We blame the seed. We blame the soil. We blame the weather gods. But the real reason your crop underperformed last season might be hiding in a mistake we all make about how plants actually eat.
A DEEP DIVE INTO WATER, NUTRIENTS & RAINFED FARMING
Imagine hiring a world-class chef, stocking your kitchen with the finest ingredients, and then… turning off the tap. No water. No cooking. The chef sits there, the food sits there, and you sit there wondering why dinner never arrived. That, dear farmer, is exactly what happens when we apply fertiliser to dry soil and walk away expecting a bumper harvest.
There is a widespread belief in farming communities — and even among some textbook-educated agronomists — that nutrition is a matter of chemistry alone. Buy the right fertiliser, apply it at the right time, and the crop will thrive. It sounds logical. It is, unfortunately, only half the story. The other half, the half that quietly determines whether your investment returns a profit or a loss, is water. And today, we are going to bust the myth that fertiliser alone feeds a plant.
We are going to follow a single nitrogen molecule on its journey from a fertiliser granule to the tip of a wheat root — and along the way, we will see exactly where water enters the picture, why it matters so deeply in rainfed systems, and what practical steps we can take to make every drop count.
“Apply the right fertiliser at the right time, and your crop will absorb it — job done.”
Without sufficient soil moisture, nutrients cannot dissolve, cannot move, and cannot enter the plant — regardless of how much fertiliser you apply. Water is not a supporting actor here; it is the director of the whole show.
THE SCIENCE MADE SIMPLE
How plants actually eat
Plants do not chew. They drink. Every nutrient a plant absorbs — nitrogen, phosphorus, potassium, calcium, zinc, and the rest — must first dissolve into the soil water before a root can take it in. Think of it this way: a fertiliser granule sitting in dry soil is like a sugar cube sitting beside a glass of water. Nothing happens until the two meet. The moment water arrives, the cube dissolves, and the sugar becomes available. The same principle governs every bag of urea, DAP, or potash we apply to our fields.
Once dissolved, nutrients travel toward plant roots through two main mechanisms. The first is mass flow — as the plant drinks water through its roots, that water carries dissolved nutrients along with it, the way a river carries sediment. The second is diffusion — nutrients slowly spread from zones of high concentration near the fertiliser application to zones of low concentration near the root, moving through the thin film of water that coats every soil particle. A third process, root interception, happens when roots physically grow into contact with nutrient-rich soil zones. All three processes are either facilitated or crippled by the presence or absence of soil moisture.
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MASS FLOW
Nutrients ride water into the root as the plant absorbs moisture. Responsible for most nitrogen and calcium delivery.
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Nutrients spread through soil water films from high to low concentration. Critical for phosphorus, which barely moves by mass flow.
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Roots grow toward nutrient-rich zones. Vital for trace elements in dry soils where other mechanisms slow down.
Here is the troubling part that most fertiliser bags will not tell you: when soil moisture drops below a certain threshold, diffusion effectively stops. Phosphorus, which is almost entirely dependent on diffusion for its short journey to the root surface, can become completely locked out even when soil phosphorus levels are technically adequate. We have tested the soil. We have applied the fertiliser. But the plant is still hungry. This is nutrient lockout, and it is far more common in rainfed systems than we admit.
“A plant in dry soil is like a man at a banquet with his hands tied. The food is right there. He simply cannot reach it.”
THE REAL WORLD CHALLANGE
Rainfed farming: where water and nutrition collide
Roughly 80% of the world’s farmland is rainfed — meaning it depends entirely on rainfall, with no supplemental irrigation.[3] In India, large portions of the central plateau, including Madhya Pradesh, Maharashtra, and Rajasthan, fall into this category. For these farmers, the relationship between water and nutrient uptake is not an academic question. It is a matter of survival.
The challenges are interconnected in ways that make them especially cruel. A dry spell hits during the critical grain-filling stage. The plant, stressed for water, reduces transpiration. Mass flow slows. Nutrients stall in the soil. At the same time, the plant’s root membranes — which actively pump certain ions inward using energy — become impaired because the plant is redirecting energy toward stress responses. The result is a triple penalty: less water, less nutrient transport, and impaired root absorption. The farmer who applied fertiliser faithfully sees thin ears, poor grain weight, and wonders what went wrong. The fertiliser did not fail. The water did.
To make things more complicated, excess water is just as damaging as a deficit. When heavy rain follows a long dry spell — a pattern that climate change is making increasingly common — nutrients that have accumulated near the soil surface can be rapidly leached downward, past the root zone, into groundwater. This is especially true for nitrate-nitrogen, which carries a negative charge and does not bind to soil particles the way phosphate does. One well-timed cloudburst can undo weeks of careful fertiliser management.
