Interpreting and Applying Soil Fertility and Soil Health Lab Reports
Step 1: Considering the inherent and dynamic properties of the Andisol soil order:
- Kawiki series is an Andisol, new soil but highly weathered due to high rainfall from the local climate;
- It’s a new soil that acts like a old soil (like Kauai shores);
- Soil has a high SOM (due to the clay mineralogy)
- Reference: Soils of Hamakua with Dr. Deenik
Fertility of Kawiki series:
- Inherent property has low P
- Also low in K and Ca
- P is easily balanced by adding manure (chicken manure is the best source)
Step 2: Review the soil health score on your S(HEE)R lab report.
- To learn more about the process for determining the soil health score, please review the following publication:
- Measuring the immeasurable: A structural equation modeling approach to assessing soil health. Tai McClellan Maaz, Ronald H Heck, Christine Tallamy Glazer, Mitchell K Loo, Johanie Rivera Zayas, Aleric Krenz, Tanner Beckstrom, Susan E Crow, Jonathan L Deenik. https://pubmed.ncbi.nlm.nih.gov/36731562/
Step 3: Identify the nutrient ranges for your key crop:
- Hawaii is lacking nutrient ranges on a lot of crops, but FAO has good resources from the Ivory Coast and Tamarind that are on soils which are applicable since they are tropical, highly weathered soils.
- Pete Bunn with Crop Nutrient Solutions also has an excellent understanding of how to interpret soil and tissue lab reports and recommend appropriate nutrient ranges for many of our key crops.
Step 4: Identify the best sources for applying the recommended fertilizers and soil amendments.
- P is hard to correct with soluble fertlizer (e.g. Triple 16).
- Adding mature is a better solution.
Reference:
Dr. Deenik: Nutrient levels of various organic fertilizers and soil amendments.
Essential Nutrients for Plant Growth: Nutrient Functions and Deficiency Symptoms. R. Uchida.
Step 5: Use field observations of any nutrient imbalances in your crop and don’t rely solely on your lab reports.
Take Aways:
- Many scientist debate that improving soil organic matter (SOM) levels, improves overall soil health. We know this in theory but the science is still debatable.
- Improved soil fertility (balancing nutrients) has a positive correlation with crop productivity, soil health indicators do not have a positive correlation with crop productivity at this time.
- Increasing your total organic carbon (TOC) will increase other soil health indicators. However, increasing TOC requires time (e.g. years).
- The UH S(HEE)R lab is yet to determine the proper frequency to conduct soil health tests. It might be important to test every six months, annually or more.
- The lab is also trying to link management practices with improved soil health indicators on the lab report, but they have not completed this work and are still building their database.
- Producers can do their own trials by using their soil health reports as a baseline, adopting a new practice, and then testing again to see if indicators are improving after applying the new practice.
- Although UH S(HEE)R lab is not a commercial lab, producers who participated in this cohort and have an established baseline can send Christine Tallamy Glazer an email to request additional samples. The turn around time is likely two months.
- Testing TOC on a soil fertility test could be another indicator to use. This test can be completed with Pete Bunn. However, this indicator is not easy to improve in a short timeline which might be required for management and depending on your crop (annual crops often needing quicker lab information and decision-making than perennial crops).