CORN, SUNFLOWER, AND SOYBEAN EMERGENCE INFLUENCED BY SOIL-TEMPERATUREAND SOIL-WATER CONTENT

The influence of soil temperature and initial soil water content on su bsequent germination and emergence of corn (Zea mays L.), sunflower (H elianthus annuus L.), and soybean [Glycine max (L.) Merr.] needs to be understood. Previous research has not determined whether emergence of corn and sunflower is reduced by soil water content that is high enou gh for seed imbibition but too low for radicle emergence from the test a. Our objective was to evaluate corn, sunflower, and soybean emergenc e influenced by initial seed-zone soil water content of 0.05, 0.07, an d 0.09 kg kg(-1) and soil drying at three day/night (17/8, 21/12, 25/1 6 degrees C) soil temperature regimes as the number of days of soil wa ter deficit and temperature stress increased. A factorial experiment w ith two replicates was conducted under controlled temperature conditio ns in an incubator. This experiment was conducted using a Glyndon silt y clay loam (coarse-silty, frigid Aeric Calciaquolls). Corn emergence was > 85% at all three initial soil water contents and temperature reg imes. Sunflower emergence increased from 59% at the low initial soil w ater content to 90% at the higher initial soil water content. Soybean emergence was 22% after stress was imposed by a 0.07 kg kg-L initial s oil water content (high enough for seed imbibition but too low for ger mination). If soil water content is sufficient to imbibe seeds of soyb ean and sunflower, but too low for germination during the 6 d after pl anting, producers may need to replant, especially when soil temperatur e is above 21/12 degrees C.