Grow - Store - Steam - Re-peat: Reuse of spent growing media for circular cultivation of Chrysanthemum

Abstract

Substantially extending the life span of peat-and perlite-based growing media is a measure to increase the sustainability of soilless cultivation. The extraction of peat from pristine peatlands threatens these sensitive ecosystems and carbon sinks, meanwhile resulting in increased emissions of greenhouse gasses. Each batch of peat that is reused, results in a clear reduction in CO 2 emissions and a lower impact on the climate. After using growing media for one cultivation, we aim at reusing the spent material as growing medium for another crop. Spent peat and perlite based growing media from strawberry and cucumber cultivation were upcycled after steam treatment. We tested the effectiveness of steaming to reduce phytosanitary risks. The hygienisation efficiency of the steam treatment was confirmed: plant pathogenic fungi, larvae of vine weevils and weed seeds added or already present before the process were killed by the steam treatment. As the upcycled spent growing medium already contained high nutrient levels, the fertilizer application in the reused growing medium should be reduced, especially for P and K. Five indicators for assessing stability of the materials were used: CO 2 flux measurements, oxygen uptake rate (OUR), biodegradation potential, mineral N content and risk for N immobilization. The spent growing media had a low decomposition rate and the release of nutrients in a leaching experiment was lower than for a fertilized peat-based growing medium, being a reference blend for open field cultivated Chrysanthemum. N mineralisation and P uptake were tested in an incubation and pot trial, respectively, and the upcycled spent growing medium was found to be an important source of plant-available K and P. Steam treatment did not severely affect the microbial biomass and diversity of the spent growing media. Blending the steam-treated spent media with other materials or inoculating by a commercially available biocontrol fungus also had a limited effect, indicating that newly introduced microorganisms do not easily establish in steamed-treated spent growing media (SSGM). Acidification of the SSGM was achieved by a low dose of elemental S. The steam-treated growing medium was tested for growing Chrysanthemum cuttings and plantlets. Spent growing media were not able to supply sufficient mineral N, but the stored amounts of P and K in the media were sufficiently plant available for optimal crop growth.

Agro-industrial-residues as potting media: physicochemical and biological characters and their influence on plant growth

“…Spent PM can be reused as PM with or without modifications. High degradability/low stability, presence of harmful microorganisms (animal and plant pathogens), weed seeds, high residual nutrient, and salt content are some of the major challenges in the reuse of spent PM [ 215 , 216 ]. On reuse, a highly degradable substrate in PM may result in O 2 deficiency [ 86 ], altered physicochemical properties and nutrient depletion, and thus compromise plant growth, which must be studied in detail.…”

Recirculation, circular fertilizers and resilience: the potential of growing media systems for circular production

“…However, several peat alternatives in themselves harbour unique properties which could make growing media cultivation relevant for society. A first example is the re-use of local organic waste materials as growing medium (Vandecasteele et al, 2018;Vandecasteele et al, 2020). Some examples are composts, park waste-based wood fibers, and used growing media.…”

Effects of Biochar and Biochar–Compost Mix on Growth, Performance and Physiological Responses of Potted Alpinia zerumbet

“…The production of potted ornamental plants is highly specialized, intensive horticulture [1], which heavily relies on nonrenewable resources to attain uniformity and quality standards [2]. Among the nonrenewable resources, the horticulture industry broadly relies on peat [3], using it worldwide as a fundamental component of growing media for ornamental plant production [4]. Peat is the preferred organic component due to its excellent physiochemical characteristics, including relatively high cation exchange capacity (CEC), water retention, aeration, and suitability for supporting plant growth in a limited volume container [3,5].…”

“…Among the nonrenewable resources, the horticulture industry broadly relies on peat [3], using it worldwide as a fundamental component of growing media for ornamental plant production [4]. Peat is the preferred organic component due to its excellent physiochemical characteristics, including relatively high cation exchange capacity (CEC), water retention, aeration, and suitability for supporting plant growth in a limited volume container [3,5]. However, peat use is restricted or regulated in some parts of the world because peatlands are natural carbon sinks, and peat is a nonrenewable resource [3].…”

“…Peat is the preferred organic component due to its excellent physiochemical characteristics, including relatively high cation exchange capacity (CEC), water retention, aeration, and suitability for supporting plant growth in a limited volume container [3,5]. However, peat use is restricted or regulated in some parts of the world because peatlands are natural carbon sinks, and peat is a nonrenewable resource [3]. There are ecological concerns related to peat harvest/mining, including declining biodiversity and climate change issues [6].…”