Cultivation of fiber hemp using solid and liquid residues from municipal composting in a closed system

Progressing degradation of agricultural soil demands a change to more sustainable cropping systems accounting for crops that can sustain the soil health. Hemp is known for the improvement of soil physical, chemical and biological properties. The objective of the research is to analyze the hemp plant capability to grow under nutrient poor soil conditions and dense canopy and to assess hemp’s ability to uptake plant nutrients applied with/by soil amendments produced from biowaste. Additionally, the research aims to analyze how the hemp nutrition affects its morphogenesis, thus the fiber content.

In the greenhouse set up, Cannabis Sativa L. was grown in sandy substrate, with limited water supply that corresponded to the common drought periods in Brandenburg (Germany) and with addition of soil amendments in form of pellets from organic waste (OW) digestives. The treatments included: 5 control pots, 10 pots with pellets (19 kg soil / 230 g pellets according to the allowed application of 13 t/ha) and 10 pots with 19 kg soil / 3 kg pellets. When needed, a universal liquid fertilizer was applied which contained water soluble minerals like N, P2O5 and K2O. After 92 days, the plants were harvested, dried and weighted. The root structure was examined visually. The stems were decorticated using BMS-FLAKSY® (Rossmanith GmbH) to analyze the fiber content. The Elementar vario MAX cube analyzer device was used to analyse C and N contents.

The results showed that hemp could still flourish in water and nutrient limited environment. A deeper and denser rooting was observed in the treatments with pellets. It was observed that fine roots were encircled and attached to the pellets to access the nutrients stored there. The highest C:N ratio in soil and in leaves was found in treatments that contained the most pellets. The option to apply pellets produced from OW in larger quantities instead of a fertilizer application had a striking effect on hemp growth and biomass accumulation hence, increased dry matter amount and fiber yield.