The effect of fertilization and precipitation on the yield of maize (Zea mays L.) in a long-term experiment

This study examines how the amount of precipitation, the NPK fertilizer treatment and their interaction affects maize yield. The measurements were carried out at the Latokep experiment site of the University of Debrecen (Debrecen, Hungary N: 47 degrees 33', E: 21 degrees 27', 113-118 metres above sea level) on mid-heavy calcareous chernozem soil in a multifactoral long-term field experiment established in 1984. 17-year-long data series were used (1990-2008) in the study. We examined how the precipitation during the growing season and the winter period affected maize yield and demonstrated into that there was a strong positive correlation (r = 0.710; p<0.01) between the amount of precipitation during the growing season and yield. Based on the effective heat units (EH) and the potential evapotranspiration (PET) values, the growing seasons of the long-term experiment were separated to dry and wet years. The difference between the average yields of dry and wet years was significant (p<0.05). Significant difference was obtained (p<0.05) between the non-fertilized and fertilized treatments (60 and 120 kg N ha(-1)). The 120 kg N ha(-1) treatment did not significantly increase the maize yield in comparison with the 60 kg N ha(-1) treatment. The evaluation of the joint effect of fertilization and precipitation on yield showed that fertilization is responsible for nearly twice as much of the standard deviation of yield as the amount of precipitation. In dry years, there was a significant difference only between the non-fertilized and fertilized treatments, whereas in wet years, we even found a statistical difference between fertilizer doses. As regards fertilizer treatments, higher yields were obtained in wet years than in dry ones. Altogether, statistical evaluations showed that the nutrient utilization of the applied fertilizer is determined by precipitation supply. In dry years, only smaller fertilizer doses (60 kg N ha(-1)) were utilized, higher doses were not necessary. In wet years, higher doses (120 kg N ha(-1)) induced significantly higher yield and higher extent of nutrient utilization.