Nutritional variation of vermicompost obtained from different organic waste mixtures and its influence on earthworm...

Vermicompost is a nutrient-rich organic fertilizer produced mainly by the activity of earthworms. Its nutrient concentration, development and reproduction of earthworms depend directly on the type of waste processed. The aim of the study was to evaluate the behavior of nutrient concentration and earthworm population development during vermicomposting of different wastes mixed in different proportions. Eighteen waste combinations from three types of manure (cow [C], horse [H] and goat [G]), two plant wastes (vegetable [V] and corn stover [S]), and three proportions of manure:plant waste (50:50, 60:40 and 70:30) were evaluated. A randomized complete block design with a 3 × 2 × 3 factorial arrangement was used. The results showed that the chemical properties of the vermicompost were significantly influenced by the type of manure, plant residue, and their proportions. After 90 days, the pH of the mixtures remained alkaline, ranging from 8.5 to 9.1 depending on the manure type, while EC decreased markedly, with average reductions of 72%, 66%, and 70% in mixtures with cow, horse, and goat manure, respectively, reaching values below 4 mS cm⁻¹, which are suitable for agricultural use. NO₃⁻ concentration initially ranged from 875 to 1800 mg kg⁻¹ but decreased by up to 41% at 30 days; later it increased at 60 days and finally declined again at 90 days, with final values between 607 and 1667 mg kg⁻¹ depending on the treatment. K concentration decreased progressively throughout the process, with reductions of 75-80% compared to the initial values, while Ca content increased progressively after 30 days, reaching final concentrations of up to 36.7 mg kg⁻¹, representing increases of more than 200% in some mixtures. Na concentration showed a clear decreasing trend, with reductions of 33-65% at the end of the process, with lower final values observed in mixtures with corn stover. These results demonstrate that the dynamics of nutrient availability during vermicomposting depend strongly on the type and proportion of organic residues used, and that the final vermicomposts showed EC and nutrient values suitable for agricultural use.