Epsilon Archive for Student Projects

Abstract

This study aimed at evaluating the suitability of biochar and hemp as partial or
complete replacement of peat in horticultural growing media, with specific
emphasis on the effects on nutrient availability and plant nutrient uptake. The
study was motivated by the environmental concerns surrounding the use of
peat, along with a desire to explore possible uses for biochar and a crop
residue from hemp cultivation. In total, 13 growing media treatments were
evaluated, comprising of six peat/biochar-treatments, six hemp/biochar
treatments (biochar rates 0 – 31.25 % v/v) and one control treatment (a
commercial peat-based growing media).
A greenhouse pot experiment was set up to assess the effect on plant
growth of lettuce, Lactuca sativa L. Prior to cultivation, important
physicochemical properties of the media were determined; dry bulk density,
water-holding capacity, total porosity, air-filled porosity, pH and electrical
conductivity. In order to study the impact on nutrient availability and plant
nutrient uptake, growing media samples were analyzed for readily available
plant nutrients, both before and after lettuce cultivation. Additionally, the
harvested lettuce was analyzed for its nutrient content. Overall, the
physicochemical measurements showed more suitable properties in the
control treatment and the peat-based growing media, compared to the hempbased growing media. However, all treatments except the control had a
slightly to highly alkaline pH, which was unfavorable for plant growth.
Regarding lettuce plant performance, both the peat-based growing media and
the hemp-based growing media performed much below a satisfactory level.
Severely impaired plant growth could be observed in all treatments except the
control but particularly in the hemp-based treatments. The negative plant
response was associated with an overall N deficiency and/or reduced N
availability in the growing media with increasing biochar rates. This was most
likely caused by N volatilization, due to the alkaline pH of the growing media.