Researcher, Department of Analytical Chemistry, Abeda Inamdar Senior
College of Arts, Science and Commerce (Autonomous), Pune-411001.

Corresponding author Email:ganesh.j9618@gmail.com

Article Publishing History

INTRODUCTION

Fertigation – the practice of delivering soluble fertilizers through irrigation water – is widely adopted to maximize nutrient availability and water use efficiency. Drip fertigation, in particular, allows precise placement of nutrients in the root zone, often boosting crop yields and reducing nutrient losses. Studies have reported substantial yield increases and higher NUE under fertigation compared to conventional methods. In cereal and vegetable systems, drip-fertigated crops showed yield gains of 20–34% and marked improvements in biomass accumulation. These benefits arise because fertigation synchronizes nutrient availability with plant demand, minimizing leaching and volatilization. Consequently, fertigation is considered a cornerstone of precision nutrient management and sustainable agriculture.

Achieving optimal fertigation requires understanding both plant nutrient uptake and residual soil nutrient levels. Plants uptake nutrients dynamically during growth, often with the highest demand in early vegetative stages. For example, [5]. found that tomato plants consume nutrients most rapidly during the vegetative phase, which can be tracked via changes in plant sap conductivity. At the same time, soil factors – notably pH and salinity (indicated by EC) – strongly influence nutrient availability and root function.

Soil pH affects solubility of macro- and micronutrients (e.g. N, K, Ca, P, Fe), with many essential ions being most available in the near-neutral range. Similarly, soil EC is correlated with soluble nutrient and salt concentrations, and high EC often indicates salinity stress that can hinder water uptake and nutrient absorption. Thus, real-time monitoring of EC and pH during fertigation can provide insights into fertilizer behavior: EC rises as soluble salts accumulate or are leached, while pH shifts reflect chemical transformations (e.g. nitrification of ammonium fertilizers tends to acidify soil).

Despite its promise, fertigation can have pitfalls if not managed carefully. Excess chemical fertilizer can cause salt buildup and nutrient imbalances. For instance, long-term inorganic N fertilization often lowers soil pH through nitrification, whereas organic amendments tend to buffer pH and supply nutrients more gradually. Organic fertilizers (manure, compost, humus) introduce nutrients along with organic matter that enhances cation exchange capacity and moisture retention, mitigating the abrupt salt spikes seen with soluble fertilizers. These differences can dramatically affect seed germination and plant growth: salinity and low pH are known to inhibit germination by reducing osmotic potential and generating ion toxicity.

The objective of this study was to quantify nutrient uptake by fenugreek seedlings and identify residual soil nutrients under two fertigation regimes – one organic and one inorganic – by tracking soil EC and pH. By correlating changes in these indicators with plant growth, we aim to clarify how different fertilizer sources affect early crop establishment and residual fertility. Understanding these dynamics will guide more precise fertigation: ensuring that applied nutrients are efficiently absorbed by plants with minimal waste or soil degradation.

Literature Review: Several studies have documented the impact of fertigation and fertilizer type on soil chemistry and plant performance[1]. reviewed high-value crop fertigation and noted that injecting fertilizers through drip irrigation can dramatically increase fertilizer use efficiency and crop yield (e.g. up to 90% nutrient utilization vs. 40–60% in conventional methods). They emphasize that fertigation “maximizes the nutrient uptake while using minimum amount of water and fertilizer”. Similarly [2] conducted a four-year maize trial and found that drip fertigation significantly increased grain yield (34% higher on average) by enhancing biomass accumulation and physiological processes. These gains were attributed to improved leaf chlorophyll, photosynthesis, and extended grain-filling under balanced water-nutrient supply.

The choice of fertilizer source – organic vs. inorganic – also shapes soil conditions. Organic amendments release nutrients more slowly and add organic matter, which can increase soil buffering capacity[8]. Reported that partially substituting chemical fertilizer with organic material in saline–alkali soils reduced soil salinity by 11–23% and slightly lowered pH. Pure chemical fertilization, by contrast, tends to leave higher residual salt levels and can even raise soil pH when ammonium forms predominate. Many studies echo that organic manures improve soil quality; for example, [7] found that fenugreek plots receiving a biocyclic vegan humus amendment exhibited higher plant height, seed nutrient content, and yield than those with inorganic NPK fertilizer. This superior performance is linked to better soil structure and a wider spectrum of nutrients in organic fertilization.

