*2.1. Study Area*

Three research sites cropped with winter wheat (*Triticum aestivum* L.) or winter triticale (*Triticosecale* Witt.) (Table 1) were located in Bro˙zówka, northern Poland, in the land of the Great Masurian Lakes (location A), in Zdziechów, central Poland, in the Mazowieckie Voivodeship (location B), and in Kryłów, southeast Poland, close to the border with Ukraine (location C) (Figure 1).



\* Approximated soil data based on early spring field examination obtained during soil augerings done in locations of spike sampling (see Figure 3). \*\*—means and standard deviations in parentheses. \*\*\*—using Mehlich 3 extract.

**Figure 1.** Location of the three research sites in Poland (Open Geospatial Consortium (OGC) Web Map Service).

According to the Köppen classification [19], the majority of Poland lies in the warm temperate climate zone with fully humid continental climate and hot summers (Cfb). The locations of Kryłów (C) and Zdziechów (B) are situated within this zone, while the location of Bro˙zówka (A) is placed in the transitional area between the Cfb zone and the snowy climate zone, with fully humid and warm summers (Dfb).

The sum of precipitation in two studied seasons (from the beginning of September to the end of August) ranged from about 520 mm (location C, season 2016/2017) to 740 mm (location A, season 2016/2017). The lowest air temperatures were observed for location A, while locations B

and C were characterized by similar air temperatures. Growing degree days calculated at a base air temperature of 5 ◦C for the period from the sowing date to the end of July were much lower in 2017 (for locations: A—1364, B—1531, and C—1492) in comparison to 2018 (for locations: A—1795, B—1975, and C—1930). Monthly sums of precipitation and mean air temperatures for the nearest meteorological stations from the Institute of Meteorology and Water Management National Research Institute IMGW-PIB (https://danepubliczne.imgw.pl/) are presented in the Figure 2.

**Figure 2.** Monthly sums of precipitation, mean air temperature and growing degree days (GDD) for meteorological stations located closest to the research sites (for location A—Olecko, for location B—Puławy, for location C—Strzy˙zów) from the IMGW-PIB national institute (source of data: https: //danepubliczne.imgw.pl/).
