Nitrogen and potassium effects on the macronutrient and micronutrient content of zoysiagrasses 1

Zoysiagrass has more potential for utilization in the Gulf Coast states. There has been minimal research on the nitrogen (N) and potassium (K) fertility response of zoysiagrass and the resulting effect they have on the macronutrient and micronutrient content. The objective of this study was to evaluate the effects of N and K fertility on the nutrient content of zoysiagrass. A study was conducted on four zoysiagrasses: Zoysiajaponica x Z. tenuifolia Willd. ex Trin. ('Emerald'); Z. japonica Steud. ('El Toro’ and ‘Meyer'); and Z. matrella. The study was a completely randomized design with 3 replications. It was a 2x2 factorial with the factors being N and K at two levels that were imposed on the four zoysiagrass cultivars. The N and K treatment combinations consisted of high (H) and low (L) rates of N and K at the following levels: N levels of 454 and 227 g N 93 m^‐2 month^‐1 and K levels of 454 and 227 g K 93 m^‐2month^‐1. The treatment combinations were (N and K): HH, HL, LH, and LL and were applied in 2 split applications monthly from July through November. All plots received two applications of a micronutrient fertilizer (June and August), were irrigated as needed, and maintained at a height of 3.8 cm weekly. Plant tissue samples were collected in September and analyzed for nitrogen (N), phosphorus (P), K, calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) concentrations. There were significant differences for the concentrations of N, K, P, Ca, Mg, B, Cu, Fe, Mn, and Zn. The concentrations of K, Ca, and Mg were below the sufficiency range for these nutrients for all cultivars and treatments.     

The Effect of Moderate Salinity on Nitrate Leaching from Bermudagrass Turf: A Lysimeter Study

A column lysimeter study was conducted under greenhouse conditions to determine the impact of moderately saline irrigation water on NO₃ leaching from turfgrass. Bermudagrass (Cynodon dactylon L. ‘NuMex Sahara’) was fertilized at three N levels (25, 50 and 75 kg NH₄NO₃-N ha^?1 month^?1) and irrigated with saline water (0, 3.0 and 6.0 dS m^?1) in a factorial arrangement. Leachate was analyzed for salinity and NO₃, and clippings were collected and analyzed for total N. Nitrate leaching was not affected by either N level or salinity. Nitrate concentrations in the leachate were low, averaging approximately 0.3 mg N L^?1; less than 1% of the applied N leached. Longer-term N allocation to leaf growth accounted for up to 98% of applied N, whereas short-term allocation, determined using ¹⁵N, ranged from 46–67%. Salinity had no affect on clipping yield, the biomass of root and verdure, or root distribution. These data indicate the potential for moderately saline irrigation water to be used on bermudagrass turf without increasing NO₃ contamination of groundwater, as long as leaching is adequate to prevent rootzone salinity reaching damaging levels.     

Effects of lime and applied Mn on plant Mn,growth and chlorophyll concentration of ‘Tifway II’ bermudagrass

Abstract

A glasshouse study was conducted to determine effects of lime and Mn applied to three Florida soils on plant Mn, growth, and chlorophyll concentration of ‘Tifway II’ bermudagrass (Cynodon dactylon x Cynodon transvaalensis). Four replications of three lime rates (0, 1000, and 2000 mg CaCO₃/kg as dolomite and Ca(OH)₂ for Astatula fine sand (Typic Quartzipsamment, hyperthermic, uncoated) and Pompano fine sand (Typic Psammaquent, siliceous, hyperthermic); 0, 2000, and 4000 mg CaCO₃/kg as dolomite and Ca(OH)₂ for Myakka fine sand (Aeric Haplaquod, sandy siliceous, hyperthermic) and three Mn applications (none, 10 mg Mn/kg as MnSO₄, and 5 mg Mn/kg as MnEDTA) were used in a randomized, complete block, factorial design. A wide range of plant Mn concentrations existed across treatments for each soil. Differences in plant Mn concentration did not cause significant differences in growth or chlorophyll concentration. The critical plant Mn concentration was not reached, but it appeared to be below 20 mg Mn kg for bermudagrass. Models for prediction of plant Mn concentration using soil pH and extractable soil Mn (Mehlich I, Mehlich II, DTPA‐TEA) were obtained. The applications of MnSO, and MnEDTA each resulted in increased plant Mn under acidic soil conditions. Neither Mn application resulted in increased plant Mn concentration in grass grown on Pompano fine sand with soil pH values of 7.0 or above.     