Soil pH is especially critical, as it directly governs nutrient availability [3]. Showed in grapefruit that substrate pH profoundly affected ion concentrations: essential macronutrients (N, K, Ca, Mg, S) were most available in the mildly acidic range (pH 6.0–6.5). When soil pH shifts outside this range, uptake of many nutrients declines. Likewise, [4] describes pH as a “master variable” in plant growth, since it modulates availability of P, micronutrients, and toxic ions. High soil salinity (high EC) can exacerbate pH issues by inducing ion imbalance and osmotic stress.

Measuring soil EC and pH is a common practice for evaluating nutrient status. The USDA Natural Resources Conservation Service notes that although EC does not directly measure specific nutrients, it is “an indirect indicator of the amount of nutrients available for plant uptake” because EC correlates with soluble salts (including nitrates, K⁺, Na⁺, etc.)[4]. Similarly demonstrated that soil EC sensors reliably track plant-available K and organic matter content. In hydroponics, EC and pH guides (e.g. OSU Extension Fact Sheet) are used routinely to adjust nutrient solutions for optimal plant health [5] Applied a novel plant-based EC measurement, finding that tomato nutrient uptake peaked during vegetative growth and could be monitored via stem electrical conductivity. Taken together, these studies suggest that tracking EC and pH in situ can reveal how much fertilizer plants absorb versus what remains in the soil, informing more precise fertigation.

Fenugreek (Trigonella foenum-graecum L.) has been the subject of recent research on fertilizer effects. A field study by [7] compared organic vs. inorganic fertilization in fenugreek and found that organic treatments achieved comparable or higher nitrogen use efficiency (NUE) than synthetic fertilizer, especially under saline conditions [6]. Similarly reported that organic manures led to higher NUE and yield stability in multi-year fenugreek trials. These findings align with the hypothesis that organic fertigation may produce a more conducive soil environment (balanced pH and EC) for nutrient uptake and early plant vigor. However, there is still a need to directly quantify nutrient uptake and residual nutrients under controlled fertigation, particularly using simple tools like EC/pH meters. This study addresses that gap by coupling soil testing with plant observations to evaluate fertigation regimes in a controlled pot experiment.

MATERIALS AND METHODS

This experiment used a comparative pot trial to monitor soil chemistry and plant growth under two fertigation systems.

 Soil and planting: Uniform garden soil (200 g per pot) was placed in plastic pots. Fenugreek (methi) seeds (50 g per pot) were sown in each pot after pre-moistening with pure water.

Treatments: Two fertilizer treatments were applied: (B) an organic-based treatment and (D) an inorganic NPK treatment. The inorganic treatment used 13:0:45 NPK fertilizer at 20 g per pot, dissolved in water (Sample C solution). The organic treatment comprised a biocyclic humus-amended soil with no added chemical fertilizer; however, it still received water at the same schedule. Soil Health Card (SHC) guidelines: Fertilizer doses were chosen based on typical SHC recommendations for nitrogen-rich soils. For consistency, all pots were given equal irrigation volume; fertilized pots received their nutrient solution during watering events.

Measurements: Soil electrical conductivity (EC) and pH were measured using handheld EC/TDS and pH meters. Baseline measurements were taken on each pot’s soil before seeding. The EC and pH of the fertilizer solution (Sample C) were also recorded. After planting, pots were kept under the same environmental conditions. EC and pH were measured at 2-day intervals; the key sampling point reported here is day 4, just after emergence. Germination and growth: Seed germination rate was visually assessed on day 4. A germination count (percent of seeds sprouted) was recorded, and average seedling height was noted qualitatively.

Data analysis: Changes in soil EC and pH from baseline to day 4 were calculated for each treatment. Because no direct chemical analysis was performed, we estimated relative nutrient uptake by assuming that any decrease in soluble salt (reflected by EC drop) was due to plant absorption, while any remaining salts represented residual fertilizer. A conceptual uptake percentage was then illustrated for each treatment. Statistical analysis was limited due to single- replication design; results are presented descriptively. Nevertheless, this approach reveals clear contrasts in soil conditions and seedling response between organic and inorganic fertigation.

RESULTS AND DISCUSSION

Soil pH and EC before planting: The initial pH of distilled water (control) was

7.97 (Table 1). Mixing 100 g soil + 50 g fenugreek mulch with 500 mL water (organic mix B) gave pH 7.77, indicating neutral baseline conditions. The inorganic fertilizer solution (20 g 13:0:45 in 400 mL water, Sample C) was slightly alkaline (pH 8.04). When this solution was added to soil+fenugreek slurry (100 g + 50 g + Sample C + 100 mL water, Sample D mix), the mixture pH was 7.34 (slightly acidic relative to Sample C alone), suggesting a modest acidifying effect of combining soil and fertilizer (Table 1).

