Effects of initial plant spacing and applied nutrients on stand development and productivity of Texas bluegrass in the Louisiana coastal plain

The native rhizomatous cool‐season perennial grass, Texas bluegrass (Poa arachnifera Torn), has recently been recognized again as a plant with considerable potential for range and pasture plantings. Throughout the first half of this century, sporadic efforts at evaluation and commercial use of Texas bluegrass were thwarted primarily by slow stand establishment and difficulties with seed processing. Subsequent advances in seed harvesting, processing, and planting equipment and selection of superior plant genotypes could reduce effects of these limitations. In much of the southern mid‐ and tall‐grass prairie regions and lower southeastern states where Texas bluegrass appears to have potential, there is no currently available sustainable cool‐season forage grass. Effects of initial plant spacing and lime, phosphorus (P), and nitrogen (N) application were evaluated in a field and a green house experiment on acid infertile Louisiana Coastal Plain soils. Stands from transplanting on 10‐ and 30‐cm spacings were comparable by the third growing season as the sparsely planted stand spread aggressively. The only consistent response to soil amendment was enhanced forage production from N fertilization in the spring. A plant photoperiodic response appears to limit potential to respond to N in autumn and winter. Forage production of dense stands and responses to spring application of N indicate that Texas bluegrass has considerable potential as a productive, sustainable cool‐season forage grass for at least some soils on the southeastern Coastal Plain as well as that recently reported for the southern mid‐ and tall‐grass prairie regions.     

Response of texas bluegrass to season of nitrogen fertilization on the Louisiana coastal plain

Texas bluegrass (Poa arachnifera Torr.) has shown potential for use as a cool‐season perennial pasture grass in the southern Great Plains, where it occurs as a natural component of rangeland plant communities, and into the western Coastal Plain. Responsiveness of this grass to nitrogen (N) fertilization appeared to be limited to the spring growing period in initial evaluations in Louisiana. A field plot experiment was conducted to assess forage production and quality responses to season of N fertilization on the Syn‐1 population of Texas bluegrass. Winter forage production responses to 50 kg N ha^‐1 were obtained in the 1997–98 growing season but not in 1998–99 after stands had been depleted by summer drought. Greatest yield increases resulted from spring N application, however, fall plus winter fertilization provided the most uniform distribution of forage through the cool season. Forage fiber fractions, in vitro digestibility, and crude protein were not affected by N fertilization. Both amount and distribution of Texas bluegrass forage, but not forage quality, can be manipulated by time of N fertilization.     

Effects of Compost Sources and Seeding Treatments on Germination and Emergence of Four Turfgrass Species

Greenhouse pot trials were conducted to compare the effects of compost sources and planting treatments on turfgrass germination and emergence. Eight seeding treatments and 4 turfgrass types were factorially combined and replicated four times in a completely randomized block design. The seeding treatments were: 1) seed planted on surface of 2.6 cm compost overlying soil, 2) seed planted on soil surface below 0.65 cm compost, 3) seed planted on soil surface below 1.3 cm compost, 4) seed planted on soil surface below 2.6 cm compost, 5) seed planted on soil surface covered with a 2.6 cm straw mat, 6) seed planted below 1.3 cm soil, 7) seed planted below 1.3 cm of 1:1 compost:soil mix, and 8) seed planted on soil surface. Tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.), bermudagrass (Cynodon dactylon L.), and zoysiagrass (Zoysia japonica Steud.) were used as the bioassay crops. The experimental design was repeated over time using composts produced with the following feedstocks: yard waste, food waste, dairy manure, biosolids, and paper mill sludge. Emerged seedlings were counted at 11 days for tall fescue, at 3 weeks for Kentucky bluegrass and at 7 weeks for bermudagrass and zoysiagrass. There were significant (P<0.05) effects of seeding treatment x turfgrass type on germination and emergence for each compost type. All of the composts appeared to be well stabilized using routine compost laboratory testing except the biosolids compost, whose use resulted in the lowest overall germination and emergence rate. The highest rates of germination and emergence occurred in the treatments in which the seeds were planted on the surface, regardless of whether the surface was compost or soil. The lowest rate of germination and emergence occurred where the seed was placed under 2.6 cm compost, regardless of compost maturity.     