FERTILIZER RATE EFFECTS ON FORAGE YIELD STABILITY AND NUTRIENT UPTAKE OF MIDLAND BERMUDAGRASS

Our objectives were to document effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on forage yields and uptake of N, P, and K by Midland bermudagrass [Cynodon dactylon (L.) Pers.] on a Minco fine, sandy loam in southern Oklahoma. After six years of this long-term experiment, forage yield responses to fertilization were mixed and depended on year. Stability analysis indicated forage yields responded positively to N fertilization during favorable weather conditions but negatively during poor weather conditions. Application of 112 kg N ha^?1 provided the best yield stability and mean annual forage yield among treatments, 11.5 Mg ha^?1, across years. In years with near-average weather conditions, uptake of N, P, and K increased linearly with N application rate. Limited water holding capacity of the soil and high soil P and K may have contributed to the limited yield responses to fertilization in this semi-arid environment.     

Mineral composition of bermudagrass as influenced by maturity and nitrogen in a cool,temperate environment

Abstract

Warm‐season grasses contribute substantially to herbage supply during summer in cool‐temperate environments, when the productivity of cool‐season grasses declines. Herbage digestibility as well as mineral concentration may limit the amount of essential nutrients available to meet grazing animal requirements. A field study was conducted to determine the productivity and quality of a new selection of bermudagrass [Cynodon dactylon (L) Pers.], RSl, which is capable of growth and persistence in areas where other cultivars of bermudagrass are likely to winterkill. Concentrations and uptake of mineral nutrients in RSl bermudagrass were determined in response to N levels (0, 120, 240, and 360 kg N/ha) and delayed initial harvest (advancing maturity) at 2, 4, and 6 weeks after active growth began. Concentrations of P, Ca, K, Mg, and S in early season growth generally declined with advancing maturity. Concentrations of elements showed mixed response to N levels, and generally were not affected by treatments late in the growing season. Early in the growing season, mineral uptakes increased with advancing maturity. Increasing N levels early and late in the growing season enhanced mineral uptake. Mineral ratios, such as N:S and K (Ca + Mg), were within critical limits for adequate animal nutrition, but the Ca:P ratio was less than 2:1 and could contribute to known mineral‐related disorders in male sheep. Herbage mineral concentrations of RSl generally met or exceeded mineral nutrient requirements for sheep and cattle in growing or lactating physiological states.     

Response of hybrid bermudagrass to sulfur application

Abstract

The S requirement of crops has traditionally been meet by using S‐containing fertilizers and the S in rainfall. With the reduction of S in these sources, S deficiencies are becoming more widespread. Over four million hectares of the genus Cynodon are grown in the southeastern U. S. for forage. The primary objective of this study was to measure the response of ‘Coastal’ and ‘Alicia’ bermudagrass [Cynodon dactylon (L.) Pers.] to S application. Sulfur was applied to established stands in May annually for three years. Soil type was Marietta fine sandy loam (fine‐loamy, silicious, thermic Fluvaquentic Eutrochrept). Yield data were collected by clipping a swath through the length of each plot when the forage on the lowest yielding plot had reached a height of approximately 30 cm. A response to S application was obtained each year for the first clipping only. Regression analyses indicated that maximum yield of Coastal and Alicia cultivars was obtained with 13 and 16 kg S/ha, respectively. The maximum yield of Coastal corresponded to a forage S concentration of 2.0 g/kg, N/S ratio of 11, and P/S ratio of 1.7. Maximum yield of Alicia was obtained at 2.1 g S/kg, N/S ratio of 10, and P/S ratio of 1.6. Sulfur concentrations for the second and third clippings were below those for the first clipping. Both N/S and P/S ratios for the third clipping were above those for the first clipping, yet there was no response to applied S for either the second or third clipping. If S concentration, N/S ratio or P/S ratio are to be used to predict the response to applied S, they should be limited to the first clipping.     

