Improving the yield of organic meadows and pastures through regular reseeding and supplemental fertilization with phosphorus and sulfur

The "BioNaDü" project focused on improving the productivity of organically managed meadows and pastures through regular reseeding and supplemental fertilization with phosphorus and sulfur. The study was conducted over five years (2018–2022) at two sites: a four-cut meadow and a short-grass pasture. 

Key findings:

1. Reseeding: Effects on vegetation: Reseeding showed no significant improvements in the botanical composition. Grasses such as perennial ryegrass, which were the focus of the trial, declined continuously in all variants during the trial (from 75% of the area in 2018 to 51% in 2022). Technical limitations: A low proportion of bare soil (0–4%) and the limited effectiveness of mechanical cultivation (harrow) prevented sufficient germination and establishment of the sown grasses and legumes. Stand development: There were no differences between the variants with and without reseeding, neither in grazing nor in the cutting system.
2. Supplementary fertilization: Phosphorus (P): Additional phosphorus fertilization showed no significant effects on yields. The measured differences in P levels were small and inconsistent. Sulfur (S): Although higher S levels were measured in the plant samples after supplementary sulfur fertilization, this did not lead to higher yields or improved development of the forage legumes. Legumes: White clover, the main component of the legumes in the pastures, did not increase in the variants with P and S fertilization. On the contrary, its proportion decreased across all variants during the trial period.
3. Yields and Quality: Dry Matter (DM): Yields remained at a high level (9,000–12,000 kg DM/ha) and showed no significant increases as a result of the measures. Constituents: Neither reseeding nor fertilization led to an improvement in crude protein yields or energy content. Site Conditions: The good initial conditions of the fields limited the possibility of achieving yield increases through additional measures. 

Conclusion:

The study shows that on already well-developed organic grassland areas, reseeding and supplemental mineral fertilization do not offer significant benefits. Successful reseeding requires sufficient open soil and reduced competition from existing vegetation, which was not adequately present in this study. For long-term sustainability, farms should focus on optimizing the use of their own manure resources before applying supplemental mineral fertilizers. 

Image gallery of the research project: