The Role of Vermicompost and Vermicompost Tea in Sustainable Corn Production and Fall Armyworm Suppression

Abstract

Integrating organic soil amendments such as vermicompost (VC) and vermicompost tea (VCT) in agriculture has received increasing attention as a sustainable strategy to improve soil fertility, enhance plant growth, and suppress pest infestations. This study aimed to evaluate the effects of varying concentrations of VCT (10%, 20%, and 40%), alone and in combination with VC (2.47 ton/ha), on the development and yield of corn (Zea mays), and suppression of fall armyworm (FAW, Spodoptera frugiperda) infestation. The experiment was conducted in seven raised beds with seven treatments: V0 (control), VCT10, VCT20, VCT40, VC1 + VCT10, VC1 + VCT20, and VC1 + VCT40. Six weekly applications of VCT were applied starting at the V2 stage, and soil and plant nutrient contents were determined post-harvest. Additionally, relative chlorophyll content, height, cob yield, dry biomass, and FAW infestations were assessed. Results show that both VC and VCT significantly enhanced soil nutrient content compared to the control treatment (V0). VCT20 and VC1 + VCT10 improved plant N, K, and micronutrient uptake. Corn treated with VCT10 and VC1 + VCT10 had the highest biomass (6.52 and 6.57 tons/ha, respectively), while VCT20 produced the highest cob yield (6.0 tons/ha), which was more than eight times that of V0. SPAD values and corn height were significantly high across all treatments, with VCT20 achieving the highest SPAD readings while the control achieved the lowest. For FAW infestation, the control treatment experienced moderate infestation. At the same time, there was complete suppression in VCT20 and VCT40 treatments and a reduction in VC + VCT treatments, likely due to the bioactive compounds and beneficial microbes in VC and VCT that strengthened plant immunity. The results suggest that VCT20 is a cost-effective, eco-friendly amendment for improving corn performance and FAW resistance. This study contributes to sustainable agriculture by demonstrating how organic amendments can enhance crop resilience while supporting environmentally friendly farming practices.

1. Introduction

The global population is steadily increasing, with projections indicating that it will reach 8.6 billion by 2030 and 9.8 billion by 2050 [1]. As a result, there is unprecedented immense pressure on agriculture, like never before, necessitating a significant increase in food production to meet the global food demands. This requires increased output with greater efficiency, where more food is grown with less water, land, and other resources in the face of climate change [2,3]. Consequently, to meet this need, modern farming systems often rely heavily on synthetic fertilizers and chemical pesticides, which, while effective at boosting crop yields, pose significant risks to soil health, biodiversity, and human safety [4,5,6], leading to substantial environmental degradation. As such, sustainable agriculture is becoming an increasingly important priority in addressing the twin challenges of food security and environmental degradation [3,7,8]. Organic amendments such as vermicompost (VC) and vermicompost tea (VCT) have emerged as promising alternatives to synthetic agrochemicals, offering a sustainable approach to improving soil fertility, promoting plant growth, and enhancing natural pest resistance [9,10,11]. These organic inputs are nutrient-rich and host diverse microbial communities and bioactive compounds that can profoundly influence soil and plant health [12,13].

Vermicompost, which is produced when earthworms break down organic waste, has been widely recognized for enhancing soil structure, increasing nutrient availability, and promoting microbial activity [14,15]. Meanwhile, VCT, a liquid extract produced by steeping VC in water under aerated or un-aerated conditions, is known for its bioavailability and rapid action in delivering essential nutrients and beneficial microorganisms directly to plants [10,16,17]. Studies have demonstrated that VCT applications can enhance crop productivity, increase chlorophyll content, and suppress pest infestations in crops by improving nutrient uptake and inducing systemic resistance [10,17]. Although several studies have focused on VCT application in horticultural crops and vegetables as biofertilizers and biopesticides [18], the relative efficacy of VCT concentrations with or without the addition of VC remains an area of active research, especially for nutrient-demanding crops like corn.

Corn (Zea mays) is a nutrient-intensive crop that is produced worldwide with global production that exceeded 1.23 and 1.22 billion metric tons in the 2023/2024 and 2024/2025 trade years, respectively [19,20], and it is considered a staple food for one-third of the global population including Sub-Saharan Africa, Asia and Latin America [21]. The crop is susceptible to pest infestations, including fall armyworm (FAW, Spodoptera frugiperda, JE Smith) [22,23]. FAW is a destructive phytophagous pest that feeds on over 350 different plant species belonging to 76 families [24,25]. It originated in the Americas in 1797, and it has since spread to over 80 countries in other continents, including Africa in 2016, Asia between 2018 and 2020, the Middle East in 2018, Australia in 2020, and Europe in 2021 [26,27,28], causing significant crop loses. Therefore, the dual challenge of meeting corn’s nutrient demands while managing pest infestations, such as FAW, presents an opportunity to explore the potential of VC and VCT as sustainable agricultural inputs.

Therefore, this study aims to determine the role of VC and VCT in sustainable corn production and the suppression of FAW in corn. The specific objectives were to (1) evaluate the effects of various concentrations of VCT (10%, 20%, and 40%) and their combinations with VC (2.47 ton/ha) on corn growth, physiology, and suppression of FAW; (2) determine the role of VC and VCT in enhancing soil fertility and nutrient availability in soils; and (3) identify the most effective treatment combinations for maximizing crop productivity while minimizing pest damage. The study hypotheses were that (i) increasing concentrations of VCT would improve soil nutrient status, plant growth, and FAW suppression, and (ii) combining VC with VCT would yield additive or synergistic benefits for corn performance and soil fertility compared to VCT-alone treatments. This study aims to provide a comprehensive understanding of how VC and VCT can contribute to sustainable agricultural practices. The findings advance knowledge of the interactions between organic amendments and agroecosystem functioning, providing insights into optimizing organic inputs in corn production systems in the context of climate change.

