Application Of Humic Substances Research Articles

Impact of Humic Substances on Alleviation of Soil Salinity and the Enhancement of Plant Productivity: a review

Humic substances (HS) are a major component of organic matter in soil, and they have long been recognized for their ability to promote plant growth in a sustainable manner. Recently, there has been a lot of effort put into using multiple approaches to study the connection between the chemical structure of HS compounds and their effect on plant biological processes. Positive physiological responses at the local and systemic levels have been linked to the presence of specific functional groups in HS. Hormone-like signaling pathways are responsible for eliciting these reactions. This review was written with one goal in mind: to help readers gain a firm grasp on the research surrounding the application of HSs. The spatial arrangement of hydrophilic and hydrophobic regions, as well as the dosage, source, molecular size, degree of hydrophobicity, and aromaticity, all contribute significantly to HS's biological efficacy. Therefore, our hypothesis explains the beneficial effect of HS in salt-affected rhizospheres, likely attributed to both direct and indirect influences on plant metabolism, soil microorganism metabolism, soil nutrient uptake dynamics, and soil physical conditions. Keywords: Humic substance, germination, salinity, plant growth

Productivity, morphology and mineral composition of forage palm clones biostimulated with humic substances

An initial protocol was carried out in pots with forage cactus, in a greenhouse for 90 days and, in this, the dilution of SH_6.25% [1/16 - SH (100%)] of humic substances (HS) was determined. of commercial vermicompost (earthworm humus) as the best dose of stimulus to plants through the integration of dose-response curves. This concentration was then tested in the field when planting cactus. The application of humic substances occurred one week after planting, randomizing the planting lines, so that of the 24 lines implemented, half received application of humic substances and the other half did not receive any treatment after implantation. Morphological and morphogenetic analyzes of cactus pear were carried out and it was observed that the application of humic substances provided greater positive correlations between the morphogenic variables and the production of vegetative biomass since in the treatment with humic substances the plants obtained greater vegetative biomass, height, length, width w cladode perimeter and largest cladode area index. Higher levels of potassium, magnesium, sulfur, iron, manganese and boron were also observed in plants that received humic substances. These responses show that the use of humic substances increases the production of palm biomass and positively affects the morphogenic characteristics of the crop.

Salinity stress mitigation by radicular and foliar humic substances application in lettuce plants

AbstractSalinity stress constitutes one of the main abiotic stresses that considerably reduces crop yield. An approach to enhance plant growth under salt stress involves the addition of humic substances (HS) to roots or leaves. Here, we evaluated the potential use of BLACKJAK®, an HS-based product, to enhance salt tolerance in lettuce (Lactuca sativa L.). For this aim, plants were exposed to salinity (100 mM NaCl), salinity + HS: radicular (R)-HS (0.40 mL/L and 0.60 mL/L) and foliar (F)-HS (7.50 mL/L and 10.00 mL/L), along with a control (without NaCl). Parameters related to plant growth, Na+ and K+ accumulation, photosynthetic activity, oxidative stress, enzymatic and non-enzymatic antioxidants, as well as proline levels were evaluated. Results showed that R and F-HS considerably enhanced salinity tolerance. In addition, F-HS offered a greater improvement of plant growth in relation to shoot fresh weight, shoot relative growth rate, and foliar area, being 10.00 mL/L the best dose. This tolerance could be associated with reduced Na+ translocation to the shoot and enhanced shoot K+ accumulation, decreasing Na+/K+ ratio. Furthermore, HS improved the net photosynthetic rate, Rubisco carboxylation efficiency, and photosystem II performance, and reduced ROS levels and lipid peroxidation. Hence, our data show the potential use of BLACKJAK® to improve lettuce tolerance to salinity, with foliar application slightly better than radicular to achieve this aim, especially at 10.00 mL/L dose.

