Unveiling the Implications of Organic Nutrient Management Protocols on Soil Properties, Economic Sustainability, and Yield Optimization in Fenugreek Cultivation in Acidic Soils of Northeast India

Abstract

Utilizing yield, profitability, and environmental sustainability in terms of soil quality as the goal variables, we created a methodological protocol for a thorough assessment of nutrient management (NM) technologies for feasibility and optimized fenugreek production employing organic sources of nutrients in the acid soil of Northeast India. Five organic nutrient management technologies were tried and tested comprising T₁: absolute control; T₂: 2.5 t ha⁻¹ vermicompost (VC) + 250 kg ha⁻¹ lime; T₃: 5 t ha⁻¹ farmyard manure (FYM) + 250 kg ha⁻¹ lime; T₄: 10 t ha⁻¹ FYM + 250 kg ha⁻¹ lime; and T₅: 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime with four replications laid out in a randomized block design for two consecutive growing seasons during 2018–2020. Results indicated that across the differential levels of organic amendments (treatments) employed, the addition of maximum doses of VC and FYM, in general, excelled over the other treatments concerning fenugreek seed yield, its yield attributes, soil properties, and better economic returns. Thus, the overall findings elucidated that the addition of higher doses of organic amendments (VC and FYM) can sustainably improve fenugreek productivity, soil properties, and economic returns for fenugreek growers in the acid soil of Northeast India.

1. Introduction

Fenugreek (Trigonella foenum–graecum L.), commonly known as methi, is an annual crop; a dicotyledonous plant belonging to the family Fabaceae (subfamily Papilionaceae). Fenugreek is an ancient and versatile crop cultivated for centuries across various regions of the world, particularly in the Mediterranean, Middle East, and Indian subcontinent. This annual leguminous herb has gained significant attention due to its diverse applications in the culinary, pharmaceutical, and nutraceutical industries [1,2]. Fenugreek seeds and leaves are rich sources of essential nutrients, including proteins, fibers, vitamins, and minerals, making them a valuable addition to human diets [3]. Moreover, fenugreek has been traditionally used in various folk medicines owing to its potential therapeutic properties, such as hypoglycemic, hypocholesterolemic, and antioxidant effects [4,5]. As global demand for fenugreek continues to rise, driven by its increasing popularity in cuisines and its potential health benefits, there is a growing need to optimize its cultivation practices, including nutrient management strategies [6]. Proper nutrient management plays a crucial role in achieving high yields, maintaining crop quality and soil microorganisms, and ensuring the sustainability of fenugreek production systems [7,8,9].

Inadequate or imbalanced nutrient supply can lead to suboptimal growth, reduced yields, and compromised crop quality, ultimately impacting the economic viability of fenugreek production [10,11,12]. Proper nutrient management strategies not only ensure optimal crop performance but also contribute to the sustainability of agricultural systems by minimizing nutrient losses, reducing environmental impacts, and promoting soil health [13]. By understanding the specific nutrient requirements of fenugreek and developing tailored nutrient management practices, farmers and researchers can optimize resource utilization, enhance nutrient use efficiency, and ultimately improve the profitability and sustainability of fenugreek production [8,14]. Furthermore, with the increasing demand for sustainable and environmental friendly agricultural practices, there is a growing interest in exploring alternative nutrient sources, such as biofertilizers, organic amendments, and integrated nutrient management approaches [15,16]. These strategies have the potential to reduce the reliance on synthetic fertilizers, mitigate environmental impacts, and promote soil health while maintaining or enhancing crop productivity [17,18].

Fenugreek, being a leguminous crop, has specific nutrient requirements that differ from other crop species. Understanding these requirements is crucial for developing effective nutrient management strategies. The primary macronutrients essential for fenugreek growth and development include N, P, and K [7,8]. Nitrogen is a vital nutrient for fenugreek as it plays a crucial role in vegetative growth, leaf development, and protein synthesis [9]. However, excessive N application can lead to excessive vegetative growth, delayed flowering, and reduced seed yield. Fenugreek, being a legume, can partially meet its N requirements through symbiotic N fixation by root nodule bacteria. Phosphorus (P) is another essential macronutrient for fenugreek, playing a critical role in root development, energy transfer, and seed formation [19]. Adequate P availability is particularly important during the early growth stages and reproductive phases of fenugreek. Potassium is vital for fenugreek as it regulates various physiological processes, including enzyme activation, water relations, and stress tolerance [20]. Adequate K supply ensures proper growth, yield, and quality of fenugreek crops. In addition to macronutrients, fenugreek also requires various micronutrients, such as Fe, Zn, B, and Mo, for optimal growth and development [19]. These micronutrients play essential roles in various physiological processes, including chlorophyll synthesis, enzyme activation, and N fixation. The nutrient uptake patterns in fenugreek are influenced by various factors, including soil conditions, climatic factors, plant growth stages, and nutrient interactions [21].

