Over the course of harvesting grassland, the sward inevitably becomes damaged. Over the summer months, the sward also dries out in places. Patches form, enabling low-yielding grasses and weeds to spread. The consequence: losses in yield and quality. Between August and September is a good time to improve grassland and fill in gaps. There is less competition from the old sward at this time, so new grasses have a better chance of getting established. Depending on the type of damage to the grassland, it will need to be partially or completely oversown, or even reseeded to increase the yield in spring.
Maintaining or re-establishing grassland
Over the course of the year, restorative measures are carried out on medium to high-intensity grassland to maintain a dense sward with as few weeds as possible. As such, localised overseeding is carried out once or more times a year. Smaller, existing gaps are filled in as a preventive measure. This enables weed infestation to be reduced and the stem density of valuable grasses to be increased.
In addition to localised overseeding, less damaged fields can also be completely overseeded to achieve a stronger sward with valuable, high-yielding grasses. The overriding aim is to increase the proportion of German ryegrass. This method also requires prior cultivation (e.g. harrowing, mulching, mowing). The sward itself, however, is not disturbed. This ensures that the sward is evenly developed. If the grassland is heavily infested with weeds, selective weed control is carried out beforehand. Without overseeding, a secondary weed infestation (by, for example, common chichweed, shepherd’s purse, annual meadowgrass and rough-stalk meadowgrass) can often develop. If weeds persistently penetrate the gaps in the grassland, it will need to be completely replenished multiple times.
On heavily damaged grassland with a weed infestation of over 50%, overseeding is usually insufficient, and complete reseeding is required. This should ideally be carried out in autumn. Due to the high likelihood of rainfall, the newly seeded grassland has a better chance of germinating. The first growth then appears in spring, promising a healthy yield and a high quality potential. In contrast to overseeding as a grassland maintenance measure, which is introduced as part of production-specific routines, reseeding is usually a last resort when regeneration and maintenance has been unsuccessful, or the land is being converted from arable to grassland. Reseeding requires more intensive cultivation and is associated with a longer period of forage loss during the growing season.