Postharvest management and practices of citrus in mid hills

Introduction

Postharvest losses have been estimated to be of the order of 20 to 30% for fresh fruits and vegetables and could exceed 50% under adverse conditions. Losses were reported to vary between 20 and 30% for apple, between 15 and 20% for citrus, between 10 and 15% for tomatoes and between 10 and 15% cauliflower (HARP, 2002). Losses in vegetables result from harvesting at an improper stage of maturity, direct packing and shipping without the removal of field heat, improper packaging and insufficient grading and sorting, poor transportation and handling and poor storage facilities. Losses in fruits also result from harvesting at an improper stage of maturity, improper methods of harvesting, packaging, transportation and storage. Fruits are generally harvested by shaking trees or by hitting with a stick. The fruit consequently drop with the peduncle and leaves. The majority of losses occur during transportation from the farm yard to the collection centre and thereafter to the wholesale market and retail outlets. Cellar Stores

Fruits and vegetables are generally sold in the fresh form during the season of production, owing to the shortage of storage facilities. Cold storage facilities are used primarily for the limited storage of seed potatoes. Simple low cost, natural conditioned on-farm storage structures are, however, used in Nepal for the storage of fruits (mandarin, apple and sweet orange) and vegetables without much spoilage. Use of these structures in the high hills for the storage of apples and citrus (mandarin and sweet orange) and in the mid hills has been promoted by the government, the Department of Agriculture and by the semi government through the provision of a 25% subsidy. Studies have shown that mandarin oranges can be safely stored in cellar store for more than 100 days with losses ranging between 9 and 17%. Between 30 and 35 cellar stores having a capacity of between 4 and 5 tons have been operational in Mustang for the storage of apples (personnel communication). Among the various small scale storage structures which include rustic stores, sand pits, normal storage and zero energy chambers, cellars are the most popularly used by farmers (HARP, 2002). Mandarins can be stored for 120 days with storage loss of 11% without any significant deterioration of quality (LARC, 1998). Similarly mandarin oranges in cellar stores can be stored for 60 to 90 days at 8–10°C and 90% relative humidity with a 20–25% loss. Mandarin oranges must be pre cooled and transferred to the store before sunrise (DOA, 2004). Fruits in cellar stores should be stored either in racks or in plastic crates in less than 4 layers. Construction of Stores Cellar stores, having a capacity of between 2 and 5 tons, are constructed in hillock-like places in which three sides of the structure are enclosed by hills and one north facing side Corrugated galvanized sheets are layered over the planks or bamboo roof. These sheets are further covered with a layer of either earth or mud 30–60 cm in thickness, in order to ensure protection from direct sunlight. Proper drainage is maintained.

Zero Energy Storage Structures

Zero energy storage structures are generally employed by small farmers with small landholdings, for the storage of fresh fruits and vegetables over a two to three week period. As the name suggests, these structures do not require any energy for operation. Their operation is based on the principle of evaporative cooling whereby the temperature is decreased and the relative humidity increased, creating an environment suited to maintaining the freshness of fruits and vegetables.

General Background

The potential of the mid hills of Nepal lies in the production of high value citrus fruits, offseason vegetable crops, vegetable seed, etc. (APP, 1995). Citrus, in particular mandarin, sweet orange and lime are the important cash crops produced in the region. The mandarin orange is the most important fruit crop produced in the mid hills of Nepal, given the large area under cultivation in that region, and its high commercial value (Subedi et al., 1997). The profitability of the mandarin orange depends upon its productivity and market prices. The postharvest glut situation during the harvesting season (mid November to mid January) results in low prices and marketing problems, resulting in considerable losses to farmers. This situation has endangered the entire Citrus enterprise in the country resulting in a negative impact on the livelihoods of mid hill farmers (Paudal et al., 2004). Poor returns are derived from the majority of citrus orchards, owing to poor management. Thus, despite the immense potential of the citrus industry, its level of growth has been inhibited by the lack of postharvest technology. Although cellar storage technology has been disseminated since 1977–78, the full potential of cellar stores is yet to be realized owing to poor design, and construction. The AMARC (AMARC, 2001), categorized cellar stores constructed by the District Agriculture Development Office as a wastage of financial resources, and considered them technically unfit and unsuitable for business purposes. Cellar stores were upgraded by Paudel et al. (2002) to include pre-cooling chambers, and standardized the construction norms. Pre- and post-harvest techniques for increasing the shelf life of mandarin oranges were also disseminated by that group, who trained stakeholders in the construction of improved cellar stores. The package of practices on pre and postharvest handling of mandarin oranges was developed at the farm level in collaboration with farmers. An appropriate time of harvest was determined for mandarin oranges destined for storage and for fresh consumption. Proper harvesting techniques, fruit collection, grading, and fruit treatments using garlic extractives, pre-cooling and storage techniques were disseminated to the stakeholders.

Problem Statement

Losses during Transportation

A study on losses during the transportation of horticultural produce from Bhairahwa, Nepal to Gorakhpur, India conducted by the Marketing Development Division (MDD, 1999/ 2000), determined a 74% loss in oranges, 26.3% loss in apples, 17.39% loss in cabbages and 15% loss in potatoes. Losses incurred during the transportation of apples, mangoes, cauliflower were 22.22%, 36.36%, 18.75% and 19.23%, respectively. Thapa and Shrestha (2001/02) reported that losses in mandarin oranges during transportation from Dhankuta to Kathmandu by bus ranged between 2.7 and 8.2% and thereby recommended the use of small wooden and bamboo boxes of 18''x12''x12'' for packaging these fruit. ABTRACO (2003) reported a 50% postharvest loss in mandarin oranges during their export to Tibet and Bangladesh.

Storage Losses

Paudel et al. (2004) verified that the maximum loss in mandarin oranges stored in improved cellar stores was 23% on a weight basis and 15% in number for a 120-day storage period. The MDD (1999/2000) also reported a 10% loss in apples (from Jumla) maintained in cold storage, at Kathmandu.The main factors which contribute to postharvest losses in fruits and vegetables include:

·         Harvesting of immature fruits and vegetables

·         Faulty harvesting techniques

·         Exposure of the produce to the sun after harvest

·         Rough handling of the produce after harvest

·         Dumping of produce on heaps at collection centers

·         Minimal sorting of damaged produce at selling and collection centers

·         Mishandling during packaging

·         Improper packaging during transportation from collection centers to wholesale markets

·         Use of ordinary trucks and buses for transportation of vegetables and fruits

·         Rough road conditions

·         Rough handling during loading and unloading

·         Use of ordinary rooms for storing the fruits and vegetables at the wholesale and retail markets

·         Display of fruits and vegetables on the open ground at wholesale and retail markets.