Fenugreek requires specific nutrient management to achieve optimal growth and yield. Research indicates that fenugreek benefits significantly from organic amendments such as vermicompost and compost, which enhance soil fertility and structure [22]. Vermicompost, rich in macro- and micronutrients, improves nutrient availability and soil microbial activity, leading to better plant growth [23]. Studies show that incorporating vermicompost at 2–3 t ha⁻¹ can enhance fenugreek yield and quality by providing essential nutrients such as nitrogen, phosphorus, and potassium [24]. Compost also plays a critical role in fenugreek cultivation by enriching the soil with organic matter and nutrients. Research suggests that compost application at five tons per hectare improves soil structure, water retention, and nutrient availability, which are crucial for fenugreek production [25]. Both vermicompost and compost contribute to sustainable agricultural practices by reducing the need for synthetic fertilizers and promoting environmental health [22,25].

Understanding these patterns is crucial for developing effective nutrient management strategies and ensuring timely nutrient availability throughout the crop’s growth cycle. Numerous limiting factors, including improper management of nutrients and fertilizers, contribute to a crop’s low yield. Effective nutrient management in fenugreek involves a combination of strategies, including judicious use of inorganic fertilizers, incorporation of organic amendments, and promotion of beneficial soil microorganisms [26]. When inorganic and organic sources of nutrients are used together, soil health is maintained, and almost all the nutrients needed for crop growth are provided. These strategies aim to optimize nutrient availability, improve nutrient use efficiency, and enhance the overall sustainability of fenugreek production systems.

However, inorganic chemical fertilizers offer a readily available source of nutrients for fenugreek cultivation, but their overuse poses significant challenges. The health and structure of the soil deteriorate when inorganic fertilizers are applied exclusively [27]. Excessive chemical fertilizer use can lead to a decline in soil organic matter (SOM), the backbone of healthy soil. These fertilizers lack the organic materials needed to sustain the beneficial soil microbes responsible for organic matter decomposition and nutrient cycling [28]. Reduced SOM translates to decreased nutrient retention and diminished water retention [29]. Certain fertilizers, high in ammonium, can contribute to soil acidification over time, which can disrupt the soil ecosystem, thereby causing reduced microbial activity and limited nutrient availability as acidic soils can decrease the availability of certain nutrients for plant uptake, further impacting crop health [30]. While chemical fertilizers degrade the crop quality even though they may promote rapid growth, they can negatively affect fenugreek seed quality through reduced bioactive compounds since excessive N application can lead to a decrease in the content of beneficial bioactive compounds such as trigonelline, valued for its medicinal properties [31]. While inorganic fertilizers provide readily available nutrients, their overuse harms soil health. They deplete organic matter, hinder nutrient cycling, and potentially disrupt the soil ecosystem. Additionally, unbalanced nutrient ratios can lead to leaching and deficiencies. Furthermore, despite promoting rapid growth, chemical fertilizers may compromise fenugreek seed quality by reducing beneficial bioactive compounds [32].

Incorporating organic amendments into fenugreek cultivation can enhance nutrient availability, reduce the reliance on synthetic fertilizers, and promote sustainable soil management practices. Vermicompost and other organic manures have the potential to be rich sources of macro- and micronutrients [33]. They also enhance soil structure by binding soil aggregates together, retaining more water, improving soil productivity, and boosting enzymatic activity. Vermicompost and other organic ingredients accelerate the decomposition process and provide an immediate source of energy for microorganisms to proliferate [34]. The use of vermicompost improves the soil’s ability to retain water, promotes its microbial population, releases nutrients from the soil’s humic substances, increases soil aeration, and mineralizes plant nutrients and growth regulators [35].

Despite extensive research on fenugreek cultivation, a critical knowledge gap exists for Northeast India’s acidic soils as current studies primarily focus on conventional practices. The impact of organic amendments on fenugreek productivity and soil health under these acidic conditions remains largely unexplored. Furthermore, the economic feasibility and long-term effects of organic fenugreek production in this unique ecosystem, particularly regarding soil properties, are undocumented. Developing region-specific, organic management strategies to optimize fenugreek yields in acidic soils is crucial. This study’s novelty lies in its regional focus on Northeast India’s acidic soils, offering localized solutions. It takes a holistic approach linking soil health, economic viability, and yield optimization for a comprehensive understanding. This research has the potential to significantly advance sustainable agriculture by providing valuable insights into organic methods for challenging conditions, with broader global applications. The hypothesis of the present experimentation postulates that the incorporation of organic manures in conjunction with liming will improve fenugreek yield and overall soil health. Therefore, an investigation was undertaken to unravel the impact of different sources and levels of organic amendments on fenugreek productivity and soil properties in the acid soil of Northeast India.

