Climate Rather than N Fertilisation Affects N Leaching in Winter Wheat

Abstract Excessive nitrogen (N) fertiliser application in agriculture, coupled with heightened weather variability and frequent intense rainfall, has resulted in diminished N use efficiency and nitrate leaching into drinking water resources. In this study, a 4-year N fertilisation gradient experiment was carried out at two experimental sites in the Czech Republic. The objective was to evaluate the effect of N fertilisation and weather patterns on the leaching of mineral forms of N, as well as on grain N uptake in winter wheat. Zero-tension lysimetric probes were installed in each treatment plot to collect soil water percolating freely from the soil above. The results showed that the leaching of different mineral forms of N was influenced in an opposite way by mean air temperature. While higher leaching of NH 4 + -N was found at lower air temperatures, the highest NO 3 − -N leaching was observed under higher air temperatures. NO 3 − -N leaching was closely positively correlated to rainfall. The relationship was exponential with a substantial increase in NO 3 − -N leaching occurring during vegetation season with rainfall above 400 mm. N uptake / N leaching ratio showed a positive correlation with mean air temperature and a negative correlation with rainfall. N fertilisation dose significantly increased grain N uptake in winter wheat. However, it did not significantly affect NO 3 − -N and NH 4 + -N leaching from the soil. The use of multiple regression and an artificial neural network models with input data rainfall, mean air temperature, and N dose in fertilisers led to an increase in prediction reliability to 62% and 94% in the case of NO 3 − -N leaching and 47% and 93% in the case of NH 4 + -N leaching, respectively. The results illustrate the importance of accounting for the effects of changes in mean climatic factors and climatic variability on both wheat N uptake and N leaching.