Page 12 - AJWEP-22-6

Syromiatnykov

enzymatic activity and soil microbial diversity. 52,59 When Humic substances extracted from soybean straw
humic acids are produced from composted urban green and cassava waste through composting and alkaline
waste or fish waste, their molecular structure improves, extraction primarily yield humic and fulvic acids.
further supporting plant growth and environmental These compounds have been reported to increase
resilience. 31,60 soil pH, mitigate aluminum toxicity, and enhance
Figure 2 illustrates the agronomic benefit scores nodulation in leguminous crops, particularly in acidic
(0–100 scale) of various humic substances and organic soils. 54,55,56
waste treatments used in soybean cultivation. The five Palm bunch compost, processed through
tested sources include compost (Cmpst), vermicompost thermochemical humification, is another rich source
(Vcmpst), cassava peel waste (Cassava), palm oil of humic acids. This material effectively buffers soil
bunch residues (Palm), and urban green waste (Urban). acidity and enhances microbial colonization in the
The lowest scores are observed for raw organic waste, rhizosphere, improving BNF efficiency in tropical
ranging from 50 (Palm) to 65 (Vcmpst). Processed agroecosystems. 31,54
(humic) materials exhibited marked improvement: Fish processing waste, when subjected to enzymatic
Cmpst reaches 85 (+25% compared to raw), Vcmpst hydrolysis and aerobic composting, generates highly
90 (+38%), Cassava 75 (+36%), Palm 70 (+40%), bioactive humates. These promote microbial biomass,
and Urban 80 (+38%). Biochar-enriched variants enzymatic activity, and root system development,
demonstrate moderate enhancement, with scores making them ideal for organic farming systems. 31,60
between 65 and 82, depending on the material. Urban green waste, especially when vermicomposted,
Microbial-enriched treatments perform best, scoring results in fulvic acid-enriched humus. This material is
88 for Cmpst, 85 for Vcmpst, 80 for Cassava, 78 for particularly effective under stress conditions (e.g., drought
Palm, and 83 for Urban—displaying increases of up or nutrient deficiency), as it enhances the chelation and
to 60% over raw waste. These results indicate that uptake of micronutrients (e.g., iron and zinc) and boosts
humification and microbial enrichment significantly antioxidant activity in the rhizosphere. 59-61
enhance the agronomic value of organic waste sources, Biogas digestate, transformed through hydrothermal
with microbial strategies yielding the highest overall carbonization, produces synthetic humic-like substances
benefit. with notable benefits. These include improved drought
Table 2 provides a detailed overview of humic resistance, enhanced microbial stability, and salt-
products derived from agricultural waste, focusing on buffering capacity, making them suitable for arid and
their sources, extraction methods, active components, degraded soils. 60,64
agronomic functions, and appropriate application Orange peel and fruit pomace, when composted
contexts. microbially, yield phenolic-rich fulvic acids.
These compounds stimulate hormone-like activity
(e.g., auxins), improve rhizobial colonization, and
work synergistically with plant growth-promoting
rhizobacteria (PGPR). 50,54
In urban-periphery soils, sewage sludge combined
with fly ash and processed through alkaline oxidation
produces mineral-bound humic acids. These enhance
phosphorus availability, detoxify heavy metals, and
stimulate nodulation in soybean agroecosystems. 56,59
Finally, wheat straw composted with biochar
and thermophilic microbes produces a stable humin
fraction. This compound functions as an extracellular
Figure 2. Comparative agronomic value of humic electron mediator, which improves nitrogen fixation
substances and organic waste treatments in soybean under anaerobic or compacted soil conditions. 28,64
cultivation Overall, Table 2 highlights the potential of repurposed
Abbreviations: Cassava: Cassava peel waste; organic waste to produce functional humic materials that
Cmpst: Compost; Palm: Palm oil bunch residues; enhance soil fertility, nutrient cycling, and microbial
Urban: Urban green waste; Vcmpst: Vermicompost. symbiosis in diverse cropping environments.

Volume 22 Issue 6 (2025) 6 doi: 10.36922/AJWEP025230190