*3.3. Grain Quality*

In Caslav, the average grain yield increase, following the application of mineral N, was lower than in Ivanovice. The average grain yield increase was 2.77 t ha−<sup>1</sup> (+57%) for FYM+N1 treatment and 2.38 t ha−<sup>1</sup> (+49%) for FYM+N2 treatment. The overall grain yields were affected by fertilizer treatment by 61%, while the effect of the season represents 37%. The difference between FYM+N1 and FYM+N2 treatments was significant. According to the quadratic model, the maximum grain yield was reached at FYM+55 kg N ha−<sup>1</sup> (Figure 2a).

In Lukavec, the average grain yield increase, following the application of mineral N, was the highest out of all experimental stations. The average difference between the control and FYM+N1 was only 2.10 t ha−1, but expressed as a percentage, it represents an 88% increase. Comparing the control and FYM+N2 treatments, the average grain yield increase was 3.41 t ha−1, representing a 143% increase. The effect of the fertilizer treatment was, as in the case of Ivanovice, dominant (93%), while the effect

of the season was marginal (4%). The difference between FYM+N1 and FYM+N2 treatments was significant. According to the quadratic model, the maximum grain yield was reached at FYM+155 kg N ha−<sup>1</sup> (Figure 2a).

#### *3.4. E*ff*ect of the Mineral N Applied with P and K Mineral Fertilizers*

In comparison with the control, application of mineral NPK significantly increased average grain yields in all experimental stations (Table 6).

**Table 6.** 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).

In comparison with the control, the average grain yield increase varied from 2.72 t ha−<sup>1</sup> (+61%, FYM+N1PK) to 3.57 t ha−<sup>1</sup> (+80%, FYM+N3PK) in Ivanovice. The effect of fertilizer treatment on average grain yield was marginal (69%), while the season conditions affected average grain yields by 23%. No significant differences were recorded between FYM+N2PK and FYM+N3PK treatments. According to the quadratic model, the highest grain yield was achieved at FYM+98 kg N ha−<sup>1</sup> (Figure 2b).

The lowest average grain yield increase, when compared with the control, was recorded in Caslav, ranging from 1.42 t ha−<sup>1</sup> (+29%, FYM+N3PK) to 2.77 t ha−<sup>1</sup> (+57%, FYM+N2PK). The effect of the fertilizer treatment on average grain yield was 62%, while the effect of the season was 36%. The highest grain yields were recorded in FYM+N1PK (7.64 t ha−1) and FYM+N2PK (7.56 t ha−1) treatments (without significant differences between these two treatments). According to the quadratic model, the highest grain yield was achieved at FYM+72 kg N ha−<sup>1</sup> (Figure 2b).

The average grain yield increase in Lukavec ranged from 2.35 t ha−<sup>1</sup> (+99%, FYM+N1PK) to 5.11 t ha−<sup>1</sup> (+215%, FYM+N3PK). The factor "fertilizer treatment" dominantly affected the average grain yield (98%). According to the quadratic model, the highest grain yield ought to be achieved at FYM+155 kg N ha−<sup>1</sup> (Figure 2b).
