Factors Causing Post Harvest Losses

A complex interplay of various factors contributes to the losses that occur in the post-production system. These elements can be classified as follows:

As these factors impact one another, they ought not be treated or analysed separately. For example, climatic conditions (rain, temperature, humidity level, etc.) affect the physiological conditions of plants in the field or of the grain stored, as well as the degree of infestation by fungi, moulds and other pests.

Biological and Microbiological Factors

These comprise all losses due to pests of any sort which are capable of attacking undamaged grain (primary pests) as well as damaged grain (secondary pests). Insects, mites, rodents and birds fall in this category. Losses can be of both qualitative and quantitative nature, as food is consumed, damaged or contaminated by pests, especially during the storage period. Several species of fungi (moulds, yeasts) also attack grains, some of them producing mycotoxins that can be detrimental to humans and animals (such as aflatoxin in groundnuts and maize).

Biochemical and Chemical Factors

Some of the chemical elements naturally present in stored commodities provide the bases for loss of nutritional value, flavour, texture and colour, for example through enzyme-activated reactions.

Environmental and Climate Factors

High humidity levels and temperatures can trigger an alteration of certain biochemical processes – such as oxidation and fermentation – that can lead to a deterioration of the grain in storage. These processes can also be altered by the concentration of certain substances contained in the air surrounding the grain, such as oxygen, carbon dioxide or nitrogen.

Mechanical Factors

The different farm operations that are carried out manually or mechanically (harvesting, drying, shelling, threshing, cleaning, bagging, transportation, etc.) can cause damage to the grain, which then becomes more vulnerable to enzyme-mediated chemical changes and to attack by insects and other pests.

Socio-Economic Factors

These include the nature of the equipment and facilities used at the different points of the chain, the way the different operations are carried out by the actors (production practices), as well as the conditions in which production takes place. Regarding material and equipment, inadequate (or absent) storage infrastructure or the use of low-efficiency technology (such as threshing equipment leading to a high percentage of damaged grain) are examples of equipment-driven losses. Inadequate harvesting, packaging and handling skills are production practices that have a bearing on losses.

Regarding production conditions, the legal environment – through its imposition of quality standards that can affect the retention or rejection of food for human consumption – is another socio-economic factor that may explain losses. In addition, the economic environment is important: low commodity prices may push farmers to divert their production from food to feed markets or simply to increase storage time to wait for better market conditions, thereby increasing the risk of pest infestation and related damages and losses.