the quiz.