2. Methodology

2.1. Study Site and Experimental Setup

This experiment was designed as a follow-up to our previous study [29], which demonstrated that the VC, VCT, and VC + VCT treatments enhanced corn physiological responses and reduced FAW infestation. In that study, VCT was applied at a fixed rate (20% VCT), while varying volumes of VCT (50 mL and 100 mL) were applied per plant. VC was applied at two rates (2.47 ton/ha and 7.41 ton/ha). The current study builds upon those findings by evaluating a range of VCT concentrations (10%, 20%, and 40%), both alone and in combination with VC (2.47 ton/ha), to determine which treatment best enhances plant physiological traits, soil chemical properties, and FAW suppression.

The current study was conducted from May to August 2024 at the organic garden (25.7539281, −80.3800388) of the Agroecology program (Department of Earth and Environment, Florida International University, Miami, FL, USA). The garden is 0.61 ha in size and is recognized as a People’s Garden Initiative by the United States Department of Agriculture [30]. It has calcareous, sandy loam soils and has been maintained under organic amendments. During the study period, the average monthly rainfall ranged from 3.56 mm in May to 14. 73 mm in June, while the average monthly temperature ranged from 28.4 °C in June to 29.8 °C in July (weather data source: National Oceanic and Atmospheric Administration; https://www.weather.gov/wrh/Climate?wfo=mfl accessed on 22 May 2025).

Seven metallic raised beds (large modular metal raised bed kit, Vego Garden, Houston, TX, USA) with dimensions of 243.84 cm × 60.96 cm × 30.48 cm (L × W × H) were set up on a foundation of pre-laid wood mulch and weed control fabric (Agfabric, Gardenport, Corona, CA, USA) in an open area with full exposure to ambient weather conditions. Each raised bed was filled with potting mix soil supplied by RGS Nursery (Miami, FL, USA), which served as the study’s background soil (BS). Corn seeds (Organic Top Hat Sweet Corn variety, Hudson Valley Seed Co., Accord, NY, USA) were planted in two rows, with six plants per row per raised bed. The plants were irrigated manually with a sprinkler every morning, except on days when a rainfall event occurred, and the irrigation schedule was adjusted accordingly. Furthermore, the 12 plants in each bed were then divided into three equal groups to make three replicates per treatment per raised bed. Each of the seven raised beds were randomly assigned to one of the following seven treatments: V0 (control—no fertilizer or organic amendments applied); VCT10 (10% VCT); VCT20 (20% VCT); VCT40 (40% VCT); VC1 + VCT10 (2.47 ton/ha VC and 10% VCT); VC1 + VCT20 (2.47 ton/ha VC and 20% VCT); and VC1 + VCT40 (2.47 ton/ha VC and 40% VCT). The VC was applied as a dry basal amendment during sowing. The VCT was applied at 100 mL per plant per week as a foliar spray and soil drench, starting from the V2 corn growth stage (when the second leaf collars are visible) [31], for six consecutive weeks. Additionally, to ensure consistent moisture levels across treatments, the control treatment, V0, received 100 mL of plain water per plant per week for six weeks on the same schedule as the VCT applications. The V2 stage was selected based on findings from our previous study in maize, where VCT application at this stage significantly enhanced physiological performance without inducing stress in seedlings [29]. At the V2 stage, plants typically possess a more developed root system and expanded leaf area, which are critical for efficient uptake of bioactive compounds. This timing aligns with research suggesting that early vegetative stages, particularly V2–V3, offer an optimal window for foliar and root-applied treatments due to increased metabolic activity and nutrient demand [32,33].

The VC was made from mushroom waste blocks at the Lions Fruit Farm in Redlands, Miami, FL, USA, and consequently the VCT was prepared from the VC. The vermicomposting process and VCT preparation followed the procedure described by [29]. The VC was produced using approximately 2000–3000 individuals of Eisenia fetida (red wiggler earthworms), a species widely recognized for its high composting efficiency, high tolerance to a wide range of substrates and rapid organic matter turnover. These earthworms facilitated the breakdown of mushroom waste blocks over a four-month period through mechanical fragmentation, enzymatic activity, and enhancement of microbial decomposition. Furthermore, the prepared VCT was then diluted to the desired experimental concentrations (10%, 20%, and 40%) with distilled water. The physicochemical properties of the BS and VC are provided in

Table 1. Physicochemical properties of background soil (BS), vermicompost (VC), and post-harvest soils from vermicompost and vermicompost tea (VCT) treatments at two soil depths (0–10 cm and 10–20 cm).

