International Turfgrass Society Research Journal Volume 8, 1997. 437 THE EFFECTS OF HUMATE AND ORGANIC FERTILIZER ON ESTABLISHMENT AND NUTRITION OF CREEPING BENT PUTTING GREENS Stephen P. Dorer and Charles H. Peacock Dept. of Crop Science, North Carolina State University, Raleigh, North Carolina, USA. ABSTRACT Humate, the salt of humic acid reactions, is one of several humic substances being marketed as soil conditioners for turfgrass. According to previous research, humic substances can provide an energy source for soil microbes, improve nutrient retention in the soil, and enhance water holding capacity of the soil. Humates and a natural organic fertilizer were incorporated into a USGA soil mix, respectively, to a depth of 10 cm, before seeding with creeping bent (Agrostis stolonifera L.). Monthly treatments of liquid humate and quarterly treatments of granular humate were applied following germination. Effects on germination rate, percent coverage, and turf quality were measured. Additionally, semi-monthly analysis of harvested leaf tissue using NIRS technology was completed to study the effects of humates and natural fertilizer on nutrient availability. Germination rate and percent coverage increased significantly in plots receiving humate plus natural fertilizer. Micronutrient status of leaf tissue was increased by humate application. Humate and natural fertilizer treatments each improved root growth over the control. INTRODUCTION Humate, the salt of humic acid reactions, is one of several humic substances being marketed as a soil conditioner for turfgrass. Although the marketed product often includes humic and fulvic acids, in addition to actual humate, it is still referred to as a humate. Humate is partially decomposed humus, or soil organic matter. It is one of the least soluble components of humus and is relatively slow to decompose. In a review concerning the effects of humic substances on plant growth, Chen and Aviad (1990) cite studies that show improved germination, seedling growth after germination, increased shoot and root growth, enhanced nutrient uptake, and increased microbial population and activity. The greatest effects on plants appeared when humic substances were added to sterile nutrient solutions or soils high in sand content and low in organic matter. Golf course putting greens built to United States Golf Association (USGA 1993) standards originally contain at least 80% sand and at most 20% organic matter (by volume) in the top 30Omm. Pressure to quickly establish a dense and uniform stand of turfgrass on a putting green may
438 lead to excessive fertility, much of which may be lost to leaching from the sandy profile. Karnok (1990) examined the effects of a humate product on creeping bent (Agrostis stolonifera L.) grown on a USGA standard green. He found no negative plant growth effects from humate application, and found increased root growth during one month of the study. This experiment examined the effects of humate and natural fertilizer on germination rate, turf quality, nutrient uptake, and root growth of creeping bent grown on a USGA standard putting green. MATERIALS AND METHODS The experiment took place from 4 October, 1994 to 1 September, 1995 at the North Carolina State University Turfgrass Field Laboratory in Raleigh, North Carolina. The putting green was seeded with a 1:1 mix of 'Cato' and 'Crenshaw' creeping bent (Agrostis stolonifera L.) on 4 Oct at a rate of 4.8 g m- 2. The putting green soil profile was constructed to USGA standards with mix of 85% sand and 15% Canadian sphagnum peat moss (by volume) in the top 30 cm. Fertilisation of all plots included: 4.4 g N m'2, 4 g P m'2, and 7.6 g K m- 2 incorporated to 10 cm on 30 Sept, 5 days before seeding; and 29 g N m'2, 3.7 g P m- 2, and 14.8 g K m- 2 following seeding through September 1, 1995. Turf was mowed three times per week from March through September at 4.8 mm. Irrigation was supplied at 0.6 cm daily for 30 days following seeding until mowing began. Afterwards, irrigation was supplied to prevent wilt. From April, irrigation was 1.3 cm every 2 days to supplement rainfall. Treatments were applied beginning with incorporation before seeding on October 4, 1994. Three different granular humate products were applied in a split-plot design with three replications. Each plot was split again to test combination of the products with a natural-based fertilizer. Following seeding, to test different humate application methods, granular humate treatments were applied once every three months (three times total), and liquid humate treatments were applied at seeding and once every month thereafter (11 times total). Major plots received granular humate treatments incorporated to a depth of 10 cm at a rate of 2.5 g m- 2 and/or the natural fertilizer incorporated at a rate of 10 g fertilizer m- 2. Minor plots received humate in granular applications at 2.5 g m- 2 every 3 months, liquid application at 0.48 ml m'2 every month, or granular at 2.5 g m- 2 plus liquid at 0.24 ml m- 2. Granular humate products tested included Vigoro modified humate (7-0-0-8 Fe - 2.5 Mn -2.5 Mg -5.5 Ca -6 S -0.2 Zn); Earthgreen Menefee humate, ( 0.88-0.07-0.06-0.5 Fe -0.02 Mn - 0.07 Mg -0.45 Ca - 0.14 S - 0.008 Zn); and Humate International AG 16-35 humate, (0.62-0.03-0.01-0.1 Fe). Liquid materials included Earthgreen Grow Plex humate suspension (10-10-10-4 Fe -4 Mn -4 Ca); and Humate International LS humate suspension (0.62-0.03-0.01-0.1 Fe). Since Vigoro did not produce a liquid suspension of humate, a finer grade form of the granular treatment was applied at 0.75 g material m'2. The natural organic fertilizer was Sustane 4-2-3 (N-P20s-K 2 0), created from composted turkey litter.
