Yield and Yield Components Stability of Winter Wheat and Spring Barley in Long-Term Experiment in Poland

The aim of this study was to evaluate the effect of long-term crop rotation and fertilization treatments on the yield and yield component stability of spring barley and winter wheat on the basis of selected data over 30 years. The stability was measured using statistical methods (the Shukla stability index and linear mixed models). The long-term field experiments established in 1955 were conducted in central Poland (Chylice near Warsaw, 52°06′ N, 20°33′ E) and consisted of two crop rotations with the same fertilization regime. The first field experiment (A—NOR) is typical of the Norfolk rotation and consists of the following four crops: 1. sugar beet, 2. spring barley with undersown red clover, 3. red clover, and 4. winter wheat, while the second field experiment (B—NONleg) contains a sequence of crops without legumes: 1. sugar beet, 2. spring barley, 3. winter rapeseed, and 4. winter wheat. The following fertilization regimes are used in both experiments: a control without any fertilization (O), mineral fertilization (NPK), farmyard manure (FM), and mixed mineral and organic fertilization (½ NPK + ½ FM). The average yields of winter wheat and spring barley (in t*ha−1) were 4.34 (a max of 5.48 in NONleg_NPK) and 4.27 (a max of 5.67 in NONleg_NPK) in the NONleg rotation treatment and 5.39 (a max of 6.12 in NOR_NPK) and 4.28 (a max of 5.22 in NOR_½ NPK + ½ FM), respectively, in the legume-based NOR rotation treatment. In the legume-free rotation treatment, the highest yield stability was found in the treatments fertilized only with manure (NONleg_FM) and in a mixed manner (NONleg_½NPK + ½FM), while in the Norfolk rotation treatment, the yield stability was the highest in the treatments with mixed fertilization (NOR_½NPK+½FM) and the treatments in which only mineral fertilizers were used (NOR_NPK).