Increasing seed protein content enhances seedling emergence and vigor in wheat

Deep seeding of wheat, a common practice when soil moisture is deficient, causes poor seedling emergence and stand establishment. We investigated whether increasing seed protein content by nitrogen fertilization of parental plants might increase emergence rate and vigor of winter wheat seedlings from deep‐planted seeds. Four seeding depths, three cultivars, and three seed protein contents were compared in different soil mixtures and fertility regimes. Under all treatments, emergence rate and dry weight of seedlings markedly decreased as seeding depth was increased. Increasing protein content of seeds sometimes, but not always, increased seedling emergence rate and commonly increased seedling dry weight regardless of soil mixture or fertility regime. Differences were greatest at 4.8‐ and 12‐cm seeding depths; seedlings failed to emerge from 16‐cm depth under any treatments. We concluded that increasing seed protein content by nitrogen fertilization of parent plants is an economic and efficacious method of enhancing wheat establishment when seed must be deeply planted.     

Effect of Seeding Rate and Nitrogen Fertilization on Proso Millet Under Dryland and Irrigated Conditions

Proso millet (Panicum miliaceum L.) is a short-season grain crop in semi-arid regions of North and South America and Asia. The objective of this study was to evaluate seeding rates and nitrogen (N) fertilization on proso millet seed yield, crude protein levels, and biomass yield under irrigated and dryland conditions in a Mediterranean-type transition climate near Bursa, Turkey. Seeds per panicle, panicle length, seed weight per panicle, fertile tillers, protein yield, and plant height were also evaluated. Results indicated seeding rate did not affect seed yield significantly. Seed and protein yield increased with increasing N doses although biomass did not significantly increase. Panicle length, seeds per panicle, and seed weight per panicle decreased with increasing seeding rates. This study proved proso millet can be grown for grain and forage as a short-season dryland and irrigated rotational crop in a Mediterranean-type climate.     

Response of no‐tillage and conventional‐tillage cotton to starter fertilization on loess soils

Starter fertilizers have been utilized to improve cotton (Gossypium hirsutum L.) yields, but yield increases have differed with soil type, application method, application rates, and tillage. Starter fertilizer tests were conducted from 1991 through 1993 on a Gigger silt loam (Typic Fragiudalf) in Louisiana and on a Loring silt loam soil (Typic Fragiudalf) in Tennessee to evaluate methods and application rates of 11–37–0 liquid fertilizer for cotton. Treatments were evaluated under conventional‐tillage (CT) and no‐tillage (NT) production systems. Application methods included in‐furrow application at planting (IF), spraying a 4‐inch wide surface band behind the planter (SB), and banding fertilizer two inches to the side and two inches below the seed at planting (2×2). The IF treatments were applied at 1.5, 3.0, and 4.5 gal/A. The SB and 2×2 treatments were applied at 7.5 gal/A. Starter fertilizer treatments were supplemented with broadcast granular fertilizers to achieve a total fertilization rate of 80–40–60 (N‐P₂O₅‐K₂O lb/acre). Starter fertilizer treatments were compared to broadcasting 80–40–60 and 80–0–60. Soil test levels for phosphorus (P) were high on both soil types. In‐furrow applications of 3.0 and 4.5 gal/acre usually reduced plant population for both tillage systems on both soil types. The 1.5 gal/acre IF treatment was less detrimental to stand establishment than the higher IF rates. The effect of starters on plant height varied from year to year. Starter fertilizers usually did not affect early‐season plant height relative to broadcast treatments. In several experiments starter fertilization increased plant height compared to one, but not both, of the broadcast fertilization treatments. High IF rates (3.0 and 4.5 gal/acre) reduced plant height in one experiment. The 2×2 starter fertilizer treatment increased leaf area per plant relative to the broadcast fertilization treatments in two of six experiments on the Gigger soil. Responses for NT and CT studies were similar. In one CT experiment on the Loring soil, the 1.5 gal/acre IF treatment increased leaf area relative to the broadcast treatments. Lint yield responses to starter fertilization were inconsistent. Starter fertilization increased lint yield in one of six experiments on the Gigger soil and in two of six experiments on the Loring soil. Increased yields from starters varied with year and application method, however, the 2×2 and SB treatments tended to provide better responses than IF treatments. Starter fertilizer responses for NT and CT tests were generally similar.     

