Understanding the Role of Humic Acids on Crop Performance and Soil Health

Abstract

Humic acids (HA) are organic molecules that play essential roles in improving soil properties, plant growth, and agronomic parameters. The sources of HA include coal, lignite, soils, and organic materials. Humic acid-based products have been used in crop production in recent years to ensure the sustainability of agriculture production. Reviewed literature shows that HA can positively affect soil physical, chemical, and biological characteristics, including texture, structure, water holding capacity, cation exchange capacity, pH, soil carbon, enzymes, nitrogen cycling, and nutrient availability. This review highlights the relevance of HA on crop growth, plant hormone production, nutrient uptake and assimilation, yield, and protein synthesis. The effect of HA on soil properties and crops is influenced by the HA type, HA application rate, HA application mode, soil type, solubility, molecular size, and functional group. This review also identifies some knowledge gaps in HA studies. HA and its application rate have not been tested in field experiments under different crops in rotation, nitrogen fertilizer forms, sites and climatic conditions. Furthermore, HA chemical and molecular structures, their water and alkaline soluble fractions have not been tested under field experiments to evaluate their effects on crop yield, quality, and soil health. The relationship between soil-plant nutrient availability and plant nutrient uptake following HA application should also be further studied.

Deciphering the Effectiveness of Humic Substances and Biochar Modified Digestates on Soil Quality and Plant Biomass Accumulation

“…Nevertheless, the variant D + B + H had the highest soil TC at the end of experiment, probably due to the synergistic effect of biochar and Humac on soil carbon sequestration. These results were partially in line with the results of our previous study carried out with biochar and Humac-enriched digestate [54].…”

“…We hypothesized that the long-term effect of digestate + biochar on nutrient mineralization would be negative, because of the tendency for biochar-mediated immobilization and sequestration. Both humic acids and biochar represent amendments that are rich sources of carbon and also act as nutrient storehouses [51][52][53][54]. However, biochar contains both labile (easily available) and recalcitrant carbon, leading to higher heterogeneity of organic matter in the digestate.…”

Impacts of humic-based products on the microbial community structure and functions toward sustainable agriculture

“…Humic-based products are carbon-rich organic amendments in the forms of extracted humic substances from manure, compost, and raw and extracted forms of lignites, coals and peats. For decades, HPs have been widely reported to improve soil health and crop productivity (Guo et al, 2019;Nardi et al, 2021;Ampong et al, 2022). HPs can be synthetic, recycled wastes, or natural and have wide industrial applications (El-shazly et al, 2015;Dong et al, 2017;Bezuglova et al, 2019;Guo et al, 2019;Zhou et al, 2019).…”

Response of Red Chili (Capsicum anuuum L.) to Humic Acid Application in Dryland

“…Humic acid can improve soil structure, increase soil cation exchange capacity and soil buffering capacity, and increase soil microbial population including beneficial micro-organisms (Ampong et al, 2022). Improvement of soil properties by giving humic acid changes the architecture and dynamics of plant root growth, there is an increase in root size, branching and/or more root hair density, with a larger surface area (Canelass & Olivares, 2014).…”

“…The increase in the number and weight of red chilies planted on dry land with humic acid application was caused by the increased ability of the soil to hold water (Ismail & Almarshadi, 2013), thereby increasing the availability of water for plants. Ampong et al (2022) state that humic acid can affect the photosynthetic process of plants, so that the plants that are given humic acid are better able to carry out the photosynthesis process. The increase in photosynthesis increases the photosynthate produced by the plants which is needed for the formation and enlargement of fruit.…”