The Growth-Promoting Effect of Earthworm Vermiwash on House Tomato Plants

Earthworm vermiwash, a by-product of the vermicomposting process and a light-brown-colored liquid rich in macro- and micronutrients that are essential for plant growth, has recently emerged as a potential tool for sustainable agriculture. It is expected to have antimicrobial, antipest, and soil-stabilizing effects. However, little is known about the optimal composition and dosage of vermiwashes, and the long-term stability is still unknown. Here, we investigated the long-term stability of vermiwash content and conducted a growth test on house tomatoes treated with different concentrations of vermiwash. The phosphate and potassium contents of the vermiwash were remarkably stable over time; however, if the initial ammonium content was high, the content changed with temperature, and nitrate-nitrogen was increased. Our results suggested that the vermiwash can be preserved at any temperature as both nitrogen components are helpful for plant growth. The vermiwash treatment outperformed the other two treatments in terms of plant height and fruit size. The threshold vermiwash nitrogen level was approximately 17.5-35 mg/L per week. Although an ideal ratio is advisable, earthworm vermiwash does not inhibit growth even at high concentrations. Thus, vermiwash is a sufficiently stable, beneficial liquid plant fertilizer.