The Hidden Costs of Soil pH Imbalance and Nutrient Stratification

Managing soil chemistry is like tuning an engine; get it right, and everything runs smoothly. Yet often, two key soil challenges—pH imbalance and nutrient stratification—can quietly undermine fertilizer efficiency, reducing crop yields and cutting into farm profitability. Understanding these issues and taking proactive steps to correct them can significantly improve nutrient use efficiency (NUE) and return on investment (ROI). 

The Price of Soil pH Imbalance

Soil pH is much more than just a number—it’s a vital factor that affects nutrient availability, microbial health, and overall plant vigor. While many of us are familiar with its impact on phosphorus, the fact is, the availability of other nutrients—such as potassium, iron, zinc, and manganese—are also influenced by pH.  A low pH can trigger aluminum toxicity and reduce microbial activity, while a high pH can lock up key micronutrients, limiting crop health. 

When we apply that to the field, Eastern U.S. soils tend to be more acidic, for example, requiring regular lime applications, while Western U.S. soils are more alkaline, often needing acidifying fertilizers to improve nutrient uptake. Crops also have varying pH tolerances; corn thrives in slightly acidic conditions, while crops like alfalfa and barley experience yield losses as pH drops.  Soil pH can even vary significantly through different layers of the soil. These variations depend on factors such as land management practices, crop type, irrigation methods, and fertilization history. 

When pH drifts too high or too low, certain nutrients become locked in the soil, making them unavailable to plants. For example: 

• Low pH (<6.0): Phosphorus, calcium, and magnesium become less available, while toxic elements like aluminum can hinder root growth. 

• High pH (>7.5): Micronutrients like zinc, manganese, and iron become less accessible, limiting plant development. 

This inefficiency forces us to apply more fertilizers than necessary, increasing costs without a proportional yield benefit. Correcting soil pH through amendments such as lime (for acidic soils) or acidifying fertilizers (for alkaline soils) helps unlock nutrients and ensures that every dollar you spend on fertilizer goes further.  

The Hidden Challenge of Nutrient Stratification: The “Layer Cake” Problem

While soil pH gets a lot of attention, nutrient stratification is an equally important—but often overlooked—barrier to nutrient efficiency. Just as pH can lock up nutrients, another hidden challenge—nutrient stratification—can keep your crops from accessing those nutrients. Nutrient availability often differs greatly between the surface and deeper layers, particularly in no-till systems or fields with surface-applied fertilizers. In many fields, a ‘layer cake’ effect forms: the soil near the surface is rich in nutrients, while the deeper layers remain nutrient-poor and plant roots struggle to access them. This stratification can limit nutrient uptake, especially during dry conditions when roots extend deeper in search of moisture. 

Consider phosphorus, a relatively immobile nutrient. When applied without incorporation, it tends to accumulate near the soil surface. If crop roots can’t reach these concentrated nutrients due to stratification, plant uptake declines, reducing yield potential. Similarly, potassium, while slightly more mobile than phosphorus, can also become stratified, leading to inconsistent nutrient availability. 

 No-till practices offer many agronomic benefits—conserving water, supporting healthy microbial populations, and enhancing nutrient cycling. However, nutrient stratification can develop after continuous no-till, especially near the soil surface where no mixing occurs. This layering can limit nutrient availability in the root zone. To address this, practices like deep banding or incorporating fertilizers into the soil profile can help ensure nutrients are placed where roots can access them. Today, in precision agriculture, we aren’t just thinking about managing zones—we’re thinking about managing depth and understanding how nutrients move (or don’t) within the soil profile. 

  Phosphorus Use Efficiency, pH, and Stratification

Soil pH has a major influence on phosphorus availability. At high pH levels (above 7), phosphorus tends to bind with calcium, while in more acidic soils, it becomes fixed by iron and aluminum—both scenarios limiting its availability to crops. Micronutrient availability, including copper, manganese, zinc, and iron, is also pH-dependent. Complicating this further, irrigation water across North America often has a high pH and elevated calcium content, which can exacerbate phosphorus tie-up, even in acidic soils. This highlights the need for pH management strategies not just in soil but in fertigation systems as well. 

