Effects of organic substrate reuse on growth and yield of everbearing 'Capri'strawberry

As sustainability has become a major concern in our society, the use of low substrate amounts per plant and the possibility of reuse play a role in minimizing the environmental impact and in reducing the crop costs. The cultivation in used substrate increases dramatically the risks associated to root-borne pathogens and pests and/or by root exudates (allelopathy), and strawberry (Fragaria × ananassa Duch.) has a very sensitive root system. The aim of the trial was to investigate the possibility of reusing organic substrates in everbearing strawberry soilless culture without loss of yield and quality. Two factors were analysed: the growing medium, 3 one-year used substrates (85% peat and 15% coir (PC), 50% coir and 50% conifer wood (CW) and 100% coir (CC)) and a New PC substrate as reference; the substrate disinfection, steam sterilization or control. There was both a substrate-dependent effect in the structure of the microbial communities and an influence of the sterilization on the bacterial and fungal communities. Sterilized substrates determined more vigorous plants, which were however weaker than the New PC plants. In addition, steam sterilization reduced the loss of yield in respect of the production obtained on new PC substrate. Sterilized CC performed as well as the New PC. One-year PC reached the lowest yield values, despite the disinfection treatment, and it confirmed the unsuitability of this growing media to be reused because of the inability to maintain the original characteristics.