Ground Apple (Smallanthus sonchifolius)
Among the exotic crops in Nepal, ground apple is one of them which have maximum possibility but being under-utilized root crop. Some farmers are getting attracted towards commercial cultivation of ground apple at present. Ground apple or Yacon is bushy perennial root tuber crop which is cultivated as annual crop like sweet potato. Its rhizome size & shape is somewhat similar to sweet potato root tuber. The plant is similar like Dahlia plant with 15-20, 100-500 grams rhizomes or roots. It is believed to be originated from Andes of South America.
Ground apple can be cultivated from tropical to temperate climatic zones (Inner-Terai to High Hills) in Nepal. It is extremely susceptible to frost & extreme cold. It can be grown from 700m to 2800m altitude above from sea level free from frost.
Suitable range of temperature for this crop is 18-24 degree Celsius that can tolerate upto 40 degree Celsius. Frost attack during kartik mangsir leads to death of upper part of ground apple. Temperature below -3-degree celsius cause breaking of rhizome. Flowering occurs in hot climatic areas like that of sunflower whereas in cold areas no flowering occurs but rhizome development takes place in both areas being sweeter rhizome in cold area. It takes 173 days for rhizome development.
Well tilled land with good drainage system as like in potato or sweet potato, it is ready in ground apple. For this crop, as in potato, ridge planting should be followed at spacing of 90-100cm between ridges raised upto 60cm height.
It cannot be propagated through seed as productive seed does not set in ground apple. For commercial cultivation, rhizome is best suited for propagation. Harvesting at Mangsir, storing rhizome underground upto Magh & finally planting is dome in Falgun.
Sprouts are developed in rhizome of ground apple. During Mangsir-Poush period, small rhizomes are developed just below the surface with 10-25 grams weight which are used as planting materials. Several buds are developed in these rhizomes from which new plant emerge. Only 3 buds at maximum in a pit is ensured during planting. Per kattha, 250-300 rhizomes are needed for plantation.
Stem or nodal cutting can be taken for propagation if ground apple. Stem under any media can give rooting which can be transplanted later in main field.
It can be planted from Magh to Chaitra. During planting, sprouts from buds must face upward for earlier growth.
It can be planted in ridges or in plain field like potato or sweet potato. Spacing recommended is 90-100cm * 60cm (RR * PP).
For commercial cultivation, 20 tons well decomposed FYM is applied during field preparation, with 100: 100 kg Nitrogen & potassium /ha is applied after 4 weeks of planting which is found to be quite effective in case of ground apple.
Also, 1000 kg FYM with 5 kg DAP, 4kg Urea, & 5kg Potash is also recommended per ropani in some places.
Harvesting & yield:
The harvesting of ground apple continues from Mangsir to Poush. Maturity index in ground apple is leaves turn yellow & fall down. Irrigation must be stopped one month before harvesting which means uprooting is done especially during the dry weather condition. The size & sweetness also determines the harvest of ground apple.
The weight of ground apple within same plant also differs. The weight varies from 50 gram to 1kg in highest. Average weight lies between 200 to 500 grams. Per plant yield varies from 5kg to 15 kg with irrigation differences.
Physical loss during harvest, storage & transport is higher in ground apple than other root crops. Avoid rhizome splitting during harvest that harbor bacterial & fungal disease during storage. Use sharp knife for harvest or separation from mother plant. Carry only 15-20 kg of tuber in a pack during shipment to avoid injury. Soil helps in insulating during shipment that’s why they are not cleaned upto the storage room.
Ground apple is sweeter after sun drying it for few days. However, rhizome weights may decline by 40% within a week. After that storage at low temperature is beneficial.
Crop rotation, drainage, weeding ensures low disease attack in ground apple. Major diseases of this crop include: Stem or leaf blight, wilting & rhizome rot.
Apart from this rhizoctonia blight, Nematode & grey mold are also serious in this crop.
Marketing & Opportunities:
In Nepal, marketing status is very poor at present. At present ground apple cost Rs. 70 to 100 per kg in the market in Nepal. But growing in high quantity of ground apple & marketing is very difficult because there is no processing industry in Nepal for ground apple. Some middlemen are purchasing ground apple from farmers & channeling in the market. Ground apple tuber consists of Inulin which is very useful to diabetic patients. So, ground apple can be grown to supply raw materials for inulin production industry. Ground apple`s syrup cultivated by organic method has highest demand in international market. So, it can be easily marketed in international market.