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Published in Crop Sci 13:10-13 (1973)
© 1973 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
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Maturity Index as a Measure of Vegetative Development of Sudangrass and Related Sorghum Crosses1

D. C. Summer and R. L. Holmes2

To develop a method for establishing indices of vegetative development harvests were made twice weekly during the vegetative growth phase of ‘Piper’ and ‘Sudan 23’ sudangrass [Sorghum sudanense (Piper) Stapf.] and the cross ‘Sweet Sioux’ and ‘SX-12’ [Sorghum bicolor (L.) Moench x Sorghum Sudanese (Piper) Stapf.]. Heights from ground level to the uppermost exposed leaf collar (tiller height) and to the apical meristem were recorded for all tillers over 16.5 cm. The sum of meristem heights divided by the sum of tiller heights and the quotient multiplied by 100 describes a mean point, termed maturity index, of morphological development for each sample. This figure may be used to compare qualitative or quantitative measurements among cultivars, seasons, locations, or treatments at the same degree of morphological development.

Cultivars at the same morphological degree of development differed in stand height and percentage crude protein. Flag leaves were first evidenced at an index of approximately 70. At this stage of development there is a rapid increase in dry matter and lignin percentages, and a rapid decrease in crude protein concentration. The data indicate that harvesting at a maturity index of 70 (first evidence of flag leaves) may be a good compromise between maximizing quantity and quality of these forage crops.

Key Words: Plant height • Crude protein • Lignin

1 Contribution from the Department of Agronomy and Range Science, University of California, Davis 95616.

2 Specialist and Technician (deceased), Department of Agronomy and Range Science, University of California, Davis 95616.

Received for publication January 28, 1972.




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Copyright © 1973 by the Crop Science Society of America.