Weather uncertainty is becoming one of the biggest challenges in modern agriculture. Delayed monsoons, uneven rainfall distribution, and prolonged dry spells are increasingly affecting crop productivity across major agricultural regions.

Recently, the India Meteorological Department (IMD) projected below-normal rainfall for the 2026 Southwest Monsoon season. According to the forecast, seasonal rainfall is expected to remain around 90% of the Long Period Average (LPA). This has increased concerns among farmers because moisture stress during critical crop growth stages can directly affect crop development, nutrient uptake, and final yield.

In such situations, the common response is to increase fertilizer application. The assumption appears logical. If crop growth slows down, supplying additional nutrients should help the crop recover.

However, field observations often reveal a different outcome.

Even after fertilizer application, crops may continue to show weak growth, poor tillering, reduced branching, flower drop, poor fruit set, lower grain filling, and visible nutrient deficiency symptoms.

This raises an important question:

If nutrients are already present in the soil, why does the crop still struggle during periods of low rainfall?

The answer lies beneath the soil surface, where soil moisture, root activity, microbial processes, and nutrient movement work together to determine how efficiently a crop can access available resources.

Low Rainfall Does Not Always Mean Low Soil Moisture

A common misconception is that low rainfall automatically means the soil contains very little water.

In reality, soil moisture availability depends on several factors, including soil texture, soil structure, organic matter content, and water-holding capacity. Fields with higher organic matter often retain moisture for longer periods because organic matter acts like a sponge, helping store water within the soil profile.

This is one reason why two fields receiving the same amount of rainfall may perform very differently. The field with better soil health and higher organic matter generally maintains moisture for a longer duration and experiences less stress during short dry spells.

However, when dry conditions persist, even moisture-retaining soils begin facing challenges related to nutrient movement and root activity.

The Real Problem: Nutrients Stop Reaching the Root Efficiently

Most plant nutrients move toward roots through two primary mechanisms.

The first is mass flow, where nutrients such as nitrogen, sulphur, calcium, and magnesium move along with water as the plant absorbs moisture from the soil.

The second is diffusion, where nutrients such as phosphorus and potassium gradually move from areas of higher concentration toward the root surface.

Both processes depend heavily on adequate soil moisture.

As soil moisture declines, water movement slows, nutrient diffusion becomes restricted, root growth weakens, and microbial activity begins to decline. As a result, crops face a double challenge. They experience moisture stress while simultaneously losing efficient access to nutrients that may already be present in the soil.

This is why nutrient deficiency symptoms often appear during dry periods even when recommended fertilizer doses have already been applied.

Why Root Health and Rhizosphere Activity Matter?

When moisture becomes limiting, the crop’s performance depends largely on what happens around its root system.

The area immediately surrounding plant roots is known as the rhizosphere. This is one of the most biologically active regions in the soil, where roots interact continuously with beneficial microorganisms. Many important processes occur within this zone, including nutrient cycling, nutrient solubilization, organic matter decomposition, and microbial signaling.

Under prolonged dry conditions, rhizosphere activity often declines. Root growth slows, microbial populations become less active, and nutrient transformation processes become less efficient.

This is why modern crop nutrition is increasingly focusing not only on fertilizer application but also on improving root-zone biology and nutrient-use efficiency.

Why Biological Solutions Are Becoming Important

Modern agriculture is no longer focused solely on adding more nutrients to the soil. The bigger challenge is ensuring that crops can efficiently utilize the nutrients and water that are already available.

This has increased interest in biological technologies that support root development, nutrient mobilization, and rhizosphere activity. Among the most widely adopted approaches are Mycorrhiza.

Rather than functioning as direct nutrient sources, biological technologies help improve nutrient accessibility and nutrient-use efficiency within the root zone.

Mycorrhiza: Expanding the Crop’s Underground Absorption Network

Mycorrhiza, particularly Arbuscular Mycorrhizal Fungi (AMF), forms a natural symbiotic association with plant roots. After colonizing the root system, AMF develops an extensive network of microscopic fungal filaments known as hyphae that extend far beyond the root surface. These hyphae function as natural extensions of the root system and can explore soil pores that roots and root hairs cannot easily access.