Applied phosphorus and potassium effects on yield of dallisgrass‐bermudagrass pastures 1

There are substantial areas of dallisgrass (Paspalum dilatatum Poir.)‐common bermudagrass (Cynodon dactylon (L). Pers.) summer‐type pastures in the Southeastern Central Plain, but little information is available on their response to P and K fertilization. The purpose of this study was to measure the response of dallisgrass‐common bermudagrass pastures to P and K fertilization with and with‐ out N. Phosphorus and K were applied to two soils in May each year for three years. Yield data were collected by clipping a swath through the length of the plots when the minimum forage height was approximately 30 cm. Responses to P and K applications were obtained when the soil test levels were low to very low, but not when they were medium as determined by the Mississippi Soil Test (MST). Forage P concentration of the control in the medium P and K soil was within the adequate range of 2.8 to 3.4 g/kg, but forage K concentration was below the critical range of 16 to 18 g/kg. Forage P and K concentrations of the controls in the low P and K soil were below critical levels. At both locations forage P and K concentrations were increased by P and K fertilization. Available soil P increased with rate of P application but soil extractable K was unaffected by K application. No yield response to P and K are likely at medium soil test levels (MST) even at high rates of N. There was no response to P and K application without N.     

Growth response and ion homeostasis in two bermudagrass (Cynodon dactylon) cultivars differing in salinity tolerance under salinity stress

Bermudagrass (Cynodon dactylon) is a salinity-tolerant turfgrass that has good use potential in the saline-alkali lands of warm regions. However, the systematic Na⁺ and K⁺ regulation mechanisms under salinity stress remain unclear at the whole plant level. Two bermudagrass cultivars differing in salinity tolerance were exposed to 0, 50, 100, 200, or 300 mM NaCl in a hydroponic system. Growth, absorption, transportation, and secretion of Na⁺ and K⁺, and gas exchange parameters were determined in both cultivars. K⁺ contents were decreased and Na⁺ contents and Na⁺/K⁺ ratios were increased in both bermudagrasses with increased salinity; however, lower Na⁺ content and Na⁺/K⁺ ratio and more stable K⁺ content were found in the leaves of the salinity-tolerant ‘Yangjiang’ than the salinity-sensitive ‘Nanjing’. Higher Na⁺ contents in root cortical cells were found than in the stele cells of ‘Yangjiang’, but the opposite was observed in ‘Nanjing’. Lower Na⁺ contents and higher K⁺ contents were found in vessels for ‘Yangjiang’ than for ‘Nanjing’. Salinity stress increased the selective transport of K⁺ over Na⁺ from roots to leaves and the Na⁺-selective secretion via salt glands, which were stronger in ‘Yangjiang’ than ‘Nanjing’. Net photosynthetic rate and stomatal conductance decreased in the two bermudagrasses with increased salinity; however, they were more stable in ‘Yangjiang’. The results suggested that bermudagrass could reduce Na⁺ accumulation and maintain K⁺ stability in leaves under salinity stress by restricting Na⁺ into vessels in roots, selectively transporting K⁺ over Na⁺ from roots to leaves, selectively secreting Na⁺ via leaf salt glands, and maintaining suitable stomatal conductance.     

Nutrient Uptake of Swine Effluent-Fertilized Bermudagrass During Primary Spring and Summer Growth

