R ESEARCH 49 October 2000 October anagement M EY POINTS Heavy application ofHeavy humic bentgrassacid to in hydro- significantly ponic culture photosynthesis,increased root enzyme activity and root mass, but not chlorophyll length. or root content bentgrass rooting Creeping mixing by was increased into granular humates of 4 inches the top the root zone. However, turfgrass shoot growth and visual quality from rarely differed turf. untreated Although treatments with sometimes substances humic caused a significant increase in the concentra- or decrease tion of nutrients, several relatively were the changes small, not and probably of biological significance. K ourse C olf G dedicated to enriching the environment of golf the environment to enriching dedicated substances that is not soluble in water that is not soluble substances (pH less than under acidic conditions 2) but is soluble at higher pH values. derived from plant and animal residues plant and from derived usually dark in color.and are Humic humic divided can be into substances acids, fulvic acids and humins, on the basis of solubility their in acidic and basic solutions. (1) have Researchers the fractions: characterized • is the fraction acid of Humic humic • acid is the fraction of Fulvic humic SCIENCE FOR THE GOLF COURSE GOLF THE FOR SCIENCE In recent years, recent In commercial many be generally can substances Humic

GCM - October 2000 - Research - Humic substances influence creeping bentgrass growth bentgrass creeping influence substances Humic - Research - 2000 October - GCM Granular humate mixed into the top 4 inches of a greenhouse sand culture improved bent- grass rooting. Subtle effects are sometimes noticeable and perhaps statistically significant. are sometimes noticeable Subtle effects Ph.D. Richard J. Cooper, Chunhua Liu, Ph.D., and Humic substances influence influence substances Humic growth bentgrass creeping products containing humic substances humic containing products for use on turf- promoted been have grasses. Although the effects of humic grasses and numer- on cereal substances been studied for ous other plants have some time, their effects on turfgrass documented. not been well growth have occurring,“naturally described as highly with organic substances a decomposed structure”very complex (1). They are Photos courtesy of Chunhua Liu Chunhua of courtesy Photos ). Agrostis stolonifera Agrostis Manufacturers ofManufacturers humic commercial The purpose of was to our research bentgrass creeping plugs Crenshaw ofMeasurements photosynthesis, In recent years,In recent humates commercial root system root tolerances and pesticides Though popular for its quality on in the northernputting greens United and in the transitionStates zone, bent- manage duringgrass difficult to is often summer. in a results often stress Heat system, root shallow and less healthy dis- to prone bentgrass more becomes ease and insect damage. turf- claim benefits to often products grasses, including: • and deeper A better-developed • establishment rate Increased • plant vigor and survivability Improved • salt, Improved heat and other stress • nutrient uptake Increased •structure soil Improved • of effectiveness Increased fertilizers the effects ofinvestigate sub- humic stances, and including both humates acids, humic on the growth of creeping bentgrass (2,4). Photosynthesis, chlorophyll and rooting in a 25 per- hydroponically grown were nutrient solution con- Hoagland’s cent acids at zero,taining humic 100, 200 or 400 parts per million in the greenhouse. solution con- A 100-parts-per-million oftains 1 liquid ounce acid in humic about 78 gallons of solution. Hoagland’s all ofsolution contained the mineral nutrients needed for plant growth. solution plants in Hoagland’s Growing nutri- adequate that they have ensures ents during the study. and root concentration chlorophyll enzyme activity were dehydrogenase for one month.made weekly Root enzyme activity the vigor and reflects health of roots; the active the more enzyme tis- is in the root dehydrogenase and humic acid products have been pro- have acid products and humic for use on turfgrasses,moted especially bentgrasscreeping ( Cation exchange capacity (meq/100 g) capacity (meq/100 Humic substances are not traditional are substances Humic Humic substances are essentially are substances Humic substances that is soluble in water that substances under all pH conditions. at that is not soluble in water stances pH value. any fertilizers. Carbon, hydrogen,nitrogen, oxygen, phosphorus and sulfur of 100 percent for nearly account the ofcomposition on an substances humic basis (5). ash-free • is the fraction of Humin sub- humic ofcomponents and can organic matter anywhere:be found almost streams, and virtually that contains soil lakes any organic matter, animal or plant