Types of grain losses while harvesting with a combine harvester
The basic operation of a combine harvester is to recover the seed, free from any kind of plant residue, with minimum seed loss. Before these huge machines were invented, harvesting, threshing and cleaning was highly time consuming and labor intensive. To know more about the basic working of a straw walker type harvester, go through the attached link - http://varunchhabra.hubpages.com/hub/Straw-walker-Combine-Harvesters-Function-and-working
The word Minimum Seed Loss mentioned in the definition of a combine harvester is a very important aspect of an efficient harvester. In this hub, I would like to briefly explain different types of grain losses that can occur during harvesting through a conventional combine harvester.
First of all, everyone should be aware of a few terms that I will be using throughout the explanation of various losses. These are explained below:
1. MOG: Material Other than Grain – All plant material entering the combine except the grain.
2. Grain/Non-Grain Ratio: Ratio of grain mass to mass of non-grain material. Unless stated otherwise (Eg: walker grain/non-grain ratio), the ratio refers to material entering the machine.
3. Non-Grain Feed Rate: Rate at which the non-grain material is delivered to the cylinder by the header. Walker non-grain feed rate and cleaning non-grain feed rate applies to non-grain material fed onto these components.
4. Grain Feed Rate: Rate at which grain is delivered to the cylinder by the header. It is the sum of the grain into the grain tank plus the losses from the rear of the machine, per unit time.
5. Total Feed Rate: Sum of Grain and Non-Grain feed rate.
Below mentioned are the names of different kinds of losses that occur during harvesting. These are the areas or functions in a combine harvester where major loss of grain can occur. Almost all good harvesters have one or the other adjustment available to reduce these losses during the harvesting operation.
1) Header losses
2) Threshing losses
3) Separation losses
4) Cleaning losses
Although Pre-Harvest losses are not a part of the harvesting process but it is very important to have an understanding of these. Threshing, Separation and Cleaning losses are collectively called Processing losses.
These are the losses that occur before the harvesting begins. Reasons could be insects, weeds, diseases etc. As I told earlier that these are not a part of machine losses and hence, cannot be reduced with any kind of machine adjustment. But it is important to measure it so that the machine losses can be accurately separated from pre-harvest losses. If these are not measured before the calculating the machine losses, these will get added to the machine loss and one will never be able to measure accurate efficiency of the machine.
These are the losses that occur at the cutterbar or header area of the harveters. These losses can be further sub divided into three types -
A) Lodging - Lodged crop that does not get cut by the cutterbar is considered lodging loss.
B) Shatter - Shatter loss is the grain that falls on to the ground as the grain head is shattered due to the impact by the reel. The reel is normally the first part of the harvester that comes in contact with the crop. The sudden impact on the crop due to the rotation of the reel may cause some of the crop to shatter.
C) Cutterbar Loss - After getting cut by the knives, some of the grains fail to fall on the platform and fall outside. The grain heads that fail to land on the platform constitute the cutterbar loss.
The header losses may be expressed as kg/ha or as percentage of the crop yield.
Threshing or cylinder losses are those unthreshed grain heads that escape the combine at the rear, either with straw or with material from cleaning shoe.
These can expressed as percentage of total grain entering the combine.
Separation loss, also called walker loss in conventional combines, is the grain that is lost with straw.
These losses can be expressed as the percentage of total grain entering the combine
Cleaning loss is the grain lost with chaff. These are also called shoe losses.
These losses can be expressed as the percentage of the total grain entering the combine.