Nitrogen Fertilization on Pearl Millet and Guinea Grass: Phytomass Decomposition,Cellulose, Lignin,and Nutrients Release

ABSTRACT

Nitrogen (N) anticipation in cover crops, besides increasing the accumulation of dry weight and nutrients, may favor the subsequent crop by increasing the availability of N. However, N can alter the decomposition of phytomass, which could reduce the beneficial effects of cover crops. The objective of this study was to evaluate the decomposition rate and nutrients release from Pennisetum glaucum and Panicum maximum syn. Urochloa maxima as a function of N fertilization. A randomized blocks design with four replicates, constituted by four treatments (pearl millet with N, pearl millet without N, guinea grass with N and guinea grass without and six sampling times (0, 14, 34, 41, 51 and 68 days after management (DAM)). The pearl millet produces more shoot dry weight than guinea grass, and the N fertilization increases the amount of dry weight for both species, but does not alter the decomposition rate. Pearl millet accumulates and releases to the soil large amounts of nutrients followed by guinea grass, regardless of N fertilization. N fertilization increases the amount of N accumulated and accelerates the release of N into the soil. The maximum release rates occur in the period of 0–14 DAM, more intensely with the N fertilization for the N.     

Evaluation of N,P, S and B fertilization of Kentucky bluegrass seed in northern Idaho

Abstract

Current nitrogen (N) fertilizer recommendations for Kentucky bluegrass (Poa pratensis L.) seed production in northern Idaho are based on potential yield and annual precipitation. Soil test correlation information collected for other northern Idaho crops provide the basis for P, S and B recommendations. The objective of this paper is to assess the current recommendations with a series of forty field trials conducted on ten sites during four seed production seasons. All field trials were conducted on Alfisols and Mollisols initially containing less than 60 kg N/ha, 3.5 μg/g NaOAc extractable P, 40 kg extractable SO₄‐S/ha and 0.5 μg/g extractable B. Fertilization rates evaluated included: 0, 50, 75, 100, 125, 150 and 200 kg N/ha; 0, 30 and 60 kg P₂O₅/ha; 0, 25, and 50 kg SO₄‐S/ha, and 0 and 1.5 kg B/ha. Five field sites contained the cultivar ‘Argyle’ Kentucky bluegrass seed, while the other five sites contained the cultivar ‘South Dakota’.

Excellent relationships between percent maximum Kentucky bluegrass seed production and the sum of inorganic soil N + fertilizer N applied were observed for the ‘Argyle’ (R²=0.65) and ‘South Dakota’ (R²=0.72) cultivars. Phosphorus applications of 30 kg P₂O₅/ha improved seed yields from 10.0 to 51.6% when initial soil test values were less than 3.0 6 μg/g NaOAc extractable P. When initial SO₄‐S soil values were less than 32 kg/ha fertilizer additions increased seed yields from 12.6 to 107.3%. Boron applications did not improve seed yields. Analysis of these trials indicates that adequate information is available to make satisfactory P, S and B fertilizer recommendations; however, additional soil test correlation information is needed for N recommendations.     

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.     

