Key Factors for Optimal Performance of Combine Harvester

 

Agricultural mechanization is one of the main contributors to enhance crop production by increasing cropping intensity, reducing post-harvest losses, improving product quality, as well as by increasing labor productivity. Agricultural mechanization started with the irrigation mechanization. Gradually tillage machinery take place as a major part of mechanization. After that locally manufactured machinery have been contributing for intercultural operation and threshing of crop. Here and now combine harvester and rice transplanter are playing major roles in mechanization. Rice transplanter is taking place very slowly to the end users because of problems with mat type seedling raising. Contrary, combine harvesters are spreading across the nation to reduce crop damage from natural disasters as well as from harvesting losses caused by labor crisis.Approximately 10,000 combine harvesters, both head feed and whole feed types, with engine powers ranging from 50 to 120 horsepower and cutting widths of 1.2 to 2.2 meters, are currently successfully working in farmers' fields. Recently, a study was carried out under the KGF-funded project to observe the field efficiency of the combine harvester at various field lengths.With a field length of 30 to 65 meters, it was revealed that the field efficiency of both types of combine harvesters ranged from 30 to 60%. In our field size, the harvester's average field efficiency is around 50%.It indicates that the combine harvester is only operating at 50% of its potential. As a result, the issue of economic and business viability is raised.It's a popular belief that large machines are commercially viable. When operating at 50% capacity, is it still economically profitable? It will be explored in another article.In this article, key factors for achieving optimal performance from the combine harvester will be covered along with the tips for adjusting while operating in the field.

The word "combine" refers to the fact that many operations are combined inside of a single machine. In brief, combine harvesters are machines that are manufactured for exclusive use on the farm. It is mostly used for harvesting cereals, wheat, rice soya, corn etc, threshing and separating grains from non-grain components, and deliver grain to the grain wagon.How a combine harvester works! A combine harvester harvest crops by carrying out several tasks at once.These tasks include crop cutting by the header, straw-grain feeding by the feeder house, grain threshing by the multistage threshers, threshed grain separatingby the processor, grain cleaning by the cleaning system, residue control by the discharge system and grain managementby the unload auger and the grain tank.

Crop cutting by the header: the crop is chopped by the reciprocating type cutter bar and conveyed into the feeder house.Straw-grain feeding by the feeder house: the crop is conveyed from the header into the processing system of the combine harvester. Grain threshingby the multistage thresher: the grain is removed from the panicles. Removed grain separating from the straw by the Processor: once the grain is removed from the panicles, it has to be separated from the non-grain material. Separated grain cleaningby the cleaning system: air is used to remove residues of the non-grain materials from the grain. Residue control by the discharge system: material other than grain has to be discharged from the combine. Depending on the type of combine, straws or non-grain materials could be chopped and spread as green fertilizer (whole feed type) or dispensed whole threshed straw (head feed type). And cleaned grain management by the unload auger and the grain tank: The grain is conveyed into the grain bin for temporary storage before it is emptied into a trailer or bag.

However, the ground contact area of a combine harvester's crawlers has an influence on how well they perform in the field. A common belief is that, in the absence of any load, around 20 kPa (Kilopascals) of ground pressure can sustain the operational load of the combine harvester in the field. Countries with volcanic soil, including Japan, Korea, Philippines, Indonesia, and Italy, operate successfully under this pressure. For field operations to be successful in alluvium soils like Bangladesh, less than 20 kPa (about 15 kPa) is required. In the paddy field where the combine harvester will be operated, the hard soil layer should also not extend deeper than 20 cm. Any wet land agricultural equipment cannot be used effectively and cannot yield the desired results if the hard soil layer is below 20 cm. While it has no effect on the whole feed combine harvester, uniformity of the crop height is crucial to reducing grain losses during operation of the head-feed type combine harvester. Crop heights of above 65 cm but under 150 cm are typically ideal for head-feed combine harvesters with the least amount of grain loss. The field capacity of the both types of combine harvesters is greatly influenced by crop lodging. Modern combine harvesters typically keep their engines running between 2500 and 2700 rpm during harvesting, 1500 to 1700 rpm while unloading grain, and 2000 to 2200 rpm while traveling on the road.

Combine harvester's settings and adjustments for optimal performance:Depending on a number of factors related to the crop, soil, and field conditions, a combine harvester may be adjusted to a range of settings to give the machine optimal performance in the field. The main keys of combine harvester that every operator needs to be aware of ground speed, rotor RPM, concave clearance, air volume, chaffer setting, and sieve setting. Ground speed is the speed at which the combine cuts the crop as it passes through the field. Field speed of the modern combine harvester normally varied from 3.5 to 8.5 km/h. The machine operator, often known as the driver, controls the ground speed.Whether the combine is moving too quickly or slowly depends on the ground speed, which ultimately controls how much material enters into the harvester.Overloading of the combine, clogging of the conveying systems, grain losses, and engine over heating or inefficiency can occur when a combine travels too quickly.Under-loading, which leads to underutilization of the machine, grain damage, and engine inefficiencies occur when a combine moves too slowly. Depending on the soil, field, crop conditions, and type of the combine harvesters, the optimum ground speed must be maintained.The rotor's rotational speed, or rpm, determines how quickly it threshes and separates grains from panicles or non-grain materials. The throughput capacity of the combine and how aggressively the crops is threshed are both influenced by the rpm of the rotors.There is a risk of grain damage, rotor damage, shaft damage, too much material on the shoe, and shoe loss when the rotor turns too quickly.

The grain that is carried over the back of the sieves with the chaff or blown out of the combine by the fan is known as the shoe loss. Rotor clogging, unthreshed crop, and low throughput are the results of a slow-turning rotor. Operators should adjust rotor speed based on crop height, density, percent maturity and grain yield.The space between the concave and the threshing components of the rotor is known as the concave clearance. This setting of the combine regulates both the aggressiveness of the paddy threshing in the threshing section as well as the throughput capacity. It shouldn't be too narrow or too wide. The air volume setting regulates how much air is provided to the cleaning system to clean the grains.This parameter regulates how effectively grains are cleaned after threshing. If the air volume is too high, the shoe loss may be increased; if it is too low, the shoe may become overloaded and dirty grains may accumulate. The rates at which grain and other materials can pass through to the lower sieve are controlled by the chaffer settings. It shouldn't be overly open or shut down. The grain spaces that can fall into the clean grain auger for transmission into the grain tank are controlled by the sieve settings. It shouldn't be excessively open or closed either.

One of the key factors behind Bangladesh's transition from subsistence to semi-commercial agriculture is agricultural mechanization. The primary goal of the government is to mechanize agriculture in order to assure sustainable production for reducing levels of hunger and poverty. In order to coordinate agricultural mechanization initiatives, appropriate guidelines, advisory committee and a cooperative effort between public and private sector actors are required.In order to operate combine harvesters and other agricultural machinery effectively while taking all factors into account, it is also crucial to provide effective field-based training programs that include the right individuals.


Dr. Md. Anwar Hossen is
Senior Scientific Officer,
Bangladesh Rice Research
Institute, Gazipur.