Humic Products Research Articles

Biochar Regulates the Humification of Kitchen Waste and the Effects of the Humic Acid Structure of Products on Black Soil

Kitchen waste is a misplaced resource that is characterized by a high organic matter content, high water content, and a tendency to rot easily. Biochar is a black solid substance produced under high-temperature, anaerobic conditions using agricultural organic wastes as the raw material. It possesses a large specific surface area, a loose and porous structure, and functional groups, which confer high thermal stability and strong adsorption capabilities. However, little is known about how humic products made from biochar affect the composition and structure of soil humus. To solve the above problems, this study carried out a two-year outdoor field experiment by means of element analysis, infrared spectroscopy, and differential thermal analysis (0.4 kg/m2 (W4), 0.8 kg/m2 (W8), 1.2 kg/m2 (W12), 1.6 kg/m2 (W16), and 2.0 kg/m2 (W20)); CK was the blank control (no application). The samples were collected one year and two years after they returned to the field. The results showed that the application of organic materials facilitated the accumulation of soil organic carbon (SOC) and increased the total nitrogen (TN) content. The highest SOC content in the W20 treatment was 12.39 g/kg and 14.67 g/kg in one and two years, respectively. The maximum relative HA content in the W20 treatment was 22.99% one year after returning to the field. The PQ value (the ratio of HA/(fulvic acid (FA) + HA)) for the W20 treatment was 88.21%. The W20 treatment greatly increased the SOC and humus carbon contents. Compared with the CK treatment, all the organic materials applied for one year improved the structure of the humic acid to varying degrees, increased the degree of oxidation, reduced the degree of condensation and thermal stability of the HA in the soil, and gradually simplified the structure of the humic acid; among all the treatments, the W20 treatment had the greatest effect.

Antioxidant Features of Humic Products by ABTS Assay.

Oxidative stress plays a pivotal role in driving immunosenescence by disrupting cellular homeostasis and impairing immune function. Humic substances exhibit scavenging activity against reactive oxygen species (ROS), inhibit ROS generation via metal chelation, and modulate endogenous antioxidant enzyme activity. Additionally, humic substances display anti-inflammatory effects, further supporting cellular redox balance. Given their antioxidant activity, humic substances hold promise as natural compounds for mitigating oxidative stress-associated immunosenescence. Here we describe the evaluation of antioxidant capacities of humic products by ABTS spectrophotometric assay.

Cd(II) and Zn(II) adsorption on lignite‐derived humic substances and cattle manure biochar

AbstractExcessive industrial release of trace elements may pose a great risk to the environment. Conventional remediation treatments have considerable limitations, making less expensive new technologies an important research area. Batch experiments were conducted at room temperature to investigate the use of two lignite‐derived humic products (nano‐humus and humic powder) and a cattle manure biochar as adsorbents in the removal of cadmium and zinc from laboratory synthesized water. Nano‐humus was most effective in adsorbing Cd(II), wherein 89% adsorption was rapidly achieved in 15 min. The adsorbed amount of Cd(II) and Zn(II) both increased with initial metal ion concentrations from 25 to 125 mg L−1. Despite being produced from the same sources, nano‐humus and humic powder showed different properties and adsorption behaviors. The adsorption mechanism of nano‐humus followed the Freundlich isotherm model and pseudo‐second‐order kinetic model, indicating multilayer chemisorption. Humic powder followed the pseudo‐second‐order kinetic model, although it had a low isotherm model fit, implying chemisorption‐dominated adsorption. Cattle manure biochar followed the Freundlich isotherm and pseudo‐first‐order kinetics model, suggesting diffusion‐dominated multilayer adsorption. Of the three adsorbents tested, nano‐humus had greatest potential as an effective and inexpensive material for metal remediation.

Synergistic effects of coal waste derived humic substances and inorganic fertilizer as soil amendments for barley in sandy soil