ACCUMULATION OF SILICON IN CYNODON DACTYLON X C. TRANSVAALENSIS AND POA TRIVIALIS USED AS AN OVERSEED GRASS

Calcium silicate has been used to supply silicon (Si) as a plant nutrient for enhancing crop production and the suppression of turf diseases. Research was initiated to determine the effect of calcium silicate on silicon uptake, turf quality, and its residual activity in providing plant available Si in two turfgrass systems. During 2005 and 2006, calcium silicate (CaSi, 12% Si) was applied as a topdressing at eight rates ranging from 0 to 342 kg m^?2 to a ‘Tifdwarf’ (Cynodon dactylon × C. transvaalensis Burtt Davy) green in the spring and to the same plots overseeded with ‘Wintergreen’ rough bluegrass (Poa trivialis L.) in the fall. At initiation of the study, dolomitic limestone and magnesium sulfate (MgSO₄) was applied to equilibrate calcium across all treatments based on the highest rate of CaSi. Every 28 days, treatments were rated for turf quality and then harvested to determine Si accumulation. One month after applying CaSi in 2005, Si concentration in the leaf tissue of Tifdwarf had increased linearly with increasing rates. This response continued through the months of May, June, July, August, and October with a 9%, 21%, 40%, 22% and 21% increase in Si concentration in the leaf tissue between the control and the 342 kg m^?2 rate, respectively. Although the rate response remained, there was an overall drop in average percent Si accumulation in leaf tissue across the treatments beginning three months after the first application. Similar responses were noted with the overseeded rough bluegrass with a 46%, 85%, 69%, 111% and 58% increase in Si concentration in the leaf tissue between the control and the 342 kg m^?2 rate, respectively. In contrast to the bermudagrass, over the five month period following application, the residual activity of Si in rough bluegrass remained high, suggesting that rough bluegrass might be a better Si accumulator in comparison to Tifdwarf bermudagrass. The second run of the experiment (2006–2007) and the residual trial had the same response with Si concentration in the leaf tissue increasing as the amount of CaSi applied increased. Although turfgrass quality was not well correlated to CaSi rate for Tifdwarf bermudagrass, there was an increase in quality ratings for rough bluegrass from December 2005 to April 2006.     

Effects of White Clover Inclusion on Turf Characteristics,Nitrogen Fixation,and Nitrogen Transfer from White Clover to Grass Species in Turf Mixtures

Abstract

An irrigated field trial was conducted to test the effects of white clover in three turfgrass species (perennial ryegrass, Kentucky bluegrass, and creeping bentgrass) on color, clipping yield, and botanical composition and to estimate nitrogen (N)₂ fixation and N transfer from white clover to associated turfgrass species under different N‐fertilization conditions in 1999–2002.

Nitrogen fertilizers significantly increased color ratings in all observations. Grass–white clover mixtures had better color ratings than pure grass at all sampling dates and seasonal averages in unfertilized conditions. Fertilized pure grass plots yielded significantly more than control plots in all turfgrass species. Nitrogen fertilization did not affect clipping yield greatly in turfgrass–white clover mixtures. Nitrogen application significantly decreased white clover percentage in the harvested clippings in second and third year.

Nitrogen fertilization increased tissue N concentration positively in all turfgrass species grown alone. In contrast, N fertilization did not greatly affect tissue N concentration of either turfgrass species or white clover in the mixtures. Nitrogen fixation of white clover was estimated as 24.6, 30.7, and 33.8 g m^?2 year^?1 in perennial ryegrass, Kentucky bluegrass, and creeping bentgrass, respectively. The total estimated N₂ fixation gradually decreased with increasing N fertilization. Nitrogen transfer from white clover to the associated turfgrass varied from 4.2 to 13.7% of the total N that the white clover fixed annually.     

