Objavljen članek Kompostiranje hmeljevine na kmetijah: vpliv prekrivanja kupov na količino izcedne vode in kakovost komposta (v angleščini).
Prekrivanje kompostnih kupov iz hmeljevine s polprepustno membrano po termofilni fazi do pomladi, ko je bil kompost pripravljen za uporabo, se je znatno zmanjšala količina izcedne vode in izpranih hranil. V zimskem in spomladanskem obdobju je bila pri vseh obravnavanih količinah izcedne vode zanemarljiva, prav tako pa je bila nizka tudi količina izpranih hranil. Pri obravnavi z dodatki (biooglje, pripravek učinkovitih mikroorganizmov) v večjem deležu majhnih delov (velikosti 2–5 cm) se je pokazalo, da bi bil kompostni kup verjetno smiselno pokriti že v prvih mesecih kompostiranja in ga odkrivati le ob obračanju/mešanju. Po drugi strani pa je bil pri kupu brez dodatkov in z delci velikosti 2–10 cm ob času pokrivanja izcedek bistveno manjši (za 2,2- oziroma 2,5-krat), prav tako tudi količino izpranih hranil. Vsa obravnavanja so proizvedla sabilen kompost brez neprijetnega vonja, s skupno vsebnostjo dušika nad 2 % (razmerje C:N pod 20), obenem pa je bil dosežen tudi pri pragu higienizacije biomaze. Kljub temu so bile med obravnavami nekatere pomembne razlike. Kompost iz kupa z dodatkom biooglja in začetnimi delci hmeljevine velikosti 2–5 cm je bil fitotoksičan (indeks kalitve rdeče tekočine znašal 31 %), poleg tega pa so bili tudi drugi rezultati manj obetavni v primerjavi z ostalimi obravnavanji. Najboljše rezultate je dosegel kup brez dodatkov in z začetnimi delci hmeljevine velikosti 2–10 cm, ki je bil pravilno mešan glede na redne meritve temperature v termofilni fazi. To obravnavanje je imelo najmanjšo količino izcedne vode in izpranih hranil, končni kompost v aprilu pa je vseboval precej več hranil in imel najvišji indeks kalitve.
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Published scientific article: Composting hop biomass on farms: the effect of pile covering on leachate volume and compost quality (in English).
Covering hop-biomass compost piles with a semi-permeable membrane after the thermophilic phase until spring, when the compost was ready for use, significantly reduced the amount of leachate and nutrient losses. During the winter and spring period, leachate volumes were negligible in all treatments, and nutrient leaching remained low. In the treatment with additives (biochar and an effective microorganism preparation) and a higher proportion of small particles (2–5 cm), the results suggested that the compost pile would likely be better covered already during the first months of composting and uncovered only during turning/mixing. In contrast, in the pile without additives and with particle sizes of 2–10 cm, both leachate volume (2.2–2.5-fold lower) and nutrient losses were substantially lower at the time of covering.
All treatments produced stable compost without unpleasant odour, with a total nitrogen content above 2% (C:N ratio below 20), and the sanitisation threshold temperature for biomass hygienisation was achieved. Nevertheless, important differences among treatments were observed. Compost from the pile amended with biochar and initial particle size of 2–5 cm was phytotoxic (cress germination index 31%), and other quality indicators were also less favourable compared with the remaining treatments. The best overall performance was obtained with the pile without additives and an initial hop-biomass particle size of 2–10 cm, which was properly turned based on regular temperature measurements during the thermophilic phase. This treatment produced the lowest leachate volume and nutrient losses, while the final compost collected in April contained higher nutrient levels and achieved the highest germination index.