Research has shown that mycorrhizal associations can significantly increase the volume of soil explored by plants, allowing access to water and nutrients beyond the immediate root zone. This becomes particularly important under low-rainfall conditions when nutrient movement slows and root access to soil resources becomes restricted.

Mycorrhiza is especially important for the acquisition of relatively immobile nutrients such as phosphorus and may also support the uptake of micronutrients including zinc, copper, and iron. Beyond nutrient acquisition, mycorrhizal hyphae contribute to soil health by helping bind soil particles into stable aggregates. In addition, the production of compounds such as glomalin can improve soil aggregation, enhance soil structure, support water infiltration, and improve moisture retention within the root zone.

How Mycorrhiza Helps During Water Scarcity

Water scarcity affects crops far beyond simple water shortage. As soil moisture declines, root activity slows, nutrient movement becomes restricted, and the crop’s ability to access available resources decreases. Mycorrhiza helps crops cope with these challenges by expanding the effective root absorption network and improving access to water present within the soil profile.

Extends the Effective Root Surface Area

After colonizing plant roots, Arbuscular Mycorrhizal Fungi (AMF) develop an extensive network of microscopic hyphae that can extend several centimeters beyond the root surface. These hyphae are much finer than root hairs and can explore soil pores that roots cannot physically enter, effectively increasing the plant’s absorptive surface area.

Improves Water Extraction from Soil Micropores

As soil dries, a significant proportion of the remaining water becomes trapped within very small soil pores. Because mycorrhizal hyphae are considerably thinner than roots, they can access water from these micropores and transport it back to the plant, helping maintain water uptake under moderate moisture stress.

Reduces the Root Depletion Zone Effect

Plants rapidly remove water from the soil immediately surrounding their roots, creating what soil scientists refer to as a root depletion zone. Mycorrhizal hyphae extend beyond this depleted region and continue extracting water from surrounding soil volumes, increasing the crop’s access to available moisture.

Improves Soil Structure and Water Retention

Mycorrhizal fungi contribute to soil aggregation through extensive hyphal networks and the production of glomalin-related compounds. Improved soil aggregation enhances pore stability, promotes water infiltration, and helps soils retain moisture for longer periods.

Enhances Root System Development

Mycorrhizal colonization is often associated with improved root branching and root growth. A larger and more developed root system enables crops to explore a greater volume of soil for both water and nutrients, improving overall resource acquisition.

Supports Plant Physiological Responses to Water Stress

Research has shown that mycorrhizal plants often maintain higher leaf water status, better stomatal regulation, and improved photosynthetic activity under moderate drought conditions compared with non-mycorrhizal plants. This helps sustain growth and productivity when water availability becomes limiting.

Improves Water Use Efficiency (WUE)

By improving both water acquisition and nutrient uptake, Mycorrhiza can enhance Water Use Efficiency (WUE), allowing crops to produce more biomass or yield per unit of water consumed. This characteristic is becoming increasingly important under conditions of irregular rainfall and growing water scarcity.

How Mycorrhiza Improves Nutrient Uptake During Dry Conditions

Reduced soil moisture affects nutrient uptake long before visible drought symptoms appear in crops. Most nutrients reach plant roots through processes such as mass flow and diffusion, both of which depend heavily on adequate soil water. As soils dry, nutrient mobility declines, root activity slows, and the effective volume of soil explored by roots becomes increasingly limited.

Under these conditions, Mycorrhiza plays an important role by extending the plant’s nutrient acquisition network beyond the immediate root zone and improving the efficiency with which nutrients are captured from the soil.

Improves Phosphorus Acquisition Beyond the Root Depletion Zone

Phosphorus is one of the least mobile nutrients in soil and is primarily transported to roots through diffusion. Under dry conditions, diffusion rates decline significantly because the water film surrounding soil particles becomes thinner, restricting the movement of phosphorus ions toward the root surface. As a result, crops may show phosphorus deficiency symptoms even when adequate phosphorus is present in the soil. 

