How often should I test soil for micronutrients?
Written by
Tina Carter
Reviewed by
Prof. Martin Thorne, Ph.D.Plants' need for micronutrients necessitates frequent soil testing to prevent hidden hunger. I test my blueberry fields every year because pH can change quickly in sandy soils, rendering iron unavailable. In row crops, like corn, I only test once every two to three years, unless the rotation scheme has changed, or there has been a liming event that would disrupt nutrient flows.
Annual Testing
- High-value crops: Berries, orchards, vineyards
- Trigger events: Heavy lime/sulfur applications
- Method: Grid sampling + tissue tests
2-3 Year Testing
- Field crops: Corn, soybeans, wheat
- Trigger events: Major yield drops
- Method: Zone sampling pre-planting
Adjusting soil pH essentially resets the clock on micronutrient availability. For example, liming acidic soil increases the availability of molybdenum but recognizes zinc. I added lime to my raspberry planting area, and the Zn concentrations dropped 40% in only 6 months! Annual soil testing has helped alleviate this problem, since pH and availability change annually. Always retest soil following any change in pH, typically within 8 months.
Shifting crop rotations impact demand. For example, growing alfalfa (boron-hungry crop) followed by corn (zinc-dependent crop) requires new tests. In this scenario, a client had sufficient boron before switching but had extremely low zinc levels after rotation tests (levels undetected previously, then immediately after the rotation). Keep testing extra in mind during major agronomic management changes.
Read the full article: 7 Essential Micronutrients for Plants: Complete Guide