439 Measurements of treatment effects included: percent coverage during germination on a scale of 0-100% covered, collected every 14 days for three months following seeding; turf quality, based on a scale of 1 to 9, where 9 is best, collected every 14 days following seeding for 11 months; root length, measured from a 10-cm diameter plug removed from each plot, collected at two and six months after seeding; root density as dry weights from a lo-cm diameter plug 15 cm deep, collected at six and 11 months after seeding; and leaf tissue nutrient levels using Near infra-red reflectance spectometry (Dara and Mayland 1990), collected every 14 days, beginning 6 months after seeding. Data were analysed using Statistical Analysis Software (SAS 1995) through analysis of variance for a split-split plot design, and mean separation using Waller's Least Significant Difference Test (Waller and Duncan 1969). RESULTS From the data collected in 11 months of study, no differences existed in response to individual humate products. When humate products were analysed together as one treatment, differences between the control and the other treatments did exist. Application method was found to affect leaf tissue nutrient status. Plots incorporated with humate plus natural fertilizer, or natural fertilizer alone were 15% covered by germinated bent after three weeks. Plots where humate alone was incorporated showed only eight percent coverage after three weeks. The control plot showed only 5.5 percent (Figure 1). Figure I. Effect of humate and fertilizer on turfgrass cover (%) 3 weeks After seeding. 16 A 14 12 :g, 10 ~ ~ 8?f!. 6 Control Humate Humate + NO NO NO - Natunl or:.nic: r~rcilizcr *Trutment, with the same leuer are not sl:nifiuntly dlffcnnt. Turfgrass quality responses after ten weeks of growth were similar to percent coverage responses. Plots treated with the combination of humate and natural fertilizer received the highest turf quality response (Figure 2), although
440 it was not different from the natural fertilizer alone. There was no difference in turf quality responses to granular or liquid humate applications. Figure 2 Effects of humate and fertilizer on turf quality (TQ) 10 weeks following seeding. 10 >- ~ d 5 t- NO = Natural organic (enhizer.trcamcnt with the same letter arc not significantly different at p=o.os. Similar turf quality responses were also found when averaged over all dates in the experiment. Turf quality responses to natural fertilizer, with and without humate, were significantly higher than turf quality responses to humate alone and the control. Turf quality in plots treated with humate alone was not significantly higher than the control (Figure 3.). No differences in turf quality" due to liquid or granular humate application methods were noted. Figure 3 Effect of humate and fertilizer on turf quality (TQ) over 11 months following seeding. B B A AB d I- Control Humate Humate + NO NO NO" Natural organic fertilizer -Treatments with the same letter are not significantly different at p,,",o.os.
