Trends in Forage Yield and Nutritive Value of Hay-Type Sorghum spp
2004
Moyer, J. L. | Fritz, J. O. | Higgins, J. J.
Sudangrass [Sorghum bicolor (L.) Moench], other Sorghum spp., and sorghum–sudangrass hybrids are used extensively for hay on U.S. cropland because of their production potential. Performance evaluations have emphasized yield and other agronomic characteristics but seldom emphasized forage quality. Available hay-type sorghum cultivars released over a period of four decades were grown in five trials over a 21-yr period to evaluate trends in forage yield and nutritive value. First-cut (boot stage to head emergence) forage was harvested for yield and subsampled for one or more quality components. The first trial in 1977 tested forage crude protein (CP), and subsequent trials included more quality traits. In 1993 and 1998, the traits measured included leaf/stem ratio and leaf and stem concentrations of CP, neutral-detergent fiber (NDF), and acid-detergent fiber (ADF). Pearson correlation coefficients by year and correlations pooled across trials by two methods indicated similar relationships between forage characteristics and year of cultivar release. Year of release was positively associated with forage yield in two of the five trials and for the pooled correlations. Forage CP and CP of leaf and stem fractions were negatively correlated with year of cultivar release for the pooled trials and in most individual trials. Leaf NDF and ADF were positively correlated with year of cultivar release in the pooled trials. Yield gains of about 0.5% per year were found, but concomitant relative reductions of 0.1% or more per year in forage CP and leaf NDF run counter to the perceived need for improved hay quality. These findings emphasize the need to locate and incorporate cost-effective sources of germplasm to enhance nutritive value of forage in hay-type Sorghum spp.
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