Why are the nutrient levels in my soil report high? (ASK Around)

Spring is the time of year for many of us to submit our anual soil samples for nutrient testing (unless you already tested your soil in the fall!), review the results and recommendations, and make a plan to add the right fertilizers or amendments to supplement any nutrient deficiencies that showed up. It's often straightforward to address a low nutrient test result: just add back what is missing! But what can you do when your results come back with nutrient levels through the roof? Can excessive soil nutrient levels be detrimental to your plants?

First, let's consider how your soil nutrient levels could have gotten so high in the first place. There are three main ways that nutrients come to be present in your soil and show up on your test results: natural minerals, soil amendments, and irrigation water. The physical stuff in your soil, besides organic matter, is essentially made up of rocks that have been broken down over time into tiny grains and mineral particles by forces such as water, wind, living creatures, and chemical reactions. Depending on the original types of rock your soil developed from, known as "parent material," the minerals in your soil might naturally be able to supply an abundance of certain elements to your plants. For example, soils that developed from limestone parent material tend to be high in calcium. Besides natural causes, your soil can develop excessive nutrient levels due to the amendments that are added--not just fertilizers but also water. Even if you don't use synthetic fertilizers, organic amendments such as compost can be extremely rich in nutrients. For example, adding household compost specifically to a garden or flower bed can concentrate nutrients in that area and cause elevated nutrient levels compared to the rest of your lawn. Even watering can add nutrients to the soil if you live in an area with hard water, meaning water with high levels of dissolved minerals such as magnesium and/or calcium. Severe hard water issues, such as mineral buildup building up and causing blockages in your sprinklers, can warant installing a water softener system to decrease the amount of minerals flowing through pipes and ending up in your soil.

So, are there any risks associated with high nutrient levels? Some micronutrients, such as boron and copper, are in fact toxic at high levels. Nutrient toxicities can cause severe plant health symptoms such as "burnt" leaf edges, chlorosis, and stunted growth. You can reach out to us for an ASK an Expert Consultation (available through the SoilKit365 platfrom) if you suspect you are dealing with this issue, especially since other issues such as plant diseases and nutrient deficiencies can also have similar symptoms (hence the importance of soil testing!) Another element that is detrimental in high quantities is sodium (Na), since it can disrupt soil structure and block root uptake of essential nutrients. However, for most nutrients, an abundance is simply a sign that fertilizing with that amendment is not needed, so you can avoid it. Check out our previous article for more details about when "balancing" soil nutrients is an important consideration.

What should you do if your nutrient levels come back high? If your plants aren't showing any negative effects, you might not need to do anything for now! Just keep in mind that prevention is the best medicine. By testing your soil anually and sticking to recommended fertilizer levels, you can avoid exacerbating excess nutrient levels and keep your soil at a healthy balance.