Increasing pressures on land resources requires increased land use efficiency. Over 900 million ha of sandy soils throughout the world are extensively used for agricultural crop production, most requiring nutrient inputs. Although use of humic substances together with inorganic fertilizer as soil amendments has been introduced, their synergistic effects on plant growth in sandy soils are not well addressed. We assessed the efficacy of a lignite waste derived humic substance on barley (Hordeum vulgare L.) growth, with and without inorganic fertilizer. Ten treatments were applied to sandy soils, comprising sole application of the humic product at four rates (NH1, NH2, NH3, NH4), sole application of fertilizer (F), and their combinations (F + NH1, F + NH2, F + NH3, F + NH4). Synergistic effects of nano humus and fertilizer were more notable than the corresponding sole application, particularly on plant biomass and seed production. Combined application with inorganic fertilizer increased root biomass by 92 % (0.1 g per plant), shoot biomass by 80 % (0.5 g per plant), root length by 24 % (3.6 cm), and seed production by 38 % (5 seeds per head) averagely relative to the untreated control, suggesting a strong synergistic effect. The increased seed production was particularly important from an agricultural perspective. Four application rates of nano humus all showed beneficial effects on barley growth with no significant differences. The most distinct positive effect of the humic product as a sole application was on root growth. Our study confirmed that a lignite waste derived humic product, nano humus, together with fertilizer may be an effective soil amendment to enhance agricultural plant growth in sandy soil regions.

Humalite enhances the growth, grain yield, and protein content of wheat by improving soil nitrogen availability and nutrient uptake

AbstractBackgroundThe application of synthetic chemical inputs in current agricultural practices has significantly increased crop production, but their use has caused severe negative consequences on the environment. Humalite is an organic soil amendment that is rich in humic acid and found in large deposits in southern Alberta, Canada. Humic products can enhance nutrient uptake and assimilation in plants by reducing nutrient losses and enhancing bioavailability in the soil.AimHere, we evaluated the effects of different humalite rates in the presence of nitrogen, phosphorus, potassium (NPK) at recommended rates on soil nitrogen availability, wheat growth, grain yield, seed nutritional quality, and nitrogen use efficiency (NUE) under controlled environmental conditions.MethodsA series of studies were conducted by applying five different rates of humalite (0, 200, 400, 800, and 1600 kg ha−1) with NPK at recommended rates. Soil nitrogen availability and shoot and root growth parameters were recorded at flowering stage. NUE was calculated based on the grain yield at maturity stage.ResultsPlants grown in the presence of humalite augmented root morphological parameters (root length, volume, and surface area), plant biomass (shoot and root), and nutrient uptake (N, P, K, and S) compared to the plants supplied with recommended fertilizer alone. Furthermore, humalite application significantly increased grain yield (14%–19%), seed protein content (23%–30%), and NUE (14%–60%) compared to the fertilizer application alone.ConclusionThese findings suggest that humalite can be used as an organic soil amendment to reduce synthetic fertilizer application and improve plant growth and yield while enhancing fertilizer use efficiency.

Innovative Method of Extraction of Humic Substances from Digested Sludge and Assessment of the Impact of Their on the Growth of Selected Plants

The paper describes a new, proprietary method of HS extraction from digested sewage sludge. HS was extracted using the processes of dissolving organic substances and precipitating mineral micropollutants. The obtained substances were tested by determining their IR spectrum, elemental composition, and content of micropollutants and comparing them with HS obtained using the classical method. Using Phytotestkit, it was shown that HSs isolated from digested sewage sludge contain relatively large amounts of the nutrients necessary for plants (including N and P) and are a good component of a biostimulating substance. The obtained HS contains more ammonium and phosphorus ions. During extraction, inorganic impurities (including heavy metals) are reduced, and the humic product does not contain pathogens, parasites, and their spores. The method is simple, economically justified, and can be used on an industrial scale.

Variable humic product effects on maize structural biochemistry across annual weather patterns and soil types in two Iowa (U.S.A.) production fields.

Agronomic benefits of humic product application to crops are receiving increasing attention, though underlying biochemical changes remain unexplored, especially in field settings. In this study, maize (Zea mays L.) concentrations of 11 phenol and five carbohydrate monomers were determined in whole plant stover (four growing seasons) and roots (two growing seasons) at physiological maturity for two rainfed fields in Iowa (USA) having humic product applications. Stover and root tissues tended toward greater phenol concentrations in a drier upland transect but greater carbohydrate concentrations in a wetter lowland transect. Two humic treatments further accentuated these trends in upland roots. Their phenol content increased significantly with humic application in the droughtier season of root sampling (2013). Phenol increases above the unamended control averaged 20% for each monomer. Total phenols increased above the control by 12% and 19% for the two humic treatments. Five carbohydrate monomers in the upland roots did not respond to humic application. In the second year of root sampling (2014), which had abundant rainfall, upland root phenols did not respond substantively to humic application, but root carbohydrates increased on average by 11 or 20% for the two humic treatments compared to the control, reaching significance (P< 0.10) in 7 of 10 cases. Upland stover phenol concentrations responded differently to humic product application in each of four years, ranging from numeric increases in the droughtiest year (2012) to significant decreases with abundant rainfall (2014). In the lowland transect, root phenols and carbohydrates and stover phenols responded inconsistently to humic application in four years. Stover carbohydrates did not respond consistently to humic application in either transect. The phenols that were more responsive to humic application or to droughtier conditions included p-coumaric acid and syringaldehyde, which are heavily involved in late-season maize lignification. In summary, humic product application further promoted root lignification, a natural response to drought. Yet under non-drought conditions it promoted root carbohydrate production. Carbohydrate production might be the intrinsic plant response to humic product application in stress-free conditions. These results indicate complex interactions in field conditions between plant biochemistry, environmental signals, and the humic product.

