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Introduction
Legislation
Rotation
Soil conditions
Seed bed preparation and sowing
Crop nutrition
Weed control
Irrigation
Illnesses and pathogens
Variety
Phenology
Harvest
Chain issues
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Introduction
In many European countries hemp cultivation was important up until WWII. Post-war competition from synthetic fibres and lower-cost natural fibres caused hemp to gradually disappear from the market. The only country that maintained some hemp cultivations has been France, where the production of specialty papers has guaranteed a sustainable demand of hemp fibres. In the Countries of Eastern Europe the decrease of hemp cultivation has been delayed compared to West Europe and in the last years very few hectares of hemp have been grown for twines and ropes and only limited amount for traditional textiles. |
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Legislation
In the 70's the European Union created a Common Market for flax and hemp under the Council regulation (of the EEC) no. 1308/70 of June 29th 1971. This regulation enabled some production systems to be reinstated.
In 2000 reforms of the Common Market under the Council regulation (of the EC) no.1672/2000 of July 27th 2000 extended agricultural subsidies to flax and hemp producers. Council regulation (of the EEC) no.1251/1999 of May 17th 1999 also instated the rule that subsidies for hemp and flax producers will only be given to those who have a contract of agreed-purchase with a recognised primary processor. Moreover, the subsidy given is calculated according to the type of fibre (long/short) for which the hemp is grown, and the maximum subsidy paid is fixed according to the largest surface area grown, and the national guaranteed quantities that for the short flax fibres and for hemp fibre will not apply anymore from the growing season 2006/2007.
Producers of hemp are obliged to use certified seeds that have a THC (tetrahydrocannabinoid) content = 0.2% (EC regulation no.1251/99 and successive modifications). Click here to see a list of registered varieties.
All the aforementioned regulations were enforced with the decree from the Ministry of Agricultural and Forestry Policy on March 8th 2001. |
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The main cultivation practices (ploughing, seed bed preparation and sowing) are approximately the same whatever the intended end-use of the hemp stems; however sowing density, harvesting time and harvesting technique might differ substantially according to the final destination of the fibre.
The general information on hemp cultivation that follow were gathered from scientific literature. Specific information on hemp cultivation for textile destination were obtained from experiments carried out in the frame of the HempSys Project.
Diagram: Unit operations in different hemp production scenarios.
Additional comments on the different production scenarios:
Traditional technique is slowly disappearing from the world’s panorama, particularly because of the cost of hand-labour for harvesting the crop, but also because of the poor sanitary conditions for those working in the retting pools.
Baby hemp technique despite its initial boom (almost 1000 hectares in both 2003 and 2004, ISTAT data) it is now produced on only about 50 hectares (ISTAT data, 2005). This drop in production was probably due to the poor quality of the stems retted in the field, as well as to the low production level obtained at high costs.
Hemp-Sys technique has high production levels (see below) and yields well matured fibres, and thanks to the controlled retting process there is a homogeneous product available for the processing industry. The lack of a prototype harvester however that is able to cut the stems into 1 m portions is a bottleneck still needing attention. |
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Rotation
Considering the deep root system, the capacity of hemp to compete with weeds, the deep soil labour and the large manuring that was given to this crop, hemp was inserted into crop rotations a crop for renewal. Even though it can be sown twice in succession, it was normally the crop that preceded or succeeded an autumn-winter cereal. Wheat in fact greatly benefited when preceded by hemp and King Phillip of Italy in 1806 referred to this rotation as a “lucrative and just method for obtaining large harvests of wheat”. This advantageous combination has been repeatedly demonstrated ever since (Gorchs e Lloveras, 2000), with advantages for the hemp also having been shown (Somma, 1923). Being particularly sensitive to herbicide residues (especially those used on maize and tomatoes), and being subject to damage by the parasites Pythium, Sclerotinia and corn borer, growing hemp after a crop infested by these parasites is not advised (Rivoira, 2001). |
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Soil conditions
Hemp is an annual crop that frowns during the hot season. Experimentally it has been grown in extremely diverse conditions (from Ath. Africa to Finland) and has been shown to have good yields in numerous climates. Traditionally, in the Padana plain in Norhtern Italy, hemp was sown at the end of winter (March 19th, Saint Joesph’s Day). Minimum germination temperature 1°C even enable sowing to be carried out at the end of February. A fast and homogeneous emergence is guaranteed when ground temperature is 10°C. 19°C is the minimum temperature for flowering to commence and 13°C for maturation. Hemp can grow in diverse soil, but prefers loam, deep, fresh, non-compact, well drained soils that are rich in organic matter. |
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Seed bed preparation and sowing
Correct sowing density is particularly important for obtaining a good emergence, and for controlling plant development. Currently in Italy some hemp is being grown very densely, up to 100 kg seeds ha-1, which corresponds with more than 500 valid seeds m-2. However, sowing 40-50 kg ha-1 (200 valid seeds m-2) is sufficient to obtain good emergence, optimum stem quality with a good fibre content, and fibres that are ideal for the harvesting technique developed in the framework of Hemp-Sys. |
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Crop nutrition
In the past the hemp crop was given large amounts of animal manure. Today the commercially used fertilisers apply 150 kg ha-1 of N, 150 kg ha-1 of P2O5 and 100 kg ha-1 of K2O (Rivoira, 2001). Hemp is sensitive to nitrogen availability and a crop with insufficient nitrogen is yellow and plant growth is stunted and inhomogeneous. Excess nitrogen on the other hand reduces fibre production, increases plant mortality due to a more intense self-thinning, and increases the probability of lodging during gails. Recent experiments carried out in Bologna showed that dry biomass production increased by approximately 20 kg for every kg of nitrogen applied (Amaducci et al., 2003).
