Calcium deficiency symptoms in forage corn ( <scp> <i>Zea mays</i> </scp> L.) due to excessive potassium supply under field conditions: Using leaf serration as a soil potassium indicator

Abstract Leaf serration in forage corn ( Zea mays L.) is often observed under field conditions. In this study, field cultivation experiments were conducted over 3 years to determine the factors affecting the appearance and development of this trait and to assess its potential impact on corn productivity. We also evaluated soil mineral conditions using leaf serration as an indicator. The number of symptomatic leaves per plant decreased after spraying with calcium chloride solution (3 g/L), and the development of leaf serration was also suppressed. Therefore, leaf serration in corn grown under field conditions may be a symptom of calcium deficiency. Occurrence of leaf serration did not significantly affect the dry matter yield of corn shoots at the yellow‐ripe stage, which is considered optimal for ensiling. This was because the yield, which included the leaves, stems, and ears, was not affected by calcium spraying. The number of leaves with symptoms increased logarithmically with an increase in soil exchangeable potassium content, owing to the decrease in calcium concentration in the corn plant caused by excessive amounts of soil potassium. The appearance of symptoms differed significantly among corn varieties, and the highest number of symptomatic leaves occurred in the variety with the highest calcium concentration. Different regression equations were obtained from the relationships between soil exchangeable potassium content and the number of symptomatic leaves in varieties with low and high calcium concentrations. The soil exchangeable potassium content was estimated using these equations, with the number of symptomatic corn leaves after silking as an indicator. With two or more symptomatic leaves per plant, the soil exchangeable potassium content was adequate for forage corn production. We suggest that a reduction in potassium input should be implemented in fertilization management if corn plants develop leaf serration.