The effect of organic, mineral and combined organic and mineral fertilization of soils on the winter wheat yields and nutrient contents in soils was evaluated in long-term field experiments. Two sites with different soil characteristics were evaluated -Lukavec u Pacova (cambisol) and Ivanovice na Hané (degraded chernozem). The type of fertilization influenced wheat yields. Nutrient uptake by winter wheat was higher under nitrogen (N) fertilization, which resulted in a negative balance of phosphorus (P) and potassium (K) and to a decrease of nutrient contents in the more fertile soils at Ivanovice na Hané. Two soil tests (Mehlich 3 method and NH 4 -acetate method) were used to determine P and K availability. The mineral nitrogen fertilization negatively and significantly affected NH 4 -acetate extractable concentrations of nutrients in the soils and these were lower in comparison with concentrations of P and K determined by Mehlich 3 method. Relative availability of P in alkaline soils from Ivanovice treated with mineral N increased while the soil pH decreased.

The boron (B) availability and uptake were studied in relation to different phosphorus rates applied into soils in a three-year field experiment (2015–2017). The experiment was carried out at the experimental station at Humpolec (Bohemian-Moravian Highlands, Czech Republic). Three rates of phosphorus (20-40-80 kg P/ha) were applied as triple superphosphate. The crop rotation was spring barley-winter oilseed rape-winter wheat. No systematic fertilization with B was used and the response of natural boron soil content to the different phosphorus supply was studied. The crop yields, B content in plants, B-uptake, and content of B (extracted by Mehlich 3 and NH₄ acetate methods) were determined. Spring barley and winter wheat B uptake was about one order of magnitude lower in comparison with oilseed rape. Significant differences in B content in soils, in crop tissues and B-uptake, were found mainly under higher phosphorus doses (40 and 80 kg P/ha). NH₄ acetate method showed better correlations between P and B contents in soils than Mehlich 3 method from the second experimental year. The P-fertilization may affect negatively the B-uptake by plants, particularly if the highly nutrient demanding crop is grown.

The boron (B) availability in soils, B uptake and possible B interactions with phosphorus (P) were studied in a pot experiment with increasing P rates. Three soil types of different characteristics were used for the experiment that lasted two years. The two soil tests were used in the experiment – Mehlich 3 and NH₄-acetate. Significant positive correlations were found between barley dry matter yield, B content in plants and B uptake under increasing P treatments (P ≤ 0.001). The significant relationship for B content (P ≤ 0.001) was obtained between the used soil tests for all tested soils. A decrease of soil B content in soils under increasing P doses was determined. NH₄-acetate soil test showed a significant relationship between B and P contents (P ≤ 0.001) within the studied soils in comparison with the Mehlich 3 method. Considering individual soils, the NH₄-acetate test showed more often higher significance in comparison with the Mehlich 3 test. The interactions between P and B in soils should be taken in consideration when deciding about the phosphorus fertilization.

The pot experiment with graded P doses was carried out in 2015 and 2016 in the Crop Research Institute, Prague – Ruzyně (undermentioned CRI). Three soil types were chosen for the experiment – Chernozem, Cambisol, Haplic Luvisol. The soils were treated by graded P doses (0.3–0.6–1.2 g P/5 kg of soil). The soil without any treatment served as a control. The spring barley (variety KWS Irina) was grown up to the milky ripeness stage. Plants were regularly watered with the deionised water. Two-year results of experiments showed that the increase of spring barley dry matter was noted under graded P doses particularly in the year 2015, whereas in the year 2016 the plant growth despite to increasing trends generaly was not significant. The P-uptake by plants increased in correspondence to graded P doses and correlated with the P contents in soils determined by Mehlich 3 and NH4-acetate soil tests. The proportion of readily available P-NH4-acetate fractions increased in Chernozem and Luvisol in comparison with total available P-Mehlich 3 fractions under graded P doses. No evident increase of P-NH4-acetate fractions was obtained in Cambisol having the lowest CEC from all tested soils. The correlations between P content in plants of spring barley, P-uptake and phosphorus determined by Mehlich 3 and NH4‑acetate methods, with exception of relationship between P-barley and Mehlich 3, showed significant positive relationships. The highly positive relationship between P-Mehlich 3 and NH4-acetate methods indicating the suitability of both tests to predict phosphorus supply in soils.

The three-year field experiment (2015–2017) with graded doses of magnesium (Mg) and sulphur (S) was carried out at the Humpolec experimental station (49.5546239N, 15.3485489E; Czech Republic). The interactions between boron (B), Mg and S in the soil were studied. No boron was applied into soils. Contents of B, S and Mg in the soil were determined by the Mehlich 3 and NH₄ acetate methods. The crop rotation was: spring barley-oilseed rape-winter wheat. Three Kieserite doses (S and Mg fertiliser) were applied. Sulphur treatments were 10-20-40 kg S/ha to cereals and 20-40-80 kg S/ha to oilseed rape. The doses of Mg were: 13-26-52 kg Mg/ha to cereals and 26-52-104 kg Mg/ha to oilseed rape. A significant gradual decrease of B-Mehlich 3 was observed under Kieserite treatments during the experiment (from 1.24 mg B/kg in control in the 1^st year to 0.92 mg B/kg in the 3^rd year). On the contrary, B-NH₄ acetate contents in soils remained similar during 2015–2017 in control soils (0.33–0.39 mg B/kg) and significantly decreased under Kieserite treatments, namely by 55–57% in 2016 and by 43–48% in 2017. A significant decrease of B content in soils was noted since the second year of experiment after oilseed rape. The boron contents in soils were affected in several ways – by adsorption of B on magnesium oxides and other substances, exchange with SO₄^2– anions and possible leaching, and also by the uptake by grown crops, mainly oilseed rape.