Foliar application of commercial humic substances for possible increase of nutrient status and yield of oilseed rape

Foliar application of commercial humic substances for possible increase of nutrient status and yield of oilseed rape

Response of Sunflower (Helianthus annuus L.) to Application of Bioactive Humic Substances

Response of Sunflower (Helianthus annuus L.) to Application of Bioactive Humic Substances

Chitosan combined with humic applications during sensitive growth stages to drought improves nutritional status and water relations of sweet potato

The current decline in freshwater resources presents a significant global challenge to crop production, a situation expected to intensify with ongoing climate change. This underscores the need for extensive research to enhance crop yields under drought conditions, a priority for scientists given its vital role in global food security. Our study explores the effects of using humic and chitosan treatments to alleviate drought stress during critical growth phases and their impact on crop yield and water efficiency. We employed four different irrigation strategies: full irrigation, 70% irrigation at the early vine development stage, 70% irrigation during the storage root bulking stage, and 85% irrigation across both stages, complemented by full irrigation in other periods. The plants received either humic treatments through foliar spray or soil application, or chitosan foliar applications, with tap water serving as a control. Our findings highlight that the early vine development stage is particularly vulnerable to drought, with a 42.0% decrease in yield observed under such conditions. In normal growth scenarios, foliar application of humic substances significantly improved growth parameters, resulting in a substantial increase in yield and water efficiency by 66.9% and 68.4%, respectively, compared to the control treatment under full irrigation. For sweet potatoes irrigated with 70% water at the storage root bulking stage, ground application of humic substances outperformed both foliar applications of chitosan and humic in terms of yield results. The highest tuber yield and water efficiency were attained by combining chitosan and humic ground applications, regardless of whether 70% irrigation was used at the storage root bulking stage or 85% irrigation during both the early vine development and storage root bulking stages.

Influence of the application of humic substances on the growth of watermelon and melon seedlings

Growing watermelon (Citrullus lanatus) and melon (Cucumis melo) is an important activity in the Brazilian Cerrado; however, many factors limit cultivation, including the difficulty of producing high-quality seedlings. In this study, the effect of humic substances (HS) on growth of ‘Crimson Sweet’ watermelon and ‘Yellow’ melon seedlings was evaluated. An experiment was carried out in a completely randomized design with five HS treatments applied to the soil: 0 (control), 5, 10, 15, and 20 g L-1. The growth of watermelon and melon seedlings was influenced by the application of humic substances. Use of HS increased plant height, stem diameter, root length, root volume, shoot dry biomass, root dry biomass, and Dickson’s quality index. HS boost plant growth, whose improved root system may have provided greater absorption and accumulation of mineral nutrients. Based on the quality of the seedlings (Dickson index), the application of 14 g L-1 of HS is recommended for watermelon seedling production and 15 g L-1 of HS for melon seedling production.

Effect of Foliar Spray of Iron (Fe)- Fortified Humic Substances and Humic Acid on Growth, Nodulation and Yield of Groundnut (Arachis hypogaea L.) in a Calcareous Vertisol

The response to foliar application of Fe-fortified humic substances (HS) and humic acid (HA) on the growth, nodulation and yield characteristics of groundnut (Arachis hypogaea L.) var. TMV 2 in a calcareous Vertisol was studied in a pot culture experiment. There were 16 treatments viz., Absolute control (T1), only RDF (T2), RPP: RDF +FYM @ 7.5 t + FeSO4 @ 25kg ha-1+ ZnSO4 @ 25 kg ha-1 (T3), RDF + Foliar FeSO4.7H20 @ 0.5% (T4), and T5 to T16, where two different concentrations, 0.25 and 0.50 % of humic substances (HS) (Humic acid + Fulvic acid) and humic acid (HA) were fortified separately with 250, 500 and 750 ppm Fe. Among all treatments, higher values of growth parameters like number of leaves, branch count and yield parameters like number of pods (19.33 pods plant-1), pod weight (18.84 g plant-1), kernel yield (12.85 g plant-1), shelling % (68.25 %) and 100 kernel weight (33.28 g) were recorded in the treatment RDF + Foliar Fe- fortified HS (0.50 % HS+ Fe @ 500 ppm) (T9) followed by treatment with RDF + Foliar Fe- fortified HA (0.50 % HA+ Fe @ 500 ppm) (T15). The plant height and dry matter yield were recorded maximum under foliar spray of 0.25 % HS fortified with 500 ppm Fe (T6) (21.83 cm and 6.27 g plant-1 at 60 DAS; 33.83 cm and 36.75 g plant-1 at harvest, respectively). For nodulation parameters, T3 (only RPP) recorded the best results and remained statistically on par with treatment T9.

