How Soil Tests Help Microbes and Affect BRIX

In the last post, we covered how to care for your soil microbes so they can in turn care for your plants.

Quick recap: When we support soil microbes, they become more effective at making nutrients available to plants. Those well-nourished plants photosynthesize more efficiently and send more sugars to their roots, feeding the microbes and allowing them to continue their important work. The more efficient this little symbiotic relationship is, the higher your BRIX levels will climb and the more resilient and resistant your dahlias will be.

One thing that can throw off this delicate cycle are imbalances of nutrients in the soil—too much of one thing or the absence of another. In order to know if you have an imbalance of nutrients in your soil, you need a soil test. I know, I know. But hear me out. As a gardener, I ignored this advice for several years, thinking getting a soil test would be a hassle and expensive. So each season, I just kept adding what I thought were helpful soil amendments and spot-treating plant problems as they came up. When I finally sent a soil sample off for analysis, I was honestly shocked to see that by adding things willy-nilly, I had actually been widening the gaps in nutrient levels instead of fixing them. My "plant problems" now made sense. Let me put your mind at ease. Getting a soil test is easier than you might think and it's just not that expensive for such priceless information (ours are $35 here in Cache Valley and at our extension office in Georgia they were $15). I'mmma walk you through it.

How to Get a Soil Test from Your Local County Extension Office

First, figure out where nearest local county extension office is.

When I typed "local county extension soil testing" into my search bar the following website came right up from my local university—Utah State. You can either print the soil submission form online, or if you'd rather, you can visit the extension office in person and they'll give you the submission form you need.

The front page of Utah State University's soil testing website.

Every extension office will give you clear, step-by-step instructions for collecting your soil sample.

The basics? You’ll dig down about 6–12 inches and add a scoop of soil to a clean bucket from several spots in the area you want tested. When I tested the soil on our new farm, I pulled samples from four random places across the field. Mixing those together gives you a much better picture of what’s really going on underground, rather than relying on just one spot. Mix those samples well within that bucket then bag up 2 cups (or whatever your county form says) of that well-mixed soil . This is your soil sample you'll either mail in or drop off with your submission form at the county extension office.

Soil Test Options To Choose From

County extension offices should have a variety of testing options for your garden soil.

The basic tests offered for home gardeners at my local county extension office in Cache Valley.

Trust me when I say you want to know what's going on with the micronutrients in your soil, even if it costs a little extra.

You may have noticed that your soil's nitrogen levels aren't included in either test. A test for available nitrogen requires a little variation to the way the soil's collected and is an additional $10 here in Cache Valley. If you have the option, do it! The best part after all that work of sending it in? You’ll get a detailed breakdown of your soil’s current levels of key nutrients, along with clear recommendations for what to add—and how much—to correct any imbalances.

Side note: if you’re an organic grower, you can usually note that on the form and they’ll tailor the recommendations to organic-approved amendments. And one more side note: you'll want to send in your soil sample in the fall or early spring so any amendments you need to add have time to mellow and integrate into the soil. I do a soil test every year as a commercial grower, but you can get away with only testing an area once every couple years.

Why Soil Tests Matter to Microbes and Therefore to Your Plants

It’s not much of a stretch to say that when your soil has the key nutrients in balanced amounts, both microbes and plants are going to thrive. Here’s why.

• Soil tests shows you whether nutrients are out of balance, not just missing. Too much of certain nutrients can be just as harmful to microbes as not enough. When nutrients are balanced, microbes can do a better job of cycling nutrients.

• Well-nourished plants grown in nutrient-rich soil photosynthesize better and release more sugars through their roots. As we've talked about, sugars are the primary food source for many beneficial microbes, so better plant nutrition directly boosts microbial activity, which will result in better plant nutrition...you get the idea.

• Soil test results also keep you from adding unnecessary amendments and fertilizers (your wallet will thank you). Extra fertilizers and amendments can interfere with their ability to cycle nutrients on their own.

To boil it all down, soil tests help you create balanced soil, balanced soil supports active microbes, and active microbes help drive higher BRIX which means you'll have healthier plants. Boom.

It Takes Time

Just like most good things, a thriving microbial community in nutrient-rich soil doesn’t happen overnight. Try as we might, there’s no quick fix for reaching that 12+ BRIX level.

That said, there are ways to temporarily boost BRIX levels while we work towards a consistent 12+. In the next blog post, I’ll share the recipe for a more immediate BRIX-boosting foliar spray / soil drench that we’ve had a lot of success with on our farm.