How Does a Pea Field React to Variable-Rate Seeding? We Experiment to Find Out
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In our article, we explore whether variable-rate seeding can help increase pea yield.
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When you perform variable-rate seeding, you never know which crop will respond to an increased seeding rate with a higher yield. You always have to conduct a field experiment to find out. In 2020, I had a chance to experiment with variable-rate pea seeding. In this blog post, I’ll tell you how I conducted the experiment and what the results were.

I set up the experiment on a farm in Ukraine’s Chernihiv Region. The farm’s agronomist and I chose a field where we would experiment. The field is 91-ha in area, with sod-podzolic, sandy loam soil.
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.
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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.
When you perform variable-rate seeding, you never know which crop will respond to an increased seeding rate with a higher yield. You always have to conduct a field experiment to find out. In 2020, I had a chance to experiment with variable-rate pea seeding. In this blog post, I’ll tell you how I conducted the experiment and what the results were.

I set up the experiment on a farm in Ukraine’s Chernihiv Region. The farm’s agronomist and I chose a field where we would experiment. The field is 91-ha in area, with sod-podzolic, sandy loam soil.

To conduct the experiment, I:

Examining productivity zones

To start things off, I analyzed the field’s productivity zones. Doing so is necessary to identify the limiting factor. I defined productivity zones using the OneSoil web app. You do the same for free.
Field productivity zones_OneSoil_Blog
Field productivity zones
I also studied the crops' vegetation index (NDVI) history in this field for the last three years. I only analyzed the NDVI in key growth stages. It turned out that high and low vegetation index zones were located in the same places from year to year. This means that the field’s productivity zones are stable. The low productivity zones were located on slopes in soil with low humus content, while the high productivity zones were located in humus-rich areas with a slope of up to 1°.

That meant that the humus content was a limiting factor for the yield.

Creating a prescription map

I tested three seeding rates: 230, 300, and 370 kg/ha. The farm’s standard sowing rate was 300 kg/ha. Here’s what the prescription map looked like:
Prescription map for variable-rate pea seeding_OneSoil_Blog
Prescription map for variable-rate pea seeding

Analyzing the crop yield

The field was harvested in June 2020 using a combine with a yield monitoring system. To analyze the seeding results, I defined homogeneous areas on the yield map. These are zones that have the same seeding rates and productivity. On average, the combine passed through each zone 2−4 times.
Pea yield map_OneSoil Blog
Pea yield map
You can see the average yield values for the homogeneous zones in the table. I used this data to analyze how the seeding-rate influenced the pea yield.
Average yield, t/ha

Experiment results

The yield in high productivity zones increased when the seeding rate was increased. When switching from 230 to 300 kg/ha, the average yield growth was 0.14 tons. When the rate was increased to 370 kg/ha, the yield growth was 0.18 tons.

In moderate productivity zones, the yield dropped when the 230 kg/ha rate was used. I didn’t notice a stable yield growth when switching from 300 to 370 kg/ha. In some homogeneous areas where the 300 kg/ha seeding rate was used, the yield was higher than in areas that used 370 kg/ha. In some areas, it was the opposite.

In low productivity zones, the seeding rate didn’t impact the yield. I didn’t notice a strong tendency indicating either an increase or a decrease in the yield.

What this means and what the next steps are

The experiment worked! Pea yield grew in high productivity zones with a higher seeding rate while the yield didn’t change in low productivity zones. That’s why I would recommend trying variable-rate seeding if you’re growing peas. Conduct field experiments, compare yields, and find the best planting strategy for your fields.

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Usevalad Henin
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