Identifying Phosphorus Deficiency in Plants

In this edition of Sound Advice, we join Rich Haynes, Sales Agronomist with Sound, in a central Illinois corn field as he discusses the importance of phosphorus, its impact on yield, and how to spot phosphorus deficient plants. Phosphorus is one of three key plant macronutrients and is necessary for converting energy into nutrients and transferring the energy created during photosynthesis. Phosphorus deficiency can lead to impaired growth of both plants and roots, reduced yield, and delay maturity, making it essential that growers secure enough phosphorus for their crop. 

But phosphorus in the soil is also one of the most immobile and unavailable nutrients. The most common plant-available form of phosphorus forms strong bonds with soil particles and with elements like calcium, aluminum, and iron, making them inaccessible. Traditionally, microbes in the soil biome unlock small amounts of phosphorus in exchange for glucose from plants, but traditional farming practices that regularly disturb or neglect this biome have impacted the natural phosphorus cycle and the amount available to plants. 

Plant phosphorus deficiencies can lead to:

• Diminished root growth: Shallow, weak roots limit nutrient and water uptake.
• Stunted development: Plants grow slowly, appear smaller, and have fewer leaves.
• Purple or dark green leaves: Older leaves may turn purple due to stress, especially in cool conditions.
• Delayed maturity: Slower flowering and grain fill can lead to lower yields.
• Increased stress susceptibility: Weak plants are more prone to disease, drought, and poor nutrient absorption.

Soil testing and phosphorus-releasing products like SOURCE® can help ensure plants get the nutrients they need.

Phosphorus deficiency in plants is often caused by soil conditions that limit phosphorus availability, including:

• Soil binding: Phosphorus easily binds with calcium, aluminum, and iron, making it unavailable to plants.
• Cold or wet soils: Low temperatures and excessive moisture slow phosphorus uptake, especially early in the season.
• Soil pH imbalance: High or low pH levels affect phosphorus solubility, reducing plant access.
• Low organic matter: Soils lacking organic content have fewer microbes to help release phosphorus.
• Soil erosion and nutrient loss: Runoff and leaching remove phosphorus from the root zone.

Proper soil management, microbial solutions like SOURCE, and targeted fertilization can help unlock phosphorus and improve plant health.

To address phosphorus deficiencies and ensure plants have access to this critical nutrient, consider the following solutions:

• Soil Testing: Regular soil tests help identify phosphorus levels and guide precise fertilization.
• Phosphorus Fertilizers: Applying phosphorus-rich fertilizers, such as superphosphate or monoammonium phosphate (MAP), can quickly correct deficiencies.
• Microbial Inoculants: Products like SOURCE use soil microbes to release bound phosphorus, improving availability to plants.
• Adjust Soil pH: Maintaining a balanced pH (6.0 – 7.0) improves phosphorus solubility, making it easier for plants to absorb.
• Increase Organic Matter: Adding compost or cover crops can enhance soil structure and microbial activity, aiding phosphorus cycling.

Implementing these strategies ensures plants have the phosphorus they need to grow and thrive.