Treatment	pH	N (%)	P (%)	K (%)	Ca (mg kg−1)	Mg (mg kg−1)	Zn (mg kg−1)	Na (mg kg−1)	C (%)	OM (%)	CEC (cmol/kg)
BS	7.93 ± 0.06 a	0.71 ± 0.13 b	0.042 ± 0.010 b	0.127 ± 0.030 b	5272 ±153 a	1353 ± 124 a	24.5 ± 2.60 a	222.9 ± 39.6 a	14.2 ± 0.89 b	25.2 ± 1.59 b	20.4 ± 0.78 b
VC	7.5 ± 0.00 b	1.55 ± 0.05 a	0.176 ± 0.035 a	0.502 ± 0.038 a	1831 ±140 b	1391 ± 208 a	30.5 ± 5.87 a	296.0 ± 24.7 a	22.8 ± 0.47 a	39.3 ± 0.81 a	33.6 ± 3.41 a
Surface Soils (0–10 cm)
V0	7.83 ± 0.06 a	0.09 ± 0.00 b	0.002 ± 0.000 b	0.001 ± 0.000 b	267 ± 69 b	43 ± 15 b	1.6 ± 0.07 b	2.0 ± 0.3 b	1.80 ± 0.14 c	3.1 ± 0.24 c	1.7 ± 0.03 b
VCT10	7.77 ± 0.06 a	0.69 ± 0.08 a	0.018 ± 0.001 a	0.010 ± 0.001 a	2517 ± 54 a	385 ± 27 a	17.0 ± 0.99 a	19.5 ± 1.2 a	12.4 ± 1.19 ab	21.3 ± 2.04 ab	16.0 ± 0.50 a
VCT20	7.83 ± 0.06 a	0.80 ± 0.10 a	0.017 ± 0.000 a	0.008 ± 0.001 a	2578 ± 68 a	368 ± 12 a	17.0 ± 1.41 a	18.7 ± 1.8 a	14.2 ± 2.10 ab	24.4 ± 3.62 ab	16.2 ± 0.36 a
VCT40	7.7 ± 0.00 a	0.86 ± 0.19 a	0.016 ± 0.002 a	0.009 ± 0.002 a	2694 ± 67 a	373 ± 55 a	14.1 ± 1.96 a	17.2 ± 2.3 a	17.6± 4.22 a	30.2 ± 7.27 a	16.8 ± 0.21 a
VC1 + VCT10	7.77 ± 0.06 a	0.72 ± 0.08 a	0.018± 0.003 a	0.009 ± 0.003 a	2676 ± 136 a	372 ± 56 a	16.3 ± 2.83 a	15.2 ± 3.4 a	13.1 ± 1.78 ab	22.6 ± 3.07 ab	16.7 ± 1.22 a
VC1 + VCT20	7.9 ± 0.00 a	0.62 ± 0.08 a	0.017 ± 0.003 a	0.008 ± 0.002 a	2579 ± 113 a	356 ± 81 a	15.1 ± 2.27 a	21.2 ± 2.9 a	11.0 ± 1.26 b	18.95 ±2.17 b	16.1 ± 1.24 a
VC1 + VCT40	7.83 ± 0.15 a	0.85 ± 0.11 a	0.019 ± 0.002 a	0.010 ± 0.001 a	2641 ± 127 a	397 ± 55 a	15.7 ± 1.92 a	21.8 ± 5.9 a	15.0 ± 2.24 ab	25.8 ± 3.85 ab	16.8 ± 0.37 a
Subsurface Soils (10–20 cm)
V0	7.87 ± 0.12 ab	0.08± 0.02 b	0.002 ± 0.000 c	0.002 ± 0.000 c	237 ± 17 b	55 ± 3.9 b	1.5 ± 0.10 c	3.3 ± 1.8 b	1.5 ± 0.28 c	2.6 ± 0.48 c	1.7 ± 0.06 c
VCT10	7.87 ± 0.06 ab	0.88 ± 0.06 a	0.018 ± 0.002 ab	0.009 ± 0.002 b	2409 ± 83 a	432 ± 62 a	13.8 ± 1.42 a	17.6 ± 4.00 a	15.4 ± 0.88 ab	26.4 ± 1.51 ab	15.9 ± 0.13 ab
VCT20	7.80 ± 0.00 ab	0.77 ± 0.06 a	0.018 ± 0.003 ab	0.009 ± 0.002 b	2505 ± 131 a	457 ± 87 a	14.6 ± 1.92 a	19.3 ± 4.18 a	13.5 ± 1.21 ab	23.1 ± 2.09 ab	16.6 ± 0.24 ab
VCT40	7.73 ± 0.06 b	0.83 ± 0.12 a	0.017 ± 0.001 b	0.010 ± 0.001 b	2416 ± 130 a	503 ± 14 a	15.4 ± 1.63 a	21.7 ± 3.00 a	16.1 ± 1.92 a	27.8 ± 3.30 a	16.5 ± 0.64 a
VC1 + VCT10	7.93 ± 0.06 ab	0.69 ± 0.03 a	0.019 ± 0.004 ab	0.011 ± 0.003 b	2512 ± 142 a	488 ± 101 a	15.1 ± 1.96 b	20.9 ± 5.53 a	12.0 ± 0.69 b	20.6 ± 1.19 b	16.9 ± 1.60 b
VC1 + VCT20	7.93 ± 0.06 ab	0.78 ± 0.06 a	0.024 ± 0.000 a	0.018 ± 0.003 a	2609 ± 168 a	590 ± 26 a	16.6 ± 1.04 a	25.0 ± 1.80 a	13.7 ± 1.30 ab	23.6 ± 2.24 ab	18.4 ± 0.78 ab
VC1 + VCT40	7.97 ± 0.12 a	0.70 ± 0.11 a	0.019 ± 0.003 ab	0.012 ± 0.002 b	2442 ± 129 a	474 ± 73 a	20.0 ± 10.56 a	21.8 ± 3.70 a	12.2 ± 1.83 b	21.0 ± 3.15 b	16.5 ± 1.24 b

Values represent mean ± standard deviation (n = 3 per treatment) per dry soil. Means that do not share a letter are significantly different (p < 0.05) according to Tukey’s HSD test. Treatments with the same letter indicate no significant difference. OM—organic matter; CEC—Cationic Exchange Capacity.

.

2.2. Corn Physiology Measurement and Fall Armyworm Infestation

Plant growth was monitored weekly from germination to maturity. Corn height was measured weekly using a meter rule. In contrast, the leaf-relative chlorophyll content was measured using a Soil Plant Analysis Development meter (SPAD 502 Plus, Spectrum Technologies Inc., Aurora, IL, USA) from the V4 to V10 vegetative stages (V4 and V10 have the 4th and 10th leaf collars visible, respectively) [31]. The FAW damage on corn leaves was evaluated weekly from the critical V2 to V12 growth stages, when corn is highly susceptible to pest damage, following the procedure by [29]. Leaves from each plant were carefully inspected for characteristic FAW feeding damage, such as holes bored by larvae, and the severity of damage was recorded.

