*3.1. E*ff*ect of the FYM*

Application of the FYM to the maize three years before wheat was sown (see the crop rotation description in Section 2.2.) significantly affected average wheat yields in all experimental sites (Table 4).


**Table 4.** Comparison of average grain yields (t ha−1) as affected by locality, year, and fertilizer treatment.

Mean values with the standard error of the mean SE, followed by the same letter (A vertically, a horizontally), are not significantly different (α < 0.05).

The average grain yield increase between the control and FYM treatments ranged from 0.48 t ha−<sup>1</sup> in Lukavec to 0.78 t ha−<sup>1</sup> in Caslav. However, the highest percentage increase was recorded in Lukavec (20%), followed by Caslav (16%) and Ivanovice (13%). The differences in average grain yieldswere not achieved by the only application of the FYM, as the effect of the year also significantly affected the compared grain yields. While the overall effect of the fertilizer treatment and weather conditions on average yield was equal in Ivanovice (49% for fertilizer treatment; 51% for weather conditions) and Caslav (47% for fertilizer treatment; 52% for weather conditions), the higher effect of the fertilizer treatment was recorded in Lukavec (62% for fertilizer treatment; 35% for the weather conditions), showing a lower fluctuation of grain yields between the years.

#### *3.2. E*ff*ect of the Mineral N Applied without P and K Mineral Fertilizers*

In comparison with the control, application of mineral N fertilizers applied without mineral P and K fertilizers significantly increased the average grain yields in all experimental stations (Table 5).


**Table 5.** Comparison of average grain yields (t ha−1) as affected by locality, year, and fertilizer treatment.

Mean values with SE, followed by the same letter (A vertically, a horizontally), are not significantly different (α < 0.05).

The average grain yield increase was 2.79 t ha−<sup>1</sup> (+63%) for FYM+N1 treatment and 3.37 t ha−<sup>1</sup> (+76%) for FYM+N2 treatment in Ivanovice. The effect of the fertilizer treatment on overall grain yields was dominant (86%) when compared with the effect of the season (9%). The difference between FYM+N1 and FYM+N2 treatments was significant. According to the quadratic model, the maximum grain yield was reached at FYM+70 kg N ha−<sup>1</sup> (Figure 2a).

**Figure 2.** The average wheat grain yield as affected by fertilizer treatment ((**a**)—control, FYM+N1, FYM+N2; (**b**)—control, FYM+N1PK, FYM+N2PK, FYM+N3PK), and locality over the period 2015–2018.
