Growth of Subtropical Forage Grasses under Extended Photoperiod during Short‐Daylength Months

Abstract

One constraint on cattle production in the southeastern USA is the low productivity of perennial forage grasses during the short-daylength months. Evidence indicates that total growth during these months could be enhanced by exposing these grasses to extended photoperiod. A detailed analysis of their year-round productivity and nutritive value is needed to understand fully the consequences of overcoming the photoperiod-induced decline in growth. A 2-yr experiment was established at Ona, FL, in which photoperiod was extended to 15 h throughout the short-daylength months. Four grasses were studied: ‘Pensacola’ bahiagrass, Paspalum notatum Flugge var. Saurde Parodi; ‘Tifton 85’ bermudagrass, Cynodon spp. L. Pers.; ‘Florakirk’ bermudagrass; and ‘Florona’ stargrass, Cynodon nlemfuensis Vanderyst var. nlemfuensis Growth increases were observed in all grasses during the short-daylength months as a result of the extended-photoperiod treatment, with increases in the January through March harvests of 3-fold or more for Pensacola bahiagrass and 1.5- to 2.5-fold for Tifton 85 bermudagrass. Generally, there was no evidence of adverse consequences from sustained growth during the short-daylength months either in the subsequent spring and summer growth or in traits measured in below-ground tissue. With one exception, there was no major influence of the sustained growth on forage nutritive value during the short-daylength months for any of the year-round harvests. Pensacola bahiagrass had decreased crude protein under the extended-photoperiod treatment relative to the natural-daylength treatment. Overall, these results indicated that the selection and genetic incorporation of photoperiod insensitivity into these grasses could enhance productivity without adverse consequences.