Boosting strawberry yield and fruit sweetness with humic substances and biofertilizer in soilless cocopeat-based culture

Farmers usually apply more chemical fertilizers to enhance the yield of strawberries in soilless culture. Humic substances and biofertilizers are now considered essential nutrient sources in sustainable agriculture. The objective of the greenhouse experiment was to observe the effect of humic and fulvic acid (humic substances), and biofertilizer on root growth, nitrogen (N) and phosphor (P) of the growing media, populations of N-fixing and P-solubilizing bacteria in the root zone, and yield of strawberry grown in the cocopeat-based substrate. The experiment was set up in a randomized block design consisting of seven treatments and four replications. The treatments included humic acid, fulvic acid, and biofertilizer in single or combined applications. All data were subjected to analysis of variance and followed by Duncan's Multiple Range Test with p<0.05. All treatments received 50% of the recommended dose of NPK fertilizer. The results showed that all treatments did not affect root length and dry weight. Mixed application of humic substances and biofertilizer together with NPK fertilizer increased total N and P as well as the population of N-fixing bacteria in the growth substrate. Still, P-solubilizing bacteria did not grow in the cocopeat-based substrate. Moreover, mixing humic substances and biofertilizer increased strawberries' fruit yield and sweetness levels.

Effects of the combined application of biochar and humic substances on the improvement of saline cropland in the Yellow River Delta of China

AbstractSoil salinization has become a global environmental problem with the potential to cause serious land degradation. Thus, improving salt‐affected soils and enhancing the nutrient utilization efficiency of saline farmlands through scientific and effective measures are urgent scientific problems. In this study, a 2‐year field experiment was conducted to evaluate the effects of different soil amendments and their combinations on the dynamics of soil salinity, soil nutrients, and crop yield in a moderately salinized soil (EC1:5 of 0.78 dS m−1 and total salt content of 3.06 g kg−1). Nine soil treatments were implemented: biochar (B), lignocellulose (L), humic acid (H), fulvic acid (F), biochar + humic acid (B + H), biochar + fulvic acid (B + F), lignocellulose + humic acid (L + H), lignocellulose + fulvic acid (L + F), and control (CK). The results demonstrated that the application of F led to a certain reduction on the contents of soil salt, Na+, and Cl− among the soils amended with a single amendment application. The combined application of B and F or H could increase the soil desalination rate and increase the mineral N and Olsen‐P concentrations at a soil depth of 0–20 cm, which improved the grain yield, biological yield, N recovery efficiency (REN), N agronomic efficiency (AEN), N partial factor productivity (PFPN), P agronomic efficiency (AEP), and P partial factor productivity (PFPP). Although the single application of L led to decreases in the grain yield, biological yield, REN, AEN, PFPN, REP, AEP, PFPP, and P physiological efficiency (PEP), the combined application of L and F had superior effects on enhancing the winter wheat grain yield and accumulative nutrient use efficiency. In conclusion, the combined application of B and F or H is recommended to ameliorate salt‐affected soils and improve nutrient availability.

Bio-inputs promoting marandu grass growth: productivity, physiological response and nitrogen accumulation

