Nitrogen leaching from the soil lysimeters after autumn and spring nitrogen application to winter wheat

In 1985 - 1988 in lysimetric trials performed in Praha-Ruzyne, the leaching of mineral nitrogen was studied under winter wheat in dependence of natural precipitation. Lysimeters with an area of 527 cm2 were filled every year in the autumn with 30 cm of top soil from grey brown soil on loess and the soil was fertilized with 120 kg of nitrogen per ha in the UAN fertilizer in a single autumn application, or at two separate 50 kg nitrogen rates (one applied in ammonium sulphate in autumn and the other in urea in spring). The fertilizers were applied in a solution. Analysing the mineral nitrogen in lysimetric waters, it was found that from the 30 cm layer of topsoil 46 to 58 per cent of the 50 kg nitrogen application rate was leached before mid April and 51 to 71 per cent was leached from the 120 kg batch applied per ha. At the first percolate sampling (January, February), the proportion of fertilizer nitrogen out of the total amount of leached mineral nitrogen was 12 to 24 per cent at the lower application rate and 28 to 50 per cent at the higher rate; nitrates produced in the soil formed a substantial proportion after the filling of the lysimeters. At the second sampling (April), the proportion of fertilizer nitrogen increased to 29 - 41 per cent at the lower rate and to 53 - 63 per cent at the higher nitrogen application rate. In the third sampling, when winter wheat was ripe, the concentration of mineral nitrogen was comparatively low in lysimetric waters (up to 7 mg per l), 0.1 to 0.2 per cent of nitrogen was leached from the autumn fertilizer and only a trace amount from the fertilizer applied in spring. The grain and straw of winter wheat were found to contain 5 to 13 per cent, and the soil, 13 to 30 per cent, of the nitrogen applied in autumn; as to the divided spring nitrogen application rate, the plant utilized 27 to 37 per cent and 50 to 54 per cent remained in the soil.