Growth Performance of Varieties of Bean (Phaseolus vulgaris) Seedlings in Earthworm-Bioturbated Soil and Crab-Bioturbated Soil

Abstract

Earthworms and crabs are known to influence the physicochemical state of their respective soil habitats through their bioturbation actions. While earthworm-bioturbated soils have been well documented to positively affect plant growth, not much is known about the effects of crab-bioturbated soil on plant growth. In this study, we compared the growth performance of four varieties of Phaseolus vulgaris (bean) seedlings in earthworm-bioturbated soil, crab-bioturbated soil, and unbioturbated soil collected within the same proximity of a wetland habitat. Seeds of Phaseolus vulgaris were planted in replicates in each soil type, and allowed to grow for 15 days. Physical growth was measured using a metre rule. Biochemical growth parameters were measured using standard procedures. The differences in stipule length of bean seedlings grown in all the soil types were generally not significant (p > 0.05). However, seedlings grown in earthworm-bioturbated soil and crab-boturbated soil recorded significantly higher (p < 0.05) stipule weight, relative to those grown in unbioturbated soil. Bean seedlings grown in earthworm-bioturbated soil recorded the highest and significant (p < 0.01) concentrations of chlorophyll, total sugar, starch, nitrogen, and crude protein, relative to those grown in crab-bioturbated and unbioturbated soils. This was followed by seedlings grown in crab-bioturbated soil which recorded significantly higher (p < 0.01) concentrations of these biochemical parameters, relative to those grown in unbioturbated soil. The significantly higher biochemical and marginally better physiological growth recorded for seedlings in bioturbated soils indicate that earthworms and crabs both contribute significantly to wetland productivity, through their bioturbatiion activities.

Keywords

• bioturbation
• plant growth
• plant hormones
• vermicasts