Cultivation of minor tuber crops in Peru and Bolivia

A collection mission of three Andean tuber crops, oca (Oxalis tuberosa, Oxalidaceae), ulluco (Ullucus tuberosus, Basellaceae) and aiiu (Tropaeolum tuberosum, Tropaeolaceae), was carried out in southern Peru, Bolivia and northern Argentina. This article deals with the observations made during this mission. 55 ulluco fields were visited. In general, the fields are small, 240 m 2 on average, and they are mostly situated on mountain slopes. The fields are fertilized with animal dung; chemical fertilizers are quite rare. In the fields, people work with hoes ang ploughs as they did hundreds of years ago. Mechanization of agriculture would prevent full utilization of the mountainous area of the Andes. Ulluco is usually interplanted with other crops, usually, many forms of ulluco in one field. Because of crop rotation description of the fields is partly valid for the cultivation of other crops, too. Due to drastic climatic variation, cultivation of mixed varieties may be the best way to guarantee some yield. When results of the investigations are wished to benefit developing countries, knowledge of social, agricultural and environmental factors is of great value. Index words: Ullucus tuberosus, Oxalis tuberosa, Tropaeolum tuberosum, cultivation, tubers, Andean zone


Introduction
Three endemic Andean tuber crops, ulluco (Ullucus ft/berasi/s-Basellaceae), oca (Oxalis tuberosa-Oxalidaceae) and ahu ( Tropaeolum   tuberosum-Tropaeolaceae) have been investigated at the University of Turku since 1983.The objective of the study is to produce basic knowledge that is needed to breed ulluco, oca and ahu, with special reference to the varia- tion pattern of these crops, their reactions to day-length and the problems related to seed formation of ulluco (Rousi et al. 1986,  1988 a, 1988 b).Viruses of ulluco and production of disease-free material by tissue culture technology are under investigation at the Uni- versity of Helsinki.
A mission for collection of the above tuber crops was carried out in southern Peru, Boli- via and northern Argentina during March - May in 1987 (Jokela and Pietilä 1988).This article deals with observations made during the mission.
Characteristics of ulluco, oca and ahu Ulluco, oca and ahu are viewed as a pre- viously underestimated group of minor edible tuber crops.They are receiving increasing interest in agricultural research.They are culti- vated at the same altitude as potato, 2 500 - 4 000 metres above sea level, from Colombia to the northern parts of Argentina.Occasion- ally, oca is cultivated in Mexico and New Zealand, too.Their tubers are of the same size or slightly smaller than those of potato.
Tubers of ulluco are white, yellow, orange, red, purple or green, sometimes spotted; those of oca and ahu may be white, yellow, red, purple, violet or variegated, with great di- versity also in other characteristics.
Ulluco, oca and ahu are consumed like potato; their tubers are prepared in a number of ways.The tubers are prepared fresh, or they can be freeze-dried, after which they may be stored for years.They are all important ingredients of soups.Ulluco, which has a slight taste of earth, is prepared in a variety of re- gional dishes, for instance, with dried meat of alpaca or llama.Tubers of oca contain oxalic acid that gives them the characteristic bitter taste.Possibilities to produce flour, starch and alcohol of oca have been investigated (Cortes 1981).Ahu has a very strong taste.It is also a possible source of flour (Cortes et  al. 1982).Its tubers have a medicinal and anti- reproductive value.In the empire of Inca, for instance, the soldiers were given ahu as antiaphrodisiac, to make them fight better (Johns  et al. 1982).
A high percentage of the dry matter con- tent of the tubers is starch.The protein con- tent of ulluco varies from 10.8 to 15.7 °7o, that of oca from 3.0 to 8.4 %, and ahu from 6.9 to 15.7 °/o of the dry matter content.The moisture content is 78 -92 % of fresh weight (King 1987).
According to Tapia (1986), ulluco pro- duces a yield of 3-15 tons per hectare, but it may be as much as 40 tons per hectare if the fields are heavily fertilized (Herquinio et al.   1986).Oca and ahu yield 4-30 tons per hectare (Tapia 1986), in optimum conditions up to 45 tons per hectare (Herquinio et al.  1986).Yields of ulluco and potato, which is the most important tuber crop in the Andean highland, are of the same size in some regions.According to Salis (1986), in the Valley of Taray, Cusco, the potato yield averages 9.5 tons per hectare and that of ulluco 9.65 tons per hectare.Ulluco is available everywhere in Peruvian and Bolivian markets, even in places where it is not cultivated.Oca is not parti- cularly common, and ahu is a rarity in the markets.
Previously ulluco, oca and ahu were basic nutrients like potato, maize and some seed crops.Nowadays, with new customs and crops increasingly being imported from other parts of the world, cultivation of ancient crop plants and/or their varieties has declined (King 1987).Nevertheless, ulluco, oca and ahu cannot be substituted.They are an im- portant part of the diet of the Andean people (De Dios Cutipa et al. n.d.) and an indistin- guishable part of traditional rotation of crop plants (De Dios Cutipa et al. n.d., Caceda   and Rossel 1985).Freeze-dried tubers of potato, ulluco, oca and ahu, called chuho, balance the most extreme variety of yields be- cause they can be stored for years (King 1987).Andean people believe that these tuber crops are more reliable in poor years than imported crops (Garay 1987).Cultivation of ulluco is labour-saving because it needs only half the labour compared to potato (Salas 1986).
Ulluco, oca and ahu are resistant to frost and drought and produce well in poor soils (Re- Fig. 2. Routes of the collection mission villa 1983).They are potential reserves for many parts of the world, including other mountainous regions of the world (King 1987).
During the last few years, the value of en- demic Andean crop plants has been recognized and much effort is being put to preserve them as part of the Andean agriculture.In Peru, projects to promote investigation, cultivation and utilization of ancient crop plants are being financed by the Government and co-operative organizations.