Nutrient replenishment is one of the significant factors limiting the full development of extensive pasturelands. As a result, bio-inputs have been increasingly used under field conditions to improve plant growth in low-fertility soils. This study aimed to evaluate their effects on the productivity, physiological responses to and nitrogen (N) accumulation in marandu grass (Urochloa brizantha cv. marandu). The experiment was carried out using a randomized block design with four treatments and three replicates in a greenhouse under controlled conditions. In low-fertility soils, lower synthetic fertilizer inputs were simulated (40% N-P-K) (Control), and three bio-inputs were additionally applied (bio-inputs + 40% N-P-K): Azo (Azospirillum brasilense seed inoculation); HS+Herb (leaf application of humic substances combined with a cocktail consisting of Herbaspirillum species), and Coinoc (a combination of Azo and HS+Herb). We evaluated the plant biometrics (shoot and root dry matter, stem diameter and height) and physiological parameters (CO2 assimilation rate, internal CO2 concentration, transpiration, instantaneous carboxylation efficiency, and the maximum quantum yield of photosystem II), as well as the N accumulation 45 days after seedling emergence. Azo-treatment did not differ from the control in most of the variables studied. HS+Herb and Coinoc significantly (p ≤ 0.05) increased the dry matter of shoots (+237% and +255%, respectively) and roots (+106% and 83%, respectively) compared to the control. These treatments (HS+Herb and Coinoc) significantly (p ≤ 0.05) increased (almost double) the size and stem diameter, improved physiological parameters, and accumulated more N (up to 89%) compared to the control. Applying humic substance-based bio-inputs combined with the Herbaspirillum species cocktail was more efficient in stimulating the growth of marandu grass grown in soil of reduced fertility.

Effect of humic substances on yield and nutrient contents of Eggplant Santana (Solanum melongena) plants in gray-brown soil

Humic substances promote the conversion of nutrients into forms available to plants. It also stimulates seed germination and viability, and its main effect usually being more prominent in the roots. This study was conducted in a randomized complete block design with three replications in Gobustan, Azerbaijan, in 2021 growing season, to determine the effects of different doses (0, 250, 500 and 1000 ppm) of humic substances such as humic acid (HA), fulvic acid (FA) and humic fulvic acid (HFA) on fresh yield and nutrient contents (N, P and K) of Eggplant Santana (Solanum melongena var. esculentum Santana) plants in a field experiment. According to the results of this study, humic substance treatments increased the fresh yields and leaf nutrient contents of Eggplant Santana, and this increase was found to be significant. The highest value for highest fresh yields and leaf NPK contents of Eggplant Santana plants were obtained from 1000 ppm HFA dose. These results suggest that 1000 ppm HA and FA combination to the standard humic substances application will be sufficient to obtain adequate fresh yield and nutrient contents in Eggplant Santana leafs.

Influence of straw-derived humic acid-like substance on the availability of Cd/As in paddy soil and their accumulation in rice grain

Humic acid amendments have been widely advocated for the remediation of heavy metal-contaminated soil. However, the impacts of straw-derived humic acid-like substances on the remediation of cadmium (Cd) and arsenic (As) co-contaminated paddy soil remain unclear and the potential mechanism required clarification. In this study, we employed a pot experiment and chose a straw-derived humic acid-like substance (BFA) as the amendment with four doses to investigate how BFA affects the availability of Cd and As in soil and their accumulation in rice. The results showed that grain Cd decreased by 25.65–36.03%, while there was no significant change in total As (TAs) with the addition of BFA. The contents of DCB-Fe, DCB-As and DCB-Cd on the root surface decreased by 6.07–40.54% during the whole growth stage. The addition of BFA significantly decreased the pe + pH and enhanced the transformation of crystalline iron oxides (Fed) into amorphous forms (Feo) in the soil. The CaCl2-extractable Cd decreased and the KH2PO4-extractable As increased with the decrease in pe + pH and Fed and the relative increase in Feo. The correlation analysis showed that the decrease in availability of Cd and translocation factor of Cd effectively decreased the grain Cd and the decrease in DCB-Cd may also contribute to decreasing the uptake of Cd by rice. However, the increase in As of roots and shoots might play key roles in restricting the transport of As to rice grains. Consequently, the addition of BFA could effectively reduce the Cd accumulation in rice under flooding conditions, while no risk of As accumulation in rice grain was observed. The present work provides a new perspective for the application of straw-derived humic acid-like substances as amendments on Cd–As co-contaminated soils, which should be advocated as an eco-friendly, economical and effective soil amendment in the future.

Combined exogenous selenium and biochemical fulvic acid reduce Cd accumulation in rice.

