Grain storage: methods and measurements

Abstract

Reducing post-harvest losses is considered as a major step towards food security. However, losses vary significantly by climatic region, country, crop and of course the infrastructure and methods of storage followed. In India, the post-harvest losses of food grains amount to more than 20 million tons per year, which is approximately 10% of the total food grains produced. This can be attributed to the poor infrastructural facility and unscientific methodologies followed for food grain storage in the country. In a country where about 20% of the population is undernourished, post-harvest losses of 20 million tons annually is a substantial avoidable waste. Safe grain storage methods play a crucial role in preventing losses caused mainly by weevils, beetles, moths and rodents. It is estimated that 60–70% of food grain produced in the country is stored at domestic level. To ensure safe and scientific storage, careful selection of storage site, storage structure and proper aeration of grains, regular inspection of grain stock, cleaning and fumigation needs to be performed when required. Traditionally two approaches are employed for grain storage in India: temporary and long-term storage methods. Under temporary storage, aerial storage, storage on the ground or on drying floors and open timber platforms which is normally done at farm level are followed, whereas under long term storage, methods storage baskets (cribs) made exclusively of plant materials, calabashes, gourds, earthenware pots, jars, solid wall bins and underground storage can be employed. Bulk storage of produce is done in warehouses owned by the Food Corporation of India (FCI) and the Central and State Warehousing Corporation (CWC/SWC). Warehouses are scientific storage structures especially constructed for the protection of the quantity and quality of stored products. Under bulk storage, sealing and aeration play an important role. Aeration may be ambient or refrigerated based on the requirement. Over 420 standard test methods including more than 75 internationally accepted methods are available to test the quality of stored grains. Of the wide range of properties used for testing, the bulk density and the foreign matter are commonly assessed for most grain types. For foreign matter content analysis, the screens of sieves used for the assessment should consist of perforated metal plate conforming to specifications laid down by national or international standards organizations. Moisture content is another important parameter which should be considered during grain quality analysis. The indigenous storage structures are not suitable for storing grains for very long periods. Thus, improved storage structures and scientific storage of grains in form of warehouses is the need of the hour to strengthen traditional means of storage with modern inputs and to provide cheaper storage facility to farmers as well as to prevent enormous storage losses.