Methods
During the collection mission 55 ulluco fields in the area ranging from southern Peru to northern Argentina were visited.The route is shown in Fig. 2. Peasants were interviewed on the cultivation of ulluco, and some field properties were investigated.

Results and discussion
The ulluco fields visited were classified according to their size (Fig. 3).They are usually small, average size 240 m 2. According to De Dios Cutipa et al. (n.d.), in the Province of Puno, Peru, the arable land per family ave- rages 1.59hectares, in some areas only 200-500 m 2. Generally the cultivation area consists of five or six fields.
65 % of the fields were on mountains, with a slope of up to 45°.According to Caceda  and Rossel (1985), 95 -98 */o of the fields in Puno are on mountainslopes.
In ulluco fields, like in any other field, the peasants work with hoes (e.g.chaquitaclla) and ploughs drawn by men or animals as was done hundreds of years ago.None of the farmers interviewed had a tractor or any other machines to work with.In the flat Altiplano there were some tractors in wealthy villages.
According to Seppänen (1986) mechanization of agriculture would prevent full utilization of the Andean highland.
85 °7o of the fields were manured with animal dung and, in addition, 29 °7o were ferti- lized with chemicals.In Puno, according to Caceda and Rossel (1985), no chemical fer- tilization is applied to ulluco, oca and ahu fields, and less than 10 % of the fields are fer- tilized with dung.
The differences between the present investigation and that of Caceda and Rossel   (1985) may be due to the fact that the ulluco fields visited were widely distributed, the area ranging from southern Peru to northern Argentina, where the agricultural practice, num- ber of domestic animals, wealth of the people and fertility of the soil vary greatly.Caceda   and Rossel (1985) carried out their investiga- tion in Puno, in one of the Provinces of Peru.
A field usually carries several crops.Ulluco was grown alone in 25 % of the fields visited, it was the principal crop in 20 % and equal or secondary crop in 55 °7o of the fields.Most commonly it is interplanted with oca, in 52 % of the fields, but we found also ulluco growing with ahu, oats, barley and beans.Each species is planted in one or several separate strips.Crop rotation is common in the whole area visited.All the farmers interviewed utilized the method.Potato is grown in the first year, in the second year ulluco, oca and arm or beans, and in the third year cereals, like oats and barley, are grown.Thereafter the field lies fal- low for several years (Kohler 1986).So, the characteristics of ulluco fields are valid for po- tato and cereal fields, too.But one must take into consideration that ulluco is usually culti- vated in poor land and potato and cereals also in lower altitudes and in better fertilized fields.
In a field there were maximally six forms of ulluco classified according to tuber colour and shape.The numbers of tuber forms per field and farmers' stock are shown in Fig. 4. Apparently we did not find all tuber forms in one field, because their numbers in stocks and in fields were significantly different (X 2 = 11,10; P = 0,1; d.f.= 2).Potato, for instance, is grown mixed (Jackson et al. 1980).
So, the degree of variation in ulluco field is probably underestimated.
Each ulluco form is usually consumed in a different way.Red tubers are grown in some regions because of their medicinal value, e.g. for gastrointestinal diseases of domestic ani- mals.Plants with red tubers are also thought to be more frost-resistant than others.Yellow tubers are the most popular ones for food, and they are grown for sale.In the markets, yel- low tubers of ulluco were generally by far the most common.However, some farmers claim that there is no difference in the consumption of different tuber forms.

Conclusions
In the high Andes the climate varies in dif- ferent years drastically.It is probably impossible to produce a variety that could give a good yield every year.According to Martin  and Adams (1987), heterogeneous crop populations may be better buffered against climatic and biological factors.So, the traditional way of cultivating several varieties by one farmer is perhaps the best way to guarantee the yield.
Investigations made in developed countries with the intention to benefit developing coun- tries, should consider tradition and the possi- bilities to utilize the results.In this respect knowledge of social, agricultural and environ- mental factors may be of great value.In the breeding of ulluco, oca, and ahu, for in- stance, attention should be paid to the fact that most peasants who cultivate these plants cannot afford machines.Another point is that it may be nearly impossible to work with them: the fields are small and they are situated on steep mountain slopes withrough erosion- sensitive soil.So there is no use improving ulluco, oca and ahu varieties for cultivation by machines in Peruvian or Bolivian fields.