Soil Testing and Enhanced Crop Health — Complete Guide

Fertile soil — rich with minerals, abundant microbial life, humus, and organic matter — produces vibrant plants and healthy crops. The availability of nutrients varies with each growing season due to factors like crop uptake, past fertilizer applications, leaching, denitrification, and more. Rather than speculate about the specific nutrients crops might need in a given year, growers can evaluate soil nutrient composition prior to the season using a soil testing kit. This allows them to base their fertility management decisions on quantifiable results.

Soil testing results, used in combination with a grower’s production goals, can lead to optimal use of a field’s nutrient profile and help growers achieve high yields and the best possible economic outcomes in a growing season.

How Soil Testing Benefits Growers

Regular soil testing provides essential data that helps growers optimize soil fertility, improve crop health, and maximize yields. By analyzing soil nutrient levels, farmers can make informed decisions about fertilizer applications, soil amendments, and long-term soil management.

Soil testing enables growers to:

• Make data-driven soil fertility management decisions – Base fertilizer application on actual soil test results rather than assumptions.
• Identify nutrient deficiencies early – Detect imbalances in essential nutrients like nitrogen, phosphorus, potassium (NPK), and micronutrients before they affect plant growth.
• Optimize nutrient applications – Fine-tune fertilizer programs with site-specific and crop-specific recommendations to improve nutrient efficiency.
• Select the right soil amendments – Apply organic matter, lime, gypsum, or bio-stimulants that enhance soil structure and nutrient availability.
• Maximize crop yields and plant health – Ensure crops receive the necessary nutrients for optimal growth, stronger root development, and higher productivity.
• Increase return on investment (ROI) – Reduce costs by applying the right soil nutrients and fertilizers in the correct amounts, avoiding waste.
• Monitor and improve long-term soil health – Track changes in soil pH, organic matter, and nutrient levels over time to support sustainable farming practices.

By incorporating regular soil testing into their crop management strategy, growers can make precision agriculture decisions that lead to higher crop yields, improved soil fertility, and long-term agricultural success.

Before Soil Testing

Prior to soil testing, choose a lab analysis that targets primary concerns such as deficiencies of plant-available nutrients like nitrogen, phosphorus, potassium, and micronutrients. Analyses that target properties such as pH, cation exchange capacity, texture, organic matter, estimated nitrogen release, and soluble salts can help growers address specific soil issues. The results of these targeted tests provide a roadmap to use throughout the growing season.

How to Sample Soil for Testing

Step one is to start digging. Using a clean shovel or probe, collect soil from a depth of 0 to 6 inches and place it in a sealable bucket. Collect a deeper sample, 6 to 12 inches down, to evaluate the subsoil. Then, following any directions provided by the lab, place the samples in labeled containers to send for analysis. Gathering multiple samples can help evaluate conditions across a field and the overall health of the soil.

When to Conduct Soil Testing

Pre-season nutrient analysis is key for adequately preparing fields prior to planting. These analyses can be used to help determine how much fertilizer is needed throughout the season to support plant vitality, production goals, and longer-term soil health.

Post-harvest soil tests allow growers to develop a nutrient management plan for the winter season that may include planting cover crops or applying fertilizer in the fall.

Analyzing samples at the same time each year is important for establishing a consistent dataset. Keeping annual records of nutrient levels and comparing soil composition and crop performance year after year can help growers optimize crop performance over time.

Key Nutrients Evaluated in Soil Tests

Routine soil testing helps growers assess essential nutrients like nitrogen (N), phosphorus ℗, and potassium (K) to maintain soil fertility and maximize crop yields.

• Nitrogen (N) testing is crucial for evaluating soil nitrogen levels, which directly impact plant growth, chlorophyll production, and photosynthesis. Sufficient nitrogen ensures healthy crops and high yields.
• Phosphorus ℗ testing identifies deficiencies that can hinder root development, energy transfer, and plant growth. Low phosphorus levels in agricultural soil often require amendments to support crop production.
• Potassium (K) analysis determines the soil’s ability to regulate water absorption, nutrient transport, and enzyme activation, all essential for photosynthesis and plant vitality.

