Reuse of rockwool slabs and perlite grow-bags in a low-cost greenhouse: Substrates' physical properties and crop production

Multiannual inert substrates, especially perlite grow-bags and rockwool slabs, are widely used over several cropping seasons in low-cost plastic greenhouses in mild winter climates, such as the Mediterranean coast of South-east Spain. This work analyses how the physical properties of rockwool slabs and perlite grow-bags change with time and use, as well as studying the response of sweet pepper and melon crops grown in new and reused perlite grow-bags and rockwool slabs. The main aims are to reduce expenditure and the environmental impacts of soilless crops grown in low-cost greenhouse areas. The main physical properties, including air capacity and easily available water, of reused rockwool slabs remained quite steady over three cropping years, and no negative effects were found in the fertigation, growth and productivity of sweet pepper and melon crops when grown in reused slabs, compared to new ones. The main physical properties of 5-year-old reused perlite grow-bags also remained steady and had no negative effect on the fertigation, growth and productivity of sweet pepper and melon crops. Therefore, the life-span of rockwool slabs and perlite grow-bags can be extended to 3 or 5 cropping years, respectively, for both crops.