Different Seeding Rates for Wheat: Is it Worth a Try
Reading time — 6 minutes
Tentatively selecting the most cost-effective winter wheat seeding scheme
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.
Variable-rate seeding has two advantages: it helps increase yield and reduces seed costs. But not all crop reacts positively to variable-rate seeding. Also, the sowing outcome may be affected by soil and weather conditions. Since 2014, I've been conducting field experiments on different crops to develop one-fits-all recommendations for those who plan to implement variable-rate seeding. In 2020, some testing was done on winter wheat. In this article, I'll tell you more about one of those experiments.
This field test was conducted at IMC's holding in Ukraine. They cultivate corn, wheat, and sunflower. This holding owns around 124,000 ha. I selected an 87-ha field in Chernihiv Region for this experiment, the purpose of which was to determine the most cost-effective winter wheat seeding scheme.
This field test was conducted at IMC's holding in Ukraine. They cultivate corn, wheat, and sunflower. This holding owns around 124,000 ha. I selected an 87-ha field in Chernihiv Region for this experiment, the purpose of which was to determine the most cost-effective winter wheat seeding scheme.
Variable-rate seeding has two advantages: it helps increase yield and reduces seed costs. But not all crop reacts positively to variable-rate seeding. Also, the sowing outcome may be affected by soil and weather conditions. Since 2014, I've been conducting field experiments on different crops to develop one-fits-all recommendations for those who plan to implement variable-rate seeding. In 2020, some testing was done on winter wheat. In this article, I'll tell you more about one of those experiments.
This field test was conducted at IMC's holding in Ukraine. They cultivate corn, wheat, and sunflower. This holding owns around 124,000 ha. I selected an 87-ha field in Chernihiv Region for this experiment, the purpose of which was to determine the most cost-effective winter wheat seeding scheme.
This field test was conducted at IMC's holding in Ukraine. They cultivate corn, wheat, and sunflower. This holding owns around 124,000 ha. I selected an 87-ha field in Chernihiv Region for this experiment, the purpose of which was to determine the most cost-effective winter wheat seeding scheme.
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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I conducted the experiment by:
Finding the limiting factor for wheat
To start off, I identified the field's productivity zones. This can be done for free in the OneSoil web app. Sign up, save your field, open the 'Sowing rate' tab, and in just a few minutes, the app will delineate the zones.
Productivity zones from the OneSoil web app
To find the limiting factor, I studied the previous four years' worth of field vegetation index data and analyzed the relief, slope map, and soil brightness.
The multiple years of vegetation index data show that areas with high and low NDVI in the key phases of plant development are located in the same spots each year. As such, the vegetation zones are stable, and productivity doesn’t depend on crop features or climate conditions. The yield is limited by an internal factor, which required me to analyze the relief, slope map, and soil brightness to identify it.
The multiple years of vegetation index data show that areas with high and low NDVI in the key phases of plant development are located in the same spots each year. As such, the vegetation zones are stable, and productivity doesn’t depend on crop features or climate conditions. The yield is limited by an internal factor, which required me to analyze the relief, slope map, and soil brightness to identify it.
The test field's slope map
Relief
When comparing these maps with the productivity zones, it became clear that neither the relief nor the slope was affecting the field's productivity. On the contrary, the soil brightness and productivity zone map had lots in common.
The test field's soil brightness
The soil in high-productivity areas was dark, which indicated high organic nutrient content. In low-productivity areas, the soil was light, meaning that the humus content is the limiting factor for yield.
Creating a prescription map
Basing myself on the field's productivity zones, I put together a prescription map for variable-rate wheat seeding. I selected four seed rates of wheat to test: 2, 4, 6, and 8 million seeds per hectare. IMC's average winter wheat sowing rate is 4 million seeds per ha, or 200 kg/ha.
If I were to use a uniform sowing rate, I would have needed 17.4 tons of seeds for the 87-ha field. That's about $5000 (139,000 UAH) in average 2020 prices for Ukraine.
This prescription map was created manually
Analyzing the winter wheat yield
I analyzed the yield map after the harvest was gathered on August 16. I identified homogeneous zones in which the sowing rate corresponded to productivity. I then calculated the yield and entered those data into a spreadsheet.
Experimental field yield map
Average yield, t/ha
How the crop yield changed
In the high-productivity zone I received nearly the same yield with 2 and 4 million seeds per ha rate. The 2 mln/ha rate resulted in a higher yield than 4 mln/ha rate in some areas and vice versa in others. What's more, the yield dropped by 0.4 t/ha when the seeding rate was increased to 6 mln/ha.
The situation was similar in the moderate-productivity zone. With sowing rates of 2 and 4 million seeds per ha, the yield didn't differ much; however, with a 6 mln/ha rate, there was a clear yield drop.
In low-productivity areas I noticed that the yield increased when I decreased the seeding rate. For example, when switching from a 4 mln/ha seed rate of wheat to 2 mln/ha, the yield increased by 0.15 t/ha.
The situation was similar in the moderate-productivity zone. With sowing rates of 2 and 4 million seeds per ha, the yield didn't differ much; however, with a 6 mln/ha rate, there was a clear yield drop.
In low-productivity areas I noticed that the yield increased when I decreased the seeding rate. For example, when switching from a 4 mln/ha seed rate of wheat to 2 mln/ha, the yield increased by 0.15 t/ha.
What this means and what the next steps are
This means that the variable-rate wheat seeding wasn't needed in this field. Take a look at the table above. It turns out that stable wheat yield growth can be achieved with a uniform winter wheat seed rate of 2 million seeds per hectare. A variable rate won't result in a strong yield increase. Nevertheless, I consider the experiment to be successful.
It helped me discover that the standard 4 mln/ha sowing rate can be decreased to 2 mln/ha to save on seeds, which will result in an average savings of 40−50%.
I conducted the same experiments in 13 more winter wheat fields in different soil types and climate zones in Ukraine and Russia and got the same result. That means that the sowing rate can be decreased at least in low-productivity zones when sowing winter wheat.
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