Soil Testing: Taking the pulse underground

Soil Testing: Taking the pulse underground

Our soil is the foundation of everything we do at Frog Hollow Farm. As regenerative farmers, we are constantly working to foster soil health to ensure it is vital and alive. Our regular – some might say zealous – care of the soil contributes to the flavor and deliciousness of our fruit, harvest after harvest. It’s also essential to the long-term viability of our farm and the health of the ecosystem we are a part of. 

We take steps throughout the year to foster soil health: 

  • We keep the ground covered with wild grasses, forbs, and selected cover crops that protect the soil’s structure and foster microbial life.
  • We spread thousands of tons of compost every year, which adds life and nutrients to the soil. 

Just as important are the things we DON’T do:

  • We don’t disturb the soil mechanically with tillage.
  • We don’t disturb the soil chemically with synthetic amendments.

Annual testing for a holistic picture

Soil testing is part of our stewardship. We test our soil in the fall and winter after the harvest and when life on the farm slows down. We’re looking for essential nutrients in our soil that are available for the trees to take up. 

We don’t sample the entire farm every year. Instead, we cycle through different orchards and that gives us a holistic picture over time. We start with a soil probe (a hollow tube) and a few buckets. Tree roots extend 10 to 30 centimeters. We plunge the tube 0 to 10 centimeters and 10 to 30 centimeters into the soil. We put the soil in buckets, let it dry for a few days, and then we send it to an agricultural lab for testing. 

Soil testing gives us an underground snapshot:

  • We analyze the levels of essential nutrients that are available to the trees at different depths.
  • We plan how we’ll amend the soil to bring it back into balance and keep it vital and alive. 

Here’s a summary of what we look for with our soil tests:

  • Levels of potassium. Fruit trees use potassium more than any other nutrient. Potassium helps trees distribute water through their root systems. It also helps trees form their fruit, and it contributes to fruit sugar, color, and size. 
  • Levels of nitrogen. Trees absorb nitrogen to help them form leaves and shoots. Balance is the key. If trees don’t have enough nitrogen in the soil, they won’t produce enough leaves or fruit. If they get too much nitrogen, the fruit will be large and tasteless. Pests and many tree diseases thrive on nitrogen, which is another reason we monitor this nutrient very carefully.  
  • Levels of calcium. Calcium helps fruit trees maintain their trunk, branches, leaves and shoots, and resist the diseases that harm their fruit. The right amount of calcium allows the fruit to hang on the tree longer and build up its sugar, or brix levels. Farmer Al tests for high brix before he and the farm crew start picking.
  • Levels of phosphorus. Trees use this nutrient in many different ways. It helps the tree convert the sun’s energy into sugar to promote healthy wood and roots.

We amend the soil with such nutrients every year, but the levels we find through soil testing guide our plans. 

An infinite web

We are not being overly dramatic when we say that soil chemistry and microbiology are some of the most engaging teachers on the planet! The more you learn about soil, the more there is to discover. Testing helps us find the insight we need to navigate complex interactions and relationships to nurture a balanced and healthy ecosystem. 

We’ve skimmed the surface here, and we’ll be diving into other aspects of soil health in the weeks to come. Stay tuned!

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