How to Identify the Limiting Factor in a Field
If I had to say what the one thing you could do to definitely get a higher yield, I would recommend identifying the limiting factor. In this blog post, we'll discuss the limiting factor, why it's so important, and how to identify it.
Usevalad Henin
Usevalad is an expert in GIS and agricultural chemistry. He has been developing precision farming tools since 2013. He is also the co-founder of OneSoil.
Let me start with an analogy. To live, a person needs food, water, warmth, and security. Imagine we're provided with all of this, and we drink about 2 liters of liquid every day. Then suddenly, we run out of water. We feel OK for a day or two. But how long can this last? I haven't checked this myself, but scientists say that, on average, a person dies after 3 or 4 days without drinking water. In this case, water is our limiting factor. Two liters of water a day is the optimal amount that helps us feel great. A glass of water once every 3 or 4 days is the minimum we need to survive. The same is true for plants.
Get all new articles straight to your inbox!
Let me start with an analogy. To live, a person needs food, water, warmth, and security. Imagine we’re provided with all of this, and we drink about 2 liters of liquid every day. Then suddenly, we run out of water. We feel OK for a day or two. But how long can this last? I haven’t checked this myself, but scientists say that, on average, a person dies after 3 or 4 days without drinking water. In this case, water is our limiting factor. Two liters of water a day is the optimal amount that helps us feel great. A glass of water once every 3 or 4 days is the minimum we need to survive. The same is true for plants.
What the limiting factor is, and why it’s important
The limiting factor is the environmental factor that is either present in very big or very small quantities in a field. It negatively affects plants' growth and weakens the impact of other factors whose values are at an optimum level.
For example, we know that phosphorus and potassium contents in a field are within acceptable levels, while soil acidity is very low. That means acidity is the limiting factor for this field. It doesn’t matter how much fertilizer you apply, it won’t work because soil acidity will neutralize the effect of any fertilizer, even the best one.
For example, we know that phosphorus and potassium contents in a field are within acceptable levels, while soil acidity is very low. That means acidity is the limiting factor for this field. It doesn’t matter how much fertilizer you apply, it won’t work because soil acidity will neutralize the effect of any fertilizer, even the best one.
Who came up with this concept? Justus von Liebig posited and proved what we know as Liebig's Law of the Minimum back in the 19th century. One day, when young Justus was sitting in a Greek lesson, a bag he was carrying with fulminating mercury inside exploded. He realized that the humanities weren't his thing; chemistry was. In 1840, Justus von Liebig formulated the Law of the Minimum, which states that plants' growth is most influenced by the factor that is present in the least quantity.
The law was further developed by Victor Shelford in 1913. He proved that the life of any living organism, including plants, depends on multiple factors, and that every organism has a certain limit of tolerance to these factors. The range from the minimum to the maximum values of the factor is the organism’s limit of tolerance. When the factor’s value approaches the minimum or the maximum threshold, the organism experiences stress. That’s pretty much the same for humans!
How to identify the limiting factor with OneSoil
The easiest way to identify the limiting factor is to determine productivity zones in the field. Productivity zones reflect the fertility of different areas in a field. They can be built using multiple years of vegetation index data. When we know multiple years of vegetation index history, we can determine the areas in which the index values were below average. This is where the limiting factor is expressed most clearly.
1. Determine productivity zones. You can do this for free in the OneSoil web app. The app builds the zones according to the last four years of relative yield calculated by our algorithm using satellite images. All you need to do is create a free OneSoil account, go to the 'Fertilizers' or 'Sowing rate' section, and select your field. The app will automatically generate a productivity zones map for your field.
1. Determine productivity zones. You can do this for free in the OneSoil web app. The app builds the zones according to the last four years of relative yield calculated by our algorithm using satellite images. All you need to do is create a free OneSoil account, go to the 'Fertilizers' or 'Sowing rate' section, and select your field. The app will automatically generate a productivity zones map for your field.
Here's what the productivity zones look like in the OneSoil web app
2. The next step is to compare the productivity zones and relief. If the productivity zone map looks like the relief map, it means the relief — its slopes, low-lying lands, or other features — is affecting the soil's chemical and physical properties and the moisture distribution in the field. The moisture, in turn, affects the yield. In this case, insufficient or excess moisture is the limiting factor in the field. (If it's not moisture distribution, go to the next step.)
You can download the relief map from your equipment's onboard computer. Render it in the OneSoil web app and start analyzing it. That's what we do when we conduct experiments. What's more, our team is planning to release the new 'field layers' feature in our web app by the end of 2020. The field relief will be one of these layers.
You can download the relief map from your equipment's onboard computer. Render it in the OneSoil web app and start analyzing it. That's what we do when we conduct experiments. What's more, our team is planning to release the new 'field layers' feature in our web app by the end of 2020. The field relief will be one of these layers.
A slope map for a field in Ukraine with the productivity map superimposed. High slopes overlapped with low-productivity zones. After reviewing these areas, I discovered soil erosion
3. Compare productivity zones and soil brightness if there's no connection between productivity zones and the relief. Are the productivity zone maps similar to the soil brightness maps? If they are, humus content is likely affecting the yield.
To analyze soil brightness, I recommend using an image of the field after it was tilled and without any plant residue on its surface. It's easiest to do this right after sowing. You can download this kind of image from a dedicated website from Sentinel. Sign up, select your region on the map, and download the image in B08 format (a near-infrared image). After that, upload the image to any GIS software, increase the contrast, and start analyzing it.
To analyze soil brightness, I recommend using an image of the field after it was tilled and without any plant residue on its surface. It's easiest to do this right after sowing. You can download this kind of image from a dedicated website from Sentinel. Sign up, select your region on the map, and download the image in B08 format (a near-infrared image). After that, upload the image to any GIS software, increase the contrast, and start analyzing it.
The map shows that the soil is lighter in areas where the slope is around 3 degrees. These same areas overlap with the low-productivity zone. That means productivity is affected by organic nutrient content
4. Check soil acidity in low productivity areas if the soil brightness, relief, and productivity aren't connected. The easiest ways to check acidity are by using a pH meter or in a laboratory.
5. Conduct a soil test. Analyze the phosphorus, potassium, and other macronutrient and micronutrient content only after you've assessed the field and made sure that neither the terrain nor the organic nutrient content is limiting the yield and that acidity levels are acceptable.
Should I always think about the limiting factor?
Yes. Here are just a few examples for you where we analyzed field productivity zones and identified the limiting factor:
If you want to discuss this article and share your own experience, please, join our Telegram community!
Usevalad Henin
Want to
conduct an experiment
with OneSoil?
conduct an experiment
with OneSoil?
Try OneSoil Yield now
Any farmer can purchase the program from an agricultural technology dealer in his region. Explore the app's features in a free demo account to take care of any doubts you may have before buying it.
More Articles
People, fields and technology
Get all new articles straight to your inbox! You can read them even in the field.