Overseeding of permanent grassland may increase the proportion of perennial ryegrass and thus extend the life of grassland. The effectiveness of overseeding was investigated in a three-year field trial on five parcels of grassland on the Dairy Campus.
The results show that the number of seedlings counted was strongly dependent on the overseeding conditions; only the fourth time overseeding, significant quantities of seedlings were counted. After the third overseeding, despite the limited emergence of seedlings (9% of the seed), the percentage of ryegrass in the following summer increased from 63% to 68% (P <0.001). Based on the results so far, overseeding seems to have perspective.
The main objective of this public private partnership program is to improve and make roughage production and soil management more sustainable. The PPP Roughage & Soil is a public-private partnership between the Ministry of Agriculture, Nature and Food Quality (LNV) and a consortium of various parties from the seed breeding industry and the agricultural production chain. The PPP falls under the top sector policy of the government, namely under the Top Sector Agri & Food.
Overseeding field trials
Seedlings after overseeding on four test fields Seedlings after overseeding on four test fields A total of four seeds were sown in the autumn. In the first two years only an average of 25 to 31 plants per m2 were counted, in the third year 84 plants per m2, and in the fourth year 418 plants per m2 (see Figure). The seedlings of the first two overseeding did not increase the proportion of English ryegrass in the following season. Overseeding in the third year (2018) resulted in an increase in the percentage of English ryegrass from 63% to 68% in the summer of 2019 (P <0.001); the effect of the last overseeding (2019) is yet to be determined next year. The conditions of overseeding (drought, wetness, temperature, closing of the cuts) have a decisive effect on the effectiveness of overseeding, measured by the number of seedlings counted. Based on this, a number of recommendations for practice have been drawn up.
Recommendations for practice
- Overseeding is best carried out with the shortest possible grass, for example immediately after mowing and the field period;
- Powerful harrows prior to overseeding remove weeds and dead organic matter from the sod. This creates extra space for seedlings;
- Sow seeds only at a moist (malleable) top layer, at a sufficiently high temperature, and preferably when precipitation is expected. If these conditions are not met, postpone overseeding;
- Do not overseed with a dried out or wet top layer;
- Do not overseed in early spring, at the beginning of the first growth period;
- Do not overseed if the night temperature permanently drops below 10 degrees;
- Use at least 15 kg of good germinating seed per ha, and sow at an average depth of twice the seed length. Usually that is 12-15 mm;
- Ensure that the overseeder is correctly adjusted; sow a test strip and check the incision, the seeding depth, the seed distribution in the cut, and the closing of the cuts (when using a Vredo);
- Ensure the best possible contact between the seeds and the soil; if necessary, re-roll with a Cambridge roll and when using a Vredo make sure that the cuts close as much as possible.
Read more about all test results in the spring of 2020 on the dutch website www.ruwvoerbodem.nl.