2.3. Plant and Soil Sampling and Chemical Analysis

Eighty-four days after sowing, the experiment was terminated, and both soil samples and plant samples were immediately collected. The soil samples were obtained from two depths, surface soils (0–10 cm) and subsurface soils (10–20 cm), for each replicate per treatment and stored in paper bags. The soil samples were then air-dried at ambient temperature (25–30 °C) until a constant mass was obtained. Once dry, the soil samples were ground and sieved through a 2 mm mesh and then prepared for chemical analysis. The soil pH was measured in a 0.01 M CaCl₂ solution, while the total N and total C were determined using dry combustion with a C/N analyzer (Truspec, LECO Corporation, St. Joseph, MI, USA) [8]. The organic matter (OM) content was determined using the loss-on-ignition method, and the cation exchange capacity (CEC) was calculated as the sum of equivalents of exchangeable K, Ca, Mg, Zn, Na, and H [8].

The Inductively Coupled Plasma Mass Spectroscopy (ICP-MS; Agilent 7900, Santa Clara, CA, USA) method was used to determine the elemental nutrient contents of P, K, Ca, Mg, Zn, and Na in the soil samples, following the procedure described by [34] with modifications. Approximately 0.5 g of the air-dried, homogenized soil was accurately weighed into Teflon digestion tubes and digested with 5 mL of trace metal-grade nitric acid and 2 mL of 30% hydrogen peroxide using a microwave digestion system (180 °C, 30 min). The digested samples were diluted to 50 mL with ultrapure water (18.2 MΩ·cm) and filtered through 0.45 µm membranes. The ICP-MS was operated in helium collision mode to reduce polyatomic interferences. Instrumental parameters included an RF power of 1550 W, plasma gas flow of 15 L/min, nebulizer gas flow of 1.0 L/min, and a sample uptake rate of approximately 1 mL/min. Calibration was performed using matrix-matched multi-element standards (0–500 µg/L) and internal standards (Sc, Y, In at 10 µg/L) to correct for matrix effects and instrumental drift. Quality control included method blanks, certified reference materials, and spiked recoveries, with acceptable recoveries between 80% and 120% and RSDs of less than 5%.

At harvest, the cobs were collected from all plants in each raised bed, and their fresh weights were recorded, as corn (the sweet corn variety used in the study) is typically sold fresh. The cob yield in tons per hectares was then determined using the equation below. Furthermore, entire plants per treatment, including roots, were harvested, air-dried at 20–30 °C, and weighed to determine their dry biomass. The dried corn leaves were then collected and ground into a fine powder using a high-energy ball mill (8000 M Mixer/Mill, SPEX Sample Prep, Metuchen, NJ, USA) to determine macro- and micronutrient content, including N, C, Ca, K, Mg, P, S, Na, B, Fe, Mn, Zn, and Cu, following the same methods described for soil samples with slight modifications [16,29].

$$\mathrm{C}\mathrm{o}\mathrm{r}\mathrm{n} \mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d} \mathrm{i}\mathrm{n} \mathrm{t}\mathrm{o}\mathrm{n}\mathrm{s}/\mathrm{h}\mathrm{a}={\displaystyle \frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{c}\mathrm{o}\mathrm{b} \mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d} \mathrm{f}\mathrm{r}\mathrm{o}\mathrm{m} \mathrm{r}\mathrm{a}\mathrm{i}\mathrm{s}\mathrm{e}\mathrm{d} \mathrm{b}\mathrm{e}\mathrm{d} \mathrm{i}\mathrm{n} \mathrm{t}\mathrm{o}\mathrm{n}\mathrm{s}}{\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a} \mathrm{o}\mathrm{f} \mathrm{t}\mathrm{h}\mathrm{e} \mathrm{r}\mathrm{a}\mathrm{i}\mathrm{s}\mathrm{e}\mathrm{d} \mathrm{b}\mathrm{e}\mathrm{d} \mathrm{i}\mathrm{n} m^2}}\times 4046.86$$

2.4. Statistical Analysis

All data were analyzed using Minitab statistical software (version 22, Minitab LLC, State College, PA, USA). One-way analysis of variance (ANOVA) was performed at a 95% confidence level to assess statistical differences among treatments. Before analysis, the assumptions of normality and homoscedasticity were verified using the Shapiro–Wilk test [35] and Levene’s test [36], respectively. When assumptions were violated, appropriate data transformations or non-parametric tests were applied. Tukey’s post hoc test was used for pairwise comparisons among treatments that showed significant differences in the ANOVA.

3. Results

3.1. Physicochemical Properties of Vermicompost (VC), Background Soil (BS), and Soils Post-Corn Harvest

The nutrient content of VC, BS, surface (0–10 cm), and subsurface (10–20 cm) soils is provided in Table 1. The results show that VC had more than double the N and over four times the P and K levels compared to BS. The OM content and CEC were also significantly higher in VC than in BS; however, VC had a significantly lower pH than BS.

In the surface soils (0–10 cm), V0 treatment had the lowest nutrient levels, with significantly lower N and OM levels than the other treatments. When comparing VCT-alone treatments to VC and VCT treatment combinations, the results show no significant advantage of the combined treatments over VCT alone across all nutrients.

Similarly, in the subsurface soils, the control treatment (V0) had significantly lower nutrient content than the other treatments. Furthermore, the VC + VCT treatments showed slightly higher P and OM content than the VCT-alone treatments, although the differences were not statistically significant. It is observed that VCT-alone treatments had comparable nutrient contents to VC and VCT (Table 1).

3.2. Plant Chemical Analysis

The leaf nutrient content showed significant differences across treatments (

Table 2. Leaf nutrient content in the corn treated with varied concentrations of vermicompost (VC) and vermicompost tea (VCT).