Table: Uptake of the main nutritional elements
N (Kg t-1 Dry Matter) |
10 - 15 |
P2O5 (Kg t-1 Dry Matter) |
3 - 5 |
K2O (Kg t-1 Dry Matter) |
15 - 17 |
CaO (Kg t-1 Dry Matter) |
15 |
MgO (Kg t-1 Dry Matter) |
2 – 3 |
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Weed control
If the field is in good condition at sowing hemp will germinate quickly and within 3-4 weeks become 30 cm tall, immediately creating full ground coverage, blocking out the light and limiting weed growth. |
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Irrigation
Irrigation can be considered unnecessary in Northern Italy, but in Central and Southern Italy irrigation levels up to 1500 and 3000 m3 ha-1 respectively per growing season are necessary (Rivoira, 2001). |
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Illnesses and pathogens
Being particularly sensitive to herbicide residues (especially those used on maize and tomatoes), and being subject to damage by the parasites Pythium, Sclerotinia and corn borer, growing hemp after a crop infested by these parasites is not advised (Rivoira, 2001). |
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Variety
Choosing the correct variety is fundamental for obtaining a good crop production with well matured fibres.
From studies carried out in Hemp-Sys, monoecious varieties were seen to be more adapted to high latitudes, while dioecious varieties had a good, stable production at low latitudes..
Click here to see the varieties studied in Hemp-Sys. |
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Phenology
Simulation of crop cycle and crop
production |
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Harvest
Dioecious varieties are harvested when female flowers begin, and monoecious varieties when full flowering is reached. Plants should be at least 2 m high. The harvesting technique developed in this project intends to cut the stems into two portions of 1 m, and lay them down in swaths parallel to the direction of the harvester.
Stems will then be left to dry on the field and baled using flax balers. Stem should be removed from the field as soon as possible in order to prevent dew retting to occur. To harvest at full flowering is a decision based both on quantitative factors (high stem yield and stem height) and qualitative information (fibre maturity).
In the following figure it is illustrated how stem biomass and fibre are distributed along the stem. To have two portion of 1 meter the crop will be cut at 10 cm from the soil, at 110 cm and again at 210 cm, this will result in a loss of approximately 1 t of stem and 0,18 t of fibre as indicated in the table aside of the picture below. It can be noted that 70 % of the fibre is concentrated in the bottom part of the stem.
The prototype harvester developed within Hemp-Sys were not able to perform harvesting as indicated above. At the moment the production of a new prototype is under way. Please write us to be inform on future development. |
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Important aspects to note before deciding to sow hemp:
a) A primary processor close to the area of hemp production is particularly important, not only because a contract with a primary processor is needed to obtain EC financial support (EC regulation no.1673/2000), but because having the processing facility close by is the only way to reduce transport costs. According to the production system developed within Hemp-Sys the first processing step separates the bark, that contains the fibre, from the woody core and the equipment used to achieve this separation is the same as that used for flax; the two principle operations are crushing and breaking the stems followed by a passage through rotating blades that remove any woody core still attached to the bark.
b) Cultivating hemp in areas where there are no processing plants is not feasible. Operating a scutching facility requires at least 1000 ha. Farmers interested in growing hemp would not only have to invest in the hemp cultivation but also in the construction of the primary processing (scutching) unit. In this way they could benefit from the added value created during first processing. For more information go to the website of Gruppo Fibranova www.gruppofibranova.com
c) Suppliers of hemp seed in Europe are not many and finding seeds from cultivars adapted to specific environments is not a simple task. A list of seed suppliers is provided in this site.
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Italian version |
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