Paddy soil Cd contamination and the related accumulation risk in rice grains have attracted global attention. The application of selenium and humic substances is considered to be a cost-effective Cd mitigation measure. However, the effect of a combined application of the two materials remains unclear. Therefore, a 2-season pot experiment was conducted, wherein sodium selenite (Se) and biochemical fulvic acid (BFA) were applied alone and together. Paddy soils with two levels of Cd contamination were used. The results indicate that Se application alone considerably decreased the rice grain Cd content by 36.1-48.7% compared to the control rice grain Cd concentration, which was above the food safety limit (0.2 mg kg-1). Although the application of BFA alone decreased the soil pH, it also increased the soil CaCl2 extractable Cd content by 0.2 to 19.3% and had a limited effect on Cd in the rice grains. The combined application of Se and BFA did not affect the soil pH or the CaCl2 extractable Cd, and more effectively reduced the Cd contents of the rice grains by 50.2 to 57.1%, except for the control rice grain Cd content, which was below the limit. The combined application of Se and BFA also inhibited Se accumulation in rice grains, maintaining the Se content at a safe level (0.33-0.58 mg kg-1) compared to Se application alone. The effects of reducing the Cd content of rice grains while safely increasing their Se contents could persist for at least two seasons. Therefore, the combined application of Se and BFA should be recommended to mitigate Cd contamination risks in Cd-contaminated paddy soil.

Application of Humic Substances in Agricultural Industry

Increasing agricultural productivity and, in particular, the productivity of livestock is one of the primary tasks in the present stage of development of society. This involves rational feeding and the use of biologically active substances, including humic preparations that activate the digestive and metabolic processes in the animal, promoting the transformation of feed nutrients in assimilable form, raising daily milk production and weight gain, and can play an important role in solving this urgent problem. The applications of humic substances in animal husbandry are diverse, but their use as feed additives is not developed sufficiently, and in the EU countries it is not sanctioned. Researchers in different countries have shown that humic substances in animals operate on the cellular and subcellular level, as they do in plants. Low molecular weight fractions HS enter the cell and are involved in metabolic processes, contributing to the optimization of inorganic ion passage through the intestinal wall, thereby promoting the absorption of minerals necessary for normal functioning of the organism. That is how the stimulating influence of humic substances on separate systems and on the organism as a whole is manifested. Humic substances formed from various natural materials are currently being tested in various branches of animal husbandry (cattle, pig breeding, poultry farming, fish farming, fur farming), and all the information received presents convincing evidence of the high efficiency of the humates. Such materials as peat and brown coal, vegetable waste, and vermicompost can act as a source of humic substances. However, in each case, more research is needed, specifying the dosage and schedule of their use.

Substâncias húmicas: efeito no crescimento e na produtividade de plantas de batata

ABSTRACT The results from humic substances (HS) application in varied crops and conditions are controversial, and the experiments with the potato crop in Brazil are scarce. The objective of this study was to evaluate the effects of HS doses on the growth and yield of two potato cultivars. Four doses of HS were tested: 0, 5.05, 10.10, and 15.15 L ha-1, applied in the planting furrows of cvs. Agata and BRS F63 Camila, in Guarapuava-PR, in the 2015 and 2016 crop seasons, between October and February. The experiment was carried out using a randomized complete block design, in a factorial scheme (crop season x dose x cultivar), with four replications. Plant samplings were performed at tuber initiation, flowering, tuber bulking, and plant maturation growth stages. After shoot senescence, the total and commercial tuber yields were evaluated. Cultivars responded similarly to HS application, with no significant interaction between HS and cultivars, for most assessed variables. At tuber initiation, there was a negative linear effect of HS doses on leaf area index, number of formed tubers, and tuber and total plant dry weight. In the other evaluations, the effect of HS application was not observed regarding the assessed variables. Likewise, no effects were detected on the number and fresh weight of tubers in total and commercial yields. We concluded that HS application affected both cultivars similarly, hampering initial plant growth and not increasing potato yield.

Substrato de bagana de carnaúba e aplicação de substâncias húmicas na produção de mudas de maracujazeiro amarelo

ABSTRACT Owing to the high prices of agricultural inputs, it is necessary to seek alternatives that minimize costs during the seedling production stage, such as the use of agro-industrial residues to formulate substrates and the application of humic substances to increase the availability of nutrients. This study aimed to evaluate the production of yellow passion fruit seedlings in substrates based on carnauba bagana under increasing doses of humic substances. The design was completely randomized, in a 3 x 4 factorial scheme, referring to three substrates formulated with carnauba bagana (0, 50 and 100 %) plus soil and four doses of humic substances (0, 12.5, 25 and 50 g L-1). The use of carnauba bagana in the substrate increased the leaf area, plant height, stem diameter, root length, root volume, shoot and root dry mass, and improved the seedlings quality. The application of humic substances to the substrate did not stimulate the seedlings development.

