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Effect of N Fertilization on Silk Synchrony, Ear Number, and Growth of Semiprolific Maize Genotypes¹

Prolific (two-eared) maize (Zea mays L.) genotypes usually yield more grain per plant than do comparable nonprolific (one-eared) genotypes. Among semiprolific genotypes a larger proportion of two-eared plants results when the top and second ear shoots emerge within 24 h of each other (silk synchrony). The present investigation was conducted to determine the influence of N fertilization on silk synchrony and the development of the second ear. A further objective was to determine the independent effects of silk synchrony and ear number on plant growth throughout the grain-filling period at different levels of N. Nitrogen rates were 56 and 224 kg N/ha. A plant density of 22 600 plants per ha was used in order to provide an adequate number of both one- and two-eared plants for sampling. Plants were classified as to silk synchrony and ear number. Leaves, stalks, and ear shoots were sampled four times during reproductive growth. Measurements were made of dry weight and N content. Increased rate of N fertilization resulted in a higher percentage of plants with synchronous silks and also increased the percentage of plants with synchronous silks that developed two ears. At a low N rate one-eared plants with synchronous silks accumulated more dry matter and N than did plants with asynchronous silks. At high N rate silk synchrony per se had no effect. The higher grain yield at the high N rate was due to a higher percentage of two-eared plants. Two-eared plants accumulated more ear and total dry weight and total N than did one-eared plants. Two-eared plants also partitioned more of the dry weight and N to the ear than did one-eared plants.

Key Words: Prolificacy • Zea mays L. • Grain yield • Dry matter partitioning

² Former graduate student, now soil scientist, USDA-ARS; professor of soil science; professor of genetics; professor of soil science, North Carolina State Univ., Raleigh, NC 27650.

Received for publication July 21, 1983.