441 The treatment of natural fertilizer plus humate produced the highest density of roots (Figure 4). Plots treated with humate and/or natural fertilizer did produce a significantly greater root density than control plots. The turf root density did not differ due to liquid or granular applications of humate. Figure 4 Effect of humate and fertilizer on root density (g) at 6 months after seeding. A 0> ::I ~1 8-0> Control Humale Humate + NO NO NO... Natural organic fenilizer -Treatments with the same letter are not significantly different at p-o.os. Nutrient composition of harvested leaf tissue was largely unaffected by humate or natural fertilizer treatment. However, when humate was applied in granular form, analysis of treated leaf tissue showed higher levels of Fe than plots treated with a liquid application alone, or the control (Figure 5). No differences in leaf composition ofn, P, or K existed. Significant differences for levels of Mn, Cu, and Zn did exist. However, the actual differences between mean levels of harvested tissue was ~ 2 m k -I Fig ure 5. E ffecl 0 f hurn ate and fertilizer on leaf tissue Fe (m g/kg) from 6 through 11 months following seeding 80 70 60 50 ~ 40 E 30 20 10 Control liquid Gran. + liquid Granular -Treatments with the same letter are not significantly different at p.o.os.
442 DISCUSSION Previous studies that describe positive growth effects from humic substances have largely been performed in the laboratory. Controlled soil conditions were necessary to isolate the action(s) precipitated from addition of humic substances. However, fewer field experiments have been attempted that produced significant effects from treatment with humic substances. The most prevalent observation from addition of humic substances to field experiments is that humic and fulvic acid concentrations in soil solutions were increased. Increased levels of mineral micronutrient solubilisation and growth were attributed to the increases in humic and fulvic acid concentrations (Chen and Aviad 1990; Syltie 1985). Karnok (1990) also found results similar to this present experiment. In this experiment, a few positive effects from humate applications appeared. Improvements in germination were largely due to treatment with the natural fertilizer. These improvements may have been due to the increased levels of nitrogen provided by the natural fertilizer (incorporated at 0.4 g N m 2 ). Although the plot with the combination of humate and natural fertilizer incorporated showed the most coverage after three weeks, it was not significantly greater than coverage in the plots incorporated with natural fertilizer alone. The biggest improvements in turf quality could be attributed to addition of natural fertilizer. At the same time, natural fertilizer did not significantly increase nutrient levels in the leaf tissue. Only application by granular humate increased leaf tissue concentrations of iron. This may be due to the increased levels of iron in the granular treatments. Improvements in mean root density, similar to what Karnok (1990) found for one date in his study, were found over both dates of measurement in this study. Syltie (1985) suggests that humic acids supply polyphenols that are catalysts to plant respiration. Increases in root growth may be attributed to the enhancement of enzyme systems stimulated by an increased level of respiration. In contrast to the few positive results, no negative effects appeared. No product or method of application produced any noticeable loss of turfgrass quality due to phytotoxicity, increases in disease, or hydrophobic conditions. A longer study may yield more positive effects. Increases in levels of organic matter from addition of humates may eventually provide benefits such as increased microbial populations, and improved nutrient and water retention, as Chen and Aviad (1990) suggest. REFERENCES Chen, Y. and T. Aviad. 1990. Effects of humic substances on plant growth, in Humic Substances in Soil and Crop Sciences: Selected Readings. American Society of Agronomy and Soil Science Society of America, Madison, Wisconsin. Dara, S.T. and H.F. Mayland. 1990. Mineral analysis of forage with near infrared reflectance spectroscopy. p. 186 in Agronomy Abstracts. American Society of Agronomy, Madison, Wisconsin, USA.
443 Kamok, KJ. 1990. The effects of non-nutritional growth enhancers on the growth and quality of 'Penncross' creeping bentgrass. Final report to Humate International (formerly Galbraith Enterprises). University of Georgia. Athens, Georgia, USA. SAS Institute USA. (1995) SAS Users guide. SAS Institute, Cary, North Carolina, Syltie, P. W. 1985. Effects of very small amounts of highly active biological substances on plant growth. in Biological Agriculture and Horticulture. A B Academic Publishers, Great Britain. United States Golf Association, Green Section. 1993. USGA recommendations for a method of putting green construction - the 1993 revision. Green Section Record. United Stated Golf Association, Far Hills, New Jersey, USA. Waller, R. A. and D. B. Duncan. 1969. A Bayes rule for the symmetric multiple comparisons problem. Journal of American Statistics Association. 64, 1484-1503.