Bare spots have been observed on newly sown grassland in the last few years. The grass comes up well but falls out after a few weeks. The problem mainly occurs on sandy soil and in some cases also in existing grass. It is difficult to determine the exact size, but various advisers report that they are aware of plots with failures.
Inquiries at Wageningen UR reveal that there are many factors that can cause bald spots. No specific research has yet been conducted into the recent problems with grass loss, but the university has conducted previous studies. One or a combination of the factors below can cause failure.
imbalance
Because it mainly concerns newly sown meadows, it may well be that the balance between nematodes and fungi has been disturbed. In existing grassland, there should be a balance between soil life and the turf. If the pasture is torn up for renewal or cultivation of corn or potatoes, for example, the balance is disrupted. The newly sown grass does not (yet) provide sufficient organic material to feed soil life. Nematodes eat too much of the fragile plant, causing it to die, resulting in bald spots. Drought after sowing can further increase this effect. The plant is more stressed and is more sensitive to diseases and pests.
A disturbance in the soil structure can also be a possible cause. Relatively speaking, the sand heads in a plot seem to have the most bare spots. A disturbing layer and/or poor moisture balance is often first visible in these places. The relatively warm weather in autumn and winter in recent years could allow insects to remain active longer. Larvae such as grubs only crawl into the ground later to overwinter.
Research ForFarmers
In October 2020, ForFarmers conducted research on 4 plots of sandy soil in the East of the Netherlands. Soil samples were taken from the good and bad places in the plots. After analysis, it appears that the fertilization and the insects present are not the cause of the bare spots. The samples did contain many nematodes and fungi.
Bob Keurentjes, Innovation Manager Roughage Cultivation at ForFarmers: "We cannot yet determine to what extent the damage is caused by the nematodes and fungi. The grass is sown in challenging - dry - conditions. This reduces the resistance of the plant and susceptibility to diseases and pests is greater. Further research should provide insight into the conditions and the population of nematodes and fungi that have the greatest effect on damage, so that these problems can be prevented in the future and targeted action can be taken if damage occurs. "
Repair
There are several options to repair bald spots. Advisors emphasize waiting until the ground is competent. Tampering in wet conditions only makes the problem worse. If there are small bare spots on the plot where there is still some grass, an early small application of fertilizer may be sufficient for recovery. If the soil is not yet sufficiently compacted, rolling is recommended. Overseeding is necessary for large bare spots with too few plants.