Soil stratification adds another layer of complexity. Nutrients and pH can vary significantly by depth due to natural soil processes, climatic conditions, and repeated fertilizer applications in specific zones. Over time, this can lead to nutrient stratification that restricts uptake and undermines root zone health. Managing stratification means thinking beyond surface applications—targeting different soil layers and using tools like acidifying fertilizers (e.g., Agrolution pHLow or Nova PeKacid) where needed to adjust pH and improve nutrient availability in the root zone. 

Research backs this up: 

• In an Oregon pear orchard, applying acidifying fertilizer Agrolution pHLow 6-31-31 led to a 8875 lb/ac increase, and a near doubling of soil P and K availability with modest application rates, simply by lowering the soil pH slightly. 

• In potatoes, Agrolution pHLow was shown to be 14 times more efficient in phosphorus uptake compared to standard APP. 

• In strawberries, Nova PeKacid improved P, Fe, B, and Mn absorption, and resulted in a 13.9% yield increase across 21 harvests. 

• In potatoes, when BIOZ Diamond (microbial food source) was paired with acidifying fertilizer Agrolution pHlow, we saw further increases in PUE and yield on Manistee potatoes 

Creating the right conditions in the rhizosphere—where roots interact with soil—is critical. That means balancing soil pH, selecting appropriate fertilizers, and fostering microbial activity to unlock nutrients and maximize phosphorus efficiency. 

  Maximizing Nutrient Use Efficiency (NUE) for ROI

The best way to tackle soil pH imbalances and nutrient stratification? Proactive soil management. Regular soil testing is your first line of defense—knowing exactly where your soil stands allows you to tailor your nutrient management strategy and maximize return on investment (ROI). By understanding your soil’s unique characteristics, you can make smarter decisions about when and where to apply fertilizers, ensuring that your investment goes further. 

Here are a few key strategies we recommend to improve nutrient use efficiency: 

• Regular soil testing: To accurately monitor pH and nutrient distribution, go beyond standard topsoil testing. Deeper soil samples can reveal unexpected subsoil acidity or nutrient stratification, enabling more precise pH correction and fertilizer application. Trials in Kentucky showed that deeper soil sampling helped identify subsoil acidity, allowing for better management. By getting a clearer picture of your soil, you can avoid overspending on inputs while ensuring optimal nutrient availability. 

• Targeted fertilizer placement: Adjusting the timing and placement of fertilizer applications can help mitigate nutrient stratification. Banding phosphorus and potassium deeper in the root zone or using liquid applications via fertigation can improve nutrient uptake. Targeted placement reduces waste, boosts efficiency, and can lead to higher yields with lower input costs. 

• Using acidifying fertilizers: For high-pH soils, products like Nova PeKacid and Agrolution pHLow modify the soil’s pH, improving phosphorus solubility and nutrient availability. These acidifying fertilizers help unlock the potential of your soil and your applied fertilizers, providing a longer-lasting benefit to nutrient uptake and improving overall fertilizer efficiency. 

• Cover crop strategies: Implementing deep-rooted cover crops, such as oilseed radish and buckwheat, can help prevent stratification by capturing and redistributing nutrients like phosphorus. While the benefits of cover crops may take a few seasons to fully manifest, they are an investment in your soil’s future health and long-term productivity. These crops also enhance soil structure and water infiltration, making it easier for crops to access deeper layers of nutrients. 

• Biological inputs for soil health: Maintaining a balanced microbial population is vital for nutrient cycling and root development. Products like BIOZ Diamond support beneficial bacteria and fungi, boosting overall soil health and nutrient efficiency. Not only are there long-term soil health benefits, but trials have shown a significant increase in yield. 

Knowing growers have limited time and money, what the research indicates is that small adjustments in soil management today lead to significant long-term gains in farm profitability and productivity.  

Supporting Growers’ Goals with Soil Management

Soil chemistry may not always be top of mind, but it’s the cornerstone of successful crop production—and it’s an area where we can make a real difference. Growers already have enough on their plate, which is why leveraging our expertise in soil management to support their goals can drive measurable improvements to the bottom line. From my experience in the field, I’ve seen how a small investment in soil health today can yield significant returns—not only in the current season but for years to come. 

Soil is often underestimated, yet it can hold the key to unlocking higher yields and greater profitability. Don’t wait for crop problems to arise—take action now. Start with a soil test to uncover a field’s hidden challenges, optimize your fertilizer strategy, and set yourself up for a more successful growing season ahead.