2. Materials and Methods

2.1. Experimental Details

The field experiments were conducted at ICAR Langol farm, Imphal, Manipur, during 2018–2019 and 2019–2020. The climate is subtropical, and the experimental site is located at 24°50.343′ N, 93°55.359′ E, 791 m above mean sea level. Throughout the crop growth period of the experiment (2018–2020), the research site had temperatures between 11.37 °C and 25.8 °C and monthly rainfall of 94.7 mm. The soil of the experimental site is sandy clay loam in texture, acidic in reaction. The experiment was laid out in randomized block design with five treatments (T₁: absolute control; T₂: 2.5 t ha⁻¹ vermicompost (VC) + 250 kg ha⁻¹ lime; T₃: 5 t ha⁻¹ FYM + 250 kg ha⁻¹ lime; T₄: 10 t ha⁻¹ FYM + 250 kg ha⁻¹ lime; and T₅: 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime) with four replications. Full organic nutrients (VC and FYM) were applied 30 days before final land preparation. FYM and VC were applied on a fresh weight basis, with an average moisture content of 40% and 30% (w/w), respectively.

To produce VC, cow dung and organic waste feedstocks were composted at 40:60 on a dry weight basis for 60 days, facilitated by ~3 kg of red earthworms (Eisenia fetida) per 100 kg of biomass. For this, cow dung and organic waste in a 40:60 ratio (dry weight basis) were mixed thoroughly to create moist bedding (around 60% moisture content).The container was filled with the prepared bedding, leaving some space at the top. The worms were then introduced gently by adding the red earthworms (around 3 kg per m³ of dry feedstock) to the bedding surface. The bedding was lightly moistened with a sprayer, and the container was covered to maintain darkness and humidity. Every 7–10 days, a thin layer of moistened organic waste was added on top as food for the worms. After 60 days, the vermicompost was harvested by separating the mature compost from the remaining bedding and worms (which can be reintroduced to a new batch).

Table 1. Chemical composition of organic inputs, farmyard manure (FYM), and vermicompost (VC).

Organic Inputs	pH	OC	N	P2O5	K2O	Ca	Mg	S	Fe
		(%)
FYM	6.8	14.1	0.84	0.38	0.51	0.87	0.42	0.35	0.24
VC	6.5	16.6	1.43	2.26	1.21	1.57	0.51	0.26	0.92

Where FYM = farmyard manure and VC = vermicompost.

presents the details of the organic manures used during the investigation.

The initial soil of the experimental site had a bulk density (BD) (1.33 Mg m⁻³), soil pH (5.40), SOC (1.17%), SOC stocks (23.07 Mg ha⁻¹), available N (403.24 kg ha⁻¹), available P (14.20 kg ha⁻¹), available K (434.60 kg ha⁻¹), exchangeable Ca (0.55 mg kg⁻¹), Mg (0.26 mg kg⁻¹), available S (15.14 mg kg⁻¹), DTPA-extractable Fe (13.08 mg kg⁻¹), Mn (10.09 mg kg⁻¹), Cu (1.12 mg kg⁻¹), Zn (0.36 mg kg⁻¹), and B (0.22 mg kg⁻¹).

2.2. Crop Husbandry

Land preparation started with the levelling of the field to facilitate uniform irrigation and water distribution, followed by ploughing the field to break the soil and turn over any vegetation. Subsequently, harrowing was performed to break down clods to achieve a fine, level seedbed. The land was prepared for better germination of seeds and growth of plants with a total of 3–4 ploughings with a harrow to bring the soil to a fine tilth. Fenugreek variety ‘Ajmer Fenugreek’ 1 was sown at the rate of 20 kg ha⁻¹ in March using seeds treated with Bavistin at 2 g kg⁻¹ seed to control early fungal diseases. Fenugreek was sown in lines in well-prepared flat seedbeds of 4 × 3 m² with a 10–15 cm spacing within the lines. Intercultural operations for fenugreek cultivation include regular weeding to control weeds and ensure healthy plant growth. Thinning fenugreek plants is important to maintain proper spacing and promote better air circulation. Proper water management is crucial, especially during flowering and seed development, to avoid water stress and optimize yield. Effective surface irrigation management is crucial to optimize water use and crop yield. Fenugreek requires approximately 500–600 mm of water per growing season, with proper irrigation scheduling essential to avoid water stress during critical growth stages such as flowering and pod formation [36]. The required water is accomplished through surface irrigation, including furrow and basin systems. Ensuring even water distribution and avoiding over-irrigation is key to preventing waterlogging and maintaining soil health [37]. Incorporating practices such as levelling the field and managing irrigation frequency can enhance water use efficiency and fenugreek yield. The observations on growth and yield were recorded as per standard procedures.