ABSTRACT

Production of bermudagrass [Cynodon dactylon (L.) Pers.] hay to manage manure nutrients may differ from production of hay intended for livestock consumption. The objective of this study was to determine the relationships between maturity and yield, nutrient concentration, and nutrient uptake in bermudagrass fertilized with swine effluent. Primary spring and summer growth of ‘Coastal’ hybrid and common bermudagrass was harvested every 7 d to 63 d maturity. Effluent applied to Brooksville silty clay loam (fine, smectitic, thermic Aquic Hapludert) during each harvest period contained 140 kg nitrogen (N), 240 kg potassium (K), and 25 kg phosphorus (P) ha^{? 1} (mean of 2 years). Coastal and common bermudagrass had similar trends for yield, nutrient concentration, and nutrient uptake. Dry-matter production followed a linear trend in the spring (maximum of 1.11kg m^{? 2} after 63 d) and a quadratic trend in the summer (maximum of 0.96 kg m^{? 2} after 56 d). Herbage N concentration declined from 33 to 17 g kg^{? 1} during the spring and summer harvest period, while P concentration declined from 3.8 to 2.4 g kg^{? 1}. Maximum K concentration (26 g kg^{? 1}) occurred at 28 d of growth. Nitrogen, P, and K uptake exhibited a quadratic response to increasing maturity during the spring and summer harvest periods, but maximum uptake was greater in the spring than in the summer. These results suggest that the spring harvest period is the best time to maximize nutrient uptake by delaying bermudagrass harvest to more mature stages.     

Effects of limestone and phosphorus on nutrient availability and coastal bermudagrass yield on an ultisol

Abstract

This field study was conducted to evaluate nutrient availability and Coastal bermudagrass [Cynodon dactylon (L.) Pers.] yield response to factorial combinations of applied limestone and P in a strongly acid (pH 4.7), infertile soil. Limestone was applied at rates of 0, 672, and 3808 kg ha^‐1 to a Lilbert loamy fine sand (loamy, siliceous, thermic, arenic Plinthic Paleudult). Phosphorus was applied at rates of 0, 30, 60, 90, 120, 240, and 480 kg P ha^‐1. Soil pH in the surface 15 cm initially increased to 6.2 in response to the high limestone rate, but subsequently declined due to N fertilization. Lime increased soil test P, Ca, and Mg and decreased K and Al. The efficiency of increasing soil test P with fertilizer P was low, but improved as a consequence of liming. Coastal bermudagrass yield increased by as much as 37 percent from P application. Maximum yield coincided with 10 to 15 mg kg^‐1 or greater soil test P and tissue P concentrations that ranged from 1.6 to 2.2 g kg^‐1. Lime Increased tissue Ca and Mg, but had no effect on plant P concentrations. Yield was unaffected by lime despite its positive effect on soil P and an apparent K‐Mg antagonism. Plant nutrients obtained from deep rooting of the bermudagrass into an argiilic horizon may have precluded any positive effect of lime on Coastal bermudagrass yield.     

Seasonal variations of soil microbial biomass and activity in warm- and cool-season turfgrass systems

Plant growth can be an important factor regulating seasonal variations of soil microbial biomass and activity. We investigated soil microbial biomass, microbial respiration, net N mineralization, and soil enzyme activity in turfgrass systems of three cool-season species (tall fescue, Festuca arundinacea Schreb., Kentucky bluegrass, Poa pratensis L., and creeping bentgrass, Agrostis palustris L.) and three warm-season species (centipedegrass, Eremochloa ophiuroides (Munro.) Hack, zoysiagrass, Zoysia japonica Steud, and bermudagrass, Cynodon dactylon (L.) Pers.). Microbial biomass and respiration were higher in warm- than the cool-season turfgrass systems, but net N mineralization was generally lower in warm-season turfgrass systems. Soil microbial biomass C and N varied seasonally, being lower in September and higher in May and December, independent of turfgrass physiological types. Seasonal variations in microbial respiration, net N mineralization, and cellulase activity were also similar between warm- and cool-season turfgrass systems. The lower microbial biomass and activity in September were associated with lower soil available N, possibly caused by turfgrass competition for this resource. Microbial biomass and activity (i.e., microbial respiration and net N mineralization determined in a laboratory incubation experiment) increased in soil samples collected during late fall and winter when turfgrasses grew slowly and their competition for soil N was weak. These results suggest that N availability rather than climate is the primary determinant of seasonal dynamics of soil microbial biomass and activity in turfgrass systems, located in the humid and warm region.     

Vanadium induced manganese toxicity in bush bean plants grown in solution culture

Seedlings of two bush bean cultivars (Phaseolus vulqaris L. cvs. Mn‐sensitive ‘Wonder Crop 2’ and Mn‐tolerant ‘Green Lord') were grown for 14 days in full strength Hoagland No. 2 nutrient solution containing 0.05 ‐ 2 mg L^‐1 of vanadium (V) as ammonium vanadate.