Treatment	N (%)	P (%)	K (%)	Ca (%)	Mg (%)	S (%)	Na (%)	B (mg kg−1)	Fe (mg kg−1)	Mn (mg kg−1)	Zn (mg kg−1)	Cu (mg kg−1)
V0	0.20 ± 0.01 c	0.10 ± 0.00 d	0.16 ± 0.01 d	0.14 ± 0.00 c	0.04 ± 0.00 d	0.02 ± 0.00 d	0.03 ± 0.00 e	1.07 ± 0.02 b	375 ± 15 d	2.68 ± 0.09 c	15 ± 1 f	1.12 ± 0.06 d
VCT10	1.30 ± 0.02 b	0.58 ± 0.03 ab	0.97 ± 0.05 bc	1.45 ± 0.07 a	0.23 ± 0.01 a	0.18 ± 0.01 a	0.21 ± 0.01 bc	9.35 ± 0.47 a	251 ± 13 b	22.1 ± 1.10 a	74 ± 4 d	2.50 ± 0.13 c
VCT20	1.41 ± 0.07 a	0.49 ± 0.02 c	0.89 ± 0.04 c	1.14 ± 0.06 b	0.19 ± 0.01 c	0.14 ± 0.01 b	0.14 ± 0.01 d	9.34 ± 0.47 a	223 ± 11 bc	19.7 ± 0.99 b	74 ± 4 d	2.14 ± 0.11 c
VCT40	1.19 ± 0.06 b	0.61 ± 0.03 a	0.95 ± 0.05 bc	1.20 ± 0.06 b	0.22 ± 0.01 ab	0.11 ± 0.01 c	0.16 ± 0.01 d	9.03 ± 0.45 a	321 ± 16 a	22.8 ± 1.14 a	104 ± 5 b	3.52 ± 0.18 a
VC1 + VCT10	1.27 ± 0.01 b	0.52 ± 0.02 bc	0.90 ± 0.01 c	1.12 ± 0.04 b	0.22 ± 0.01 ab	0.14 ± 0.01 b	0.20 ± 0.00 c	8.73 ± 0.26 a	239 ± 6 bc	18.0 ± 0.32 b	90 ± 3 c	0.9 ± 0.03 d
VC1 + VCT20	1.25 ± 0.01 b	0.53 ± 0.02 bc	1.17 ± 0.05 a	1.14 ± 0.05 b	0.22 ± 0.01 ab	0.18 ± 0.01 a	0.23 ± 0.01 ab	8.59 ± 0.16 a	216 ± 9 c	18.9 ± 0.48 b	134 ± 4 a	2.03 ± 0.06 c
VC1 + VCT40	1.30 ± 0.02 b	0.49 ± 0.02 c	1.02 ± 0.03 b	1.18 ± 0.04 b	0.20 ± 0.01 bc	0.15 ± 0.01 b	0.24 ± 0.01 a	8.74 ± 0.23 a	233 ± 10 b	19.1 ± 0.73 b	63 ± 3 e	1.98 ± 0.09 b

Values represent mean ± standard deviation (n = 3 per treatment) per dry biomass. Means that do not share a letter are significantly different (p < 0.05) according to Tukey’s HSD test. Treatments with the same letter indicate no significant difference.

), with observable variation in macro- and micronutrient composition in the VCT and VC + VCT treatments compared to the control V0, which had the lowest nutrient levels across all measured elements. The N content was highest in the VCT20 treatment (1.41%), significantly higher than in the other treatments, and 7 times higher than in the control V0. There was no statistical difference in N amongst all other treatments except V0. The P content in VCT40 was significantly higher than in all other treatments, except VCT10, and was 6 times higher than in V0 treatment. The K content was highest in VC1 + VCT20 (1.17%), significantly exceeding that of all other treatments and 7 times higher than the control V0. The Ca, Mg, and S contents were significantly higher in VCT10 treatments compared to all treatments. The Na content was highest in VC1 + VCT40, eight times higher than V0 treatment.

Furthermore, B content was significantly increased in all VCT and VC1 + VCT treatments compared to the control, V0. However, there were no significant differences among the VCT and VC1 + VCT treatments. The Fe, Mn, and Cu content was highest in VCT40 (321 mg kg⁻¹), significantly exceeding that of all other treatments, including VC1 + VCT combinations and the control, V0 (375 mg kg⁻¹). However, Zn content was highest in VC1 + VCT20 (134 mg kg⁻¹), significantly outperforming all other treatments, including VCT-alone treatments. In comparing VCT-alone and VC1 + VCT treatments, VCT-alone treatments generally achieved higher nutrient content for several elements, including Fe, Mn, and Cu. In contrast, VC1 + VCT20 showed the best performance for K and Zn.

3.3. Corn Height

Corn height significantly varied across treatments at all growth stages (V4–V12), with VC- and VCT-treated plants exhibiting taller corn than the control, V0 (Figure 1). At early growth stages (V4–V6), treatments such as VC1 + VCT10, VC1 + VCT20, VC1 + VCT40, and VCT10 had the tallest plants, although there were no significant differences among them, while V0 treatment plants were significantly shorter. As plants progressed V8 to V12, VC1 + VCT10 and VCT10 continued to have taller corn plants, with all VC1 + VCT treatments outperforming VCT20 and VCT40, although there was no significant difference among them. It can be observed that VCT20 and VCT40 consistently had shorter corn from V6 to V12 compared to all other treatments, although they were significantly taller than those in V0 treatment.

3.4. Relative Chlorophyll Content of Corn

The relative chlorophyll content, measured using a SPAD meter, generally increased, with significant variations observed (Figure 2). From V4 to V12, V0 treatment had significantly lower SPAD values (p < 0.05) compared to the other treatments. From V4 to V12 corn growth stages, VCT20 had the highest SPAD values among treatments. However, there were no significant statistical differences in SPAD values across all the VC and VC + VCT treatments (p > 0.05). Treatments VC1 + VCT20 and VC1 + VCT40 had lower SPAD values from the V6 to V12 growth stages compared to other treatments, except at V8 and V10, where VCT10 had the same SPAD values as VC1 + VCT20 and VC1 + VCT40 and lower values than VC1 + VCT40, respectively.