2.3. Soil Analysis

The soil samples were randomly collected from the experimental site and were analyzed for pH using the 1:2.5 soil–water ratio, SOC by wet oxidation method [32], oxidizable organic C (Carbon) [38], alkaline KMnO₄-extractable N (Nitrogen) [39], available P (Phosphorus) using Bray’s method, 1.0 M NH₄OAc-extractable K (Potassium), Ca (Calcium) and Mg (Magnesium) [40], available S (Sulphur) by turbidimetric method [41], DTPA (diethylenetriaminepentaacetic acid)-extractable Fe (Iron), Mn (Manganese), Cu (Copper) and Zn (Zinc) [42], and available B by hot water extraction method [43].

Five moist field soil samples, collected at a depth of 0–20 cm, were acquired both prior to the experiment’s initiation and after the fenugreek harvest using a bucket auger. The individual samples were combined to create a composite sample for each replication. The composite sample was then manually crushed and filtered through a 2.0 mm screen. The resulting material was stored for soil physical and chemical analyses. The soil bulk density (BD) was determined using the core method [44].

The soil organic carbon (SOC) stock was calculated using bulk density (BD) for the corresponding soil depth, as follows [45]:

SOC stock (Mg ha⁻¹) = SOC concentration (g kg⁻¹) × BD (Mg m^–3) × Depth (m) × 10^–3 Mg kg⁻¹ × 10 ⁴ m² ha⁻¹

2.4. Quality Parameters Analyses

The protein content of fenugreek seeds was quantified by the Kjeldal method [46] using a conversion factor of 6.25. The seeds were also determined to have crude fibre content [47], total phenol content by the Foiln-Ciocalteau method [48], antioxidant capacity by the DPPH assay [49], and diosgenin content by the HPLC method [50].

2.5. Financial Analysis and Assessment of Financial Indices

The cost of cash inputs (CCI) was calculated as the sum of disbursements acquired for the procurement of critical farm inputs (₹ ha⁻¹), such as seed, fertilizer, FYM, and pesticide for farm operations.

CCI (₹ ha⁻¹) = ∑ C_{1,2,3, …… n}

where C_{1,2,3, …… n} signifies cost for diverse inputs and labor.

The gross returns (GR) were assessed as an output of crop yield (kg ha⁻¹) under diverse treatments and minimum support price (MSP) of produce (fenugreek) fixed by the Government of India (₹ ha⁻¹).

GR (₹) = Crop yield × MSP

The net returns (NR; ₹ ha⁻¹) were estimated as the difference in GR and CCI.

Benefit–cost ratio (BCR) is calculated as the ratio of gross returns to cost of cultivation incurred.

$$\mathbf{B}\mathbf{C}\mathbf{R}={\displaystyle \frac{\mathrm{N}\mathrm{e}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{n}\mathrm{s}\left({\mathrm{₹}\mathrm{h}\mathrm{a}}^{-1}\right)}{\mathrm{C}\mathrm{o}\mathrm{s}\mathrm{t}\mathrm{o}\mathrm{f}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{h}\mathrm{i}\mathrm{n}\mathrm{p}\mathrm{u}\mathrm{t}\mathrm{s}\left({\mathrm{₹}\mathrm{h}\mathrm{a}}^{-1}\right)}}$$

2.6. Resources Utilization Efficiencies

Production Efficiency (PE) of diverse treatments was computed as a ratio of crop yield (kg ha⁻¹) and crop duration (days) [51].

$$\mathbf{PE}({\mathbf{kg}}^{\mathbf{-}\mathbf{1}}{\mathbf{ha}}^{\mathbf{-}\mathbf{1}}{\mathbf{day}}^{\mathbf{-}\mathbf{1}})={\displaystyle \frac{\mathrm{C}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}}{\mathrm{D}\mathrm{u}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{o}\mathrm{f}\mathrm{f}\mathrm{e}\mathrm{n}\mathrm{u}\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{k}\left(\mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}\right)}}$$

Monetary efficiency (ME; production/economic) efficiency evaluated the net benefit of individual crops per unit investment and was computed as follows [51]:

$$\mathbf{M}\mathbf{E}={\displaystyle \frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{n}\mathrm{e}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{n}\mathrm{s}\mathrm{o}\mathrm{f}\mathrm{f}\mathrm{e}\mathrm{n}\mathrm{u}\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{k}\left(\mathrm{₹}{\mathrm{h}\mathrm{a}}^{-1}\right)}{\mathrm{D}\mathrm{u}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{o}\mathrm{f}\mathrm{f}\mathrm{e}\mathrm{n}\mathrm{u}\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{k}\left(\mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}\right)}}$$

2.7. Statistical Analysis and Data Visualization

All the relevant data under investigation were subjected to analysis of variance to determine the statistical significance. In the post hoc analysis, Duncan’s multiple range test (DMRT) was used to compare the means of variables. Principal component analysis (PCA) was performed using the biplot method in Matlab R2019b version 9.7 (Math–Works Inc., USA) to identify the important information in the data, designated as variables called principal components (PC), and show the relationships between the variables and observations [52]. Similarly, Pearson’s correlation coefficient was worked out between all the parameters under investigation and visualized via “correlogram” using the same software.