The reaction of soybean and pea crops in the Priobye region to a humic antistress agent to herbicides in the foreststeppe of Western Siberia

In the article, the authors presented those enticing actual herbicidal treatments (the active ingredient is cloquintocet-mexyl, fenoxaprop-P-ethyl), spring-summer and summer droughts, are stress factors for the development of early-ripening soybean varieties and zoned pea varieties in the forest-steppe of the Priobye region. They limit the realization of the biological yield potential of soybeans and reduce the coarseness of pea grains and their total protein. Use with the herbicide of humic preparation from leonardite Cytogumat at a rate of 0.4 l/ha relieves physiological stress on soybean plants, providing a rapid increase in biomass and grain yield of 4.2-5.5 c/ ha, or 19%. Furthermore, the humic product in a single year can increase the duration of soybean vegetation by 3-4 days and the height of lower bean attachment by 24%. The authors analyze the stress resistance to the anti-cereal herbicide of 5 varieties of peas. They also found that the varieties Altaysky Usatiy and Novosibirets mediumresistant, Yamal, and Astronaut are sensitive to the herbicide. The application of Cytogumat in susceptible varieties increased green mass by 30.1% and 24.0%, grain yield by 10.5-12.0%, weight of 1000 grains by 7.1-7.4%, and total protein. In moderately resistant varieties, the reaction to Cytogumat was less pronounced and was accompanied by an increase in yield by 8–10%, grain size by 5–5.4%, and protein content by 1.9%. The Yamalsky pea variety in the Ob River region proved to be tolerant to stress, and it is inexpedient to use Cytogumat on it.

Differentiation Between Humic and Non-Humic Substances Using Alkaline Extraction and Ultraviolet Spectroscopy.

Although humic substances are the principal ingredients in processed humic products, there has been no practical way to determine if a material is humified, allowing fake products to be used by farmers instead of genuine humic substances. To develop a test method using conventional laboratory techniques to determine if a material is humified. A neutralized extract is prepared using the standardized extraction protocols specified in ISO 19822:2018(E). A portion of the extract is used to determine the concentration of dissolved organic matter on an ash-free basis. A portion of the remaining neutralized extract is diluted to a concentration of 30 mg/kg of dissolved organic matter and transferred to a quartz UV cuvette for ultraviolet-visible (UV-Vis) spectroscopy. UV-Vis absorbance is recorded over a wavelength range of 220-500 nm at 5 nm intervals. The absorbance data are normalized by conversion to scaled absorbance, which is compared to a reference scaled absorbance spectral curve for humic substances to determine if the tested material is humic or non-humic. This method was able to differentiate legitimate humic substances from non-humic adulterants in a multiple-laboratory validation study (P ≤ 0.05). This method can differentiate humic from non-humic substances in materials intended to be used as ingredients in commercial humic products or for research. This method uses common laboratory procedures and equipment.

The Coal Humic Product EldORost Shows Fertilizing and Growth Stimulating Properties on Diverse Agricultural Crops

The use of environmentally safe products of natural origin is a global trend today. A particular point of interest is the use of humic fertilizers. This is due to the growing awareness of the positive impact of humic substances on plant growth and development as well as on the quality of agricultural products and soil fertility. Humates are physiologically active substances. As a result, they regulate and intensify metabolic processes in plants and soil, and contribute to the bioavailability of nutrients to plants. EldORost is a new-generation humic product that contains humic substances with a high humification degree. In addition to humates, this product contains a complex of amino acids, macro-, and microelements in a bioavailable form for plants. The product is eco-friendly and completely soluble in water, which is a substantial advantage for drip irrigation systems. It can be used for all types of agricultural crops on a wide diversity of soils and climatic zones. It displays the properties of plant hormones while its optimum concentration is as low as 0.0001% (wt). The efficiency of this novel humic product was tested in laboratory and field tests conducted on potatoes and vegetable crops (tomatoes, cucumbers, cabbage, carrots, onions, beets). The obtained results showed high efficiency displayed in the significantly improved sowing quality of vegetable seeds, nominally increased the germination degree and seed germination energy, intensively stimulated the side root development in plants, accelerated the growth of biomass, increased the fruiting period, and reduced maturation on the yield of potatoes and vegetable crops. The obtained data allowed us to characterize this novel humic product from the perspective of an eco-friendly fertilizer and growth promoter.

