What is drying?

The grain moisture content that avoids breakage at harvest and threshing may be too high for effective storage or milling.  Drying is usually necessary before cereals can be safely stored or processed. Natural drying or sun drying is a low-cost method used widely by smallholder farmers. Mechanical drying reduces the drying time, allows improved moisture control, and avoids losses associated with drying in open air, but many remote farm producers lack access to mechanical drying technology. A safe moisture content for most crops is below 13 percent. Higher moisture levels will allow mold, fungal or aflatoxin growth resulting in In addition to reducing grain quality, aflatoxin is associated with up to 35 percent of child stunting.

What causes postharvest loss at this stage?

Sun drying can expose grain to loss from birds, insects, and other animals, damage from rain or other weather events, and contamination from dirt, dust and insects that can diminish the value of the crop. Losses associated with weather may be growing more severe due to changes in climate. Properly used machine dryers can eliminate drying losses, but improper temperature control during mechanical drying can reduce grain quality and germination rates.

How large are drying losses?

Drying losses vary widely but one example places the range from an average of 3.1% with open sun drying of paddy to an average of .39% with machine drying. (Alam 2019)

What does research focus on?

Finding the best alternative drying tools for different crops under different circumstances is the primary focus of much of the research. The cost of alternatives to natural or sun drying often place them out of reach for many smallholder farmers, so finding economical solutions is also of interest.

To read research about drying, click here.

References: Alam, Md. Ashraful, et al. “Mechanical Drying of Paddy Using BAU-STR Dryer for Reducing Drying Losses in Bangladesh.” Progressive Agriculture, vol. 30, May 2019, pp. 42–50. Crossref, doi:10.3329/pa.v30i0.41556.