3. Results and Discussion

Results indicated that the yield attributes and fenugreek yield (

Table 2. Influence of different nutrient management technologies on the Fenugreek seed yield and yield attributes (2 years pooled data).

Treatments	Plant Height (cm)	Days to First Flowering	No. of Primary Branches	No. of Secondary Branches	No. of Pods/Plant	Days to Maturity	No. of Seeds/Pod	Seed Yield/ Plot (g)	Seed Yield (kg ha−1)
T1	25.15 c	43.29 b	3.33 c	6.33 c	19.56 c	130.23 e	3.44 c	42.67 d	840 e
T2	27.22 c	44.63a b	3.49 b	8.33 b	23.67 c	133.11 d	5.10 b	51.67 d	1060 d
T3	29.44 b	45.82a b	3.84 b	10.67 ab	28.89 b	140.95 c	5.11 b	58.11 c	1198 c
T4	30.78 b	46.23 a	3.88 b	11.33 a	31.11 ab	142.71 b	6.78 a	67.33 b	1325 b
T5	32.33 a	46.71 a	4.56 a	11.67 a	33.33 a	147.66 a	7.01 a	74.21 a	1498 a
SE	1.27	0.62	0.21	1.02	2.51	3.19	0.65	5.58	112.34
Mean	28.95	45.33	3.82	9.67	21.71	138.93	5.49	54.73	12.32

Note: According to the Duncan multiple range test for mean separation, different superscript letters within the same column indicate a significant difference at p ≤ 0.05. (Values are means of three replicates).

) increased significantly (p ≤ 0.05) across the various treatments with the addition of different levels and sources of nutrients, except the number of primary and secondary branches. Such an increase was highest in plots fertilized with 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime, while the lowest was logged in control plots, and the trend of such increase can be ranked as T₅ > T₄ > T₃ > T₂ > T₁, respectively.

The productivity of fenugreek seeds was significantly impacted by varying nutrition levels and sources. The higher productivity may be due to the slow and sustained release along with the availability of nutrients, especially N, which is essential for optimal nutrition to produce a large seed output of fenugreek from organic sources [53,54]. Moreover, the greater productivity of FYM and VC–manured plots could be ascribed to the inherently better quality of available nutrient concentration in soil owing to mineralization and consequent release of these elements contained in the organics (VC and FYM). The available N concentration in initial and post-harvest soils validated the claim (

Table 3. Soil chemical properties and available nutrient status in soil as influenced by the nutrient management technologies under fenugreek (2 years pooled data).

Treatments	Physicochemical Properties				Available Macronutrients			Secondary			DTPA Micronutrients
	BD (Mg m–3)	Soil pH	SOC (%)	SOC Stock (Mg ha−1)	N	P	K	Ca	Mg	S	Fe	Mn	Cu	Zn	Available B
					(kg ha−1)			(mg kg−1)
T1	1.32 a	5.44 ab	1.19 c	23.20 bc	407.52 e	14.22 d	439.41 e	0.55 c	0.28 c	15.23 d	13.11 c	10.11 d	1.14 d	0.38 b	0.23 c
T2	1.21 ab	5.51 a	1.33 b	23.25 bc	429.38 d	14.48 c	452.41 d	0.68 bc	0.40 b	19.20 c	18.55 b	16.11 c	1.62 c	0.51 a	0.45 b
T3	1.18 ab	5.58 a	1.42 ab	23.94 bc	443.18 c	15.54 b	464.27 c	0.72 bc	0.52 ab	20.21 c	19.22 b	19.44 b	1.85 b	0.53 a	0.48 b
T4	1.14 ab	5.67 a	1.46 ab	24.09 b	457.89 b	16.68 ab	477.66 b	0.86 b	0.65 ab	22.41 b	21.54 b	20.23 b	1.92 b	0.58 a	0.52 ab
T5	1.02 b	5.72 a	1.55 a	25.13 a	472.66 a	17.32 a	498.18 a	0.98 a	0.75 a	25.23 a	25.42 a	22.01 a	2.05 a	0.62 a	0.58 a
SE	0.05	0.05	0.06	0.35	11.27	0.60	10.16	0.07	0.08	1.67	2.01	2.10	0.16	0.04	0.06
Mean	1.17	5.69	1.39	23.92	442.13	15.65	466.39	0.76	0.52	20.46	19.56	17.58	1.72	0.52	0.45
Initial	1.33	5.40	1.17	23.07	403.24	14.20	434.60	0.55	0.26	15.14	13.08	10.09	1.12	0.36	0.22

Note: According to the Duncan multiple range test for mean separation, different superscript letters within the same column indicate a significant difference at p ≤ 0.05. (Values are means of three replicates).

).

