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Grain Yield and Yield Components of Soft Red Winter Wheat as Affected by Management Practices¹

The use of intensive management practices could substantially increase soft red winter wheat (Triticum aestivum L. em Thell.) grain yields in the northeastern USA, but more information is needed about the influence of management factors on components of yield. Our objective was to determine the effects of seeding rate, row spacing, seeding depth, and rate of spring-applied N fertilizer on grain yield components and to calculate the yield changes associated with changes in the yield components. ‘Roland’ wheat was grown on eight Pennsylvania farms during 1981 and 1982 on either Typic or Ultic Hapludalf soils. Treatments were row spacings of 12.7 and 17.8 cm, seeding depths of 1.9 and 3.8 cm, seeding rates of 101,168, and 235 kg ha^–1 and spring N topdressing rates of 0, 34, 67, and 101 kg ha^–1. Plot subsamples were used to determine grain yield, tiller number, kernel number per tiller, and kernel weight. The over all treatment means for locations ranged from 291 to 420 g m^–2 for yield, 440 to 585 for tillers m^–2, 20.0 to 27.6 kernels/tiller, and 27.2 to 35.5 g/lOOO kernels. Kernel number per tiller appeared to be consistently below genetic and phenotypic potentials. Yield changes associated with increasing levels of N varied from positive to negative quadratic responses at the low and high yielding sites, respectively. The primary component of yield decreases was reduced kernel weights. Increasing the seeding rate beyond 101 kg ha^– always resulted in increases in tiller number and decreases in the number of kernels per tiller while increases in kernel weight occurred at six locations. When row spacing was decreased to 12.7 cm, grain yields increased by an average of 8.2%, and the primary contributing component was more tillers per unit area. This was the only treatment without consistent negative responses in at least one other yield component. Increasing planting depth to 3.8 cm reduced the number of tillers and was associated with increased kernel number per tiller at most locations. The only yield change was a decrease at a location where planting date was delayed.

Key Words: Nitrogen fertilization • Seeding rate • Row spacing • Seeding depth • Tiller number • Kernel number • Kernel weight • Triticum aestivum

² Former graduate research assistant, Dep. of Agronomy (current address: Dep. of Agronomy, Univ. of Illinois, Urbana, IL 61801); and research agronomist, ARS, USDA, and adjunct professor of plant breeding, Dep. of Agronomy.

Received for publication July 30, 1984.