Soil Nutrients and Field Health: What You Need to Know

The soil on your field is like the brain to your body. It tells your crops everything they need to know to produce a healthy yield; how many organisms live there, what the pH balance is, whether or not something is performing well… For the brain, if something isn’t performing well, the body can react catastrophically. The same thing happens with soil. If you have too much potassium in your field, your plants will not regulate water intake and outtake like they should, thereby reducing your field’s sustainability.

Healthy soil will have all the essential elements in the right proportions to support healthy plant growth throughout its lifecycle. But, not every field will have the ideal level of every nutrient for crop production and sustainability naturally without outside help. In agriculture, the primary soil nutrients are nitrogen (N), phosphorus (P), and potassium (K), or NPK. These nutrients occur naturally in the soil but are also increased or decreased manually depending on your crops’ needs.

Many factors can affect each of these nutrients’ availability, including organic matter decomposition, soil erosion, leaching, and improper fertilizer application. So how do you manage it? Each nutrient has its own prevention plan to consider, but they all have one thing in common; precision agriculture. Using precision ag technology is the most efficient way to manage your soil needs, regardless of the nutrient variabilities in each zone or field. One technique we recommend to our farmers is Variable Rate Technology (VRT). It ensures a crop receives only the nutrients it needs to reach maximum yield. It also limits the potential impact of excess fertilizer on waterways and other natural areas.

When you use VRT to apply the right amount of nutrients combined with the ideal seeding rate, you can produce more from every acre of your land while reducing the amount of wasted product. You can maximize every opportunity when you customize both seeding and crop nutrition applications to each zone. The most and least productive areas in each field are then matched with the corresponding seed rates and applications. Implementing technology like VRT into your soil management plan ensures sustainability, increased productivity, and it reduces your financial output because you’re not spending extra on unnecessary fertilizers.

So, let’s talk about the role N, P, and K each play in the soil, how implementing VRT can prevent nutrient loss, and some tips for adding loss prevention to your nutrient management plan. 

Nitrogen (N)

Nitrogen is the most important nutrient for crop production, but it’s also most susceptible to being lost before your crop can use it. The vast majority of nitrogen exists as a gas in the atmosphere, making it unavailable to plants. This unavailability means that gaseous nitrogen must be fixed into a form that plants can use, either through the production of commercial fertilizer or symbiotic nitrogen fixation. Nitrogen exists in the soil in two forms, ammonium and nitrate.

How nitrogen is lost:
As ammonium, it is a positively charged ion, so it’s held by soil particles making it not susceptible to leaching. However, as soils warm, ammonium is converted to nitrate, a negatively charged ion, and is vulnerable to leaching. Another contributor to nitrogen loss is a process known as denitrification. During this process, nitrate is converted to gaseous nitrogen and is released into the atmosphere. 

How to prevent nitrogen loss:
When crops are young and small, they have low nitrogen demand. As the temperatures rise, crops enter a rapid growth phase, and the need for nitrogen dramatically increases. So the best method for loss prevention is to match your nitrogen application with crop demand through precision agriculture. Splitting the total amount of nitrogen fertilizer into multiple applications can ensure the crops use the nitrogen you applied. For example, to match nitrogen availability with crop demand, apply a small amount of nitrogen in your starter fertilizer. Follow it up with multiple side-dress nitrogen applications.

Phosphorous (P)

With phosphorus, it’s all about plant reproduction and energy transfer. This nutrient is essential for grain production. P doesn’t typically have significant leaching issues (unless in sandy soils), but a field can suffer from low P levels or P-deficiency. P-deficiency can result in reduced growth, lower yields, and delayed maturity. Additionally, because of phosphorus’ immobility and soil fixation, the placement of fertilizer phosphorus can affect its availability to plants.

How phosphorus is lost:
Because leaching isn’t a huge problem for P, the main thing that impacts phosphorus retention is reduced organic matter in the soil. Soil erosion, water runoff, and surface flow, in general, are all contributors. It should be mentioned here that there is also potential for substantial losses in drainage water from drain tiles installed in the ground, though less so.

How to prevent phosphorus loss:
Phosphorus is most readily available in the soil between pH 6 and 7, so proper variable rate application of lime is necessary to ensure that phosphorus is available to the crop. Management practices such as grassed waterways and cover crops can reduce erosion and keep phosphorus on the farm.

Another excellent method to help prevent P loss from your fields is to involve a reduced-tillage approach. Several studies have shown that the total phosphorus loss is less with any system that reduces soil exposure. An effective farm management plan will include precision soil sampling to monitor P levels in the soil because it relies heavily on soil pH for replenishment. 

Potassium (K)

It’s all about the movement of water. Potassium regulates the exchange of water, oxygen, and carbon dioxide. This means that if it lacks in the soil, plant growth is stunted, and yields are reduced. K is also the activator for a significant number of enzyme reactions within a plant and is a big part of how a plant manages environmental stress. Because the amount of available K in the soil is only about a day’s supply at any one time, we need to apply additional amounts of the nutrient to keep up with plant requirements.

It’s important to note that while it’s necessary to supply more K to your soil, adding too much or placing the nutrient too close to seed or transplant can throw off your pH levels resulting in fertilizer injury. Utilizing precision methods like VRT to spread potassium across a field is one of the best ways to prevent fertilizer injury.

How potassium is lost:
Potassium can leach in sandy soils and in areas that experience a lot of rainfall.

How to prevent potassium loss:
The majority of potassium used in crop production is surface-applied as a dry product, like potash. As a result, it’s crucial to incorporate potassium into the soil where the crop can use it. Like phosphorus, taking annual precision soil samples is the most efficient way to make informed data-driven decisions regarding how to apply your K nutrients. 

Loss Prevention and Your Nutrient Management Program

Now that you know why loss occurs and when it’s most likely to happen, you can build prevention and remediation into your nutrient management program. A reliable precision program can help you reduce input costs, prevent fertilizer overuse and waste, and increase your farm’s sustainability.

Not sure where to start? Try starting with test your soil to determine nutrient levels. If you don’t have any samples taken within the last 12 months, you are overdue to take new samples. The information you receive on these reports will let you know what nutrients are where and at what level throughout your zones. Remember, the key is only to apply what you need, where you need to.

Overall, precision methods such as variable rate application and precision soil sampling are the most cost-efficient and streamlined ways to ensure that you are laying down fertilizer at the right rate across your farm. Applying fertilizers at the same rate regardless of the pH levels, current soil nutrients, or organic matter will result in lower yields and stunted crops in some areas. It will also increase the risk that your farm won’t be sustainable in the long term.