How to determine effectiveness of variable rate seeding without special equipment_Cover_OneSoil Blog

Variable-Rate Seeding Without Using Special Equipment

Estimated reading time — 15 minutes
Corn Field Experiment
Philip Kondratenko_OneSoil Agronomist
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.
Farmsteads often don't have the equipment needed to conduct variable-rate seeding. What they can do is experiment in their own field to evaluate the economic advantages of variable-rate seeding and start practicing with it. How advantageous this method is depends on the relief, soil texture, and other factors related to fertility. That's why no one else's particular experience will do you much good. In cases like that, we here at OneSoil help you set up an experiment right so you can avoid errors and get an accurate result after harvesting your crop.
In this article, I’ll tell you about one such experiment that took place in a cornfield in central Ukraine. As far as equipment was concerned, the farm only had a seeder with a manually set seeding rate. I had two objectives: to set up an experiment right and to determine whether the seeding rate influences the corn yield.

I managed to pull it all off, by the way! You can read more about the experiment’s results in my conclusions.
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Farmsteads often don't have the equipment needed to conduct variable-rate seeding. What they can do is experiment in their own field to evaluate the economic advantages of variable-rate seeding and start practicing with it. How advantageous this method is depends on the relief, soil texture, and other factors related to fertility. That's why no one else's particular experience will do you much good. In cases like that, we here at OneSoil help you set up an experiment right so you can avoid errors and get an accurate result after harvesting your crop.
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.
In this article, I’ll tell you about one such experiment that took place in a cornfield in central Ukraine. As far as equipment was concerned, the farm only had a seeder with a manually set seeding rate. I had two objectives: to set up an experiment right and to determine whether the seeding rate influences the corn yield.

I managed to pull it all off, by the way! You can read more about the experiment’s results in my conclusions.
Stages of the experiment
  1. Identifying productivity zones
  2. Analyzing the relief and soil brightness
  3. Selecting a plot for variable-rate seeding
  4. Creating a prescription map
  5. Analyzing the crop yield

Stages of the experiment
  1. Identifying productivity zones
  2. Analyzing the relief and soil brightness
  3. Selecting a plot for variable-rate seeding
  4. Creating a prescription map
  5. Analyzing the crop yield

How I conducted the experiment in corn field

The field covered an area of 68 hectares. The soil was chernozem with varying levels of degradation.

I identified the field's productivity zones using the OneSoil web app. They were pretty stable. That means that high- and low-productivity plots stayed in the same places from year to year.
Productivity zones in_ the_field_OneSoil Blog
Here's what the map looked like with productivity zones. You can create a map just like it for your field in the OneSoil web app. Sign up, add your field, and select the 'Sowing rate' tab. It's all free
After that, I analyzed the field's relief and soil brightness. In my experience, these two factors more often than not impact fertility and, as a result, crop yield in the field. This field was no different.

Relief. The field had an elevation difference of over 30 meters. And although there weren't any drainage hollows, low-lying areas, or higher grounds, the slope in some areas exceeded 4 degrees.
Relief map
Slope map
It’s hard to come to a straightforward conclusion on how the relief affects productivity using a relief map. But if you compare the slope map with the productivity zones map, you’ll see that they align almost perfectly. Productivity is low in areas that have a high slope and is high where the field is even. It turns out that one of the reasons for a field’s heterogeneity is precisely because of the relief.

Soil brightness. This depends on organic nutrient content. The darker the soil is, the richer it is in nutrients. Here’s an image of tilled soil with its top layer air-dried.
Soil brightness map_OneSoil Blog
The lighter the soil is, the more likely soil erosion is in this area
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 that both the relief and the soil nutrient content affect productivity.

After that, I had to select a plot in the field where I would conduct variable-rate seeding. Since the seeding rate on the seeder could only be adjusted manually, I had to choose the most homogenous plot.

After analyzing information about the field, I outlined the zone that showed high productivity year after year. The soil in this zone is rich in organic nutrients, while the slope and the relief’s other morphometric properties (slope curvature, aspect, length, and direction) are the same. To determine more precisely the seeding rate’s impact on yield, I added a small nearby moderate-productivity plot to the zone.

I didn’t analyze the low-productivity zone in the experiment. It’s mostly on the field’s left side, far from the zone I selected for seeding. It’s impossible to sow at a precise rate there without special equipment.
Plot_to_conduct_variable-rate-seeding_OneSoil Blog
I decided to use this part of the field to use variable-rate seeding
To create a prescription map for the onboard computer, I set two seeding rates: 65,000 seeds/ha and 85,000 seeds/ha. I sowed the right part of the selected zone at the higher rate and the rest of the field at the smaller rate. Here’s what the prescription map looked like with a breakdown by rate.
Prescription zmap_OneSoil Blog
Prescription map
Analyzing the crop yield. In the zone that I selected for variable-rate seeding, the harvest was done using a combine equipped with a yield monitoring system. That made it very easy for me to transfer all the data on the harvested crop to a computer.
Yield map_OneSoil Blog
Yield map
You can tell by looking at the map just how much seeding rate affected field productivity. To understand by how many quintals the yield grew in moderate- and high-productivity zones, I divided the section of the field I experimented with into homogenous zones. That means that these zones had the same yield and seeding rate across their whole area. The combine passed through each zone two to four times.
Average yield, t/ha

How the crop yield changed

In the high-productivity zone. It increased on average by 5.5 quintals per hectare when increasing the seeding rate from 65,000 to 85,000 per hectare.

In the moderate-productivity zone. The yield increase was insignificant: only 0.7 quintals per hectare. On top of that, the grain weight recorded in certain areas was actually 1.5 quintals lower at 85,000 seeds/hectares compared to 65,000 seeds/hectare.

Remember that I couldn’t experiment with the low-productivity sections of the field.

Conclusions and Recommendations

The experiment worked! Even with only a manually adjustable rate, I was able to increase corn yield in the experiment zone. That means that the farm where I conducted the experiment can confidently plan to buy variable-rate seeding equipment and know that they’ll get a return on their investment.

Last year, I conducted variable-rate seeding experiments in 23 cornfields located in different zones and different conditions. In every single one, the experiment yielded positive results. I make the following recommendation to everyone who applies variable-rate seeding:
Increase the corn seeding rate in high-productivity areas and decrease it in low-productivity areas. The yield will increase for most hybrids.

Experiment conducted by our expert Usevalad Henin
Illustrations created by Nastia Zenovich and Dasha Sazanovich
Text edited by Tanya Kavalchuk
Article layout by Anton Sidorov
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