Optimisation of nitrogen fertilisation and seed density in hemp crop

To study the influence of nitrogen fertilisation and seed density in hemp (Cannabis sativa L.) field trials were carried out in Switzerland and South Germany. A high seed density (30-60 kg/ha) and nitrogen fertilisation did increase stem and bast yields. Nitrogen also increased seed yield, plant height but also lodging. Seed yield was higher at lower seed density (10 kg/ ha). At this plant density no sufficient cover against weeds was observed. Low seed density and also high nitrogen supply may increase difficulties for mechanical grain harvest.<br>We recommend for grain hemp a seed density of at least 30 kg/ha and a maximum nitrogen fertilisation of 50 to 85 kg N/ha. For fibre hemp the maximum nitrogen fertilisation should be 85 to 120 kg N/ha.