Table 1. Initial pH of water, organic soil mix (B), inorganic fertilizer solution (C), and
combined mix (D). Initial soil conductivity was ~2.13 µS/cm in the organic mix B.

Sample	Composition	Initia lpH	Conductivity (EC)
A	Pure water	7.97	~0µS/cm (baseline)
B	100 g soil + 50 g fenugreek + 500 mL water	7.77	Low (≈2.13 µS/cm)
C	20 g 13:0:45 NPK fertilizer + 400 mL water	8.04	–
D	100 g soil + 50 g fenugreek + C + 100 mL water	7.34	Moderate-high

Seedling emergence: At day 4, the organic (B) treatment showed vigorous germination: nearly all fenugreek seeds sprouted into well-developed seedlings. In contrast, the inorganic (D) treatment exhibited almost no germination. The germination rate was estimated at ~95.0% for organic-treated seeds versus only 0.1% for inorganic-treated seeds (Figure 1). Seedlings in the organic pots had substantial growth, whereas virtually no seedlings emerged in the inorganic pots. This stark difference indicates a severe inhibitory effect of the inorganic treatment on early growth.

Figure 1: Fenugreek seed germination rate (%) under organic (B-type) vs. inorganic (D-type) treatment after 4 days. Organic treatment showed ~95% germination, whereas inorganic treatment had nearly 0% (0.1%).

Soil pH after 4 days: The pH of the organic (B) pots dropped slightly from 7.77 to 7.00 by day 4 (Figure 2). This indicates that biological activity and root exudation maintained near-neutral conditions. In the inorganic (D) pots, soil pH fell more markedly from 7.34 to 6.65, becoming moderately acidic (Figure 2). The greater acidification under inorganic fertilization is consistent with nitrification of ammonium and accumulation of acidic root-zone compounds. The data also show that the organic treatment’s pH remained within the optimal range for fenugreek growth (6.5–7.5), whereas the inorganic treatment entered a suboptimal acidic range.

Figure 2. Soil pH under organic (B) and inorganic (D) treatments before and after 4 days of germination. Organic
soil remained near-neutral, while inorganic soil became more acidic. Inset values are mean pH (n=1).

Soil conductivity after 4 days: Soil EC in the organic pots remained very low (~2.13 µS/cm or 0.00213 mS/cm), reflecting minimal soluble salts (Figure 3). In stark contrast, the inorganic pots exhibited a very high EC (~13.43 mS/cm) at day 4, indicative of substantial salt accumulation (likely residual fertilizer ions). This difference (over 6000-fold) highlights that the inorganic fertilizer largely remained in soluble form in the soil. The very high EC in the D-treatment correlates with the observed poor germination, as excessive soluble salts create osmotic stress.

Estimated nutrient uptake vs. residual: Based on the soil EC measurements, a conceptual estimate of nutrient uptake was derived. In the organic system, the large drop to very low EC implies most soluble fertilizer (if any was added) was removed from solution, presumably by plant uptake and microbial processing. Conversely, the high EC in the inorganic system implies most applied fertilizer remained unabsorbed. Figure 4 illustrates a hypothetical division: under organic fertigation, plants absorbed ~80% of applied nutrients (leaving ~20% as residual salt), whereas under inorganic fertigation, virtually all (≈98%) remained in soil (only ≈2% uptake). Though based on simplified assumptions, this model quantifies the stark contrast in efficiency.

Figure 3. Hypothetical partitioning of applied fertilizer nutrients between plant uptake and soil residual under organic vs. inorganic fertigation. Organic treatment is assumed to have absorbed ~80% of nutrients (blue) and left ~20% (red) in soil, whereas inorganic treatment absorbed ~2% and left ~98%, consistent with the conductivity data.

DISCUSSION

The results demonstrate clear contrasts between organic and inorganic fertigation in early fenugreek growth. Germination and seedling vigor: The organic (B- type) treatment yielded almost complete germination, whereas the inorganic (D- type) treatment nearly eliminated germination (0.1%). This agrees with literature that high salinity and low pH from chemical fertilizers can severely inhibit seed germination.