3.5. Fresh Cob Yield and Total Dry Biomass

The cob yield was significantly higher in the VCT20 treatment, at 6.0 tons/ha, compared to the other treatments (

Table 3. Cob yield and total dry biomass for each treatment.

Treatment	Cob Yield (ton/ha)	Dry Biomass (ton/ha)
V0	0.72 ± 0.07 e	0.91 ± 0.02 e
VCT10	3.06 ± 0.2 d	6.52 ± 0.02 a
VCT20	6.00 ± 0.4 a	5.81 ± 0.02 c
VCT40	5.71 ± 0.3 ab	6.38 ± 0.02 b
VC1 + VCT10	5.29 ± 0.2 b	6.57 ± 0.02 a
VC1 + VCT20	4.52 ± 0.2 c	2.76 ± 0.02 c
VC1 + VCT40	3.63 ± 0.2 d	5.39 ± 0.02 d

Note: Values are presented as means ± standard deviations (n = 3) of three replicates per treatment. Treatment means that do not share a letter are significantly different at a 95% confidence level (p < 0.05).

), except for the VCT40 treatment. The yield of VCT20 and VCT40 treatments was more than 8 times that of V0 treatment. Furthermore, the yield in the control treatment (V0) was significantly lower than in all the other treatments (p < 0.05). It was also observed that the cob yield obtained in the VCT10 treatment was more than 50% less than those of the VCT20 and VCT40 treatments, although it was four times higher than that of V0 treatment. Furthermore, the results show that doubling the VCT concentration from 10% (VCT10) to 20% (VCT20) resulted in a twofold increase in yield. However, increasing the VCT concentration from 20% to 40% (VCT40) led to a slight decline in corn yield. Additionally, VC1 + VCT10 treatment resulted in 70.8% higher cob yield than VCT10 treatment. However, VC1 + VCT20 and VC1 + VCT40 treatments resulted in 24.3% and 37.1% lower cob yields compared to those of VCT20 and VCT40 treatments, respectively.

For total dry biomass, the VC1 + VCT10 and VCT10 treatments yielded the highest biomass (6.52 and 2.57 tons/ha, respectively), significantly higher than that of all other treatments. Similarly, V0 treatment gave significantly lower biomass (p < 0.05) compared to all other treatments. Among the VCT-alone treatments, VCT20 had the lowest biomass, which was statistically similar to that in the VC1 + VCT20 treatments. In contrast, VC1 + VCT40 had the lowest dry biomass compared to the VCT-alone and VC + VCT treatments. Upon comparing the dry biomass and cob yield, a direct correlation was observed between biomass and yield for most treatments (Pearson correlation coefficient, r = 0.806 at a 95% confidence level), except for VCT10 and VCT20. In the VCT10 treatment, the corn ear yield was low, given that it had the highest biomass. In contrast, the cob yield from VCT20 was high, yet it had one of the lowest biomass levels among the VCT and VC + VCT treatments.

3.6. Fall Armyworm Infestation in Corn

The analysis of FAW infestation on corn leaves, measured as the number of damaged corn leaves across growth stages V2–V12, showed moderate infestation levels in the control treatments, V0, compared to slight or no infestation in the VCT- and VC+VCT-treated plants (Figure 3). In V0, infestation began at V4 with two out of twelve plants infested, which progressively increased to six plants by the V12 growth stage. VC1 + VCT10, VC1 + VCT20, and VC1 + VCT40 treatments resulted in only one plant being damaged from the V4 to V12 growth stage. In addition, the VCT10 treatment had one infested plant starting from V4, which increased to two slightly infested plants by V6 and remained the same up to the V12 stage. However, no FAW infestations were recorded in VCT20 and VCT40 treatments throughout the experimental period.

4. Discussion

4.1. Physicochemical Properties of Vermicompost (VC), Background Soil (BS), and Soils Post-Corn Harvest

The findings from this study show the critical role of VC and VCT treatments in enhancing soil fertility and nutrient availability, as evidenced by their significant impact on the physicochemical properties of surface and subsurface soils (Table 1). The higher nutrient content in VC compared to the BS indicates the potential of organic amendments in improving soil quality by enriching soils with essential macro- and micronutrients.

In surface soils, V0 treatment consistently had the lowest nutrient content across all elements since it received no fertilizer application or organic amendments. VCT-alone treatments performed comparatively well, as did VC + VCT treatments, in improving surface soil fertility. This suggests that VCT may deliver sufficient nutrient bioavailability to support plant growth without the need for additional VC.

In the subsurface soils, while VCT and VC + VCT treatments showed improved nutrient content compared to the control treatment (V0, Table 1), the benefits of combining VC with VCT were minimal and not statistically significant. These findings are similar to those of our previous study [29], where VCT100-treated soils had identical nutrient content to VC1 + VCT50-treated soils, and VC had higher nutrient content than BS. The slightly higher P and OM content in VC + VCT treatments could be attributed to the slow-release properties of VC [37], which may have contributed to nutrient retention in the deeper soil layers.

Furthermore, a notable difference in Na content is observed across treatments and soil depths between the current and previous study [29], which can be attributed to the change in VC substrate used. In the previous study, VC was produced using coconut coir, a substrate known to have high Na content, which resulted in high Na content in both the VCT- and VC-treated soils. In contrast, the current study utilized mushroom waste as the composting substrate, which yielded VC with substantially lower Na levels (296.0 mg kg⁻¹ vs. 831.1 mg kg⁻¹ in the previous study). Consequently, both surface and subsurface soils in the current study had significantly lower Na concentrations across all VCT and VC + VCT treatments compared to the earlier study. These differences suggest that the choice of feedstock in VC production has a direct influence on Na accumulation in soil and potential uptake by plants.

4.2. Plant Chemical Analysis

The results of the leaf nutrient analysis demonstrate that treatments with VCT and its combinations with VC significantly enhance corn nutrient uptake compared to V0 treatment, which consistently had lower nutrient levels across all elements analyzed. The observed differences in nutrient content in the leaves among treatments show the direct influence of soil amendments on nutrient availability and plant physiological processes, with potential correlations between soil fertility, plant nutrient status, and growth performance.

