How to Improve Your Soil Sample Analysis
Soil Analysis Provides Key Insights
Soil testing should be an integral part of every crop and nutrient management program. Whether you use grid, zone or another regimen (no composite samples!), a good soil analysis provides key insight into the hidden, perhaps mysterious, world that gives the crop a firm foundation to survive and thrive. As part of my interactions with growers, agronomists and consultants, I find that the information available is often incomplete, dated, or both.
At a minimum, I think that a good sample analysis should contain information regarding:
- Organic matter
- Soil pH (either water or salt pH, depending on circumstances)
- Buffer pH, if soil pH is below a specified threshold, often 6.6
- Cation Exchange Capacity (CEC)
- Phosphorus (P1), with extractant method identified
- Potassium (K)
- Parts per million and base saturation percentages for cations (hydrogen (H), calcium (Ca), magnesium (Mg), K, sodium (Na))
Increasing Concerns Around Sodium
Sodium (Na) is a nutrient that has not been a large concern in Midwestern crop production. However, I am noticing a trend of increasing concerns with sodium, particularly in areas that utilize liquid manure sources, have challenges with good irrigation water quality, as well as sodic soils.
Sodium’s negative effect on soil tilth and related poor plant growth is well documented but has not been included on many soil tests previously. I would recommend adding it to the soil test package you are utilizing, if not already included.
Evaluate Soil Sampling Frequency and Data Collected
The frequency of soil testing is less of an issue as many growers sample every two years. I think this is a good tactic to consider, as it gives a good basis for understanding current levels and supports looking at multi-year trends. It also allows for flexibility if sampling is delayed due to weather.
Of these two areas (analysis and frequency), I feel that the analysis area should be scrutinized more specifically. The labor and time required for collecting samples for a basic or comprehensive soil test are identical, usually differing only in cost of the analysis chosen. The knowledge gained however, can be greatly different and instrumental in deciphering the clues that are often overlooked from a lack of awareness.