In the current investigation, the addition of VC and lime increased fenugreek productivity. The added VC enriched the soil with essential nutrients, organic matter, and beneficial microorganisms, promoting soil fertility, water retention, and nutrient availability, resulting in enhanced fenugreek productivity [55]. This enhances root development, nutrient uptake, and plant vigor, increasing fenugreek yield. Additionally, VC improves soil structure, aeration, and drainage, creating favorable conditions for fenugreek growth [56].

Furthermore, the lime application raises soil pH, mitigating soil acidity and aluminum toxicity, which can inhibit fenugreek growth [11]. In the present study, it might possibly be due to the optimal pH levels that have facilitated nutrient availability and microbial activity, supporting fenugreek growth and productivity. The combined effect of VC and lime could have encouraged synergistic interactions, thereby maximizing soil fertility, nutrient availability, and plant health, ultimately enhancing fenugreek productivity.

3.1. Physicochemical Properties

The physicochemical properties (Table 3) exhibited no significant (p ≤ 0.05) difference across the diverse treatments due to the imposition of increasing levels and sources of nutrients; however, favorable nominal improvement in the status of soil chemical properties was seen, and BD showed a decreasing trend during the two years of investigation. The decrease in BD under manured plots could be due to the higher addition of organic amendments (VC and FYM), which increased root growth, improved aggregation, and enhanced biological activity [57]. The lowest BD was observed in plots where VC and lime were added. This can be attributed to their effects on soil structure and composition. VC is rich in organic matter and improves soil aggregation and porosity, reducing soil BD [58]. The organic matter in VC acts as a binding agent, promoting soil particle aggregation and the formation of stable soil aggregates, decreasing BD [55].

Lime application, on the other hand, can indirectly influence soil BD by reducing soil acidity and Al toxicity, which can lead to better soil aggregation and decreased compaction [11].

In general, the pH of the experimental plots increased marginally, and this could be best elucidated by the addition of lime at the rate of 250 kg ha⁻¹. The build-up of SOC status and SOC stocks in the soil might be ascribed to the high C supplementation through VC and FYM [59].

The addition of VC and lime increases soil pH through different mechanisms. VC contains organic acids that release hydroxyl ions (OH^–) upon decomposition, buffering soil acidity and raising pH levels [55]. The organic matter in VC also enhances CEC, reducing the concentration of acidic ions in the soil solution and consequently increasing pH [56]. Additionally, VC promotes microbial activity, leading to the production of compounds such as ammonia, which react with acidic ions and contribute to soil pH elevation [58]. Lime application directly increases soil pH by reacting with hydrogen ions (H⁺) in the soil solution, forming water and raising pH levels [60]. This neutralization of soil acidity by lime effectively increases soil pH.

3.2. Available Nutrients in the Soil

3.2.1. Macronutrients

Averaged over the years, the macronutrient content (N, P, and K) (Table 3) in soil showed a significant (p ≤ 0.05) improvement due to the application of varied levels and sources of nutrients. The highest available nutrient content in soil was with 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime (T₅), while the lowest was observed in control plots. The increase in the available nutrients was 16, 21.8, and 13.4%, respectively, over the control, and the trend of improvement in the available nutrient status followed the order as T₅ > T₄ > T₃ > T₂ >T₁, respectively.

The increase in available N content may be attributed to the release of mineralized N caused by the addition of organic matter, as well as the simultaneous release of N from fenugreek roots’ symbiotic biological N fixation [53]. The addition of VC and lime increases soil available N as VC enhances N availability by supplying organic nitrogen compounds that mineralize gradually, releasing N into the soil [55]. Additionally, organic manures improve soil structure and microbial activity, enhancing N mineralization and turnover rates [56]. Lime application indirectly influences N availability by reducing soil acidity, which can inhibit microbial N transformations and N uptake by plants [60]. The combined effect of VC and lime promotes N mineralization, microbial activity, and soil pH, increasing soil available N levels.

The increase in available P might possibly be due to the addition of organic manures (VC and FYM), which decreased the P adsorption by Fe and Al oxides in soil, leading to slow and sustained release of P in soil [61]. Furthermore, the improvement in available P and K contents under manured plots was mainly due to VC and FYM addition, as both directly contribute to the available pool of P and K in the soil, thereby increasing their availability [53]. The addition of various sources of organic manures and lime increases available P as VC contains organic acids that chelate soil P, making it more soluble and readily available for plant uptake [62]. Additionally, organic manures enhance microbial activity, promoting the release of P from organic matter and minerals through mineralization processes [63]. The lime application raises soil pH, reducing P fixation by Al and Fe oxides and increasing P availability [61,64]. Furthermore, organic manures and lime improve soil structure, porosity, and CEC, facilitating P diffusion and uptake by plant roots [65,66]. They also enhance root development and nutrient uptake efficiency, further promoting phosphorus acquisition [67].

