Abstract
Container crop production has become increasingly popular over the last 50 years. A major component of container or potting media is peat. Peatlands are a natural carbon sink, and peat is a nonrenewable natural resource. Peat harvesting has become an important environmental issue. There is a growing effort to explore alternative organic materials to completely or partially replace peat as a medium component. Biochar is a carbon-rich product that has gained increasing interest as a component of growing media. In the present study, biochar was produced from rice straw. Peat/perlite/biochar (PPB; 40/30/30 v/v) and peat/perlite/biochar/vermicompost (PPBC; 30/30/35/5 v/v) were evaluated relative to a basal or control medium of peat/perlite (PP; 70:30 v/v). Alpinia (Alpinia zerumbet ‘Variegata Dwarf’) was used as a test plant. Amending biochar and biochar–compost mix increased the pH of the growing media. Hydrophysical properties including container capacity, bulk density, air space and total porosity were all within or near the standard ranges for soilless growing media. Chlorophyll a and b contents of A. zerumbet plants grown in PPB medium were reduced by more than 20% and 28%, respectively, compared to those grown in PP or PPBC media. The net photosynthetic rate of PPB-grown plants was more than 28% lower than those grown in PP and PPBC media. As a result, shoot and root dry weights of plants produced in PPB medium were more than 42% and 22% less, respectively, than those grown in PP and PPBC media. Although visual quality of PPB-grown plants was lower, they still exhibited marketable quality, which was largely due to the fact that their side shoots, leaf numbers, leaf areas, leaf thickness, and shoot diameters were comparable to those produced in PP and PPBC media. The present study showed that in a peat/perlite basal medium, substitution of peat by biochar derived from rice straw at 30% affected the growth of A. zerumbet plants, mainly in dry matter accumulation, but the plants were still marketable. On the other hand, plants grown in the same basal medium with peat replaced by the biochar at 35% plus an amendment of compost at 5% were comparable to those grown in the control medium. As the value of ornamental plants depends on their aesthetic appearance, a potting medium comprised of peat/perlite/biochar/vermicompost at 30/30/35/5 by volume is recommended for the production of A. zerumbet plants. The substitution of peat at 35% suggests that peat use can be reduced in the formulation of potting media, thus contributing to the conservation of peatlands.
Highlights
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]
According to Chen et al [37] and Abad et al [38], the bulk density (BD) of an ideal organic substrate should be
Our study showed that marketable Alpinia plants were produced in modified potting media supplemented with 30% of rice biochar (PPB) or 35% of the biochar with 5% of compost (PPBC)
Summary
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]. The horticulture industry broadly relies on peat [3], using it worldwide as a fundamental component of growing media for ornamental plant production [4]. There are ecological concerns related to peat harvest/mining, including declining biodiversity and climate change issues [6]. In light of this situation, interest is increasing among researchers to find economical and sustainable peat alternatives in potted plant production. Fascella et al [18] reported that amendment with conifer wood biochar (25% v/v) in peat-based growing media affected growth, mineral content, water use efficiency, and ornamental plant quality of potted Rosa rugosa. Guo et al [21] reported that 80% biochar amendment had no negative impact on the growth of Easter lily (Lilium longiflorum Thunb.)
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