By integrating soil nutrient testing into their management strategy, growers can enhance soil health, optimize fertilizer applications, and improve crop productivity.

Understanding Various Soil Test Types and Procedures

Soil tests vary in scope and focus, each offering insight into specific aspects of soil health and fertility. Choosing the right type of analysis depends on your goals — whether it’s maximizing yield, correcting deficiencies, or tracking long-term soil trends.

Common Soil Test Types:

• Basic Nutrient Analysis: Measures levels of nitrogen (N), phosphorus ℗, and potassium (K), as well as micronutrients such as zinc, boron, and magnesium. This is foundational for seasonal fertility planning. 
• Soil pH and Cation Exchange Capacity (CEC): pH indicates soil acidity/​alkalinity, which affects nutrient availability. CEC helps assess the soil’s ability to hold nutrients. 
• Organic Matter & Texture: These tests measure organic content and classify the soil as sandy, loamy, or clay — helping determine water retention and nutrient-holding capacity. 
• Soluble Salts (Salinity Testing): Assesses salt concentration in soil, which can affect seed germination and root function, especially in arid regions or irrigated fields. 
• Contamination Testing: Optional but important in areas with industrial runoff or known heavy metal exposure. These assess the presence of contaminants like lead, cadmium, and arsenic.

Each test provides specific metrics — like nitrate (NO₃⁻) levels, phosphorus in ppm (parts per million), or electrical conductivity for salinity — that allow for precision management throughout the season .

Sampling Methods

Accurate soil testing starts with proper sampling. The method used can significantly impact the reliability and usefulness of results.

Standard Sampling Instructions (from the blog):

• Use a clean shovel or probe 
• Collect soil at 0 – 6 inches for topsoil, and 6 – 12 inches for subsoil 
• Take multiple samples from different parts of the field to form a composite sample

• Grid Sampling: Divide the field into equal-sized grids (e.g., 1‑acre blocks) and collect samples from each. This provides detailed spatial nutrient mapping and is useful for variable-rate fertilization. 
• Zone Sampling: Group areas of a field based on soil type, yield history, or topography. Fewer samples are needed than grid sampling, and it’s more cost-effective for fields with known variability.

Tailoring Methods to Soil Type:

• Sandy Soils: Require more frequent testing due to higher leaching and nutrient loss. 
• Loamy Soils: Offer more consistent nutrient profiles — zone sampling often works well. 
• Clay Soils: Can hold nutrients longer but may have drainage issues; sample at multiple depths to assess compaction and moisture retention.

When and How Often to Collect Soil Samples

The timing and frequency of soil sampling should align with the crop rotation cycle, soil type, and overall field management strategy.

When to Sample:

• Pre-Season: Best time to establish a baseline nutrient profile and plan fertilizer applications. Test before planting in spring. 
• Post-Harvest: Ideal for understanding nutrient depletion after crop removal and for planning fall amendments or cover crop strategies.

How Often to Sample:

• Annually: Recommended for high-value crops or fields with variable conditions. Testing at the same time each year helps track changes. 
• Every 2 – 3 Years: Sufficient for fields with consistent management, stable soil types, and low variability. 
• More Frequently: Needed in sandy soils or in fields under intense cultivation, irrigation, or new fertility programs.

By maintaining consistent records over time, growers can spot trends, prevent deficiencies, and fine-tune input use — supporting both productivity and sustainability.

Using Soil Test Data for Better Soil Health

Nutrient management is one of four strategies recommended by Purdue Extension for improving soil health, with soil testing serving as a fundamental component of a well-designed nutrient management plan. Using the data provided by scientific analyses, growers are able to more accurately adjust the nutrient profile to enhance plant health or — if nutrient levels are sufficient — choose to minimize fertilizer application, reducing costs and protecting natural resources.

Soil testing provides a quantifiable way to inform crop management decisions and maximize crop productivity. With the insight provided, growers are able to gain a clear picture of overall nutrient composition and leverage that to create healthier, more productive soils.

Soil testing is just the first step in unlocking your land’s full potential. With Sound AG’s innovative soil health solutions, you can enhance nutrient availability, improve crop resilience, and maximize yields.

Contact us to explore how Sound Agriculture can take your soil management to the next level.