WHAT SMART FARMERS ARE DOING
Five strategies that actually work in rainfed systems
Synchronise fertiliser application with rainfall. In rainfed systems, we should apply fertiliser just before an expected rain event — not weeks before. If granules sit in dry soil for long periods, losses from volatilisation and surface runoff increase significantly. Timing is everything.
Use split applications. Instead of applying the full recommended dose at sowing, we should split it into two or three smaller doses aligned with rainfall patterns. Research from ICRISAT shows that split nitrogen application in rainfed sorghum can improve nitrogen-use efficiency by 20–35% compared to a single basal dose.
Mulch to hold moisture at the nutrient-rich surface. Organic mulch — crop residue, dry leaves, sugarcane trash — dramatically reduces evaporation from the top 10 cm of soil, which is where most fertiliser is applied and most root activity occurs. In trials across dryland India, mulching has been shown to maintain soil moisture significantly higher than bare soil during dry spells, keeping nutrient dissolution active when it would otherwise shut down.
Practice conservation tillage. Minimum tillage or zero-till systems preserve soil structure, improve water infiltration, and reduce runoff. Healthy soil aggregates hold more water in the root zone, giving nutrients a longer window to dissolve and move. Tillage-disrupted soils, by contrast, crust over easily, repelling rain and accelerating evaporation.
Build soil organic matter. Every meaningful increase in soil organic matter raises the soil’s water-holding capacity. More water held means more water available for nutrient transport during dry periods. Incorporating farmyard manure, green manure crops, or compost does not just feed microbes — it builds the moisture infrastructure that makes all other fertiliser inputs work better.
FROM THE FIELD
Rainfed pulses and the ridge-furrow method
Pigeon pea and chickpea together account for a huge share of India’s protein supply, yet both are grown almost entirely without irrigation. According to ICRISAT, over 92% of the area under pulses in India is rainfed, and the low productivity of pulses is attributed not to any inherent weakness of the crop but to the moisture-stressed, low-input conditions of rainfed agriculture.
The puzzle is this: pulses carry nitrogen-fixing bacteria in their root nodules, so they should, in theory, partially feed themselves. But moisture stress disrupts nodule activity, and when rainfall is erratic, fixation slows or stops entirely. ICRISAT’s own field protocols address this directly: the broad bed-and-furrow system for chickpea and ridge-and-furrow for pigeon pea are recommended precisely because the raised bed improves aeration and nodulation, while the furrow collects and slowly infiltrates rainwater at the root zone. Research published in Agricultural Water Management (2023) confirms that ridge-and-furrow planting can increase water productivity of pulses by 20–40% compared to conventional flat sowing. That is not a small gain — it is the difference between a stressed crop and one that can fix atmospheric nitrogen through its nodules, effectively getting free fertiliser from the air above the field.
BRINGING IT HOME
Practical recommendations for the next season
The science is clear, and the stories from the field confirm it: water and nutrients are not two separate decisions on the farm management calendar — they are one decision. Before any fertiliser decision, we should assess the soil’s water-holding capacity. Sandy soils hold less water and need more frequent, smaller applications. Clay soils hold more but drain slowly, risking waterlogging and nutrient leaching in one go. Wherever micro-irrigation is even partially feasible, it pays: drip irrigation places water and nutrients directly at the root zone, virtually eliminating both leaching loss and the evaporation that defeats surface-applied fertigation.[10]
We should look at the crop’s growth stages and match nutrient applications to the stages when demand is highest: vegetative growth for nitrogen, early root establishment for phosphorus, grain filling for potassium. Those windows are also the windows when soil moisture must be adequate for uptake. And we should keep investing in soil organic matter. It is not glamorous, and the results take two or three seasons to show up clearly — but it is the single most reliable insurance policy against both drought and nutrient loss.
We started this article with a chef and an empty tap. We end with a more hopeful image: a farmer who understands that water and nutrients are partners, not rivals for the crop’s attention. Managing one without the other is like trying to clap with one hand. When we bring them together — through timing, through conservation, through organic matter, through simple but effective water management — we give every fertiliser rupee the best possible chance to return a full harvest. The soil has the food. Let us make sure it also has the water to serve it.
References
ICRISAT. Rainfed Agriculture — Integrated Farm Management Practices. OAR@ICRISAT, Chapter 12 (Sreedevi & Wani). https://oar.icrisat.org/3619/1/Rainfed_Agriculture222-257.pdf
Rainfed Upland Ecosystems of Odisha. Project Completion Report (2011-2015)
https://oar.icrisat.org/8746/1/FInal%20%20Odisha%20Proj%20Comp%20Rep%20Myer%20Mula.pdf