Substitution of peat moss with softwood biochar for soil-free marigold growth

Abstract

A B S T R A C TPeat moss has historically been a key component of soil-free substrates in the greenhouse and nursery industries. However, the increasing expense of peat, negative impacts of peat mining on wetland ecosystems, and growing perception of peat as unsustainable have led to investigation for alternatives. Biochar (BC) is a promising substitute for peat, yet the majority of studies examine additions of BC to peat-based substrates rather than replacing the peat component or employ relatively low substitution rates. Furthermore, at high substitution rates the alkalinity common to many BCs may increase substrate pH and adversely impact plant production. We evaluated BC substitution for peat and pH adjustment of resulting substrates on marigold (Tagetes erecta L.) performance under standard greenhouse conditions. A high pH (10.9) softwood BC (800°C) was substituted for peat in a standard 70:30 (v/v) peat:perlite mixture at 10% total volume increments. Substrate pH was either not adjusted or adjusted to pH 5.8 using a BC by-product, pyroligneous acid (PLA). Germination was inhibited in pH adjusted substrates with high BC substitution (50-70% total substrate volume) likely due to higher dosages of PLA needed to neutralize pH. At harvest (flowering stage, 9 weeks) the initial pH gradient (4.4-10.4) in substrates that were not pH adjusted had converged to pH 5.6-7.5, and BC substitution for peat did not negatively impact marigold biomass or flowering. At low substitution rates (10-30% total substrate volume), marigold biomass and leaf SPAD values were greater than the control peat-perlite mixture (0% BC). This study demonstrates that softwood BC can be considered as a full replacement for peat in soil-free substrates, and even at high rates (70% total substrate volume) does not require pH adjustment for marigold production. Crop-and BC-specific considerations and economic potential should be investigated for wider application.

Effects of Biochar on Container Substrate Properties and Growth of Plants—A Review

“…The reason was that the incorporation of superabsorbent polymer increased the porosity and water-holding capacity and also effectively prevented an excessive increase of pH and EC at the high biochar rates [70]. Margenot et al [62] also showed that mixes with 10%, 20%, 30%, 40%, 50%, 60% or 70% softwood biochar and 30% perlite with the rest being peat (by vol.) led to similar seed germination and plant height compared to control (mixes with 30% perlite and 70% peat by vol.).…”

Enhancing Carbon Sequestration Using Organic Amendments and Agricultural Practices

“…Another research was conducted and wood chips and straw were applied in the soil and the results showed that nitrogen mineralization and nitrification rates were higher significantly in the soil-applied wood chips. The bad thing is that when we applied wood chips in the soil, nitrogen deficiency occurs and then an additional supplement of nitrogen is required [89]. Carbon contents of early woods are higher than late woods [90].…”

Biochar or Biochar-Compost Amendment to a Peat-Based Substrate Improves Growth of Syngonium podophyllum

“…Dispenza et al [18] reported that incorporation of conifer BC (60% or 80% by volume) in a brown peat-based substrate increased the dry weight and canopy height of potted Euphorbia × lomi plants due to improved physiochemical characteristics of the substrate. Margenot et al [19] found that softwood BC in a soilless substrate can completely replace peat at 70% (v/v) without pH adjustment for producing containerized marigold. Similarly, Guo et al [20] demonstrated that pinewood BC produced at 450 • C can be used in a peat-based substrate for up to 80% (v/v) without negative effects on the growth and development of containerized Easter lily (Lilium longiflorum).…”