Characterization of a USDA Kentucky Bluegrass (Poa pratensis L.) Core Collection for Reproductive Mode and DNA Content by Flow Cytometry

Kentucky bluegrass (Poa pratensis L.) is an important turf and forage grass species with a facultative apomictic breeding behavior. In this study, mature seed and leaf tissue from 38 accessions of a USDA core collection of Kentucky bluegrass were analyzed with flow cytometry to characterize the reproductive mode and DNA content for each accession. Major reproductive pathways for each accession were determined based upon the presence and the position of the peaks observed and the known methods of reproduction for Kentucky bluegrass. While the majority of the accessions exhibited facultative apomictic reproductive behavior with a combination of reduced, zygotic and unreduced, parthenogenic embryo production, obligate sexual or obligate apomictic accessions were also found to be present in this core collection. In addition, reduced, parthenogenic and unreduced zygotic embryos were also detected in several accessions. Flow cytometric analysis of somatic tissue revealed a large range of DNA variation within this core collection. We also examined the sensitivity of flow cytometry in analyzing bulked samples containing a large number of plants with varied DNA content and determined that flow cytometry can effectively detect a plant having a different DNA content within a 15-plant bulk sample. Overall the combination of mature seed and somatic tissue analysis generated important information for the Kentucky bluegrass core collection and can be an effective and affordable tool to characterize even greater numbers of Kentucky bluegrass accessions.     

Grass mixtures for afforested opencast spoils in South Wales

An experiment that investigated the establishment of seven grass and legume seed mixes on opencast coal mining spoil in South Wales is described. After three years, mixtures containing Poa pratensis and Festuca rubra var. rubra were the most successful in covering the spoil; the ‘Johnson JR33’ seed mix proved the best of those commercially available that was tested. Tree growth was not detrimentally affected by the establishment of a grass ground cover. Erosion was not an important process at the experimental site, though slumping occurred locally from plough ridge to plough furrow.     

Phosphorus Sources and Rates Associated with Nitrogen Fertilization in Mombasa Grass Yield

Nitrogen (N) and phosphorus (P) deficiency is one of the important causes of degradation of cultivated pasture under tropical conditions. The aim of this study was to evaluate phosphate rates and sources, and N rates on the concentration and uptake of N and P, and shoot dry mass (SDM) yield of Megathyrsus maximum grass cv Mombasa in an Ultisol. The trial was carried out in a greenhouse in pots with 4.0 dm^?3 of soil. The experiment was arranged in a completely randomized design with four replicates. The 3 × 3 × 3 factorial treatments consisted of phosphorus sources [reactive rock phosphate from Morocco (RPM), reactive rock phosphate from Algeria (RPA) and triple superphosphate (TSP)], three phosphorus rates (0, 150, and 300 mg kg^?1), and three N rates (0, 250, and 500 mg kg^?1). The SDM and tillering of Mombasa grass were significantly influenced with the TSP, RPM, and RPA application associated with N fertilization. The RPM, RPA, and TSP met the nutritional demands of Mombasa grass. The three P sources showed the same effect on the total N uptake by Mombasa grass. The P use efficiency (PUE) when fertilizer-P sources were added alone by Mombasa grass was <12% of the added P, and PUE decreased as follows: TSP > RPA > RPM. When P and N-fertilizer were added together, the fertilizer-N use efficiency (NUE) was 62%. The reactive phosphate (RPM and RPA) is an efficient P sources for Mombasa grass, but requiring higher rate of application compared to TSP source.     