Increasing V concentration in the solution decreased total dry weight of both cultivars. Plant tops were stunted and leaf color became dark green at 1 ‐ 2 mg L^‐1 V, especially in ‘Green Lord’. Veinal necrosis similar to that of Mn toxicity was observed in the primary leaves of ‘Wonder Crop 2’ at 0.2 mg L^‐1 V or above, but not in those of ‘Green Lord’.

The V concentrations in the roots increased exponentially with increasing V concentration in the solution; however, V concentrations in the leaves and stems were not affected. The Mn concentrations in the primary leaves increased under the higher V treatment in ‘Wonder Crop 2'; but not in ‘Green Lord’. In contrast, Fe concentration in the leaves of ‘Wonder Crop 2’ decreased markedly with increasing V concentration in the solution. Enhanced Mn uptake and greater reduction of Fe uptake by ‘Wonder Crop 2’ may explain the incidence of V‐induced Mn toxicity.     

Legume cover crops as a nitrogen source for pecan

Crimson clover (Trifolium incarnatum L.) plus hairy vetch ( Vicia villosa Roth), red clover (Trifolium pratense L.), white clover (Trifolium repens L.), red clover plus white clover, and bermudagrass (Cynodon dactylon [L.] Pers.) were evaluated as cover crops for pecans. Crimson clover plus hairy vetch supplied the equivalent of 101 to 159 kg nitrogen (N)/ha. Red clover plus white clover supplied up to 132 kg N/ha. Either white clover or red clover alone were less effective in supplying N than when grown together. Soil Kjeldahl‐N was usually not affected or increased using the legumes compared to fertilized bermudagrass sod. Soil nitrate (NO₃) concentrations during October were occasionally higher in unfertilized legume plots than in bermudagrass plots with March‐applied N.     

Stand recovery of coastal bermudagrass following stand loss induced by potassium deficiency

Abstract

‘Coastal’ bermudagrass (Cynodon dactylon L. Pers.) stand loss resulting from K deficiency has been reported. The recovery of this perennial grass from K deficiency could very well take a significant time after the deficiency is corrected. Experiments were conducted on two soils, Darco (Grossarenic Paleudult; loamy, siliceous, thermic) and Cuthbert (Typic Hapludult; clayey, mixed, thermic). Previous P and K factorial rate studies had been conducted on the experimental sites. Annual K and P fertility rates used on prior studies were 0, 112, and 224 kg/ha K and 0 to 136 kg/ha P. These earlier treatments were overlaid with rates of 112 and 224 kg/ha of P and K, respectively. Data were taken for yield, stem length, stem weight, and rhizome production. Yield was found to be related directly to stand. Yield was also related to plant height under severe stand loss. Yield loss was not related to stem weight. Rhizome production recovered after two years. Yield had recovered by the end of the first year.     

Preemergence Herbicides Affect Hybrid Bermudagrass Nutrient Content

Preemergence (PRE) herbicides negatively impacting turfgrass root growth may compromise macro- and micronutrient accumulation in foliar tissue. Research was conducted to determine the effects of indaziflam (35 and 52.5 g ha^?1), prodiamine (0.84 kg ha^?1), oxadiazon (3.36 kg ha^?1), and isoxaben (1.12 kg ha^?1) applications in hydroponic culture on hybrid bermudagrass [C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] tissue nutrient content. Prodiamine, indaziflam, and isoxaben reduced visual root mass relative to non-treated plants. Consequently, these herbicides reduced phosphorus (P), sulfur (S), and potassium (K) content in turf foliar tissue. Treatment with indaziflam reduced magnesium (Mg) and manganese (Mn) content in turf foliar tissue compared to non-treated plants. This response was not observed with prodiamine and could explain the significant foliar injury (>70%) observed with both rates of indaziflam. Data in the current study illustrate that PRE herbicide applications affect hybrid bermudagrass nutrient content. Future studies should evaluate foliar applications of Mg and Mn for either preventing or remediating leaf tissue injury following PRE herbicide application.     

