Maca is sown in small plots in empty grazing fields by broadcasting the seeds still containing floral debris mixed with soil. In the Junín area sowings with seed stored for 4 years are common. However, the viability of these seeds mar be only 50%.
One kilogram of seed with 15 kg of soil is used for high-density planting or 1 kg of seed and 25 kg of soil for low density. Then sheep are released to the field to trample the seed. This will result in 700 000-400 000 plants/ha depending on the sowing density used. Sowing takes place from September to October starting at the initiation of the rainy season, usually in the morning to avoid winds. The soil is well , prepared, with clods broken up, and is fertilized with sheep manure. Often the plants are thinned out 2 months after sowing to obtain uniform and larger hypocotyls. Weeds, if present in the field, are removed by hand. The seed is commercialized as charpu, which is the amount of seed and floral debris mix contained in an 18-cm diameter dish (Tello et al. 1992). The pastures lie fallow for as many as 10 years before maca is again planted in the same plot. This is because maca seems to exhaust the soil by extracting nitrogen and other nutrients (Tello et al. 1992). Also, fallow plots will result in less incidence of weeds, pathogens and pests when the crop is produced. The main pests and diseases, which are just a few, include a root borer called gorgojo de los Andes (Premotrypes spp.) and a leaf fungus causing mildew (Peronospora parasítica). Other fungal pathogens causing diseases present in the area are Fusarium graminium and Rhizoctonia solani (Tello et al. 1992; Aliaga-Cárdenas 1995).
The hypocotyls are harvested from May to July when they are at their maximum size, about 5 cm in diameter (León 1964; Tello et al. 1992). At this time, most of the leaves in the plants are still growing, without showing signs of senescence. A local hand hoe called a cashu is used for digging the plants one by one. The curved blade of this tool avoids damage to the roots. Estimated yields of fresh hypocotyls are 14.7 t/ha and 4.4 t/ha of dried hypocotyls with a harvest index of approximately 0.77 (Tello et al. 1992). After harvesting, the whole plants are dried during the day under the sun for 10-15 days, and covered during the night to avoid rain and frost damage. The leaves are left on the plant during drying because the local farmers believe that this will result in sweeter roots. After drying, the leaves are removed and the hypocotyls are taken to the market or stored dry in layers of less than 10 cm thick in well-ventilated sheds protected from the rain. Some of the freshly harvested plants are replanted for seed production during the following spring when the first rains appear (Tello et al. 1992). For this purpose, the whole plants are stored in pits covered with soil for approximately 45 days to allow root re growth and initiation of generative shoots. This practice results in the loss of many plants due to rotting of the foliage. After this period, when the generative shoots are about to appear, the hypocotyls are dug out and transplanted 0.6-0.7 cm apart in empty sheep stables where plenty of manure is available in the soil. Therefore, maca is handled as a biennial crop because of water limitation in the region. Each cycle, vegetative and reproductive, is coordinated with the beginning of the rainy season in the central Andes. After approximately 4 months the whole plants are lifted, when the siliques begin to turn yellow before dehiscence to avoid seed shattering. The plants are then dried and the seed is thrashed by rubbing the dry inflorescence with both hands (Tello et al. 1992).