The significantly higher N content in VCT20-treated plants compared to all other treatments, including VC1 + VCT combinations (Table 2), demonstrates the efficacy of this VCT concentration in meeting plant N demands. Interestingly, the lack of further improvement in N content with the addition of VC suggests that VCT alone provides sufficient bioavailable N to support optimal uptake [13]. Phosphorus content in leaves was highest in the VCT40 treatment, consistent with the high P contents observed in surface and subsurface soils. Interestingly, VCT10 also resulted in high P uptake, and there was no significant difference between these two treatments (VCT10 and VCT40), suggesting that both low and high concentrations of VCT can enhance P availability. In contrast, the addition of VC to VCT did not further improve P uptake, emphasizing the efficiency of VCT-alone treatments in supplying P to plants. The high K content in VC1 + VCT20 treatment suggests a synergy between VC and VCT in K availability and uptake. However, VCT10 and VCT20 also exhibited high K uptake relative to V0, indicating that VCT alone can meet the K requirements of plants.

In addition, the high Ca and Mg content from VCT10-treated plants suggests that lower concentrations of VCT may enhance the mobility and bioavailability of these nutrients without requiring VC supplementation. The absence of additional benefits from VC1 supplementation further emphasizes the efficiency of VCT-alone treatments. Similarly, S content was highest in VCT10- and VC1 + VCT20-treated plants, indicating the effectiveness of these treatments in facilitating S uptake, which is essential for amino acid synthesis and protein formation [38]. Na content was highest in VC1 + VCT40-treated plants, which, although not detrimental, may reflect an unintended accumulation due to VC application. Fe, Mn, and Cu content peaked in VCT40-treated plants, while Zn was highest in VC1 + VCT20, showing that higher VCT concentrations may favor the uptake of Fe, Mn, and Cu. Conversely, the synergistic effects of VC and VCT enhance Zn and Na uptake. Since there were no significant differences in B content between VC and VC + VCT treatments, it shows that both amendments equally supported B uptake.

4.3. Corn Height

The results show that all VCT and VC + VCT treatments significantly improved corn height compared to V0 treatment, across all growth stages, confirming the beneficial effects of organic amendments on vegetative growth. However, there were no significant differences in plant height among the amended treatments themselves, indicating that VCT concentrations or their combination with VC did not result in statistically superior growth. The uniformly taller plants under VC and VC + VCT treatments show improved nutrient availability and enhanced soil structure compared to the unfertilized V0 treatment [10,13]. The slightly lower heights in VCT20 and VCT40 may suggest a physiological shift toward reproductive development, which is consistent with their higher yield outcomes (see Section 3.5); however, these differences were not statistically significant.

The findings of this study are consistent with our previous work [29], which also reported no statistically significant differences in corn height among the organic amended treatments. In both studies, all VCT and VC + VCT treatments supported taller plant growth compared to the control. However, a key difference lies in the control treatment: the previous study used an organic fertilizer (NPK 8-4-8) in the control plot, providing baseline nutrients, whereas the current study used an untreated control with no fertilizer or organic amendment, relying solely on nutrients from the background soil. This difference likely contributed to the significant contrast between treated beds and the control observed in the current study, which was not present in the earlier experiment.

4.4. Relative Chlorophyll Content of Corn

The differences in SPAD readings across treatments reflect the effects of nutrient availability on chlorophyll synthesis and plant health (Figure 2). All amended treatments showed significantly higher relative chlorophyll content than the unfertilized V0 treatment, highlighting the role of VC and VCT in enhancing early nutrient supply, particularly N and Mg, which are required for chlorophyll synthesis [39,40]. Among the treatments, VCT20 consistently showed the highest SPAD values across most stages, suggesting optimal nutrient bioavailability for photosynthesis. However, the observed lack of statistically significant differences among the amended treatments shows that while trends were observable, VCT and VC + VCT combinations performed similarly in sustaining chlorophyll content. Slight variations in SPAD values, such as slightly lower readings in VC1 + VCT20 and VC1 + VCT40, may reflect physiological trade-offs between chlorophyll production and other growth processes; however, these differences were not statistically significant.

The SPAD values in this study closely align with our previous findings [29], where all amended treatments improved SPAD values relative to the control. In both studies, V0 treatment exhibited significantly lower chlorophyll content, showing insufficient nutrient availability, especially N and Mg, which are essential for chlorophyll synthesis [39,40]. These consistent patterns across experiments highlight the robust capacity of VC and VCT to enhance photosynthetic potential in corn, regardless of differences in application rate or VC substrate (mushroom waste in the current study and fruit farm residues and coconut coir in the previous study). Moreover, they confirm that a moderate VCT concentration (e.g., VCT20) can be as effective as higher-dose combinations in improving chlorophyll content and sustaining physiological function.

4.5. Fresh Cob Yield and Total Dry Biomass

The highest cob yield observed in the VCT20 treatment indicates that VCT20 is the most efficient concentration for maximizing reproductive output, offering a balance between nutrient availability and economic input. Furthermore, although the VC1 + VCT10 treatment yielded a 70.8% higher yield than VCT10, its performance did not surpass that of VCT20. Furthermore, VC1 + VCT20 and VC1 + VCT40 yielded 24.3% and 37.1% less cob yield, respectively, than VCT20- and VCT40-alone. This suggests that combining VC with higher concentrations of VCT may not always be beneficial and could result in nutrient dilution or altered nutrient partitioning, especially during reproductive stages. V0 treatment had significantly lower yields than all other treatments, primarily because the background soil (BS) lacked the necessary nutrients to support cob development. The observed yield in this study falls within the average sweet corn yield reported by Florida farmers in 2023, which was 17.3 tons per hectare [41].

Although corn yield data were collected during our previous study [29], they were not reported in the original publication, as the study primarily focused on physiological responses and biomass accumulation. These data have since been analyzed to complement the findings and are presented here for comparative purposes. The re-analyzed yield values, reported as the average of three replicates from the summer 2022 corn experiment, showed that V0 treatment (which received 0.74 tons/ha of organic fertilizer, NPK 8-4-8) produced a cob yield of 4.15 tons per hectare. The VC1 (2.47 ton/ha of solid VC) treatment yielded 5.12 tons per hectare, VCT100 (20% VCT applied weekly at 100 mL per plant for six consecutive weeks) yielded 5.68 tons per hectare, VC1 + VCT50 (2.47 ton/ha VC combined with 20% VCT at 50 mL per plant for six successive weeks) yielded 4.2 tons per hectare, VC3 (7.41 tons/ha solid VC) yielded 3.21 tons per hectare, and VC3 + VCT50 (7.41 tons/ha VC combined with 20% VCT at 50 mL per plant for six consecutive weeks) yielded 6.0 tons per hectare. These results closely align with the current experiment, in which VCT20 also produced the highest yield (6.0 tons/ha). This consistency across studies, both conducted under similar field conditions, emphasizes the effectiveness of moderate VCT concentrations in supporting corn reproductive performance. The comparable outcomes may be attributed to balanced nutrient delivery, particularly N and P, that optimizes cob formation. Taken together, the findings suggest that 20% VCT is a robust and efficient input rate for maximizing corn yield under organic systems.

In terms of dry biomass, VC1 + VCT10 and VCT10 treatments produced the highest biomass, indicating strong vegetative growth. However, this did not directly translate into a higher yield for VCT10, suggesting that plants may have prioritized vegetative development over cob development. Conversely, VCT20 had the lowest biomass among VCT-alone treatments yet the highest yield, suggesting a physiological trade-off that favors cob development over vegetative mass. These observations are further supported by the positive correlation between biomass and yield across treatments (Pearson Correlation Coefficient r = 0.806, p < 0.05), except for VCT10 and VCT20, which deviated from this trend. This trade-off is a significant indicator that there is a need to match treatment selection with production goals, for instance, VCT20 for fresh market corn and VCT10 or VC1 + VCT10 for silage production, where biomass is prioritized. The dry biomass findings of this study are both consistent and divergent from our previous results [29]. In both experiments, VCT applications enhanced vegetative biomass relative to V0 treatment. However, while the previous study identified VCT100 as the most effective treatment for biomass accumulation, the current study found that VCT10 and VC1 + VCT10 produced the highest biomass, significantly outperforming higher VCT concentrations. This could be due to differences in nutrient saturation thresholds.

4.6. Fall Armyworm Infestation in Corn

The results of this study show the effectiveness of VCT and its combinations with VC in suppressing FAW infestation in corn. Significantly, VCT20 and VCT40 treatments completely prevented FAW infestation across all growth stages, showing superior pest suppression even at moderate concentrations. VC + VCT treatments, which exhibited only a single plant infested throughout the study, compared to VCT10, with only two plants infested, and V0 treatment, which had six infested plants by V12 growth stage, show that VCT both alone and in combination with VC is effective at suppressing FAW pressure, and that moderate VCT concentrations may be sufficient for robust protection.

These findings are significant when compared to our previous study [29], in which VC1 + VCT50 provided the best suppression, while VCT100 and VC1 alone were less effective. The improved performance observed in the current study suggests that substrate composition and compost quality may play a crucial role in treatment efficacy. In our previous research [29], VC was derived from coconut coir (among other feedstocks), a substrate known to accumulate higher salt concentrations, which can contribute to plant stress and impair microbial colonization [42,43]. In contrast, the mushroom waste-based VC used in this study had significantly lower Na and Ca content, resulting in a reduced salt load and likely contributing to healthier plants and more effective defense responses. These differences in substrate composition could explain why complete FAW suppression was achieved with lower input rates in the current trial.

Vermicompost and VCT are known to suppress insect pests through a combination of plant defense stimulation, improved soil health, and rhizosphere microbial activity [10,17]. The bioactive compounds in VCT, including phytohormones (e.g., auxins and cytokinins), humic substances, and microbial metabolites, can enhance systemic resistance and activate biochemical pathways responsible for producing defensive compounds such as phenolics, alkaloids, and flavonoids [13,16,37]. The regular application of VCT as a soil drench also sustains beneficial microbial populations that compete with or antagonize pests through antibiosis or resource competition. These microbial and biochemical interactions, supported by improved nutrient status and soil structure, create a synergistic [44] environment that enhances plant resilience against FAW attacks. Moreover, VC is known to have beneficial microbes such as Bacillus spp., Trichoderma spp., and Pseudomonas spp., as well as enzymes like chitinases and proteases, which are known to suppress pests through microbial antagonism and interference with insect development [35].

5. Conclusions

This study demonstrates that vermicompost tea, especially at moderate concentrations (20% and 40%), and its combinations with vermicompost can significantly enhance corn growth, improve soil nutrient status, and suppress fall armyworm infestation. These organic inputs offer multifunctional benefits by stimulating physiological traits such as chlorophyll content and stomatal conductance while also improving plant resilience to pests. Importantly, the findings show that using low to moderate rates of VCT alone or in combination with solid VC can be an effective, sustainable alternative to synthetic inputs in small-scale and organic corn production systems.

These results have practical implications for farmers, extension services, and organic input producers seeking environmentally friendly solutions for soil fertility and pest management. The consistent performance of VCT and VC + VCT treatments suggests potential for on-farm adoption, particularly in regions with high pest pressure and degraded soils.

Future studies should explore the long-term impacts of repeated VC and VCT applications on soil microbial communities, pest populations, and yield stability across different climatic zones. Additional investigations into the economic viability and scalability of VC and VCT amendments will be essential to guide broader implementation in diverse agricultural systems.