ARI REVIEW FOR 2016-2017

Use of hydrochar in growing media Peat bogs are valuable habitats that need to be preserved for wildlife and because their drainage and peat exploitation represent a significant source of carbon dioxide emissions. One of the main uses of peat harvested from these bogs is in the growing media industry where peat currently represents about 80% of the materials used annually in Europe. Significant efforts are made, therefore, for peat replacement by suitable alternative materials. Organic products obtained by hydrothermal carbonisation processes (hydrochars) could fully or partially replace peat in growing media if they possess some suitable properties. The ARI evaluated this possibility by focusing on the characterisation of stability of hydrochar produced from wheat. Additionally, as inhibition to seed germination could significantly restrict the eventual use of hydrochar in growing media, a number of seed germination trials were carried out to reveal the magnitude of phytotoxicity in relation to sphagnum peat and biochar and the effect that some simple and cheap pre- conditioning treatments have on the rate of germination. This rate was greatly increased by simply watering the material a few days prior to use or by mixing it with compost. It was shown that the positive effect on seedling emergence should be attributed, at least partly, to the degradation by microorganisms of toxic substances presumably produced during carbonisation. ( P. Dalias ) Mineralisation of nitrogen after soil incorporation of the main types of animal manure produced in Cyprus Manure is a natural byproduct of livestock production and an excellent source of nutrients for crop production. Unlike inorganic fertilisers, manure contributes to soil organic matter increase, and thus on soil structure, aeration, the effective infiltration and water retention capacity. To maximize benefits and limit the negative impacts of its use, manure should be incorporated in the field at the right time and in the appropriate quantity. The natural characteristics of manure, however, such as its heterogeneity in composition and the variability of its physical properties make its handling a more complex issue compared with that of the inorganic fertiliser. Hence, in a reliable fertiliser programme using manure there is a need of accounting for soil’s capacity to supply nutrients and for: 1) the content of manure in ammoniacal nitrogen (N) which is readily available to plant and the content in organic N, 2) the bulk density and moisture content of manure, and 3) the rate or the potential of N mineralisation after incorporation in soil and its relationship with the species of animal from which the manure is coming from, the time of storage/composting and its content in housing material or leftovers of animal forage. In Cyprus, calculating the proper quantity of manure that should be incorporated in the field as fertiliser is made usually empirically. This leads possibly to non-optimal economic utilisation of manure, to environmental problems mainly due to nitrate leaching and ammonia volatilisation, and to agronomic problems associated with the lack of balance between plant requirements and inputs or the lack of synchronisation. 57 Natural Resources and Environment