Comparison of hydroponic solutions for poinsettia nutritional studies 1

Poinsettia cultivars Supjibi and Freedom were grown in eight hydroponic solutions to develop a baseline solution for further nutritional studies. Four solutions contained nitrogen (N) from Ca(NO₃)₂‐4H₂O and KNO₃ (denoted as ‐NH₄) and four contained Ca(NO₃)₂‐4H₂O, KNO₃, nitric acid, and NH₄NO₃ as the N sources (denoted as +NH₄). The four ‐NH₄ and +NH₄ solutions were further divided by an IX or 2X rate of micronutrients [boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)] (denoted as IX or 2X). A factorial of these four solutions at 2 concentrations (100 mg L¹ of N and potassium (K) and 15 mg L¹ phosphorus (P), or 300 mg L¹ of N and K and 46 mg L^‐1 P) was studied. Greater leaf and stem dry weight for both ‘Supjibi’ and ‘Freedom’ was observed in plants grown with the +NH₄ solutions, with a larger increase occurring with’ Supjibi’. Leaf NH₄‐N content for both cultivars was higher for both the 100 and 300 mg L^‐1 N and K fertilization rates when NH₄‐N was included. The leaf K content was highest for the plants grown with the +NH/2X solution for ‘Supjibi’, for both fertilization rates, and leaf K content increased as the K application rate increased. Results indicate that for nutritional studies with poinsettias, hydroponic solutions should include between 12.5% to 33% of the N in the NH₄ form, a calcium magnesium (Ca:Mg) ratio of 2:1, and a micronutrient concentration of (mg I/¹) 0.5, 0.02, 6.6, 0.5, 0.1, and 0.05, respectively, for B, Cu, Fe, Mn, Mo, and Zn, for adequate plant growth.     

Iron absorption,localization, and biomineralization of Cynodon dactylon,a perennial grass from the Río Tinto basin (SW Iberian Peninsula)

Cynodon dactylon (L.) Pers. is a perennial rhizomatous grass (Poaceae), grown for cattle nutrition on the riverbanks of Río Tinto (Southwest Iberian Peninsula, Spain), a highly acidic area with high concentrations of iron (Fe) and other metals. This study focuses on the absorption, distribution, and accumulation of Fe in the root, rhizome, and leaves of C. dactylon under controlled conditions. Plants collected from Río Tinto were grown in a Hoagland solution containing 500 mg kg^–1 of ferrous Fe. Samples were collected up to 2 months after exposure and analyzed for total Fe concentration using inductively coupled plasma–mass spectrometry (ICP‐MS) and for Fe distribution and bioformations by scanning electron microscopy (SEM) with an energy‐dispersive x‐ray analyzer (EDX). The results show high concentrations of Fe in all plant organs, with fast Fe translocation from roots to leaves. Iron bioformations composed mainly of Fe, S, and K were detected in all plant organs and were especially apparent in roots and leaves. These results differ from those reported for another species of Poaceae, Imperata cylindrica, which grows under the same environmental conditions, suggesting the existence of different resistance strategies between species of the same family.     

Effects of low nitrogen nutrition on plant growth characteristics and nitrogen accumulation in Chinese natural bermudagrass (Cynodon dactylon (L.) Pers.) germplasm resources

Bermudagrass (Cynodon dactylon (L.) Pers.) is a widely used warm-season turfgrass and has the highest nitrogen (N) fertilization requirements among turfgrasses. Wild ecotype found in N-poor habitats can potentially tolerant N limiting conditions for reducing N inputs in the turf industry. However, the extent of variation in their low N tolerance has remained unclear. We conducted hydroponic experiments to evaluate the variation on growth, N accumulation, and partitioning of wild bermudagrass from China pre-core collection under normal (5 mM) and limited (0.05 mM) N levels in two experiments. The results showed that low N nutrition significantly decreased clipping growth, while had no effects on verdure and root growth; in addition, the magnitude of clippings N accumulation reduction was higher than verdure and root across all accessions. However, significant genetic variations in all studied traits except for root N content in experiment 2 were found among accessions. Using a cluster analysis, 56 accessions in experiment 1 and 12 accessions in experiment 2 were classified into four groups and two groups separately. The accessions with superior low N tolerance had improved growth and accumulated more N in the verdure and roots; it is interesting that other accessions with low N tolerance had different tolerance mechanisms and transferred more N nutrition from the roots to the clippings to maintain better turf quality. The different molds in low N tolerance suggest that there is much potential for improving low N tolerance among Chinese natural bermudagrass accessions.     

