Soil Type Hemp will grow well in 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 prior 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. Phosphorus and potassium: Recommended levels are currently 160kg/ha of P2O3 and 80kg/ha K2O. Do not over apply potassium as this encourages changes to cannabinoid levels. If organic manures are used this must be taken into account and reduced levels of fertiliser should be applied.
Drilling Drill early to late October to early NovemberSoil temperature should be consistently above 10° 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 3 cm (1”). Recommended seed rate is 48kg/ha (300 seeds/m2).
Weed control Hemp plants are very competitive against weeds and once established will outgrow and smother other plants through the development of a tall dense canopy. Manual weed control is therefore only required during establishment.
Pests and Disease So far diseases have not caused a major a problem due to the small scale cultivation, but care will be required as areas of production increases. Rusts may become apparent with increased cultivation area. Botrytis cinera (grey mould) and Sclerotinina sclerotionim (white mould) are common on industrial hemp. The moulds lead to lesions on the stem where no fibre is laid down. This can cause stem breakage during processing. It is not recommended to sow hemp following oil seed rape due to disease carry over.
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. Stand retting is an alternative method currently being researched. The crop is desiccated with a herbicide while still standing. However, because of the height of the hemp there are problems with this method and it is not currently recommended.
Cutting/harvesting Time of harvest is usually between mid March to mid May (southern hemisphere). The exact date will depend on the time of sowing, the variety grown and the weather conditions for the growing season. Specialist equipment has been manufactured for harvesting. 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
Note: The recommendations made in this document 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. Whilst every effort has been made to offer accurate advice Hemptons accepts no liability for information provided in this document.

5 thoughts on “General Guidelines for growing Hemp

  1. Hi there, I want to grow one or two hemp plants in my backyard for my own use. Where do I get seeds that can grow? I live in the Table View part of Cape Town.

  2. Hi there.

    Is it legal in South Africa to grow industrial hemp and harvest it for building material (hurd)?

    If so, do you need a licence or permit or can you simply grow it?

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