Application timing optimization of lignite-derived humic substances for three agricultural plant species and soil fertility.

Coal is mined for energy generation around the world, producing large amounts of waste and extensive disturbances to the environment. Post-mining lands with sandy soils to be reclaimed for agricultural uses are very challenging. The use of humic substances such as soil amendments has been discussed, although little information is available regarding application timing in the field. We conducted a field experiment over two consecutive growing seasons on a former coal mine in China, to investigate soil and vegetation response to a lignite-derived humic product called "nano humus" and to determine optimal application timing. Three economically valuable agricultural species, alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), and sea buckthorn (Hippophae rhamnoides L.), were used for this study. The benefits of the humic product on soil properties and plant growth under field conditions were expressed after 2 yr of application. A single application at the beginning of each growing season provided better results than splitting into two applications, with no impact of duration (months) between applications. A single application significantly increased soil available phosphorus by 63% and potassium by 96% relative to the control; it significantly enhanced total biomass of alfalfa by 749%, barley by 250%, and sea buckthorn by 147%. Our findings provided important practical implications for using a humic material as a soil amendment in coal mine reclamation, with potential applications in other agricultural and reclamation scenarios.

Bioassay of Humic Products as Potential Remedies: A Review

Bioassay of Humic Products as Potential Remedies: A Review

Waste-free processing of lowland peat for production of liquid organomineral fertilizers

The Tyumen Region holds extensive resources of peat, which should be considered as a raw material for the production of organic and organomineral fertilizers. The purpose of this research is the development of a waste-free technology for the production of organomineral fertilizers based on humic substances of lowland peat. The tests of three grades of organomineral fertilizer were carried out in accordance with the State Test Methodology, and soil properties were determined in accordance with the relevant state standards (GOSTs). The humic acid extraction method developed at the General Chemistry Department of the Northern Trans-Ural State Agricultural University produces two types of waste in a large volume: a liquid sediment mixture after separation of humic substances from peat and a supernatant solution after precipitation of humic acids. At present, a non-waste method for obtaining organic-mineral fertilizers from lowland peat has been patented. From a liquid sedimentary mixture of peat and humic substances, a peat&ndash;humic fertilizer is prepared for application to the soil. This fertilizer increases crop productivity and humus content, and reduces soil acidity. From the supernatant solution with fulvic acids, a huminomineral fertilizer is prepared for foliar feeding of plants. After centrifugation, a humic product is prepared from the gel of precipitated humic acids for pre-sowing, foliar and root feeding of plants. The products were tested on spring wheat, spring rapeseed, onion and apple trees. All products increased the yield and quality of products. The profitability of the production of three grades of organomineral (one product of each stage of production) fertilizer in comparison with the production technology of only one biostimulant is increased by 2.3 times. Currently, the procedure for their state registration is underway.

Characteristics of Fluorescent Dissolved Organic Matter in Paddy Soil Amended With Crop Residues After Column (0–40 cm) Leaching