residues. used soil commonly Many significant organic amendments have and fulvic acid content.humic Reed- used in high-sand-sedge peat is often because it has a zones root content capacity and higher cation exchange than other sources. acid content humic October 2000 October anagement M ourse C olf GCM - October 2000 - Research - Humic substances influence creeping bentgrass growth bentgrass creeping influence substances - Humic - Research 2000 - October GCM G Average elemental composition (percentage) of soil humic substances (5). Average ElementCarbonHydrogenOxygenNitrogen Humic acid (%)Sulfur 54-59 acid (%) Fulvic 3-6 33-38 1-4 0-2 41-51 4-7 40-50 1-3 0-4 Humic contents What’s in humics? What’s Reed-sedge peatSphagnum peatRice hull compostFir bark 21.1 8.3 5.8 12.0 8.6 3.1 6.9 118.0 5.8 74.8 16.5 18.3 Amendment Humic acid (%) acid (%) Fulvic Humic and fulvic acid content and cation exchange capacity of four commonly used Humic and fulvic acid content and cation exchange capacity of four commonly organic soil amendments. 50 R ESEARCH R ESEARCH 51 October 2000 October anagement M ourse C olf G Humic acid had no promotive acid Humic enzyme root activity sug- Increased effect on root length after the original after length effect on root excised; were roots however, 400 parts root per million significantly increased dry mass on all sampling dates. enzymeRoot activity of plants acid at 400 parts humic per receiving million was significantly higher than that of plants, nontreated with the to ranging 35 percent increases from 108 percent. was increased respiration gests that root substances. humic substantially by in plants is a close connection There of the energy-releasingbetween process and the energy-consumingrespiration ofprocess growth. Thus, growth might the root be due to in increases ofstimulation enzyme by systems respiration. increased The results showed that the photo- showed The results GCM - October 2000 - Research - Humic substances influence creeping bentgrass growth bentgrass creeping influence substances - Humic - Research 2000 - October GCM A greenhouse hydroponic culture system was used for humic acid evaluation. sue,roots. the are healthy the more All acid humic clippings after harvested for nutrient combined application were analysis.end of the At study, the root length and dry measured. mass were Results and discussion ofsynthetic rate in 100 plants growing or 200 parts per million solutions of that of from differed acid rarely humic the control. However, the treatment at 400 parts per million consistently as as much by photosynthesis increased 20 percent. did not content Chlorophyll acid applica- vary humic to in response sampling dates.tion on any Thus, it in photosyn- appears that the increase application acid thesis following humic other than process some was due to production. chlorophyll increased one 0 parts per million parts per million 100 parts200 per million 400 parts per million a In general,In application of sub- humic calcium concentration and Nitrogen depths was increased by mixing granular mixing by increased depths was of inches 4 the top into humates the root zone. more been due to have This may of contact direct substances humic with roots. developing single foliar- No acid treatmentconsis- applied humic compared rooting improved tently in either sand culture with the control experiments. culture or hydroponic Similarly, application of foliar humates creep- Cato-Crenshaw on a field-grown no ing bentgrass blend also produced (3). in rooting improvement did not affect clipping drystances visual qual- weight and did not improve with turf,ity untreated compared as just (6). reported have previous researchers in leaf unaffected relatively tissue were the application ofby sub- humic stances, of regardless rate. application bb b b a bc c a b b Two commercially mined granular commercially Two bentgrass at all rooting Creeping b Roots, shoots, visual quality Roots, shoots, humates, acid, humic a commercial and acids (defined by humic reference three Substance Humic the International leonardite, Society from and extracted creeping applied to peat and soil) were bentgrass in sand,growing hydroponic or the field.culture granular Commercial the either incorporated into were humates of 4 inches top in sand cul- zone the root ture, field plots at 10, applied to surface or feet. 20 and 40 pounds per 1,000 square acid solution (100,Humic or 400 200 parts per million)either foliarly was applied (in sand culture, in hydroponic the and in the field) or applied to culture ofsurface (in sand culture) zone the root feet. at 5 gallons per 1,000 square Results and discussion a ab October 2000 October b b anagement M ourse C olf GCM - October 2000 - Research - Humic substances influence creeping bentgrass growth bentgrass creeping influence substances - Humic - Research 2000 - October GCM G greenhouse each group, solution-culture experiment. Within bars with the same letter are not significantly different. Photosynthetic rates of hydroponically grown creeping bentgrass increased with humic acid application (in parts per million) in Photosynthetic rates 52 R ESEARCH R ESEARCH 53 October 2000 October anagement M ourse C olf G Crop HortScience 55:111-118. Literature cited Literature Humic substances in soil, substances Humic sediment Humic substances in soil, substances Humic sediment 38:1639-1644. In: Journal ofJournal Turfgrass the International In: In: and water: geochemistry, isolation and char- acterization. Wiley-Interscience, York. New uptake on the growth and nitrogen influence of bermudagrass. M.Sc.Florida, thesis. Gainesville. of University 1998. acid application affects photo- Humic synthesis, development, root and nutrient ofcontent bentgrass. creeping 36(6):1023-1025 characteristic of substances. humic p.476. 457- effects of and organic fertilizer humate on establishment and nutrition of bent- creeping grass. SocietyResearch and P. MacCarthy. 1985. in soil, substances humic sediment and water. to Introduction p. 1-9. and water: geochemistry, isolation and char- acterization. Wiley-Interscience, York. New ofInfluence and on rooting substances humic ofnutrient content bentgrass. creeping Science Although rooting, photosynthesis, 6. Varshovi, A.A. 1991. Humate: properties and 4. Liu, C., R.J. and D.C. Cooper Bowman. 5. Steelink, C.A. 1985. of Implications elemental 3. Dorer, S.P., and C.H. Peacock. 1997. The Chunhua Liu, Ph.D., scientist is a research of turf- physiologygrass J. and management; and Richard Cooper, Ph.D., of is a professor turfgrass manage- in Raleigh. University State Carolina ment at North sured differences in tissue nutrient con- differences sured attributable substances, humic tent to usually verysmall. were the differences is doubtful that these differences It turfgrass in improved result would quality in the field. activity and nutri- dehydrogenase root the by improved often were ent content application of substances, humic turf- grass shoot growthand visual quality those of from differed rarely untreated turf. so, Even open-minded remain we benefits of the potential regarding mak- ing supplemental applications of humic substances.materials the to Applying low-fertility soils or newly seeded mightgreens putting be useful in some situations.green very the low Given required,application rates might one cost-effec- substances humic consider root- because they might improve tive ing during the summer months. 1. Aiken, G.R., D.M. McKnight, R.L. Wershaw 2. Cooper, R.J., C. Liu and D.S. Fisher. 1998. Iron uptake was increased in the field in the was increased uptake Iron ofApplication acid materials humic is an importantPhotosynthesis Although, in all the evaluations of GCM - October 2000 - Research - Humic substances influence creeping bentgrass growth bentgrass creeping influence substances - Humic - Research 2000 - October GCM Phosphorous uptake in sand culture was in sand culture uptake Phosphorous incorporated granular by increased of several as by well as humates the substances. foliarly applied humic hydroponic-culture but not in sand or experiments. of The influence humic on the nutritionacid application of plants was mini- grown hydroponically mal. The leaf of tissue concentration other nutrientsseveral was significantly treat- (statistically speaking) by affected ment application; however, the differ- proba- so small that they are were ences bly not important plant growth. to Summary at 400 parts per million in hydroponic mass root significantly increased culture with turf untreated compared on almost every stud- in greenhouse date sampling ies. was not rates lower to The response as conclusive. Although the materials the amount ofimproved present, roots length.they did not affect root When incorporated were granular humates a depth of to zone the root into 4 inches, than stronger were effects the rooting the effect of foliar sprays. in mind Keep plants grow- from were that these results solutions ing in sand or in hydroponic organic little or no native containing substances. or humic matter Rooting mightresponses be less evident on a significant containing putting green or naturally occurringorganic matter substances. humic the plant because it provides process for growth and with carbohydrates injury. stress from recovery Applying acids at 400 partshumic per million photo- increased culture in hydroponic turf with untreated synthesis compared when photosynthesis on most dates was measured. enzyme activity Root acid applica- humic by was enhanced tion, respiration root plant suggesting substantially by be increased may substances. humic nutrient uptake, mea- consistently we