Effect of potassium supply and plant density on maize (Zea mays L.) yields and nutrient contents: a case study in a Hungarian long-term field trial set up on calcareous chernozem soil

The effect of potassium supply and plant density on maize (Zea mays L.) was investigated in terms of the leaf weight in the flowering stage, grain yield components, grain and stalk yield and their potassium, calcium and magnesium contents, in a field trial set up in Nagyhörcsök, Hungary, on a calcareous chernozem soil with poor to moderate potassium supplies. Different potassium supply levels were achieved by the initial build-up application of 0-240-480-960-1440 kg K₂O ha⁻¹ in autumn 1989. Adequate nitrogen and phosphorus supplies were provided by yearly NP fertilization. The year studied was favourable for maize growth and development. The maize hybrid Pioneer SC 3732 (FAO 450) was sown at plant densities of 24-48-72-96 thousand plants ha⁻¹. The plant density had a more pronounced effect on grain yield than the different K supplies. Stalk yields showed trends similar to those for grain yields, but plant density had the opposite effect on the leaf weight (g 20 leaves⁻¹) in the flowering stage. K fertilization increased the K content to the greatest extent in the vegetative parts (leaf and stalk), while increasing plant density had a reverse effect. The K-Ca-Mg antagonism was also the most pronounced in the vegetative parts, i.e. maize leaves in the flowering stage. According to the results obtained in the field trial, it seems that a century ago, in our grandparents’ time, food contained more minerals than nowadays, due to the fact that plant density decreases grain mineral composition more than mineral fertilization can increase it.