Rate of Fill and Length of the Grain Fill Period for Nine Cultivars of Spring Oats1

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Abstract
We hypothesized that yield differences among cultivars of spring oats, Avena saliva L., can be partially explained by differences in the daily rate of grain fill and length of the grain fill period. To obtain information on these factors, nine cultivars of spring oats were sampled three times weekly in the field in 1975. The time between anthesis and physiological maturity was considered to be the fill period. Physiological maturity was considered to be the date beyond which there were no differences in grain yield significant at the 5% level of probability and half of the glumes and kernels no longer took up a red water soluble dye. In 1975, the mean grain fill period for nine spring oat cultivars, planted and fertilized at recommended rates, was 23 days with a range of 20 to 24 days. In 1976, for eight of the same nine cultivars, the mean grain fill period was 24 days with a range of 23 to 26 days. One variety, ‘Pennfield,’ was tested over a 3 year period. Lengths of the grain fill period were 22, 26, and 25 days, respectively, in 1975, 1976, and 1977. In 1975, the mean daily rate of grain fill at 0% moisture was 95 kg/ha with a range of 88 to 100 kg/ha. Data on rate of grain fill were not secured hi 1976. Grain yield in 1975 was significantly correlated at the 1% level with rate of grain fill, length of the grain filling period, leaf area duration, and accumulated heat units and solar and sky radiation during the grain fill period. Multiple correlation and regression analysis indicated that low rates of grain fill and short leaf area duration limited grain yield in 1975. These data suggest that it may be easier to increase spring oat yields by altering the rate of grain fill than to greatly increase the length of the fill period.