Precision Agriculture Strategies for Planting Corn Hybrids

For the experiment, we chose corn 6 hybrids that the agricultural holding used in the 2020 season:

• DKC 3939
• DKC 4590
• DKC 3972
• DKC 4351
• P 9241
• DKC 4541

As I wrote above, in this field experiment, we tested whether the corn yield would increase if the seeding rate was increased in the high-productivity zone and decreased in the low-productivity zone.
To this end, two additional controls were added to each corn field:

1. For the first control, we decreased the seeding rate in the high-productivity zone and increased it in the low-productivity zone.
   
2. For the second, the medium seeding rate was used in all productivity zones.
   
   

The medium corn seeding rate in this experiment was the agricultural holding's standard rate: 74,000 - 78,000 grains per hectare. The other rates were selected based on the corn hybrid: the low rate was 65,000-69,000 per hectare, and the high rate was 80,000-87,000 per hectare.

I'd like to emphasize that, in order to receive objective results for the experiment, it was important to apply both controls in the same field. If you compare test strips from several fields, the result is unreliable due to different planting dates and applications of plant protection products, growth regulators, etc.

I start every field experiment by doing this. NDVI data in a field correlates with yield in key growth stages. That's why I can identify productivity zones and understand how stable they are when I rely on several years of NDVI data.

You can view NDVI data for any day for free in the OneSoil web app.

Identify the nature of the productivity zones to determine if they are stable or unstable. If the NDVI zones in the field change from year to year, it means that the zones are unstable. The yield in a field like this is primarily limited by external environmental factors, such as the weather.

If the zones' locations are stable from season to season, yield is primarily affected by an internal factor. In fields like these, it's easier to delimit zones for seeding and forecast the result. These are the kinds of fields I select for experiments.

At this stage, I allocate the seeding rates across the field so that I end up with three seeding rates in each productivity zone.

It's important to harvest all the fields where experiments were held with a combine equipped with yield monitoring. Otherwise, you won't be able to correctly interpret the experiment results. After I get a yield map, I manually delimit replications on it.

These are areas that have the same yield and seeding rate values in a particular productivity zone. To get the experiment results, I compare the average yield for the replications in different zones.

Maize hybrid DKC 3939 (FAO 320) response. In fields that didn't get enough moisture, the corn yield increased in low-productivity areas with a lower seeding rate. In the fields that didn't see any drought conditions, the yield increased in high-productivity zones with a higher seeding rate and often in low-productivity zones with a lower seeding rate.

Maize hybrid DKC 3972 (FAO 300) response. In high-productivity zones, yield increased when raising the corn seeding rate to 87,000 seeds per hectare and in low-productivity zones when lowering the seeding rate to 68,000 seeds per hectare. The average yield growth when changing the seeding rate was 1.1 t/ha.

Maize hybrid DKC 4351 (FAO 350) response. This hybrid is unstable. In some fields, the yield increased when increasing the seeding rate in high-productivity zones. In others, the yield grew in both low- and high-productivity zones when decreasing the seeding rate. To understand why this happened and whether this hybrid had a dependence on any factors, we had to continue experimenting. For this hybrid, I've decided to show charts for two fields to give the whole picture.

Corn hybrids DKC 4590 (FAO 360), P 9241 (FAO 340), DKC 4541 (FAO 360) response:
The yield for these three corn hybrids in different fields and in different conditions didn't depend on the seeding rate.
That's why I'd recommend lowering their seeding rates.

In this experiment, we became convinced that all corn hybrids react to variable-rate seeding differently. For that reason, you have to test a hybrid in specific soil and climatic conditions to determine the optimal seeding strategy for variable-rate planting.

In the agricultural holding's particular soil and climatic conditions, it turned out that the lower the FAO is (below 350), the better the hybrid reacts to variable-rate seeding. In all fields where yield didn't increase, we noticed that it also didn't change when decreasing the seeding rate. This could be a basis for decreasing the seeding rate for these hybrids at the agricultural holding.