We tested two fields located in central Ukraine's Kirovograd Region. The soils were chernozem, and the crop was winter wheat. The relief was heterogeneous, with a significant difference in elevation everywhere, which causes a difference in crop yield.
In Field 1, we varied only the first round of nitrogen fertilization. In Field 2, we varied both the first and second applications. We applied fertilizers on February 22 (here's the full timeline
of field operations). To do so, we used UAN 23% liquid nitrogen fertilizer, so we'll use liters going forward. The fields were harvested on July 10, using a combine with an on-board computer and yield monitoring system.
The crop yield data from the combine often has various data outliers and discrepancies that arise during technical operations. To eliminate their impact on the experiment results, we identified homogeneous zones in the fields that were covered by 2 to 4 combine runs, and we calculated the average yield values for these plots. In these areas, there were 8 to 16 zones (replications) with similar rates in each. We considered this data, too, when conducting our analysis.