Short photoperiod inhibits winter growth of subtropical grasses

Grass development is influenced by length of photoperiod, but no direct measurements under natural conditions exist on mass accumulation in response to photoperiod by subtropical grass species. Grasslands of the subtropics are a major resource, but their growth is inhibited substantially during the short-photoperiod months. This research was designed to examine the consequences on grass production under field conditions when the limitation of short photoperiod is artificially removed. Lights, which extended the daylength to 15 h, were placed over plots of four subtropical forage grasses representing three species (Paspalum notatum Flugge; Cynodon dactylon L.; Cynodon nlemfuensis Vanderyst) to measure their mass accumulation in response to extended photoperiod in a 2-year experiment. Forage yields in all grasses at 5-week harvests during the time of shortest daylength were increased up to 6.2-fold more than the yield under the natural daylength. For the 4.5-month period of shortest daylength in each year, forage yields were increased for all grasses with one grass having a yield increase of 3.6-fold under the extended photoperiod as compared to natural daylength. These results demonstrated that selection of grasses that are insensitive to photoperiod could substantially increase forage yield of subtropical grasslands to benefit animal production and enhance carbon sequestration.