How to Fix Nitrogen Toxicity

Change the Nutrients You’re Using

Plants need different nutrient levels at various stages of their life cycle. Seeds don’t need external nutrients because they have everything they need inside. Once seeds germinate, they enter their vegetative phase. Don’t let the name mislead you because plants in this phase are very active. During this time, they engage in photosynthesis and gather the elements they need for flowering and reproduction. In the vegetative phase, plants need a lot of nitrogen. It’s very hard to give plants too much nitrogen while they’re in this phase, although it can happen.

Once plants enter the flowering stage, their nutrient needs reduce. Many growers are not prepared for this change. They continue giving their plants the same fertilizer they did during the vegetative phase, resulting in excessive nitrogen levels, or nitrogen toxicity.

Garden supply stores have different fertilizers for every stage of plant growth. Complete plant foods have relatively high nitrogen levels for plants in the vegetative phase. Once they start fruiting or flowering, switch to a bloom- or flowering-style plant food. These have lower nitrogen levels, so they’re perfect for this new plant phase. Alternatively, try a cactus plant food. Even if you’re not growing cactus, the nutrient ratios should be just right for most flowering and fruiting plants.

It’s important to switch to a fertilizer with lower levels of nitrogen, rather than just withdrawing nitrogen supply altogether. Your plants still need nitrogen to grow, just not as much as you supplied. Switching your nutrients, rather than withdrawing them entirely, ensures your plants won’t start suffering from nitrogen deficiency.

Add Brown Organic Matter to Your Soil

Nitrogen toxicity usually occurs in natural soil. Adding brown organic matter to the soil can reverse the problem. Organisms that live in soil use a lot of nitrogen to break down this organic matter, thereby removing excess nitrogen from the soil. As the organic matter breaks down, nitrogen returns to the soil at a slower, more manageable pace. Autumn leaves, straw, and coconut coir are all ideal forms of brown organic matter. Add these products to mulch and let the soil’s organisms go to work.

Water Your Soil

You can also flush nitrogen out of the soil with frequent watering. Pure water with a neutral pH will not add additional nutrients to your soil. Alternatively, you could use a flushing agent. These commercial solutions are a mix of pure water and chemicals designed for effective nutrient flushing. Flush your soil daily until you notice your plants growing in a healthy fashion. This process should take roughly five days. However, it may take more or less time, depending on how nitrogen-rich your soil was and how long you left the problem before taking action.

It’s a good idea to add some coconut coir to your soil before you break out the watering can, though. While water can flush out the nitrogen, it can also encourage fungal diseases and root rot if it sticks around. Coconut coir enhances soil drainage and absorbs moisture, so roots stay hydrated but not too wet.

Ensure your Growing Solution Has a Suitable pH Level

Most plants grow well in environments with a pH level between 5.0 and 7.0. Overly acidic environments can burn the roots. Overly alkaline environments can be just as bad. They can inhibit the growth of beneficial microorganisms and become too rich in iron, aluminum, and manganese. When soil and other growing solutions don’t have a pH level within the ideal range, nitrogen toxicity can be an even bigger problem.

High levels of nitrogen make soils and growing solutions more acidic and inhospitable for many plants. Taking steps to return nitrogen levels to normal without addressing the pH level will have limited impact, as your plants cannot thrive in an overly acidic environment. Test your soil or growing solution’s pH level and make sure it’s suitable for the plants you’re growing. If it’s not, adjust the pH level until it’s appropriate for your plants. Continue testing and adjusting while you’re treating for nitrogen toxicity to make sure your plants end up with the right growing environment.

Change Your Nutrient Reservoir

While nitrogen toxicity is less common in hydroponic setups, it still occurs. If your hydroponic plants show the signs of nitrogen toxicity, change out their nutrient reservoir. Starting again with new water and nutrients is an easy way to bring your hydroponic plants back to equilibrium.

Treat the Symptoms With Soil Additives

Treating the symptoms of nitrogen toxicity can also put your plants on the right path. A little potassium can help your plants fruit and flower and make them more resistant to damage. Diluted seaweed solution also boosts plant resistance to pests, disease, and frost damage.

Help Your Plants Recover With Gradual Reintroduction

If you follow the steps above, your plants should start looking healthy again relatively soon. However, don’t think you’re out of the woods just yet. Looks can be deceiving. Even when plants look healthy again, they’ll probably take their time to regain their full strength again. Go easy on them during this recovery period and reintroduce nutrients at ¾ strength at first. Gradually reintroducing nutrients ensures you don’t trigger another case of nitrogen toxicity.

Prevention is always better than a cure, though. Pay attention to fertilizer instructions to make sure your plants get the nitrogen they need and no more. When mixing your own nutrient solution, use a TDS, PPM, and EC meter to get the blend right every time. Take these preventative measures and adapt your approach as your plant grows and you shouldn’t have to worry about nitrogen toxicity.