Biochars and hydrochars as substrate constituents for soilless growth of myrtle and mastic

Published Date

30 December 2016, Vol.94:132–142, doi:10.1016/j.indcrop.2016.08.024

Title 

Biochars and hydrochars as substrate constituents for soilless growth of myrtle and mastic

• Author 

• Rosa María Belda ^a,,
• Antonio Lidón ^b,
• Fernando Fornes ^a,

• aInstituto Agroforestal Mediterráneo, Universitat Politècnica de València, 46022 Valencia, Spain
• bInstituto Universitario de Ingeniería del Agua y del Medio Ambiente, Universitat Politècnica de València, 46022 Valencia, Spain

Received 18 May 2016. Revised 28 July 2016. Accepted 13 August 2016. Available online 25 August 2016.

Highlights

• •
  Hydrochars (hydrothermal carbonization) had large remaining water and low air volume.
• •
  Hydrochars O₂ absortion/CO₂ emission indicated anaerobiosis.
• •
  When mixed with soil hydrochars showed N immobilization and biochars sequestered CO₂.
• •
  Biochar from olive-mill waste was toxic for myrtle.
• •
  Biochar from forest waste improved growth in myrtle and mastic.

Abstract

Recently, biochars and hydrochars have been proposed as soil amendments and, to a lesser degree, as substrate constituents for soilless cultivation. These materials are interesting because their use is a means to reclaim organic matter and because, in some instances, they have been proved to sequester CO₂ from the atmosphere. Myrtle and mastic are native to Mediterranean ecosystems and are grown for their essential oil production. This study aims to assess the properties of two biochars from different feedstock and a hydrochar from the same feedstock as one of the biochars as substrate constituents, in order to partially substitute either coir or soil in the cultivation of myrtle and mastic.

Although the physical properties of the four organic materials are reasonably adequate for their use in substrate mixes, the biochar of olive mill waste is extremely saline as a pure material and remains very saline in a 50% mix with coir. The hydrochar showed less easily available water for the plants and a lower pH than the others. In incubation experiments using mixes with soil, biochars absorbed more O₂than CO₂ emitted, which suggests they were sequestering CO₂. The hydrochar showed O₂ consumption and CO₂ emission of one order of magnitude larger than the biochars. It also showed that an outstanding amount of organic carbon was being metabolized in anaerobic routes. The biochar of forest waste and the coir displayed N immobilization when mixed with soil, whilst the biochar of olive mill waste had little microbial activity. Although hydrochars had been proved not to immobilize N as pure materials, they did immobilize N when mixed with soil. When tried for plant growth, mixes of the local soil with the biochar of forest waste and with hydrochar produced the best mastic plants. However, unmixed soil gave the best results for myrtle. The biochar of olive mill waste proved phytotoxic for myrtle in mixes with coir, whilst the biochar of forest waste gave optimal results for both species. Depending on their production process and the feedstock from which they are produced, biochars and hydrochars can vary in their characteristics and therefore in their effect on plants.

Abbreviations

• BCH-FW, BioCHar from Forest Waste
• BCH-OMW, BioCHar from Olive Mill Waste
• CF, coir
• CI, coarseness index
• Db, bulk density
• Dil, dilution
• Dp, particle density
• dw, dry weight
• EAW, easily available water
• EC, electrical conductivity
• HYD-FW, HYDrochar from Forest Waste
• Mat, material
• MM, mineral matter
• NDI, nitrogen drawdown index
• OM, organic matter
• RW, remaining water
• Sh, shrinkage
• TPS, total pore space
• Va, air volume
• Vw, water volume
• WBC, water buffering capacity
• WHC, water holding capacity

Keywords

• Char
• Coir
• Growth media
• Myrtus communis
• Nursery
• Pistacia lentiscus

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• ⁎ 
  Corresponding author.

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