Reduction of synthetic fertilizer application and heavy metal absorption on oil palm nursery related to the application of humic substances

Humic acid with amorphous and colloidal characteristics can improve soil chemical properties, especially tropical soil with lower fertility. To contribute to an environmentally friendly farming system, the capacity of humic acid to reduce the consumption of synthetic fertilizer on nursery oil palm was tested in this experiment. The experiment’s purpose was to confirm the minimizing fertilizer application and reduce the heavy metal absorption in oil palm nurseries without any deterioration effects on the growth performance. Varied composition types of humic substance products were applied, i.e., in combination with fish meal, seaweed, and chicken manure.The concentration of heavy metals Ba, Cd, Ba and the absorption of macroelements N, P, K, Ca, and Mg in the growing plants was also observed. It showed that humic acid in the dosage of 40 g/plant in the main nursery was capable of reducing the application of mineral fertilizer by 25% base on recommended standard application and at the same time reducing heavy metal Ba and Cd absorption by the plant.

Humic Substances in Combination With Plant Growth-Promoting Bacteria as an Alternative for Sustainable Agriculture.

Plant growth-promoting bacteria (PGPB) and humic substances (HSs) are promising options for reducing the use of pesticides and mineral fertilizers. Although many studies have shown the effects of PGPB and HSs separately, little information is available on plant responses to the combined application of these biostimulants despite the great potential for the simultaneous action of these biological inputs. Thus, the objective of this review is to present an overview of scientific studies that addressed the application of PGPB and HSs to different crops. First, we discuss the effect of these biostimulants on biological nitrogen fixation, the various effects of the inoculation of beneficial bacteria combined with the application of HSs on promoting the growth of nonleguminous plants and how this combination can increase bacterial colonization of plant hosts. We also address the effect of PGPB and HSs on plant responses to abiotic stresses, in addition to discussing the role of HSs in protecting plants against pathogens. There is a lack of studies that address the role of PGPB + HSs in biocontrol. Understanding the factors involved in the promotion of plant growth through the application of PGPB and HSs can assist in the development of efficient biostimulants for agricultural management. This approach has the potential to accelerate the transition from conventional cultivation to sustainable agrosystems.

Assessing the potential of biochar aged by humic substances to enhance plant growth and soil biological activity

BackgroundSoil carbon-rich organic amendments (biochar, humic substances) may improve the quality and fertility of arable soil. Their co-application can additively enhance the beneficial effect on soil. Hypothetically, the pre-treatment of biochar, by aging via soaking in a solution of commercially available humic substances, could result in synergism, which may exceed the benefit from simple co-application of both amendments to the soil. Therefore, the aim of this study was to investigate the impact of biochar, humic substances, the combination of both, and the impact of biochar aged by humic substances solution on soil microbial activities and plant growth in a short-term pot experiment with lettuce.ResultsThe aging of biochar decreased the C:N ratio as compared to non-activated biochar. The co-application of biochar and humic substances into the soil resulted in the highest microbial biomass carbon and respiration activity. The majority of enzyme activities (β-glucosidase, arylsulfatase, N-acetyl-β-d-glucosaminidase, phosphatase) were the highest in humic substances-amended soil. The application of humic substances and biochar with humic substances seemed to stimulate microbial growth and activity followed by the competition of microflora for nutrients with plants, whereas the aged biochar behaved differently. The plants treated by aged biochar achieved the highest values of dry aboveground and root biomass of all variants. However, the assumed rapid uptake of nutrients by plants resulted in lower nutrient availability for microflora, and a decline in microbial viability.ConclusionsBased on this study, the positive effect of co-applied humic substances and biochar on soil fertility, quality, and health can be concluded. The usability of biochar aging by humic solution requires further study.Graphic abstract