First Leaf Emergence Force of Three Deep-Planted Winter Wheat Cultivars

摘要

Late summer planting of winter wheat (Triticum aestivum L.) into tilled fallow is necessary for production of maximum yield in many areas of the low precipitation (30 cm, annual) zone of the inland Pacific Northwest region of the United States. Farmers plant deep to reach moisture adequate for germination and emergence. The coleoptile of deep-planted wheat remains underground. The first leaf protrudes through the tip of the coleoptile and usually emerges about 10 to 12 d after planting. Emergence may be jeopardized by below-surface buckling of the first leaf. Buckling of the first leaf occurs when its exerted force cannot overcome the density or strength of overlying soil. Small, single-point load cells were used to measure force exerted by the first leaf of one semidwarf cultivar (‘Norwest 553’) and two standard-height cultivars (‘Farnum’ and ‘Finley’) as they emerged from a deep planting depth (100 mm) in a small containerized volume of soil. The average maximum before-buckling emergence force (BBEF) of Norwest 553 and Finley was 12.2 and 11.6 g, respectively. The corresponding value for Farnum (10.9 g) was statistically similar to the BBEF of Finley and less than that of Norwest 553. The measured difference between Farnum and Norwest 553 may be a consequence of variation in coleoptile diameter. Maximum diameter measurements of 1.6 to 1.7 mm were made near the base and in the middle of the Norwest 553 coleoptile. New knowledge generated from this research can be used to make decisions about the focus of future investigations that deal with poorly understood mechanisms responsible for emergence of wheat from deep planting depths.