A Ukrainian agronomist on variable-rate seeding in zones with unstable climate conditions

I’ve been in agriculture for three years now. I started working at Petrov Farms right after I graduated from an agricultural university. It’s a private farm, just like most Ukrainian agricultural producers. It covers an area of 3,500 hectares. By Ukrainian standards, it’s neither a big farm nor a small one. We’ve been doing quite well and stay on top of upgrading our equipment fleet.

We grow winter wheat, barley, and rapeseed. We also plant corn, sunflower, and sorghum. We make money on selling grain. We sell part of it right away and store the rest to sell later at a higher price. Overall, our yield is average for the region or slightly above average.

Depending on the season, we have anywhere from 30 to 50 employees at the farm. We have 30 full-time employees. These are agronomists, agricultural equipment operators, metalworkers, accountants, and economists who work year-round. We have about 20 seasonal workers who do fieldwork.

South Ukraine (Black Sea littoral zone and Cisazovia) is in a zone with unstable climate conditions. Our yield largely depends on nature and the climate. Our challenge every season is a lack of moisture. For instance, it rained only once from January to April. None of the farms around here use irrigation systems. The pay-off is too slow, and our fields are too far from water sources. The most important thing to do in these conditions is to act fast to prevent moisture from evaporating away.

I use the normalized difference vegetation index (NDVI) to track crop growth. We don't always have an opportunity to visit the fields, and NDVI shows you which part of the field is doing alright and which isn't doing so great. The NDVI-based productivity zones from the OneSoil app correspond to the ones we identified in our last soil analysis. We conduct one every 3-4 years and do grid sampling on our own. That's why we wanted to see how productivity-zone-based variable-rate fertilizer application works, so we decided to try it out.

We applied ammonia nitrate in our first and second fertilizer applications to winter crops in March. We used 80 kilograms per hectare for the first fertilization run and 70 kilograms per hectare for the second one. We bought a special spreader for variable-rate fertilizer application, created a prescription map in the OneSoil app, and headed to the fields. We don't expect quick results. Obviously, one time is not enough to level the field out.

This spring, in April, we tried variable-rate seeding for the first time. The truth is, in mid-February, our agronomists found out that the wheat crops in some fields died because there were no typical winter conditions for this region. The temperature varied a lot, going from 15−16°C in the day to -5 to -7°C at night. Most likely, the wheat resumed vegetation, but couldn’t survive the temperature fluctuations.

We didn’t want the fields to sit empty, so we decided to reseed them. In one of these fields, covering 120 hectares, we tried out variable-rate seeding. If we can increase yield using a proven technique, why not take advantage of it? We planted sunflowers from Syngenta (a Sumiko hybrid) in the dry soil. We hoped that we’d get rain soon enough, which would provide enough moisture for seeds to sprout. We used experiments conducted by Usevalad Henin to determine our sowing rate (Note from OneSoil: Usevalad Henin is a precision farming specialist at OneSoil and agricultural chemist). We decreased the rate for low-productivity zones and increased it for high-productivity ones. We ended up with three different sowing rates: 66K, 56K, and 37K seeds per hectare.