## 2 Materials and Methods
### Soil Conditions  
Soil samples were taken using [PERSON]'s stick each year prior to setting up the experiment. They were transported to an approved laboratory of the District Chemical and Agricultural Station in Krakow, where, according to the methods in place at chemical-agricultural stations in Poland, chemical and physicochemical properties of the soil were determined.  
The following were determined in the soil samples: pH using the potentiometric method, nitrate nitrogen content by colorimetry using a spectrophotometer, humus using the Tiurin method, and available macronutrients (P, K, Ca, and Mg) by methods commonly accepted at the chemical-agricultural station [59; 60; 61; 62; 63]. The content of microelements was also indicated in the soil [64; 65; 66; 67; 68]. The results of the soil arable layer analysis are shown in Table 3.  
The potatoes were grown on podzolic soil made from light, strongly sandy clay with a granulometric composition of fine sand, which is classified as a good rye complex [69; 70].  
The soil had an acid reaction (pH = 5.86) and low humus content (1.69%). The arable layer was rich in potassium, but there were shortages of other macroelements and microelements, such as Cu, Zn, and B, and excessive iron content. The heavy metal content did not exceed the permitted standards.  
Weather conditions in the years under investigation were varied (Figure 1). They were characterized by the Sielianinov hydrothermal index (\(K\)):  
\[K=\frac{p}{0.1\cdot\Sigma t}\]  
where: \(p\)--sum of precipitation for the examined period (mm); \(t\)--average daily air temperature (\({}^{\circ}\)C).  
The analyzed years of the study had different precipitation patterns and amounts (Figure 1). The growing season in 2015 was the driest and the warmest. Only 246.4 mm of rain was recorded between April and September. During the first growing season (April-June), the total precipitation was 127.6 mm, and in the second (July-September), it was 118.8 mm. Sielianinov (\(K\)) ratios indicated optimal humidity (\(K\) = 1.5) only in July, and in the remaining months, they indicated drought (\(K\) = 0.5-0.9). In contrast, 2016 can be considered the most optimal year in terms of water supply (358.6 mm) and coverage of potato demand. However, after a very wet July (\(K\) = 2.3), a significant precipitation deficit was recorded in August and September (\(K\) = 0.5). The study period from April to September 2017 was wet (543.6 mm of precipitation) and warm. During April-June, the  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Specification** & **2015** & **2016** & **2017** & **Mean** \\ \hline pH H\({}_{2}\)O & 5.69 & 6.08 & 5.83 & 5.87 \\ \hline Salinity (g NaCl-L\({}^{-1}\)) & 0.21 & 0.14 & 0.24 & 0.20 \\ \hline Humus content [\%] & 1.73 & 1.89 & 1.45 & 1.69 \\ \hline \multicolumn{5}{c}{The content available in the soil layer of 0–30 cm (mg:L\({}^{-1}\))} \\ \hline N-NO\({}_{3}\) & 16.00 & \textless{}14.00 & \textless{}14.00 & 14.67 \\ \hline P & 29.00 & 36.00 & 28.00 & 31.00 \\ \hline K & 108.00 & 118.00 & 199.00 & 141.67 \\ \hline Ca & 182.00 & 270.00 & 258.00 & 236.67 \\ \hline Mg & 10.00 & 44.00 & 38.00 & 30.67 \\ \hline Cl & \textless{}27.00 & \textless{}27.00 & 39.00 & 31.00 \\ \hline Cu & 0.89 & 2.02 & 1.02 & 1.31 \\ \hline Zn & 2.59 & 12.54 & 5.02 & 6.72 \\ \hline Mn & 60.12 & 76.00 & 78.00 & 71.37 \\ \hline Fe & 234.60 & 268.64 & 173.8 & 225.68 \\ \hline B & 0.10 & 0.20 & 1.10 & 0.47 \\ \hline S-SO\({}_{4}\) (mg:100 g\({}^{-1}\) soil) & 0.35 & 0.32 & 1.72 & 0.80 \\ \hline Pb (mg:kg\({}^{-1}\)) & 12.26 & 16.81 & 12.63 & 13.90 \\ \hline Cd (mg:kg\({}^{-1}\)) & \textless{}0.33 & 0.33 & 0.37 & 0.34 \\ \hline Ni (mg:kg\({}^{-1}\)) & 1.50 & 4.04 & 3.02 & 2.85 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Chemical properties of the arable layer of soil.  
sum of precipitation was 243.6 mm, and between July and September, it was 300.0 mm. Potato plants were sufficiently preserved in moisture.