Do pastures need soil samples?

Nutrient management is a topic that we often associate with growing corn and soybeans.

Grain farmers apply fertilizer every year, sometimes more than once, and use methods such as grid sampling and variable rate technology to make sure that nutrients are delivered to crops precisely.

But working with grazing operations over the past couple of years has shown that most producers do not manage pasture nutrients so intensely.

They may think that growing forage does not need to be managed the same way that grain crops do, but managing nutrients in the pasture can increase profitability in those fields, the same way they do for other crops.

Troubleshooting

Let’s start by looking at what happens to fields that are low in fertility.

For corn, we can see color differences and noticeably smaller plants when they are nutrient deficient.

The same goes for our pastures, but producers often think that those plants are too old and need to be reseeded to increase growth.

Key signs that there is low fertility in pastures and hay fields can be seen by plants looking more yellow than green and limited growth.

In fields that have had low fertility for long periods of time, we can also start to lose some of our key forage species as they are not able to grow in those conditions.

Those plants get replaced by undesirable species that can handle low fertility.

For pastures that are overgrazed as well as nutrient deficient, there are areas that we see “spotted growth” when livestock discharge manure throughout the pasture.

Keeping these symptoms in mind when looking for low fertility, the only way to be sure is to have the soil tested.

Getting started

Once producers start having trouble with pasture fertility and start seeing some of the signs of nutrient deficiencies mentioned above, soil samples need to be pulled to determine what nutrients are low.

Having those soil test results gives the producer a starting point to build from to raise fertility levels over time.

Likewise, even if a producer does not have signs of nutrient deficiencies, they should take soil tests every three years to ensure that levels are maintained.

Not maintaining these levels results in having to correct long-term neglect of fertility, which can be expensive.

Timing

To split the cost of correcting fertility over time, producers should select a third of the fields and have them tested every three years.

Then start the process on the next third of fields the following year, and the final third on the third year. On the fourth year, the producer will go back and start the process over.

This method not only splits the cost of sampling up over three years but also splits the workload of taking samples up over three years. Samples can be taken in the spring or the fall, so long as you are consistent with the timing year to year.

Correction

After soil tests are taken and results are given to the producer, the amount of fertilizer or lime needed can be determined.

If the fields are low in fertility, recommendations can be given to build levels up over time.

If levels are sufficient, they need to be maintained by applying the nutrients that will be taken out.

This is the cheapest and easiest way to keep fields producing at their full potential.

Fields that have high soil test levels should not have nutrients applied to them as there will be no economical benefit to the application.

Pasture fertility is a long-term process, and correction may be as well.

Future considerations

Once the fields are corrected, producers will often see those desirable forage species begin to grow again, eliminating the need to reseed the pasture.

These fields also perform better during difficult times, such as wetness and drought. Managing nutrients in addition to rotational grazing will significantly increase forage production and allow the producer to utilize the full potential of the pasture.

Going back to where we started, lets think about managing corn nutrients again: Producers will buy the seed variety to produce the best yield, apply nutrients to ensure the crop will grow, and manage the crop throughout the season with the goal of getting the highest yield possible.

So, why should growing forage in a pasture be any different?