Mycorrhizal hyphae extend well beyond the phosphorus depletion zone that develops around roots and explore a much larger volume of soil. This enables the plant to access phosphorus reserves that would otherwise remain unavailable, supporting root development, ATP production, energy transfer, flowering, and grain formation.

Enhances Potassium Uptake Under Moisture Stress

Potassium plays a central role in stomatal regulation, osmotic adjustment, enzyme activation, and water balance within plant tissues. As soil moisture declines, potassium movement toward roots becomes increasingly restricted because potassium reaches roots primarily through diffusion, a process that depends on adequate soil moisture for ion transport through the soil solution.

The extensive hyphal network of Mycorrhiza improves the plant’s access to potassium  distributed throughout the soil profile. Improved potassium nutrition supports better regulation of plant water relations and helps crops maintain physiological activity during periods of moisture stress.

Improves Micronutrient Acquisition

Micronutrients such as zinc, copper, iron, and manganese often become less available under adverse soil conditions because their solubility, mobility, and transport toward roots are strongly influenced by soil moisture, pH, and biological activity. Under dry conditions, reduced soil moisture limits nutrient diffusion and microbial processes, making it more difficult for roots to access these essential micronutrients. Because mycorrhizal hyphae can explore soil volumes inaccessible to roots, they increase the probability of encountering and acquiring these nutrients.

Improved micronutrient nutrition supports chlorophyll formation, enzyme activity, photosynthesis, protein synthesis, and numerous metabolic processes essential for crop growth and productivity.

Increases Nutrient Absorption Surface Area

One of the most significant advantages of Mycorrhiza is the dramatic increase in the effective nutrient absorption area available to the plant. Research has shown that the total absorptive surface created by mycorrhizal hyphae can greatly exceed that of root hairs alone.

This expanded absorption network increases the efficiency with which crops acquire both macro and micronutrients, particularly under conditions where nutrient mobility is limited.

Improves Nutrient Use Efficiency (NUE)

Nutrient Use Efficiency refers to the crop’s ability to convert available nutrients into plant biomass and yield. By improving nutrient capture from both native soil reserves and applied fertilizers, Mycorrhiza enhances the overall efficiency of nutrient utilization.

This becomes particularly important under low-rainfall conditions where nutrient losses, restricted root activity, and poor nutrient mobility often reduce fertilizer effectiveness.

Supports Long-Term Soil Fertility and Nutrient Cycling

Beyond immediate nutrient uptake, mycorrhizal networks contribute to long-term nutrient cycling within agricultural soils. By linking roots with surrounding soil resources and interacting with microbial communities, Mycorrhiza helps improve the efficiency of nutrient turnover and supports sustainable soil fertility over time.

As rainfall variability increases and nutrient-use efficiency becomes a greater priority in modern agriculture, the role of Mycorrhiza in improving nutrient acquisition under moisture-limited conditions is becoming increasingly important.

Why Biofertilizers Are Becoming More Important in Climate-Resilient Agriculture

Agriculture is gradually shifting from an input-intensive model toward an efficiency-focused model.

The key question is no longer:

“How much fertilizer can be applied?”

The more important question is:

“How efficiently can the crop utilize available water, nutrients, and soil resources?”

With rising fertilizer costs, increasing weather variability, and growing pressure on soil health, biological solutions are becoming an important component of modern nutrient management programs. Biofertilizers do not replace fertilizers, nor can they replace water during severe drought. Their value lies in improving nutrient accessibility, supporting root-zone biology, enhancing nutrient-use efficiency, and helping crops perform more consistently under stress.

Conclusion

As climate variability continues to increase, improving root performance, soil biological activity, and resource-use efficiency is becoming just as important as fertilizer application itself. Mycorrhiza represents one of the most extensively studied biological technologies for supporting these processes.

However, Mycorrhiza should not be viewed as a replacement for irrigation or fertilizers. Its primary value lies in helping crops utilize available soil moisture and nutrients more efficiently while supporting root development and soil biological function. When integrated with sound nutrient management and soil health practices, Mycorrhiza can become an important component of climate-resilient crop production systems.