The addition of organic manures and lime enhances soil available K since VC contains organic acids that chelate K, making it more soluble and available for plant uptake [56]. Additionally, organic manures enrich the soil microbial community, stimulating the release of K from organic matter and minerals through mineralization processes [62]. Lime application indirectly influences K availability by raising soil pH, reducing K fixation by clay minerals and increasing K desorption from soil particles [61,64]. Moreover, organic manures and lime improve soil structure and CEC, facilitating K diffusion and uptake by plant roots [65]. They also enhance root development and nutrient uptake efficiency, promoting potassium acquisition [67].

3.2.2. Secondary and Micronutrients

Irrespective of the different levels and sources of nutrients applied, there existed no significant (p ≤ 0.05) difference in the status of available secondary (Ca, Mg, and S) and micronutrients (Fe, Cu, Mn, Zn, and B) [Table 3]. Even though the changes were nonsignificant, these nutrients exhibited a favorable and marginal improvement in their availability during the two years of investigation.

This build-up of secondary nutrients (Ca, Mg, and S) in soil could be explicated by the application of variable doses of organic manures in bulk quantity, which, upon decomposition, leads to the formation of acids, which in turn release the nutrients through mineralization from the organic pool [68]. Many organic manures contain appreciable amounts of Ca, Mg, and S, and when incorporated into the soil, these nutrients become readily available for plant uptake as the organic matter decomposes [69]. Organic matter plays a vital role in improving soil CEC, which is the soil’s ability to hold on to positively charged cations (including Ca, Mg) [70]. This increased CEC prevents these essential nutrients from leaching out of the soil profile, making them more readily available for plant roots.

Similarly, the improvement in micronutrient (Fe, Cu, Mn, Zn, and B) status could be attributed to the addition of higher variable levels of organic manures leading to better mobilization and mineralization of micronutrients in the soil. This addition of manures, coupled with vibrant microbial and enzymatic activities emanating from the symbiotic association between fenugreek and microbes, further augmented their availability [51]. Furthermore, organic manures can form complexes with micronutrients, preventing them from becoming insoluble or unavailable to plants, thus rendering them more available in soil.

3.3. Effect of Organic Nutrients on Qualitative Properties of Fenugreek

Results (Figure 1) indicated that the addition of various amounts and sources of nutrients improved the fenugreek’s antioxidant capacity, diosgenin content, protein percentage, phenol and fiber content, wherein, the greatest improvement was with the addition of 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime (T₅) followed by T₄ > T₃ > T₂ > T₁. However, there was a nonsignificant increase (p ≤ 0.05) observed in the phenol and fiber content in fenugreek, even though an increase in their content was observed.

The addition of VC and lime enhanced the protein content of fenugreek. VC enriches soil with organic matter, promoting beneficial microbial activity that aids nutrient mineralization and availability, including N uptake. Lime application modifies soil pH, potentially reducing acidity and improving N availability for plant uptake and protein synthesis [71]. This combination fosters optimal conditions for protein formation in fenugreek. Nitrogen is a crucial component of proteins, and its availability significantly influences crop protein content, including fenugreek. Studies have demonstrated a positive correlation between N uptake and protein accumulation in fenugreek seeds [72]. By enhancing N availability through optimized fertilization or other management practices, it is possible to increase the protein content of fenugreek crops. Furthermore, N influences various enzymatic activities associated with protein metabolism, thereby enhancing the overall protein content of fenugreek seeds.

The phenol content of fenugreek increases with the addition of VC and lime. VC is rich in humic substances, which can enhance the bioavailability of nutrients and stimulate the production of phenolic compounds as a defense mechanism in plants [73]. Lime, on the other hand, can increase soil pH, which can influence the activity of enzymes involved in the phenylpropanoid pathway, leading to higher phenol synthesis [74].

The increase in fiber content in fenugreek could be attributed to the fact that the organic matter in VC improves soil structure, water retention, and nutrient availability, thereby enhancing microbial activity, which can lead to increased fiber [75]. Similarly, lime (calcium carbonate) increases soil alkalinity by raising the pH, affecting enzyme activity and nutrient availability [51]. In fenugreek, an optimal pH range promotes fiber production. Lime indirectly influences fiber content by creating favorable conditions for enzymatic processes involved in fiber synthesis.

The highest improvement in the antioxidant capacity of fenugreek due to the addition of VC and lime can be attributed to the fact that VC contains humic substances that can stimulate the biosynthesis of secondary metabolites, including phenolic compounds, which are known for their antioxidant properties [73]. Additionally, the increased availability of nutrients from VC can enhance the overall metabolism and production of antioxidant compounds [76]. Lime addition can enhance the antioxidant capacity of fenugreek by modifying soil pH, which affects nutrient availability and uptake [77]. This can stimulate essential antioxidant enzyme synthesis and the production of secondary metabolites, including phenolics and flavonoids [78]. Improved Ca availability due to liming may also increase antioxidant enzyme activities in fenugreek plants [79].

