Seed Vigor and the Uniformity of Emergence of Corn Seedlings

Seed vigor is defined as those “seed properties that determine the potential for rapid, uniform emergence and development of seedlings under a wide range of field conditions.” Seedlings from high‐vigor seed lots are expected to emerge more uniformly than those from low‐vigor lots. We tested this hypothesis in a series of greenhouse and growth chamber experiments with several high‐ and low‐vigor corn ( Zea mays L.) samples that had high standard germination. Seed‐vigor levels were estimated with the saturated cold test where the seeds were stressed with low temperature (10°C) and field soil for 7 d and then germination was measured after 5 d at 25°C. The uniformity index (UI) (time from 10 to 90% of final emergence) was estimated by planting seeds 3.8 cm deep in soil and counting emergence every 6 h in greenhouse and growth chamber experiments. Lowering the soil temperature from roughly 23 to 15°C increased the time to 10% of final emergence (T 10 ) from about 100 to more than 300 h and increased the UI. Low‐vigor seed always had a larger UI than high‐ vigor seed, but the difference was less when the seedlings emerged rapidly (UIs were 20 to 30 h) than when they emerged slowly (maximum of ~80 h for high‐vigor seed and 140 h for low‐vigor seed). High‐vigor seed had more uniform emergence, but soil temperature and the time to emergence also influenced uniformity.