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Advice on Publications Available.[This summary has been extracted, with permission, from a report by the USDA Risk Management Agency, Risk and Evaluation Divisions; the full report is available on: http://www.act.fcic.usda.gov/research/feasible.html
To contact the agency:
United States Department of Agriculture
Risk Management Agency/Risk Management Education
Room 6755, Stop Code 0803
1400 Independence Avenue, SW
Washington, DC 20250-0803
Email: craig_witt@wdc.fsa.usda.gov]
U.S. growers harvested 11.1 million cwt of sweet potatoes from 80,000 acres in 1993. North Carolina and Louisiana, the top two sweet potato producing states, accounted for 57 percent of the 1993 output. California, Texas, Alabama, and Mississippi ranked third through fifth in production. U.S. sweet potato production has been decreasing since 1970. During 1989-93, production averaged 11.6 million cwt--7 percent below the average for 1970-74. Higher yields since the 1940's have partly offset a decline in acreage. While harvested area has declined by half since the mid-1960's, average yield has risen 48 percent, due to higher yield varieties and expanded irrigation use.
According to the 1987 Census of Agriculture, most farms growing sweet potatoes were small operations, with 57 percent having total crops sales of less than $25,000. Only 19 percent of U.S. farms growing sweet potatoes reported crop sales of $100,000 or more. Although we do not have statistics on enterprise diversification on farms growing sweet potatoes, industry contacts indicate that sweet potatoes are usually grown as part of a vegetable and field crop enterprise mix. In North Carolina, the largest sweet potato state, several of the largest sweet potato growers are primarily tobacco producers. In Louisiana, sweet potato farms also frequently produce cotton, soybeans, and rice.
About 60 to 65 percent of sweet potatoes sold for human consumption are to the fresh market; 35 to 40 percent are destined to the processed market. Canned sweet potato products account for the largest share of the processed market. Following World War II, per capita use of sweet potatoes began a slow downward trend which lasted through the early 1980's. Since then, per capita use has stabilised at about 4 pounds, fresh weight. The marketing season price pattern for sweet potatoes is stable compared with prices of highly perishable vegetables, such as lettuce and celery. Prices for the new marketing year, beginning September 1, become established during September and October when production prospects become clearer. They remain relatively flat or rise slowly through May or June. Prices sometimes rise sharply during July and August as storage stocks become depleted. Growers in some areas try to harvest a portion of their crop early to benefit from the high prices in July and August.
Sweet potatoes are a tropical and subtropical crop that grows best in sandy or well-drained loamy soils. They thrive on high daytime temperatures for top growth. Root formation is best when the soil temperature is above 18 C at the time of transplanting. Small, immature plants tolerate mildly cool temperatures, but their vigour is reduced if exposed to low temperatures early in the season. Freezing at the time of harvest may damage the leaves but will not usually harm the roots, unless soil temperatures drop below 13 C.
Sweet potato plants are grown from slips (transplants) that are produced from vegetative seed stock or from cuttings taken from field-planted slips. Most growers purchase vegetative seed in sufficient quantity to produce their own transplant material. Sweet potatoes are planted at 10-12 inches between plants, and 40- 44 inches between rows. Sweet potatoes are typically planted in late spring and harvested in late summer and early fall. Growers usually plant sweet potatoes over a period of weeks to spread labour and equipment use. The time between planting and harvest ranges from 70-150 days, depending on the variety, soil type, moisture, and temperature conditions. A 3-5 year rotation is recommended for sweet potatoes in order to alleviate problems of insects and diseases, particularly soil-borne diseases, and nematode attacks.
Sweet potatoes are generally harvested by hand after the roots have been exposed by disk diggers, ploughs, or bed diggers. Although it results in more damage to the roots than hand harvesting, mechanical harvesting is becoming more widely adopted because of labour-cost savings. Harvesting and marketing costs typically amount to 40-60 percent of total production costs.
The weather-related peril most likely to result in indemnity payments under a sweet potato crop insurance policy is excessive rainfall. Excessive soil moisture causes "souring" or asphyxiation of the roots and can result in complete crop losses. Drought, frost, and extended cold temperatures are also perils. Soil-borne diseases usually cause greater economic losses than foliar and stem diseases. Insects problems can generally be controlled.
Ad hoc disaster data can be used to indicate which sweet potato- producing areas received large payments relative to their acreage. NASS does not collect data on Arkansas sweet potato acreage, but that state received 4.2 percent of ad hoc sweet potato payments over the 1988-93 period. Similarly, North Carolina accounted for 40 percent of U.S. sweet potato acreage between 1988 and 1993, and received nearly 47 percent of the payments made for that crop. In contrast, California and Louisiana collected smaller shares of ad hoc payments relative to their acreage.
These data suggest that, under a potential sweet potato policy, the probability of yield losses for sweet potatoes in the North Carolina area may be somewhat greater than in California and Louisiana. Insurance issues addressed in this report include the setting of reference prices, estimating "appraised production," moral hazard, and the demand for insurance. Our research suggests that the demand for a sweet potato policy would likely be higher in the southern and eastern states than in California.
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
r.fletcher@mailbox.uq.edu.au[
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GK; latest update 17 October 2001 by: RF