Preceding the planting of corms, the soil is ploughed to a depth of about 30 cm and left to rest for a period from a few weeks to the whole winter. The cultivated area is divided up into plots of about 1000 square metres (20×40–50 m). A ridging hoe is used to prepare the bed; four parallel furrows, 2 by 2, are cut to a depth of about 10 cm for a length of 10–15 cm.
The corms are placed or lightly driven into place with the apex uppermost, generally in contact with one another (for more details see the section Planting out, below). They are then covered with the soil from the next furrow in line, to form a mound of about 10 cm in height. Four furrows make up a bed, locally called a patch. Each patch is about 80 cm wide, slightly raised to a height of 10– 15 cm and about 50 cm long. The patches are separated from each other by a furrow, about 30 cm wide, which serves to give access for cultivation and above all acts as a drainage ditch.
The soil in Navelli is fertilized with mature horse or cow manure (about 30 tons/ha). Contrary to cultivation practices in Spain and Greece, no mineral fertilizers whatsoever are used in Navelli. In Borgo Val di Taro (Parma), small saffron plantations have been planted and fertilized with both mineral fertilizers and manure.
During June and July, the corms are dug up with a hoe, taken under cover and kept for a few weeks in hemp sacks. Before being replanted they are laid out on a canvas for individual examination and selection, based on the elimination of corms with cuts or marks and especially those with rot or parasites. The external tunics (2–3 layers) are then cleaned off, leaving only the interior tunic on each corm. The residual roots, in the form of a blackish-brown flattened disk, the residue of the previous year’s corm, are then removed, as they can be the cause of fungal attacks. Selection is based primarily on diameter and weight and only corms with a diameter larger than 2.5 cm are used; corms with too small a diameter are used as fodder (pigs, cattle). However, these should not be destroyed, as they can be planted in nursery beds, until their offspring reach the critical flowering size (diameter 2.5 cm) in subsequent years.
Corms in Navelli are not subjected to disinfection. Experience gained in Val di Taro (Parma) has shown that it is advisable to treat the corm, in order to inhibit the spread of disease, by immersion in a benomyl-based fungicide (5–10 mg per 1000 ml). In Spain and India, a solution consisting of 5% copper sulfate is used.
The planting period is the second fortnight in August (in Spain from 15–30 June; in Greece before the middle of September; in India from the middle of July to the end of August).
The preferred planting order in Navelli is four rows (two by two) per patch. In each row the corms are either in contact with each other or at a distance of 1–1.5 cm, with a planting depth of 8–10 cm. When the corms are planted to less than this depth the roots become large and fleshy (contractile roots), in which case the daughter corm does not grow, as the reserve material is stored in these roots and the mother corm is almost totally consumed by them. Contractile roots are also formed when the corms are disturbed during development by other factors (overcrowded planting, lacerations, etc.).
Tests have shown that the best yields — flower and corm production — are obtained by leaving a space of 2–3 cm between each corm in the furrow. The optimal quantity per hectare is 13–15 tons; that is about 600–700 thousand corms with an average weight of 20–22 g each (45–48 corms per kg). A hectolitre weight of 50–60 kg is equal to 2500 to 2700 corms. Therefore, about 1.3 tons of corms, that is 59–62 thousand pieces, are needed to plant an area of 1000 square metres (manual planting). Recently, experiments have been carried out using agricultural machinery similar to a modified potato planter ().
Irrigation is not necessary in Navelli.
The saffron plantations in Navelli are infested with wild cereals which do not compete with saffron plants, because they are less developed during the period when the saffron plant is at anthesis (autumn) or at maximum growth (spring). As a result, no weed control is necessary. In fact the weeds are left to grow until the end of May, when they are cut together with the saffron leaves and used for cattle feed.
Production of hay is on the order of 60–80 kg/ha. The dry saffron leaves contain 12.12% nitrogenous substances and numerous mineral elements (about 7%) and have, therefore, good nutritive value. Their use as feed for cows and sheep results in increased milk production.
Flowering and Harvesting
Flowering occurs in autumn, about 40 days after planting, and lasts for about 3 weeks, from the middle of October to the 7th (10th) of November. A cold and snowy period, as well as late planting, can retard anthesis until after the middle of November. During anthesis, the highest concentration of flowers — over 60% of the plants in flower at the same time — occurs in the last 10 days of October. The Spanish call this period “the day of mantle”, that is, the period during which the greatest expulsion of anthesis occurs, and the countryside becomes as though arrayed in a mantle of flowers.
The flowers are harvested manually. The picker moves between the patches picking the two rows to his left and the two rows to his right alternately. The flower is harvested by taking it between the thumb and the index finger of one hand and cutting it with the nail. The cut flowers are placed in a wicker basket to prevent them from being pressed together. The baskets are taken under cover and emptied onto a wooden table; “peeling” begins the same morning, i.e. the flowers are opened and the stigma is separated out.