The enrichment in diosgenin content capacity of fenugreek (Trigonella foenum–graecum) through VC and lime addition could be explicated by the fact that VC enriches the soil with essential nutrients such as N, P, and K, which promotes overall plant health and supports diosgenin synthesis [80]. Lime application adjusts soil pH to slightly alkaline levels, which fenugreek prefers for optimal growth and nutrient uptake. This pH adjustment enhances the availability of essential nutrients, particularly phosphorus and micronutrients, crucial for the enzyme activity involved in diosgenin biosynthesis [81]. VC, being rich in organic matter and beneficial microorganisms, complements lime by improving soil structure and microbial activity [82]. The synergistic effect of lime and VC creates an ideal soil environment, stimulating the metabolic pathways responsible for diosgenin production in fenugreek plants [83].

3.4. Financial and Resources Utilization Efficiencies Analysis

A perusal of the financial data (

Table 4. Impact of different nutrient management technologies on financial and resource utilization efficiencies analysis of fenugreek cultivation (2 years pooled data).

Treatments	Gross Return	Cost of Cash Inputs	Net Return	Benefit–Cost Ratio	Monetary Efficiency (₹ ha−1 day−1)	Production Efficiency (kg−1 ha−1 day−1)
	(₹ ha−1)
T1	100,800	46,000	54,800	2.19	609	9.30
T2	127,200	55,000	72,200	2.31	802	11.8
T3	143,760	60,400	83,360	2.38	926	13.3
T4	159,000	66,000	93,000	2.41	1033	14.7
T5	179,760	72,450	107,310	2.48	1192	16.6

Note: (T1: absolute control; T2: 2.5 t ha⁻¹ vermicompost (VC) + 250 kg ha⁻¹ lime; T3: 5 t ha⁻¹ FYM + 250 kg ha⁻¹ lime; T4: 10 t ha⁻¹ FYM + 250 kg ha⁻¹ lime; and T5: 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime).

) shows that treatment T₅ incurred the highest input cost among all nutrient management practices. However, treatment T₅ recorded maximum gross and net returns, closely followed by T₄ and T₃, respectively. Similarly, the highest values of benefit–cost ratio, monetary efficiency, and production efficiency were registered under treatment T₅. The most likely reason for overall superiority in financial and resource utilization efficiencies can be attributed to the higher productivity under treatment T₅, which further impacted all the observed parameters.

3.5. Correlation Analysis

The autocorrelation function (ACF) plot (Figure 2) displays the univariate correlation coefficients (r) between the yield, its attributes, and the physicochemical properties of the soil. In general, correlation analysis showed significant positive correlations (p ≤ 0.05 and p ≤ 0.01) between all the observed parameters, including yield attributes and soil properties. However, SOC stock did not show any significant positive correlation (p ≤ 0.05 and p ≤ 0.01) with any parameters under investigation. In contrast, BD exhibited a negative significant correlation (p ≤ 0.05 and p ≤ 0.01) with all parameters.

3.6. Principal Components Analysis (PCA)

Depicting the loadings plots of yield attributes and soil properties, along with the scores (treatments) of the experimental site, the principal component analysis (PCA) biplots provide a simultaneous visualization (Figure 3). The results of PCA (Figure 3) showed that two principal components (PC) were extracted with eigenvalues > 1, which explained the variation up to 95.43% of the total variability. The extracted two PCs explained the variation to the tune of 88.93% (PC1) and 6.50% (PC2) of the total variability of the data. The PCA exhibited that available N (0.920), available P (0.906), SOC (0.902), and K (0.895) were the most important soil properties attributing to the fenugreek seed yield and that these parameters had high loadings on PC1 while BD showed a negative loading (–0.844) (Figure 3). Biplot (Figure 3) also showed that treatments T4 and T5 located in the 1st and 4th quadrants harbored almost all the parameters except BD, indicating that both these treatments had a significant influence on all the parameters under investigation.

4. Conclusions

This study established a comprehensive methodological protocol to evaluate the feasibility and optimization of various nutrient management (NM) techniques for fenugreek production in the acidic soils of Northeast India. The focus was on utilizing yield, profitability, and environmental sustainability through improved soil quality as key evaluation parameters. In culmination, it can be concluded that the application of 5 t ha⁻¹ VC + 250 kg ha⁻¹ lime exhibited superior results in enhanced fenugreek seed yield, improved yield attributes, enhanced soil chemical parameters, quality parameters, and higher economic returns. These findings emphasize the potential of organic nutrient sources, specifically VC and FYM, in sustainably enhancing fenugreek productivity in acidic soils of Northeast India. The established methodological protocol provides valuable insights for fenugreek growers, promoting a holistic approach to organic nutrient management that balances agricultural productivity, soil quality, and economic viability.