RELATIONSHIP OF WHEAT SEED SPROUTING SEVERITY, PLANTING DEPTH, AND SEED TREATMENT TO EMERGENCE AND YIELD

Negative effects of preharvest sprouting on wheat (Triticum aestivum L.) baking quality are well known, but limited information is available on field performance of sprouted seed and plants grown from sprouted seed. Field trials were seeded with 'Stephens' soft white winter wheat in 1989 and 1990 near Pendleton, OR, to determine the effects of sprouting severity (Trials 1 and 2), and seeding depth, and fungicide seed treatment (Trials 3 and 4) on emergence, growth, development, and yield of plants from sprouted seed. A sprouting-severity score was developed as follows: A = no visible sprouting, B = partial embryo exposure, C = full embryo exposure, and D = physically damaged embryo. Emergence and early crop growth were not affected when sprouting was not visible (A), but were significantly reduced when embryos were fully exposed (C) or damaged (D). Emergence and early seedling growth were reduced in proportion to sprouting severity of the seed. Carboxin + thiram [5,6-dihydro-2-methyl-N-phenyl-1,4-oxathiin-carboxamide + bis(dimethylthiocarbamoyl)disulfide] seed treatment had negative effects on stands produced from sprouted seed with fully exposed embryos, but these results were not consistent from year to year. Grain yield of plants grown from sprouted seed was not different from that of normal seed except when embryos were damaged (D). In seeding depth and seed treatment experiments, sprouted seed produced poorer stands and early growth than normal seed only in Trial 3. Treating sprouted seed with carboxin + thiram further reduced stands and growth in Trial 3. Sprouting did not affect seedling emergence and vigor in Trial 4 probably because the seed was less severely sprouted. Grain yield of plants produced from sprouted seed was not influenced by seed treatment in Trials 3 and 4. Shallow seedings produced better stands and yield than deep seedings, regardless of seed quality. The sprouting-severity score has potential in evaluating sprouted seed lots for use as seed wheat.