Adjustments of sufficiency ranges of selected ornamentals and turfgrasses for assessing nitrogen status with Dumas‐N data

Abstract

With recent advances in nitrogen (N) analyzers, the Dumas method may replace the Kjeldahl method for the routine diagnosis of N in plants. Since these two methods recover different N fractions and no conversion factor is available to convert Dumas N (Dn) to Kjeldahl N (Kn) data, Kn:Dn ratios were determined for selected ornamentals (anthurium, Anthurium andraeanum Linden; orchid spp. Cattleya, Dendrobium, Oncidium, Phalaenopsis, and Vanda; leatherleaf fern, Rumohra adiantiformis (G. Forst) Ching; tree fern, Asparagus densiflorus (Kunth) Jessop) and turfgrasses (creeping bentgrass, Agrostis palustris Huds. cv. Penncross; bermudagrass, Cynodon dactylon L.). Samples were dried at 70°C for 72 hr and ground to pass a 20‐mesh sieve. Kn was determined by colorimetry after digestion of 0.4 g of tissue using a CuSO₄/TiO/K₂SO₄ catalyst and 10 mL of H₂SO₄ at 450°C for 2 hr. Dn was determined using 0.2 g of sample and a LECO FP‐428 N Analyzer. Over the 0.4–6.6% N range, Dn was a good predictor of Kn; Kn = 0.90 Dn + 0.09 (R²=0.93, p‐model<0.01, n=397 obs.). The Kn: Dn ratio was significantly (p<0.01) affected by plant type (Kn: Dn = 0.85, 0.92, 0.99, and 1.00 for anthurium, turfgrasses, orchid and fern, respectively). The more practical way to use the ratios in routine interpretation was to adjust existing sufficiency ranges with the inverse of these ratios. Adjusted sufficiency ranges (in %N) were 4.9–6.6 for creeping bentgrass, 2.4–4.4 for bermudagrass, and 1.9–3.6 for anthurium. Existing sufficiency ranges for orchid and fern need not be adjusted for Dumas N.     

Nutrient Allocation of ‘TifEagle’ Bermudagrass as Influenced by Trinexapac-Ethyl

ABSTRACT

Inhibiting shoot growth of dwarf bermudagrass [Cynodon dactylon(L.) Pers. × C. transvaalensis Burtt-Davey] with a plant-growth retardant, trinexapac-ethyl (TE), may redirect nutrients and photosynthate away from leaf tissue to promote root growth and improve nutrient-use efficiency. Two greenhouse experiments evaluated three rates of TE, 0.025, 0.05, and 0.075 kg a.i. ha^?1, applied every three weeks on ‘TifEagle’ bermudagrass for 12 weeks. Lysimeters constructed to United State Golf Association specifications were arranged in a randomized complete block design with four replications. Increased TE rates quadratically reduced clipping yield 38%–75%, improved turf quality 6%–13%, and enhanced chlorophyll concentrations 30%–70% over the untreated grass. Dry-root mass increased with TE rate 11%–37% after 12 weeks. Total clipping nutrients recovered from five sampling dates were reduced by approximately 50%, 85%, and 90% for turf receiving TE at 0.025, 0.05, and 0.075 kg ha^?1 3 wk^?1, respectively. Thatch (stolons and rhizomes) and roots had higher nitrogen (N) concentration and retention with increased TE rate, suggesting inhibited leaf growth increased N storage in belowground plant tissue. Overall, TE may effectively enhance turf quality, root growth, and nutrient-use efficiency of dwarf-type bermudagrasses. Chemical name used: trinexapac-ethyl, [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethylester].