Henfaes Research Centre, University of Wales, Bangor
Flax and Hemp Project
Guidelines for growing Hemp
Guidelines for growing hemp as pdf (15kb)
Note: The recommendations made in this website are for guidance purposes only. All crops are subject to seasonal variation and results are based on knowledge currently available and 3 years of field trials. The trade names mentioned are products that have been used in this project but other equally suitable products are available. SAFS accepts no liability for information provided in this document.
Soil Type
Hemp will grow well on most good soils that are suitable for crops. Acidic soils however, will result in reduced yield. Poorly drained or sandy soils should be avoided.
Seed Bed Preparation
If soil is below pH6 apply lime before primary cultivation. A fine weed-free seedbed with minimum compaction is essential for good establishment.
Fertiliser
Nitrogen:
- Recommended N levels are currently 80kg/ha proir to sowing or applied with the seed, plus an additional 80kg/ha should be applied as a top dressing when the crop has five pairs of true leaves. If organic manures are used this must be taken into account.
Phosphorus and potassium:
- Recommended levels are currently 160kg/ha of P2O3 and 80kg/ha of K2O.
Levels of fertiliser should be reduced if organic manure is applied.
Drilling
Drill early to late April to early May when risk of frosts has passed. Soil temperatures should be consistently above 10 degrees C. Drilling time will influence fibre yield; earlier sown crops will obtain higher yields. Drill with rows 12.5–25 cm apart (5–10″), at a depth of 4 cm (1.5″). Recommended seed rate is 37kg/ha.
Weed control
Hemp seedlings are very competitive against weeds and once established will outgrow and smother other plants through the development of a tall dense canopy. Weed control is therefore only required during establishment. There are no herbicides available for hemp crops on the market at present.
Pests and Disease
So far diseases have not presented a problem due to the small scale cultivation. Rusts may become apparent with increased cultivation area. Botrytis cinerea (grey mould) and Sclerotinia sclerotiorum (white mould) are common in industrial hemp.
Retting
Retting is the fungal breakdown of straw to release the fibres from the woody core. Dew retting is the traditional method and occurs after desiccation when the crop is swathed and left to rett on the ground. The crop should be turned at least once to allow for even retting. All swathers (and rakes) must be set at the correct level and care must be taken to avoid raking stones into the fibre crop. Dew retting will take about 10 – 20 days. But the time taken will depend on weather conditions.
Cutting/harvesting
Specialist equipment has been manufactured for harvesting. In Wales twin drum mowers are recommended for dew and stand retted crops. Triple drum mowers and mower-conditioners are unsuitable.
Baling
The straw must be dry when baled (max. moisture content 18%) and kept undercover in storage. Crop will be rejected by processors if the moisture content is too high and the crop will spoil.
Processing
Industrial processors mechanically remove the fibres from the shive (the woody core). The fibres are then used for a variety of products ranging from insulation, soil stabilisation matting and plastic composite materials.
This project aims to assist farmers in supplying the emerging natural fibre industry with high yielding, quality fibre.
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