This Thesis is a study on the cost and revenue of longan plantation in 1982/1983. The data for the analysis were obtained through interviewing and using questionnaire on 50 longan plantations selected in Lampoon Province, each of which composed of the area of 20 rai. In the study the cost of plantation per rai was ascertained as well as the revenue and the profit of longan production at various years of age of the plantation. For the analysis the area of plantation is divided into sizes :- 1-5 rai and more than 5 rai but not more than 12 rai. The result of the study showed that the longan plantation begins to yield result at the end of the fifth year. Therefore the owners will begin to earn the revenue by selling the longan produce after 5 years. In the area of 1-5 rai, the average cost for one year per rai between the 5th- 20th year was 6,511.88-15,033.74 baht. The average revenue for one year per rai was 5,624.80-33,577.92 baht. The retained earnings per rai was 116,262.71 baht which was 39.95% of the total income. For the longan plantation of more than 5 rai but not more than 12 rai, the average cost for one year per rai during the 5th-20th year was 6,661.39-15,726.29 bath, the average revenue for one year per rai was 5,582.08-33,549.44 baht, and the retained earnings per rai was 110,304.43 baht which was 37.89% of the total income. The result of the analysis showed that the pay-back periods of longan plantation with area of 5-12 rai are between 12-16 years. After the pay-back period the revenue will increase every year. With the minimum required investment return of 11% and 14%, the net present value method analysis gives the plus result while the minus result will be obtained when the minimum required investment return is 18%. The longan plantation of 5 rai will yield internal rate of return of 15.47% and that of 12 rai will yield 14.92%. It is therefore concluded that, at present, the investment in longan plantation is profitable if the plantation owners have their own fund or borrow from the Bank for Agriculture and Agricultural Cooperative. The investment will yield loss if the plantation owners borrow from Commercial Banks. The problems facing the owners of the longan plantation are:- lacking of the knowledge of planting, problems in obtaining capital when the plantation is younger than 5 year old. Also the problems of price and marketing exist. Some suggestions for solving the problems are that the Government Authority dealing with Agricultural extension should conduct some short course training on the production of longan such as cultural practices, pest and disease control. The Government agency should find ways to help in solving these problems. On the shortage of capital, the Government should provide more capital fund loan for plantation of longan. As for the problem of price and market, the plantation owners should form a cooperative group in order to create more power in bargaining for reasonable price while the Government should help in expanding the foreign market for exporting of longan.
