4.2 Fertilisation

Hemp requires reasonably accurate fertilisation. Fertilisation that is too low or too high leads to yield reductions. For optimum growth, about 110 units of nitrogen (N), 80 kg of phosphate (P₂O₅) and 140 kg of potassium (K₂O) are recommended per hectare for technical applications (excluding the soil stock from the calculation).^[1] This is applied before sowing. Excessive nitrogen application can result in lower yields due to heavy stems lying flat, and stronger competition for light by individual plants leading to uneven plant height and problems at harvest. Excessive N combined with too little K can cause stem breakage.

Hemp grows well on organic fertiliser, such as manure from pigs, cattle, or chickens. It can be chosen to apply 20% of the total with a fast-acting fertiliser in the starting phase for the purpose of rapid growth. N uptake occurs mainly during the first (6-8) weeks, while P and K are mainly taken up later in growth, before flowering and seed formation. The organic farmer would only use animal manure.

For textile applications
Nitrogen application for hemp textiles is lower than for technical applications: 70 - 100 units of active nitrogen (N), 40 kg P₂O₅, 110 kg K₂O and 30 kg MgO per hectare.^[2]

[1] https://www.hempflax.com/wp-content/uploads/Hempflax-Handleiding-Hennepteelt.pdf

[2] https://onderzoek.hogent.be/sites/onderzoek/assets/File/HOGENT%20Onderzoeksresultaten%20%E2%80%98Eigen%20Kweek%E2%80%99%20en%20%E2%80%98Hemp4All'.pdf