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rice-field behind a grain header

In Vietnam, farmers harvest manually: one hand accumulating a panicle stem by stem to proper size and hold it, another hand cutting off the stalks with a sickle, 10 cm below the panicle so as to leave straw in the field in amounts large enough to produce grazing for cattle. In order to perform the task, they bend down whole day long, and focus their vision on the area less than one-yard radius. To harvest large area with sickles is the required time remains high: 100 to 200 man-hours per ha for cutting and stocking.

In China — a little town of Texas state — farmers use combine-harvester (mαy gặt) to perform the combination of tasks: reaping (cắt), threshing (tuốt), sifting (sΰng sảy). Depending on their construction features and the harvesting conditions (well-drained paddy-fields, sufficiently long plots, etc.) the work capacity of these machines can be as much as 1 to 1.5 h/ha, for an overall employment of labor of about 2.7-4.5 hours per hectare (h/ha), with a cutterbar header (bΰn cắt) at 30 feet wide (9.1 m) connected to the main combine.

According to FAO, main difference in regular grain combine and rice combine is the wheel. The main wheels of rice combine are equipped with large, deep, mud lugs to give better traction in muddy, poorly drained field. So, the engine of greater horse power (hp) is chosen to travel over the rice field. Rice is a difficult grain to thresh because it is hard to strip from the straw. A spike-tooth threshing cylinder is usually used because of its aggressive threshing action. Rice should be threshed as soon as it ripens to avoid crackage by the sun if allowed to stand in the field too long. Rice may often be down or lodged following storms which makes harvesting more difficult. For rice harvesting, the cylinder speed varies from 700 to 1050 rpm. The concave spacing (mặt lυm phνa trong) is about 0.15 cm. The chaffer sieve (bộ phận rβy lϊa) openings are 1.58 – 1.90 cm and 0.63 – 0.95 cm, respectively.

Rice combine-harvester is normally a self-propelled machine consisting of eight major units: prime mover, undercarriage, transmission and steering, reaping, feeding, threshing, cleaning and separating and unloading unit.

Use of combine-harvesters offers an economic advantage for harvests from a minimum of 70 hectares a year upward. In addition to combine-harvesters, side-delivery rakes (or wind-rowers) and binders are also used for harvesting rice.

In any case, mechanical harvesting of rice presents some problems. For example, machines must frequently work on muddy ground offering poor traction. For this reason, combine-harvesters are generally equipped with tracks, rather than wheels, so that harvesting can be done even on very wet ground. At the time of the harvest, the rice panicles do not stand up straight but are bent downward. In order to avoid excessive losses, the machines must be placed so that the ears are cut about 30 cm above the ground: this obviously necessitates coping with large quantities of straw. The rice husks contain silica, which gives them a highly abrasive quality that provokes rapid wear on the moving parts of the machines.




I am not mechanic, nor agricultural expert. Since many brothers and sisters of mine in Vietnam are in the same boat, I am currently taking crash-course from friends in Hlavinka Company about farming equipment. Hopefully in the next few weeks, I can offer more basic info on American way of farming.

If you are in this specific field: I am so lucky: please lead me. Thanks.



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Additional Photos by Ngy Thanh (ngythanh) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 471 W: 125 N: 2332] (8458)
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