Dissolved organic matter (DOM) has a critical impact on various processes in the ecological environment, especially in soil and surface water due to its mobility and reactivity. In the present study, a column experiment simulating a paddy field was conducted to evaluate the feasible application of inorganic fertilizer incorporated with three types of organic materials (wheat straw, rapeseed shell, and astragalus smicus). Researchers investigated the vertical distinctions of soil (combined with different organic materials in 0–10 cm) DOM in 0–40 cm profiles after long-term leaching. Excitation–emission matrices coupled with parallel factor analyses (EEM-PARAFAC) and UV-visible techniques were employed to diagnose the spectral characteristics of soil DOM at four depths in different treatments, qualitatively and quantitatively. The results showed that the DOM content of CF (conventional fertilizer) (0.14 g kg−1) was the highest at the 10–20 cm layer and the CK (no fertilizer) (0.05 g kg−1) at 30–40 cm was the lowest, and the mean DOC concentration decreased with the increase in soil depth. Four fluorescent components, protein and tryptophan-like, humic acid-like, fulvic acid-like, and solubility-like microbial metabolite product materials, were identified by the PARAFAC model. Relative distributions of calculated components suggested that DOM mainly contained more aromatic humic materials and litter fulvic acid with the increase in soil depth. However, the SUVA254 showed a maximum in 20–30 cm layers, indicating strong aromatic and abundant hydrophobic fractions. Fluorescent index (FI) values of soil DOM from various treatments have a similar terrestrial and allochthonous source in topsoil and microbial source in deeper soil. In short, the findings obtained in our work could commendably provide some valuable optical information of DOM released from soil column and offer technical guidance when applying organic or green fertilizer to paddy soil during rice production.

Foliar Application of a Microbial Inoculant and Alkali-Extracted Humic Product Boosts Forage Productivity and Quality on a Central Coast California Rangeland

There is increasing interest in using biostimulant products, such as microbial inoculants and alkali-extracted “humic” substances to help manage rangelands regeneratively and rebuild soil health. Understanding how plant and soil communities on rangelands respond to these products is therefore important. In this 3-year study, we examined the combined effects of a commercial inoculant and alkali-extracted “humic” product that are currently on the market (Earthfort Inc. Soil Provide and Revive®) and asked whether they influenced rangeland forage productivity and quality, soil microbial biomass and community composition, and abiotic soil parameters in Central Coastal California. Treatments were established in February 2018 and the products were applied two to three times a year during the growing season (approximately November—May). Sampling of plant and soil samples also began in February 2018 and continued in the fall and spring for three consecutive growing seasons. We found that forage productivity responded positively to the foliar application of these commercial products, with forage production on average 58% percent higher in treated compared to control sites. Some metrics of forage quality (acid detergent fiber, calcium, and fat content) also responded in a desirable way, but these benefits were not mirrored by changes belowground in the microbial community or abiotic parameters. While our study derives from one ranch and therefore requires confirmation of its ubiquity prior to broadscale adoption, our results provide new insights into the usefulness of this approach for managing rangeland productivity in California's Central Coast—and suggest biostimulants could warrant attention as a potential tool for regenerative stewardship of rangelands more broadly.

Biochemical determination of reduced glutathione concentration in pig liver and kidney in the presence of chlorinated aquatic humic materials

Disinfection of surface waters for human consumption and use often results in reaction between the disinfectant (generally chlorine) and organic substrates present at the source. These substrates are majorly in the form of aquatic humic materials. This work was designed to assess reduced glutathione (GSH) concentration in pig liver and kidney in the presence of chlorinated aquatic humic materials (CAHMs) using biochemical parameters. GSH concentration in pig liver and kidney was investigated following standard procedures using Ellman’s reagent. Effect of chlorinated local and foreign aquatic humic products on the GSH concentration of the two tissues was studied in line with standard methodologies. GSH concentration was found to be higher in pig liver (0.874 ± 0.003µmol/g) than the kidney (0.545 ± 0.002µmol/g). All the chlorinated aquatic humic samples studied were found to deplete the GSH concentration of the two tissues, with the more toxic and concentrated purified chlorinated foreign aquatic humics having higher depletion. Certain amount of GSH was also found to be left in both tissues after conjugation with the chlorinated aquatic humic samples which perhaps could be used for subsequent conjugation and detoxification of water pollutants by the tissues. In conclusion, the liver contains more GSH than the kidney. The levels of this antioxidant in pig liver and kidney were both reduced by the aquatic humic materials used. This study may therefore reemphasize earlier suggestions that the amino acids needed for cellular synthesis of GSH could be supplemented regularly through dietary sources.

Lignite derived humic products and cattle manure biochar are effective soil amendments in cadmium contaminated and uncontaminated soils

Cadmium (Cd) contamination in soils is a global environmental concern. Amending soil with low cost carbonaceous materials, such as humic substances and biochars, may provide cost effective and environmentally sound alternatives to traditional remediation technologies. Two lignite derived humic substance products, nano humus and humic powder, and a cattle manure biochar, were used as amendments in loamy sand and silt loam soils to ascertain their impact on Cd, with barley (Hordeum vulgare L.) as the response organism in a greenhouse experiment. Soil Cd had the greatest influence on barley shoot biomass, decreasing by 28% in silt loam and 37% in loamy sand relative to the control. With or without Cd addition, the beneficial effect of nano humus and humic powder were pronounced. Nano humus and humic powder (high rate), increased root biomass by 248 and 100% in uncontaminated soils, respectively; and increased by 186 and 55% in Cd contaminated soils. Biochar increased shoot biomass in soils by 32% without Cd, and 127% with Cd. Barley responded differently to amendments in two textured soils. Results of this research will help develop cost effective remediation techniques using humic materials and cattle manure biochar as soil amendments in Cd contaminated soils.

