Studies on the rate of decomposition of Parthenium grass (Parthenium hysterophorus L.) along with partially decomposed cow dung during vermicompost production

Introduction

Decades of intensive chemical fertilizer and pesticide application since the Green Revolution have degraded soil health, leading to erosion, reduced organic matter content, and chemical residue accumulation. Regenerating soil organic matter is critical for sustainable agriculture. Vermicomposting-an eco-biotechnological process utilizing earthworms to transform organic waste into nutrient-rich humic castings-offers an efficient, low-cost solution (Ghatnekar et al., 1998; Benitez et al., 2000) [2,1] . Earthworms act as mechanical blenders and biological drivers in soil systems (Norbu, 2002; Hansen, 2007) [4, 3] . While conventional composting takes 6-8 months and often yields nutrient-depleted product, vermicomposting rapidly converts biomass into high-quality bio-fertilizer. India generates 600-700 million tonnes of agricultural waste annually (Khobragade et al., 2017) [5] , representing a immense potential source of plant nutrients (Anonymous, 2014) [6] . Parthenium (Parthenium hysterophorus L.) is an aggressive, invasive weed posing significant ecological and agricultural threats. Traditional control methods like mechanical weeding and herbicide sprays are costly and environment-hazardous. Because parthenium seeds lack dormancy and germinate readily under moist conditions (Aneja, 1999; Kaur et al., 2022) [7,8] , converting parthenium biomass into vermicompost offers a dual benefit: effective weed management and organic manure production. This study evaluates the rate of decomposition of parthenium grass blended in varying proportions with partially decomposed cow dung.

Materials and Methods

Experimental site & layout

The experiment was conducted from March 25 to June 24, 2026, at the Vermicomposting Unit, Department of Animal Husbandry and Dairy Science, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra (22°42′ N, 77°02′ E, 307.41 m AMSL). Analytical testing was performed at the Department of Soil Science, Post Graduate Institute, Dr. PDKV, Akola. The region experiences a semi-arid climate with a mean annual rainfall of 740 mm.

Experimental treatments

The experiment was laid out in a Randomized Block Design (RBD) with four treatments and five replications across 20 HDPE raised beds (1.22 m × 0.91 m × 0.61 m):

Substrate preparation and inoculation

Parthenium grass was harvested fresh, chopped to < 2 cm pieces, and layered into HDPE beds with cow dung. Beds underwent pre-decomposition for 21 days to dissipate initial heat. Eisenia foetida red worms were released at a rate of 50 earthworms per 10 kg of substrate (at 21 DAF). Moisture content was maintained at 65-70% waterholding capacity via periodic sprinkling.

Analytical methods and observations

Temperature was measured in the center of beds at a 15 cm depth using a digital thermometer. Total organic carbon (TOC) was measured by dry combustion at 600 °C for 2 hours (Anonymous, 1985) [9] . Total Nitrogen was evaluated using the Kjeldahl method to determine C:N ratios (Jackson, 1973) [10] . Weed seed germination was evaluated by a grow-out test using 2 kg finished compost per tray over 10 days. Statistical analysis was performed using Analysis of Variance (Panse et al., 1967) [11] with CD evaluated at p = 0.05.

Results and Discussion

Temperature dynamics

Temperature profiles peaked at 15 DAF in all treatments due to rapid microbial heat generation, reaching 46.2 °C in T 1 and 43.7 °C in T 4 .

Temperatures declined smoothly as organic matter stabilized, settling at ambient ranges (20.1-22.2 °C) at 90 DAF (Table 2). This decline aligns with findings by Patnaik et al. (2010) [12] , Hait et al. (2011) [13] , and Rynk et al. (1992) [14] .

Weight loss and yield recovery

The highest final vermicompost weight was recorded in T 1 (47.4 kg) and T 3 (47.2 kg). Maximum percentage weight reduction occurred in T 2 (39.87%), followed by T 4 (38.77%), T 1 (34.26%), and T 3 (32.93%). T 3 gave the highest yield recovery at 67.07% (Table 3). Similar mass reductions and recovery rates have been reported by Mahala et al. (2019) [15] , Mayadevi (2016) [16] , and Attayee (2015) [17] .

Maturity period and weed seed germination

Maturity time decreased significantly with higher parthenium proportions (Table 4). T 4 matured fastest at 68 DAF, followed by T 3 (73 DAF), T 2 (76 DAF), and T 1 (87 DAF). The soft leaf structure of parthenium accelerates decomposition compared to fibrous cattle shed waste (Savant, 2016; Pawar et al., 2017) [19,18] . Germinated weed seeds per kg of finished compost were zero in T 1 and extremely low in parthenium treatments (1.50 to 3.30 seeds/kg), confirming that earthworm activity effectively neutralizes parthenium seed viability (Babu et al., 2008) [20] .

Total organic carbon (TOC) and C:N ratio

Total Organic Carbon declined steadily across all treatments from 30 DAF to 90 DAF (Table 5). T 1 recorded the lowest final TOC (23.90%), reflecting complete carbon loss via respiration (Suthar, 2007; Garg et al., 2006) [22,21] . At 90 DAF, C:N ratios ranged between 12.10 (T 2 ) and 17.20 (T 3 ). Since a C:N ratio below 20 [21,23,24] , all formulations achieved full agronomic maturity.

Conclusion

Parthenium hysterophorus grass is a highly suitable organic substrate for vermicomposting when combined with partially decomposed cow dung. Increasing parthenium inclusion from 30% to 50% accelerated decomposition and reduced compost maturity time from 87 days (control) down to 68 days (T 4 ). Weed seed viability was effectively suppressed during the process, and all parthenium treatments achieved ideal final C:N ratios (< 20). Treatment T 4 (50% parthenium + 50% cow dung) is recommended for rapid vermicompost production, whereas T 3 (40% parthenium + 60% cow dung) provides the highest total yield recovery (67.07%).

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