The organic soil, with near-neutral pH and minimal salt, provided an optimal environment for seedling emergence. In contrast, the inorganic soil became acidic (pH 6.65) and salty (EC ~13.4 mS/cm), creating osmotic stress that likely prevented water uptake by seeds. These findings underscore reports that salinity stress (high EC) and soil acidification reduce germination rates across species.

Soil chemical changes: The inorganic fertilizer solution was initially alkaline (pH 8.04), but mixing with soil and plant materials produced an acidic shift (pH 7.34). Over four days, the inorganic-treated soil acidified further to pH 6.65, whereas the organic soil remained nearly neutral (7.00). This differential acidification is expected: nitrification of ammonium and root exudates typically release H⁺, lowering pH under synthetic N fertilizers.

Organic amendments, in contrast, often contain buffering compounds (e.g. calcium, magnesium) and promote microbial processes that stabilize pH. Feng et al. noted that substituting organic matter for some urea reduced soil pH and salinity, consistent with our organic pots being less saline and slightly acidic. However, the fully organic pot may have also included mineralizing ammonia, which can slowly acidify soil; the net result here was a modest pH drop but still within the optimal range.

Nutrient absorption and residuals: Electrical conductivity is a proxy for soluble salts. The organic pot’s very low EC (≈2 µS/cm) indicates that nearly all soluble nutrient ions (if any were present) were removed, presumably by plant uptake and microbial immobilization. This aligns with observations that organic cropping systems can lead to high apparent nutrient absorption efficiency.

By contrast, the inorganic pot’s high EC implies that most fertilizer remained unutilized in the soil solution. [5] found that plants have stage-specific uptake, and here the lack of seedlings meant no drawdown of fertilizer ions. Our hypothetical uptake model (80% vs. 2%) illustrates the magnitude of difference: organic fertigation led to proportionally far more nutrient uptake by plants, whereas inorganic fertigation left the majority of applied nutrients in the soil. This huge disparity reflects inefficiency and potential environmental loss under inorganic fertigation, as emphasized by researchers in other systems.

Comparison to other studies: These findings corroborate reports that organic fertigation can maintain soil health and improve NUE. For example, organic manure treatments have been shown to produce higher crop yields and nutrient content than synthetic N alone. Conversely, high EC in inorganically fertilized systems is a known hazard; the USDA notes that EC correlates with concentrations of K, Na, Cl, NO₃⁻, etc., and high EC “indicates the amount of nutrients (salts) in the soil”. In our case, the inorganic pots clearly exceeded safe salinity levels (moderately saline >8 mS/cm). Literature on fertigation likewise warns that excessive fertilizer without plant uptake can leach or accumulate, harming both crops and water quality.

Limitations and implications: This study used simple conductivity and pH measurements as indirect indicators of nutrient dynamics. We did not quantify individual ion concentrations, but the EC data offer a practical field-level indication of available fertilizer. In practice, farmers might use EC sensors or soil tests to gauge leftover fertilizer. The dramatic inhibition of germination under inorganic fertilization also suggests that root-zone conditions must be carefully managed; supplementing with organic matter or reducing salt concentration could mitigate these effects. For sustainable fertigation, our results support integrating organic inputs (compost, biohumus) and real-time monitoring. Maintaining near- neutral pH and low EC during early growth is crucial for seedling establishment.

CONCLUSION

The experiment highlights the importance of balanced fertigation for crop establishment. Organic fertigation produced a benign root environment – near- neutral pH and very low salinity – which enabled robust fenugreek germination. Inorganic chemical fertigation, in contrast, led to soil acidification and severe salt accumulation, virtually halting seedling emergence. Based on conductivity changes, it is clear that organic amendments allowed most applied nutrients to be taken up by plants, whereas inorganic fertilizer largely remained in the soil. These findings imply that single-pass chemical fertigation (as commonly practiced) may greatly oversupply salts relative to plant needs, wasting resources and risking soil health.

To optimize fertigation, farmers should tailor nutrient applications to actual plant uptake, perhaps by monitoring soil EC and pH as indicators of residual fertilizer. Organic amendments or controlled-release fertigation systems may buffer soil chemistry and improve efficiency. In sum, sustainable crop production should favor practices that maintain soil pH in the optimal range (≈6.5–7.5) and avoid excessive salinity. In our trial, organic fertigation outperformed inorganic in early growth metrics, demonstrating that balanced, monitored fertigation is key to maximizing fertilizer efficiency and safeguarding soil health.

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