It is impossible to mechanize this operation because flowering takes place contemporaneously with leaf growth and mechanized harvesting would involved cutting the leaves. As a result, the formation of daughter corms would not take place.
The flowers are picked early in the morning, while the flower is still closed, before the corolla opens. In this state the flower is quicker to pick and consequently easier and quicker to open for the removal of the stigma. Because the flowers have to be picked while they are still closed, working hours in the fields are limited to 2–3 hours in the morning. However, as many people as possible are needed during this phase in order to finish the work as soon as possible, because when the flowers open (opening occurs after sunrise when the soil heats up), according to local tradition, stigmas are considered to be of inferior quality. Stamens and anthers which are full of pollen are not picked; in Spain on the other hand, these are picked for their carotene and xanthophyll content.
Flower Production and Yield
Flower production in Navelli depends primarily on seasonal climatic conditions and on parasite attacks (rot, virus, etc.). A hectare of saffron plants yields 4–5 tons of fresh flowers; about 75 kg of fresh flowers are needed for 1 kg of fresh stigmas. The average weight of fresh stigmas from 100 flowers is 3.47 g and average dry weight is 0.69 g. The average weight of each flower is 0.3–0.5 g, each fresh stigma 30–40 mg, and each dry stigma 7–7.4 mg. There is a weight loss of 4/5 during the toasting process, and thus 1400 to 1500 flowers are needed to obtain 1 g of dry stigmas (the marketable product).
The average yield of the dry product per hectare is 10–16 kg. The saffron plantations in Navelli have the highest recorded production per hectare in the world. The yield of dried stigma filaments (kg/ha) elsewhere is 6–29 for Albacete (Spain), 4–7 for Krokos (Greece) and 1.8–6.8 for India.
Drying and Storing Methods
Separation of the stigma from the flower, called “stripping” or “peeling”, is done by hand and carried out immediately after the flowers have been picked. The flowers (tepals) are opened and the stigma is cut with the fingers at the point where it divides into the three stigmatic branches, avoiding, as much as possible, any part of the yellowish style, as this lowers the quality of the product. The stigmas are laid on a sieve and placed about 20 cm above live oak-wood charcoal to dry. The sieve is connected by three ropes to a single support point, thus ensuring perfect roasting. Halfway through roasting the stigmas are turned over to ensure uniform drying. Roasting lasts for 15–20 min and drying is complete when the stigmas do not crumble and still possess a certain amount of elasticity when pressed between the fingers. Saffron dried over charcoal retains its purplish-red colour, its fragrance and its aroma. Results of trials carried out in electric drying ovens confirm that stigmas roasted in the traditional way over charcoal maintain their organoleptic qualities better (). During roasting, the stigmas lose 4/5 of their weight: 500 g of fresh stigmas yield only 100 g of dry stigmas. The final product retains 5–20% humidity. The dried stigmas are reduced to a powder by grinding in an electric coffee grinder. In a humid environment, saffron in filaments or powdered form is extremely hygroscopic and highly susceptible to fermentative processes, resulting in a change of colour and an unpleasant odour. It is therefore kept in well-sealed, coloured-glass jars (without rubber stoppers) or in canvas bags, and stored in a dry place.
The cultivation of saffron is never carried out on the same plot within at least 10 years of the previous saffron crop. In some cases where this custom has not been respected, a decrease in production was observed, with an increase in the number of weeds attributable to the previous saffron crop. Saffron crops are rotated with lucerne and wheat.
Pests and Diseases
The saffron plantations in Navelli are subject to adverse climatic conditions which cause damage to the part of the plant which is above ground, and to attacks by rodents (moles and mice) which damage the corms. The most ruinous diseases, however, are of fungal origin.
In the Navelli area, a mycosis produced by Penicillium cyclopium is particularly prevalent, causing mauve-coloured rot as a result of insect attacks. It is at its most virulent during the hot, humid season. In the past 15 years, the plantations have been attacked by an alarming disease which causes abnormal leaf growth (up to 50 cm) and overdevelopment of the floral sheath. The plant becomes thin and white as the sheath forms a sleeve, which prevents the leaves and flowers from emerging, even though they are perfectly formed. The corm cells deliquesce and the corm gradually dissolves. Plants attacked by this disease are called “little candles” by the growers. The pathogenic agent appears to be Fusarium, a microscopic fungus producing gibberellin, which causes abnormal growth of the leaves and sheaths. This parasitosis is also more prevalent during the hot rainy season, reducing flowering by 10 to 30%. Where plants are left in the soil for two years, the disease reaches 45%. This is yet another reason why pluriannual cultivation is not feasible in Navelli.
Selections from the book: “Saffron. Crocus sativus L.”. Edited by Moshe Negbi. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 1999