CHAPTER 7: STORAGE OF HORTICULTURAL CROPS - 3

Storage of dried and bulb crops

Onions, garlic and dried produce are best suited to low humidity in storage. Onions and garlic will sprout if stored at intermediate temperatures. Pungent types of onions have high soluble solids and will store longer than mild or “sweet” onions, which are rarely stored for more than one month.

For long term storage, onions are generally sprayed with maleic hydrazide (MH) a few weeks before harvest to inhibit sprouting during storage.

The following table lists the storage conditions recommended for these crops.

Source: Cantwell, M.I. and R.F. Kasmire. 2002. Postharvest Handling Systems: Underground Vegetables (Roots, Tubers, and Bulbs) p. 435-443. In: A.A. Kader (ed.) Postharvest technology of horticultural crops, University of California . ANR Publication 3311.

For bulk storage of onions or garlic, ventilation systems should be designed to provide air into the store from the bottom of the room at a rate of 2 cubic feet per minute per cubic feet of produce. If produce is in cartons or bins, stacks must allow free movement of air. Rows of containers should be stacked parallel to the direction of the flow of air and be spaced six to seven inches apart. An adequate air supply must be provided at the bottom of each row and containers must be properly vented.

Bulk storage:

Storage in cartons or bins:

Source: Oregon State University , 1978. Onion Storage: Guidelines for Commercial Growers. Oregon State Extension Service. Extension Circular 948.

Storage of root and tuber crops

The recommended storage conditions for root and tuber crops are listed in the following table. Potatoes for processing are best kept at intermediate temperatures to limit the production of sugars which darken when heated during processing. Potatoes meant for consumption must also be stored in the dark, since the tubers will produce chlorophyll (turning green) and develop the toxic alkaloid solanine if kept in the light. Potatoes stored for use as "seed" are best stored in diffuse light (CIP, 1981). The chlorophyll and solanine that accumulate will aid to protect the seed potatoes from insect pests and decay organisms.

Tropical root and tuber crops must be stored at temperatures that will protect the crops from chilling, since chilling injury can cause internal browning, surface pitting and increased susceptibility to decay.

Source: Cantwell, M.I. and R.F. Kasmire. 2002. Postharvest Handling Systems: Underground Vegetables (Roots, Tubers, and Bulbs) p. 435-443. In: A.A. Kader (ed.) Postharvest technology of horticultural crops, University of California . ANR Publication 3311.

Storage of potatoes

When storing potatoes, a field storage clamp is a low cost technology that can be designed using locally available materials for ventilation and insulation. The example illustrated here employs a wooden ventilator box and straw for insulation. The entire pile of potatoes and straw is covered with a layer of soil, which should not be highly compacted. To reduce heat gain, locate the field clamp in the shade (under a tree, on the cool side of a building, or under a tarp shade.)

In very cold regions, a second layer of straw and soil can be added. In hot regions, less soil is needed, but more ventilation can be added by constructing chimney type air outlets at the top of the clamp.

Field storage clamp:

Source: CIP. 1981. Principles of Potato Storage. Lima , Peru : International Potato Center (CIP). 105 pp.

Simple storage houses for potatoes can be constructed for small quantities of produce. The examples provided here can store 1 to 2 metric tons, and are used on farms and in mountain villages. The first is made from unfinished wooden planks painted white to reduce heat accumulation from the sun and covered with a large thatched roof for protection from sun and rain. It has a large door on one side for loading and unloading.

The second storage house is constructed from lath and plaster and mud bricks in a cylindrical form. It has two doors, one on top for loading, the other at the bottom for easy removal of potatoes for sale or consumption. White-wash helps reduce heat accumulation and a thatch roof protects the potatoes from rain and sun.

Source: CIP. 1981. Principles of Potato Storage. Lima , Peru : International Potato Center (CIP). 105 pp.

For large quantities of potatoes, a self-supporting A-frame storehouse can be constructed. A pit is dug about 10 feet deep and wooden air ducts are placed along the earthen floor. The roof of the building is constructed of wood, then covered with straw bales and a thick layer of soil.

Source: University of Idaho . No date. Idaho Potato Storage . Agricultural Experiment Station, College of Agriculture , Bulletin 410.

Ducts for ventilation of bulk storage rooms can be laid out vertically as well as horizontally. The storeroom for potatoes shown below provides for plenty of ventilation using simple materials. The room can be of any size or shape since air ducts can be positioned to extend evenly throughout.

Source: Lopez, E.G. 1983. Conservación de la Producción Agrícola. Barcelona : Editorial Aedos. 188 pp.

When loading potatoes into bulk storage, even distribution of the produce is important for proper ventilation. Uneven loads will inhibit air movement and result in storage losses due to inadequate ventilation.

Even distribution of potatoes in the storeroom:

Uneven distribution of potatoes in the storeroom:

Source: CIP. 1981. Principles of Potato Storage. Lima , Peru : International Potato Center (CIP) 105 pp.