Maize Growth Responses to a Humic Product in Iowa Production Fields: An Extensive Approach.

Field evaluations of commercial humic products have seldom involved replication across location or year. To evaluate the consistency of humic product efficacy in field conditions, we determined the effects of a humic product on maize (Zea mays L.) growth in high-yielding Midwestern (US) fields through the following two extensive approaches: (i) replicated strip plots in five site—year combinations from 2010 to 2013; and (ii) demonstration strips in 30–35 production fields annually from 2009 to 2011 that covered major areas of Iowa. Mechanized combine measurements of grain yield showed increases of 0.2–0.4 Mg ha–1 (1–4%) with humic product application for all five site—year combinations of the replicated strip plots. Six of 10 humic treatments within the fields responded positively (P < 0.07), and the positive responses of two more treatments approached significance at the benchmark of P = 0.10. In the demonstration strips, maize grain weight in hand-collected samples increased significantly (P < 0.004) with humic product application in each of the three growing seasons, and across all the three seasons by 6.5% (P < 0.001). Grain weight increased numerically for 76 of the 98 demonstration strips. Yield component analysis for both the replicated strip plots and the demonstration strips attributed the yield boosts largely to increased ear length, especially of the shorter ears. Humic product application caused significantly (P < 0.10) greater total leaf area in all eight field treatments at three site—year combinations. Humic product application did not consistently affect nutrient concentrations of the grain or stover or any measured soil property. These results represent among the widest geographic evaluations published on field efficacy of a humic product. They demonstrate the capability of a humic product to improve maize growth in high-yielding conditions.

Improving the efficiency of using straw as a fertilizer

The article discusses the results of investigations carried out within the framework of the research project commissioned by the Ministry of Agriculture of the Russian Federation in 2020. In August 2019, a field experiment was laid for the disposal of straw of spring barley of Vladimir variety using a special machine for this, i.e. a unit for utilizing the non-grain part of the crop as a fertilizer. When disposing straw, it was processed with biopreparations-destructors: Agrinos-1 (2 l/ha), Sternifag SP (0.08 kg/ha), Biocomplex BTU (1 l/ha), humic product Ekorost (0.4 l/ha). The straw was crushed and embedded in the soil on the control plot without treatment with biological preparations. It was found that the process of straw decomposition is more intensive compared to that of 2018-2019 on average by 5 %. The variants with Agrinos 1 and Sternifag SP treatment showed better results and accelerated the degradation process by 20 % compared to the control. The biological productivity of spring oats of Skakun variety showed that all studied biological products had a positive effect on the increase in yield. The best indicators were achieved on the variants with Agrinos-1 and Sternifag SP equal to 48.9 dt/ha and 45.4 dt/ha, respectively (the control was 36.4 dt/ha).

Evaluation of humic fertilizers on a sand‐based creeping bentgrass putting green

AbstractTurfgrass with sand‐based root zones, such as golf course putting greens, are highly important economically and require intense management. However, problems are often associated with sand‐based root zones, such as low nutrient retention and limited microbial activity. Soil additives may increase soil biological activity, improve nitrogen (N) cycling efficiency, and thus reduce fertilizer N inputs. A 2‐yr experiment was conducted on a sand‐based creeping bentgrass (Agrostis stolonifera L.) putting green to investigate whether humic products could increase soil biological activity and improve turfgrass quality. Treatments included humic‐coated urea (HCU; 2/3 rate and full rate), HCU + humic dispersing granules (HDG), HCU + black gypsum (BG), urea, HDG, and a nontreated control. Minimal differences were seen in microbial biomass and activity besides HCU + BG. The HCU + BG had 60% greater potentially net N mineralization relative to the HDG and the nontreated control. Overall, incorporating humic substances with N fertilizer did not increase turfgrass quality, cover, and clipping biomass compared with N fertilizer alone. However, the addition of BG to N fertilizer enhanced microbial activity (i.e., potentially net N mineralization).