Grass doesn’t just happen and not all species grow the same way. Understanding how different grass species grow enables producers to make good management decisions that maximize forage production in their hay fields and pastures. Jointing and non-jointing grasses respond differently to cutting, which directly affects productivity and persistence.
In an established stand, grass plants are not made up of a single stem but have many tillers. One grass plant may have dozens of tillers which arise from growing points at the base of the plant. Having the growing point at the base of the plant is an evolutionary adaptation because it protects the grass from grazing, since most animals cannot graze so close to the ground as to damage this growing point.
During vegetative growth, leaves are pushed upward from the base of the tillers. Then all grasses begin stem elongation in preparation to flower and set seed. The stem, or culm, consists of nodes separated by internodes. Each node with its associated internode is a stem segment, commonly called a joint. Technically, all grass species are jointing species because they all put up flowering stems by lengthening the internodal spaces. The designation of “jointing” or “non-jointing” refers to how the grass regrows once the seed head is removed.
When jointing grass species regrow after flowering, they go through stem elongation again. Jointing grasses have their growing point above the newest completed joint, which means that as stem elongation progresses, the growing point rises. Jointing grasses are easily damaged if the growth point is cut or grazed off at the wrong time. Defoliation will be least damaging to jointing species if it occurs either during tillering when the growth point is low, or between boot and early heading. If the grass is harvested during stem elongation, new regrowth must start from the crown of the plant and use energy reserves from the roots – just like when the plant breaks dormancy in the spring. This is a significant stress on the grass. By waiting until boot stage, the crown has time to develop additional tillers that will provide regrowth. So long as the timing is correct, jointing grasses can be cut as low as 5-7.5 cm (2-3 in.) without reducing yield potential or persistence. Jointing grass species include timothy, smooth brome, reed canarygrass, and Italian (annual) ryegrass.
When non-jointing species are cut after flowering, the regrowth remains in the vegetative state, and very few tillers attempt stem elongation again during the growing season. The growing points of non-jointing grasses remain close to the ground. It is more difficult to cut or graze off these growing points and leaf regrowth can occur faster compared to jointing species. Keeping the cut height or target grazing residual above the stem base protects the growing points and productivity of non-jointing grasses. Non-jointing grass species include orchardgrass, tall fescue, meadow fescue, Kentucky bluegrass, and perennial ryegrass. While meadow fescue, Kentucky bluegrass, and perennial ryegrass will tolerate defoliation down to 5 cm (2 in.), orchardgrass is more productive if 7.5-10 cm (3-4 in.) of residuals is left.
Mixing jointing and non-jointing species together makes management more complicated. Non-jointing grasses are better suited for pastures, as the growth point is better protected, and the vegetative regrowth is more palatable to grazing animals. Either jointing or non-jointing species can be harvested for stored forage. There may not be a time when all jointing species in a mixture are at the same optimal stage for harvest, so grass managers need to closely monitor the growth stage of each species and decide which to favour. Repeated cutting at a susceptible growth stage will push a grass species out of the stand.
Source : Field Crop News