• Experts say quick-drying causes the grains to crack and result in broken grains when milled.
• Farmers advised to dry their paddy in a sheltered area away from direct sunlight or rain to reduce losses.
Image: Courtesy
Image: Courtesy
Rice farmers know all too well the painful sting of post-harvest losses.
Massive losses demoralise and sometimes farmers opt out of production when the going gets tough but they are not tough enough to get going. The sad state of affairs reverberates across many rice-growing areas.
However, for experts, the panacea for such problems lies in proper post-harvest management.
Raphael Wanjogu, the chief research officer at the National Irrigation Authority, says post-harvest management of paddy involves a series of processes as well as any handling techniques and treatments applied to the crop just harvested from the field for purposes of edibility, value addition and increment of shelf life.
He says it determines the quality of grain and mill recovery rate and minimises losses that can be controlled.
“The several stages of post-harvest management of paddy include field drying, threshing, shed drying, cleaning, grading, storing, weighing and milling before it is fit for human consumption,” Wanjogu says.
He says the first step to post-harvest management of paddy is field drying, and that paddy should not be harvested before it has achieved 18-22 per cent wb (wet basis). This can be tested manually by biting between teeth — it should be firm, not crumbly.
Joel Tanui, the Western Kenya Irrigation schemes manager, concurs. "When the wb is above 22 per cent, the paddy is considered not ripe for harvesting,” he says.
He adds that when the wb is below 18 per cent, it does not absorb any moisture. Tanui advises farmers not to harvest their paddy before about 85 per cent of the grains in the field has changed colour from green to a matured yellow.
“After ensuring that the moisture content is right for harvesting, then cutting off the paddy straws; this can be done using a combined harvester or manually using a sickle or knife. When using a sickle or knife, ensure you cut the straws about 4cm from the ground,” he says.
Tanui recommends a combined harvester because it reduces labour costs and post-harvest losses by about 30 per cent.
Threshing is the second step. It involves separating the grains from the paddy straws. This can be done manually by beating and whipping against a framed object or by use of winnowing machines.
“This process should be done on the day of harvest. Should they stay overnight, then the paddy straws should be dried first before they are threshed," he says.
The third stage is shed-drying the grain to a moisture content safe for milling (14 per cent wb) and storing in a dry place.
"Delayed drying, incomplete drying or ineffective drying reduces the quality of the rice grain. The paddy grains are spread on a plastic sheet or canvas and turned every 30 minutes as they dry,” Tanui said.
He pointed out that quick-drying causes the grains to crack and will result in broken grains when milled, hence farmers have to dry their paddy in a sheltered area away from direct sunlight or any sudden rain.
Reinforcing the need for proper care, Wanjogu says farmers should also ensure the surface temperature of the grains being dried does not rise above 36 degrees Celsius.
He says cleaning the paddy by separating it from any foreign particles is the fourth stage and is important to increase the milling efficiency while reducing post-harvest losses and the damage to the milling machines.
"The other important stage is the milling of the paddy. The good grain is milled to remove the outer skin, hull and bran to reveal the white kernel and endosperm of the grain that is used as food for humans. The by-products can be used for other purposes such as animal feed or flour for making rice cakes,” he says.
The sixth stage, which is rice grading, involves visual observations and moisture content measurements. Visual observations indicate whole grains, broken grains, off-type grains, coloured grains and the presence of any unmilled paddy.
“They are then packed and stored as graded. Last but not least is the storage of rice. To prevent any losses by adverse weather, moisture, microorganisms, rodents or any other pests, the rice being stored should have grain moisture content of below 14 per cent wb,” Wanjogu says.
He adds that rice bags should not be placed directly on the floor but rather on a rack.
“The longer one wants their rice to stay, the lower its moisture content should be," Wanjogu says.
Edited by F'Orieny