Soil Water Effects on Low‐Temperature Seedling Emergence of Five Brassica Cultivars1

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Abstract
Identifying Brassica that are least sensitive to cool soil temperature and variable soil water availability during early spring is important to fill the forage deficit period in the southern Great Plains. A growth chamber study was conducted to determine the effect of soil water potential under low temperatures on the rate and total emergence for three Brassica spp. in Dale sandy loam (fine‐silty, mixed, thermic Pachic Haplustolls). Three turnip (Brassica rapa L.) cultivars, Purpletop, Cyclon and Tyfon, ‘Merlin’ kale (B. oleracea L.) and ‘Winfred’ rape (B. napus L.) were evaluated at a soil temperature of 7.5°C and five soil water potentials (−10, −30, −100, −250, and −500 kPa). Total emergence and rate of emergence of all cultivars were not affected by change in soil water potentials between −10 and −100 kPa. Soil water potential of −250 kPa reduced total emergence, whereas both rate and total emergence were greatly reduced with decrease in soil water potential from −250 to −500 kPa. Differences in total emergence were observed among cultivars even though seed germination potentials of all cultivars were similar. Purpletop turnip and Winfred rape were higher in total emergence and emerged in a shorter period under sub‐optimal environment conditions, comparedto other cultivars.
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