How To Manage Crop Nutrition After El Niño Heavy Rainfall

When El Niño Brings Too Much Water

El Niño is often associated with drought but many agricultural regions experience the opposite: intense and prolonged rainfalls. For crop nutrition, this creates a fundamentally different problem. Under drought, nutrients remain in the soil but become unavailable. Under excessive rainfall, nutrients are often physically removed from the system or transformed into unavailable forms. In both cases, the outcome is the same: reduced nutrient use efficiency. But the mechanisms, and therefore the solutions, are entirely different. Growers often wonder whether nutrients have been lost and whether fertilizer programs should be adjusted. The answer depends on how the soil, crop, and nutrient supply were affected.

What Heavy Rain Does to Soil Nutrients

Excess water changes soil from a nutrient reservoir into a system experiencing continuous losses.

Three key processes dominate:

• Leaching – mobile nutrients such as nitrate are dissolved and transported downward beyond the root zone with percolating water
• Denitrification – in saturated soils, lack of oxygen triggers microbial conversion of nitrate into gaseous nitrogen, which is permanently lost to the atmosphere
• Runoff and erosion – nutrients and soil particles are physically removed from the field during intense rainfall events

These processes can act simultaneously, making nutrient losses both rapid and difficult to predict. Nitrogen is the most affected nutrient, particularly in nitrate form, which is not retained by soil particles and is highly vulnerable to both leaching and denitrification.

Waterlogging: When Roots Stop Working

Beyond nutrient loss, heavy rainfall also affects the plant directly. When soils become saturated, oxygen levels drop rapidly. This creates anaerobic conditions that:

• reduce root respiration
• limit nutrient uptake
• impair overall plant metabolism

Waterlogging stress can lead to deficiencies even when nutrients are still present, particularly for elements such as potassium and calcium, due to impaired transport within the plant. This dual effect of nutrient loss plus reduced uptake capacity is what makes heavy rainfall so damaging to nutrient use efficiency.

How To Recover a Cropping System After Heavy Rainfall

From the standpoint of plant nutrition, the challenge after heavy rainfall is twofold:

1. Protect nutrients from further losses
2. Restore plant capacity to absorb and use them

Applying more fertilizer without addressing these two aspects can lead to repeated inefficiencies and further losses.

Stabilizing Nutrient Supply: Why CRFs and SRFs Are Crucial

This is where controlled-release fertilizers (CRFs) and slow-release fertilizers (SRFs) become central tools. Unlike conventional fertilizers that release nutrients rapidly, CRFs:

• encase nutrients within a protective coating
• release them gradually through diffusion
• limit immediate exposure of nutrients to excess water

This provides two critical advantages under heavy rainfall:

• Reduced leaching losses – nutrients are not fully available at once, reducing the amount that can be washed away.
• Improved synchronization with crop demand – nutrients remain available over a longer period, even after rainfall ends, when fields are often waterlogged and inaccessible for mechanization.

Research and field experience show that CRFs can significantly reduce nitrogen losses compared to conventional fertilizers, particularly in high rainfall conditions. In practical terms, CRFs act as a nutrient buffer, maintaining availability when conventional fertilizers would already be lost.

Rebuilding Nutrition Without Losing More

Once conditions stabilize, fertilization must be approached carefully. Large corrective applications carry a high risk of further loss, especially if weather remains unstable.

Instead, a more effective strategy includes:

• gradual nutrient reintroduction
• split applications aligned with crop recovery
• combining immediate and protected nutrient sources

How Foliar Nutrition Supports Recovery

Foliar applications are an effective solution for correcting nutrient deficiencies when field remains waterlogged after heavy rainfall. Under these conditions, soil applications are often impractical due to soil compaction and limited field access. During this period, foliar nutrition provides a practical solution by:

• bypassing the soil
• delivering nutrients quickly and directly to the plant
• maintaining metabolic activity during recovery

It serves as a bridge until root function and soil conditions return to normal. ICL offers several product ranges designed for foliar feeding such as Agroleaf and Nutrivant which are specifically developed to maximize nutrient uptake under challenging conditions. These products combine fully soluble macro- and micronutrients with advanced technologies that improve leaf coverage, adhesion, and penetration.

Restoring Root and Soil Function

Even with nutrients available, the uptake cannot resume until root systems become active again.

Biostimulants such as BEOZ® Opal, which contains fulvic acids and metabolite technology, are designed to

• stimulate root regeneration
• enhance nutrient uptake processes
• improve nutrient retention

At the same time, humic-based products such as Nova Humic NPK contribute to rebuilding soil structure and nutrient-holding capacity, supporting longer-term recovery. NOVA HUMIC NPK contains humic substances that are naturally occurring organic compounds formed during the decomposition of plant and microbial residues. Humic acids have a complex structure, and their main effect is on the colloidal structure of the soil and its ability to absorb minerals and efficiently transfer them to plants during recovery.

Restoring Balanced Nutrition

Excessive rainfall can influence the availability and movement of multiple nutrients in the soil, not just nitrogen. As crops recover and resume active growth, maintaining a balanced supply of essential nutrients becomes increasingly important.

Polysulphate® provides potassium, sulfur, calcium, and magnesium in sulfate form and releases these nutrients gradually over time. This can help support balanced nutrition as crops return to active growth following periods of excessive rainfall. Additionally, the nutrients in Polysulphate® promote better root development, as observed in multiple pot and field trial done globally.

Conclusion

El Niño seasons often include alternating periods of excessive rainfall and dry weather, that destabilizes the entire nutrient cycle. From an agronomic perspective, the priority is not simply replacing lost nutrients, but protecting them from further losses and restoring their uptake by plant to maintain a sufficient nutrient use efficiency.

This requires:

• minimizing further losses with protected technologies (CRFs, SRFs)
• boosting plant uptake capacity
• reintroducing nutrients in a controlled, precise manner

By combining stabilized nutrient sources, precision delivery, and plant-supportive solutions, growers can regain control over nutrient availability and uptake, even under highly variable and challenging weather conditions.