The use of comfrey as soil amendment to improve growth of maize and amaranth vegetable

Abstract

Being an organic material enriched with essential nutrients, comfrey plant (Symphytum spp) can be used as a soil amendment to improve soil characteristics and crop productivity.  This study aimed to evaluate the potential of comfrey plant on growth and yield of maize (Zea mays) and amaranth (Amaranthus spp). Two pot experiments were conducted where in first experiment, maize was grown in soil amended with Comfrey leaves powder (CLP) at 0, 2, 4 and 8% (w/w) for 6 weeks and in second experiment, Amaranthus was grown in soil amended with Comfrey roots powder (CRP) at 0, 2 and 4 % (w/w) for 5 weeks. Application of 8% of CLP to the soil increased maize height significantly (by 29 cm, p = 0.045) compared to maize in control treatment. Maize leaves number increased significantly (from 5 to 8 leaves, p = 0.001) following soil amendment with 2% of CLP. Stem diameter increased significantly with increasing CLP from 0 – 4% (diameter from 0.7 to 1.2 cm, p <0.001) compared to control, further increase in CLP up to 8% had no further significant effect. Total maize plant biomass increased significantly (from 8.21 to 28.25 g, p <0.001) following the soil amendment with 0 – 8% of CLP. Soil amendment with 2% of CRP increased significantly Amaranthus shoot biomass (0.48 to 1.31 g, p = 0.048) and total plant biomass (0.66 to 1.48 g, p = 0.018), further increase in CRP had no further significant effect. Positive growth responses noted in both crops following soil amendment with comfrey could be linked to high nutrients composition noted in comfrey powders.  From this study, the use of 2 to 8 %(w/w) comfrey powders is recommended to improve vegetative growth of amaranth and maize, however further studies on use of comfrey as soil amendment are highly recommended.