This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension. Finding profit in 2016 is something we are all focusing on. Seed, fertilizer, and chemical usually make up 30-40% of your production cost. We are going to focus on the foundation for wise fertilizer expenditures, soil sampling.
That’s right, before we talk about fertilizer, we need to discuss soil sampling and soil nutrient analysis. Spending a little money to get a more recent soil sample and analysis is worth it. There are various sampling methods including portions of a field less than 40 acres, management zones and grids that can improve your profitability by targeting fertilizer applications where they are needed most. However, before that we need to consider the answers to three basic questions.
- How often do I need to take a sample? I recommend sampling every 2 years to 4 years depending on soil test levels, fertilizer program, and land tenancy.
- What depth do I sample to? Soil test interpretations and fertilizer rate recommendations are be based on a standard sampling depth. Iowa State University, Kansas State University, South Dakota State University were developed at a 0-6” and University of Nebraska-Lincoln at 0-8”. Mark soil probes with v-shaped notch on the front to make it easy to see and control depth (see picture above).
- How many cores in a composite sample do I need? About 15 to 20 cores, with more needed in fields with a history of manure or banded fertilizer applications.
If you hire someone to soil sample, ask them these three questions. Sampling to deep is a great way to increase your phosphorus fertilizer cost without the added yield benefit. Creating a composite sample from only 6 to 8 cores means you are farther away from determining a good average. This means you are basing your fertilizer rate decision on an unreliable value.
For more information about soil sampling, call me at 727-2775 or visit our locally-focused website at croptechcafe.org. Know your crop, know your tech, know your bottom line. This is Dr. Nathan Mueller, your local agronomist for Nebraska Extension on KTIC radio.