We tested two fields located in the central part of the Ukraine, in the Kirovograd region. The soils are black earth, the crop was winter wheat. Non-uniform terrain: there is a significant difference in elevation everywhere, which causes the difference in crop yield.
On field 1 we differentiated only the first nitrogen nutrition and on field 2 we differentiated the first and the second nutritions. The application of fertilizers was performed on February 22 (here's the full timeline
of field operations). For this purpose we used liquid nitrogen fertilizer "КАС 23" (23 kilograms of nitrogen per 100 litres), therefore in the following we will always use litres. The fields were reaped on July 10 using a combine harvester with an on-board computer for the monitoring of crop yield.
The crop yield data from the combine harvester often have various interferences and discrepancies which arise during technical operations. To eliminate their influence on the experiment results, we identified homogeneous regions on the fields which were covered by 2 to 4 runs of the combine harvester, and we calculated average values for these regions. In these regions there were 8 to 16 zones (repetitions) with similar rates in each, and we also took this data into account when analysing.