Effect of the fertiliser supply for the maize micro nutrient content depending on the part of the plants under long-term field experiment

The long-term experiment was carried out at the University of Debrecen, Institutes for Agricultural Research and Educational Farm, Debrecen Edcuational Farm and Landscape Research Institute (DTTI), Látókép Crop Production Experiment Site (47° 83, 030" N, 21° 82, 060" E, 111 m a.s.l.). The experimental area is an excellent site for field crop production, with suitable agrotechnical biological and soil conditions. The trial was established in 1983 by Prof. Dr. János Nagy and has been continued for 39 years with the same parameters, nutrient replenishment system, site, tillage and agrotechnology. The total area of the experiment is more than 1.3 ha, with 1248 plots. The climatic-meteorological conditions of the experimental area are continental and often extreme, with calcareous chernozem soil with a topsoil depth of 80-90 cm and a humus content of 2.71 Hu%. The pH of the soil is 5.76 (slightly acidic). The soil is less susceptible to acidification because the 80-90 cm deep calcareous layer is a good buffer against acidification. In terms of soil acidification, nearly 40 years of high-dosage nitrogen fertilization (300 kg/ha of active ingredient) in the experiment resulted in a pH decrease of only 0.6 units compared to the control.  For this study, nitrogen doses of 0-300 kg/ha were applied at 5 different levels, with a gradual increase in nitrogen and a constant high level of phosphorus and potassium. In a micronutrient uptake effect study of nitrogen fertilisation, it was found that the concentration of zinc, the primary essential micronutrient for maize, was significantly reduced in all crop parts by increasing nitrogen dosage compared to control values. The most significant of these effects was the reduction in stalk zinc concentration in the vegetative parts of the crop, which was at least 39% in all treatments, with the greatest reduction in treatment N4 at 18.61 mg/kg.  In the case of the generative parts of the plant, the zinc content of the grain yield decreased statistically in all treatments, with the greatest negative change in this case also in treatment N4, with a decrease of 39 % (9.14 mg/kg). The iron content responded positively to the increase in nitrogen fertilisation. An increasing trend was measured for all plant parts, which was significant in several cases. Significant increased iron accumulation was observed during the leaf analysis of maize under all fertiliser treatments, with the highest increase of 47 % under the treatment N5. Based on the correlation between copper content and nitrogen supply in plant parts, it was found that increasing nitrogen fertiliser treatments resulted in significant increased concentrations in both maize leaves and cobs, ranging from 5 to 56 % and 8 to 38 %, respectively. The values obtained from stem and grain yield analyses did not show significant changes in effect.