Peat reduced substrates for vegetable seedlings

The major part of substrates, used for the production of press pots for vegetable seedling production in Germany is highly decomposed peat. The main reason is that the growing media for press pots should be sticky and compressible. In regions of intense vegetable production, producers appreciate press pots' advantages, such as superior crop safety and a lower transplant-shock. Political decisions for adaption to climate change account for more sustainable horticulture. Hence, the focus is on renewable materials used as growing media components for press pots. We started several trials to investigate the suitability of different materials used as growing media components to produce press pots for lettuce. Up to 30 to 50% of peat volume was replaced by raw materials such as wood fibre, coir pith and compost, amended by clay. We investigated the biological, chemical and physical properties of peat reduced growing media, such as the nitrogen-dynamics, pH-value, salinity, and air and water capacity. Apart from substrates, we assessed press pot stability beneath standard conditions. Furthermore, we tested the application of an automatic transplant machine and the performance of crops in the open field. We found that the stability of peat reduced press pots was similar to standard press pots. On average, approximately 95% of all seedlings could be transplanted successfully into the field. Thus, it can be assumed that the problem of press pot stability can be solved. Another issue for peat reduction in seedling production has not been investigated sufficiently yet - N-immobilisation - due to microbial activity.