What is harvesting?

Harvesting is the process of removing the crop from the fields. Smallholder farmers often harvest manually, using hand tools, including sickles, knives, scythes or cutters. Mechanized technologies exist that reduce harvest losses while conserving labor. Mechanical reapers  have been developed for use on small plots and mini combines that simultaneously harvest and thresh grain are also available for some crops in some regions Large combines dominate harvesting on large-scale farm operations.

What causes postharvest loss at this stage?

Harvesting is the first step in the postharvest grain value chain, and plays a role in determining overall crop quality. Harvest timing and methods dictate losses during this stage. Losses can be large if cereals are harvested before they are fully mature or when the moisture content is too high or too low. Excessively dry crops will be subject to breakage while excessively wet crops will be subject to spoilage, among other things.

How large are the harvest losses?

Harvest losses vary with the technology and the crop, as well as other factors. Harvest losses can be measured by gleaning cereals found in fields after harvest, but this is an incomplete measure as harvest practices can lead to breakage and other losses later in the value chain. Losses tend to be highest with manual harvesting and lowest with use of a combine. However, improper speed and field conditions can lead to high losses with combines. Harvest losses for rice have been estimated to range from 1 to 5% (Hodges, Buzby and Bennett, 2011). Estimated harvest losses for maize in Africa can be as high as 8% (NRI, https://postharvest.nri.org/scenarios/grains )

What does research focus on?

Harvest-related research into postharvest loss often covers issues around mechanization and moisture content. To read related research articles, click here.

References: Hodges, R. J., et al. “Postharvest Losses and Waste in Developed and Less Developed Countries: Opportunities to Improve Resource Use.” The Journal of Agricultural Science, vol. 149, no. S1, Feb. 2011, pp. 37–45. Crossref, doi: 10.1017/S0021859610000936.