User:Retomax
About me
Reto Flückiger is a Biologist absolving, as a further education, a Master course in Agricultural Science. In this aim he is involved in a lecture about the improvement of Wikipedia-Entries on selected Alternative Crops.
Oxalis tuberosa
Edibility
Oca are fairly high in oxalates, concentrated in the skin[1]. The traditional Andean preparation methods were geared towards reducing the oxalate level of the harvested vegetable. This is done by exposure to sunlight which decreases the organic acid content and thereby increases the sweet taste of the oca. The bioavailability of oxalate appears to be similar to spinach [2]. Recent oca cultivars have a lower oxalate content, and have also been selected for more flexibility in day lengths.[citation needed]
| fresh | dried | |
| Energy (J) | 255 | 1360 |
| Water (g) | 84.1 | 15.3 |
| Protein (g) | 1.0 | 4.3 |
| Carbohydrates (g) | 13.3 | 75.4 |
| Ash (g) | 1.0 | 3.9 |
| Calcium (mg) | 2 | 52 |
| Phosphorous (mg) | 36 | 171 |
| Iron (mg) | 1.6 | 9.9 |
| Retinol (µg) | 1 | 0 |
| Riboflavin (mg) | 0.13 | 0.08 |
| Niacin (mg) | 0.43 | 0.85 |
| Vitamin C (mg) | 38.4 | 2.4 |
Cultivation
Oca is one of the most important staple crops of the Andean highlands, second only to the potato due to its easy propagation, and tolerance for poor soil, high altitude and harsh climates [3].
Distribution
Outside of the Andean region Oxalis tuberosa is cultivated commercially in Mexico and New Zealand. Compared to potatoes, which are now cultivated in 130 countries around the world, these tubers are essentially still unknown outside of the Andean region.
Propagation
Oca is usually propagated vegetativly by planting of whole tubers. Further is propacation by aerialis stems, which is sometimes applied, or by seed propagation, which is never used, possible.[3]
Climate requirements
Oca need a long growing season, and are day length dependent, forming tubers when the day length shortens in the autumn. In areas with harsh winter climates, early frosts may cut back the foliage before the tubers have a chance to form. In tropical areas where the days are unchanging in length, oca will not set a crop successfully.[citation needed]
Soil requirements
The crop is grown with very low production inputs and in generall on plots of marginal soil quality and tolerates acidities between about pH 5.3 and 7.8.[3]
Cropping factors
The cultural practice is similar to potatoes. Planting is done in rows or hills 80-100 cm apart with plants, spaced 40-60 cm apart in the rows (Rea 1975).. Monoculture predominates, but interplanting of several tuber species in one field is in Andean production common. In many instances Andean farmers will allow a mixture containing two or three tuber crops to be planted in one field. Often this mixture consists of several different clones of each species. Such mixed fields may later be sorted into tuber types during harvest or before cooking. Mixed planting with legumes or grain crops is occasionally practiced.[3]
Pest and Deaseas
Crops in the Andes are usually infected with viruses, causing chronic yield depression. Adequate techniques to remove viruses have to be applied before the varieties can be used outside the Andean region.[3] Cultivation is also constrained by the oca weevil (Ariodistus tuberculatus), Andean potato weevil (Premnotrypes spp) and the ulluco weevil (Cylydrorhinus spp), beetles often destroying entire crops. Further notable pests are nematodes. [4]
Yields
Yields vary with the cultural method. Annals from Andean countries report about 7-10 tons per hectare for Oxalis tuberosa production. But with adequate inputs and virus free propagation material, oca production can range from 35 to 55 tons per hectare.[4] [3]
Limitations
As already mentioned can virusis, daylengt restrictions and the precence of oxalates be concidered as limitation factors. Scientists work with specific breeding, selection and virus cleaning programs on these porposes [3]
Agricultural potential
Potential distribution to other suitable ecogeographical zones of for example Asia and Africa is possible.[5]. The cultivation and use of Oxalis tuberosa in New Zealand already indicates a wider utilization and agricultural interest than has been previously recognized (Vietmeyer 1983).
(http://www.cipotato.org/artc/oca.asp)
References
- ^ Albihn, P. B. E.; and Savage, G. P. (2001). "The effect of cooking on the location and concentration of oxalate in three cultivars of New Zealand-grown oca (Oxalis tuberosa Mol)". J. of the Science of Food and Agr. 81: 1027-1033.
- ^ The Bioavailability of Oxalate from Oca (Oxalis tuberosa) [1]
- ^ a b c d e f g National Research Council. (1989). Lost Crops of the Incas: Little-Known Plants of the Andes with Promise for Worldwide Cultivation. National Academy Press, Washington, D.C.
- ^ a b Sperling, C.R.; and King, S.R. (1990). "Advances in new crops: Worldwide potential.". J. Janick and J.E. Simon (eds.). Advances in new crops. Timber Press, Portland, OR. p. 428-435.
- ^ King, S.R.; and Gersoff, S.N. (1986). "Nutritional Evaluation of Three Underexploited Andean Tubers: Oxalis tuberosa (Oxalidaceae), Ullucus tuberosus (Basellaceae), and Tropaeolum tuberosum (Tropaeolaceae) ". Economic Botany, 41 (4). p. 503-511.