Where do SoilKit nitrogen recommendations come from?

Nitrogen: one of the most critical elements for soil fertility and plant growth, but it’s not measured during routine soil testing. We test for the other two soil macronutrients, potassium and phosphorus, along with many micronutrients… so why not nitrogen? And with no soil data, where do the recommendations in SoilKit’s test reports come from?

Based the large yearly nitrogen requirement for most lawns, farms, and gardens alike, you might expect nitrogen testing to be helpful in calculating how much fertilizer needs to be applied. However, soil nitrogen isn’t so easy to pin down. It’s found in various forms, such as nitrate and ammonia, and it’s in constant flux; it converts from one form to another, leaches from the soil with rainwater, and releases into the atmosphere in gaseous forms. Scientists call it the nitrogen cycle: the movement and exchange of nitrogen throughout the whole ecosystem through different chemical and biological processes. The activity of this natural cycle causes the amount of nitrogen in soil to change constantly, especially with the seasons of the year and weather patterns. Because of nitrogen’s volatility, a single test isn’t very helpful in determining how much nitrogen is present in the soil and accessible to plants. It’s so variable that a low test result could turn into a high one or vice versa within a short period of time—with changes even happening in transit between digging a soil sample and analyzing it in the lab!

Chemical and biological pathways for nitrogen movement within and around the soil...it might seem like a lot, but in reality there are many more! Image attribution: US EPA

Instead of relying on ever-changing test values, the SoilKit treatment recommendations from AgriTech for nitrogen are based on grass or plant variety, region, and time of year, using data from field experiments and research. It’s the same method used by farmers and agronomists, who determine fertilizer needs for crops based on known needs of the plants rather than the amount of nitrogen detected in the soil at any given moment. In plants, nitrogen is a fundamental building block for proteins and enzymes, a major element in DNA, and a critical component of chlorophyll, so there’s no guesswork in calculating what plants are likely to need. This value can also be adjusted based on the soil’s estimated nitrogen release (ENR), which accounts for the contribution of organic matter to plant-available soil nutrients. The nitrogen plants absorb from the soil allows them to maintain growth and health in terms of disease immunity, cell development, root structure, and more, so it’s important for your lawn or garden to amend the soil as needed.

One the flip side, excessive nitrogen applications can have detrimental effects down the road—or down the river. Following SoilKit test results and recommendations support environmental stewardship by recommending the right nutrient treatment, at the right time, and for the right plant. The constant fluxes of the nitrogen cycle not only make it more difficult for plants to meet their nitrogen needs without soil amendment, but also make it easy for nitrogen to leak from the system as a pollutant in waters and a greenhouse gas in the atmosphere. The two challenges of getting fertilizer nutrients into plants and keeping it out of fragile ecosystems go hand-in-hand. The professional test results and exact recommendations from SoilKit prevent over-application of nitrogen that otherwise can run off into our streams, estuaries, bays, and oceans, causing damage to marine life (for example, promoting toxic red tide events or forming anoxic dead zones). Not to mention, it saves you the cost of buying more fertilizer than what your plants can realistically handle.

Like so many aspects of soil management, nitrogen is about balance. We test the soil when information is helpful, while realizing some numbers change too quickly to keep up with. We amend with necessary nutrients, remembering the law of diminishing returns and knowing there is such a thing as too much. And the element nitrogen itself is in constant flux as if seeking its own balance among its diverse states, from solid minerals to liquid solutions to gas in the atmosphere. Thankfully, SoilKit test results cut through all the noise to the bottom-line nutrient recommendations you need to keep your yard green and healthy.

See also what Dr. Unruh from University of Florida has to say about Nitrogen Testing in this video -