Diurnal patterns of nitrate assimilation in Kentucky bluegrass

Kentucky bluegrass (Poapratensis L.) is a major C₃‐type forage and turfgrass, but it is less efficient than many grasses in utilizing nitrogen(N). To determine how this grass can accommodate its greater N need, diurnal patterns of nitrate reductase activity (NRA) and nitrite reductase activity (NiRA) in its leaves and roots were examined and compared with those in barley (Hordeum vulgare L.). Plants were grown under greenhouse or growth room conditions and assayed for NRA and NiRA by optimized in vivo methods. The diurnal patterns of NRA and NiRA indicated that Kentucky bluegrass could assimilate nitrate during the night at rates greater than or similar to those during the day. Leaf NRA of Kentucky bluegrass was minimal approximately 4 and 10 h after illumination commenced and increased at night. The diurnal pattern of leaf NRA among Kentucky bluegrass cultivars did not differ significantly. In roots, NRA of Kentucky bluegrass was high in the morning and decreased sharply during the afternoon and evening, but increased again late at night. Unlike Kentucky bluegrass, barley exhibited greater leaf NRA during the day than during the night and exhibited the greatest activity 6 or 10 h after illumination commenced. In both species, the equilibrium leaf nitrate pool was 20 to 30 times larger than the ammonium pool and 3, 000 to 13, 000 times larger than the nitrite pool. Leaf nitrate pool size showed a diurnal pattern complementary to that of leaf NRA. Our results suggest that a nighttime N use strategy might exist in Kentucky bluegrass.     

三种锦鸡儿属植物的克隆生长特性及其植被恢复意义

 了研究适于甘肃定西黄土丘陵沟壑区植被恢复的主要灌木种,以本地种白毛锦鸡儿(Caragana licentiana) 和甘蒙锦鸡儿(C．opulens)以及外来种中间锦鸡儿(C．intermedia)为对象,研究其克隆生长特性。白毛锦鸡儿和甘蒙锦鸡儿由根状茎产生很多无性系分株,均为松散游走型克隆生长构型,其根状茎错纵复杂,结成网状结构。在黄土丘陵沟壑区相对干旱的环境以及动物胁迫下,白毛锦鸡儿种子繁殖受到限制,无性繁殖有助于其种群的更新和扩展。白毛锦鸡儿的分株种群在半阳坡比在半阴坡有显著大的分株数、根状茎数、基株最大半径、根状茎长和根状茎生物量分配,反映出其形态的可塑性。游走型的克隆生长构型和根状茎的网络结构,赋予白毛锦鸡儿很好的水土保持性能。中间锦鸡儿为单轴型构型,在定西地区不产生无性系分株。     

Use of integrated weed management tools in crop rotations with grass seed production

This paper presents the results of studies quantifying the effect of some of the tools available in an integrated weed control strategy focusing on problematic annual grasses in crop rotations with grass seed production. The paper presents the results of experiments demonstrating the influence of competitiveness of the crop on the development of annual grass weeds. The experiments quantify the influence of establishment at different row distance, plant density, sowing depth and cultivar type. The paper further presents the results showing how a change in establishment time from autumn to spring influences the germination rate of four important annual grasses. The study demonstrated that springtime establishment offers the opportunity to reduce problems with Apera spica-venti and Poa trivialis and to a lesser extent with Alopecurus myosuroides and Vulpia myuros. The study further showed that the false seedbed technique can be a very effective tool to reduce problems with annual grasses. The populations of two of the investigated species, P. trivialis and V. myuros, were reduced by almost 80% applying the false seedbed technique. Dependent on the density and species composition of annual grasses expected these IWM tools can be used in strategies to secure a high quality in grass seed production.     

Tillage System and Seeding Time Effects on Forage and Seed Yield of Alfalfa and Bromegrass

Abstract

Perennial forages are an important component for the cropping systems of the Parkland region in the Canadian prairies, but only a few studies have reported on direct seeding of forages in northeastern Saskatchewan. The objective of this study was to compare the effects of tillage (conventional tillage, CT, and zero tillage, ZT) for seedbed preparation and different seeding times (October 1993, May 1994, and June 1994) on forage and seed yield of alfalfa (Medicago sativa Leyss) and bromegrass (Bromus inermis Lyess) on Gray Luvisol (Typic Cryoboralf) soils (sandy at Gronlid and clayey at Ridgedale) in northeastern Saskatchewan. Visual inspection of plant stands in the establishment year indicated that plant densities were generally higher under CT than ZT and with spring than autumn seeding. Forage yield in 1994 was greater under ZT than CT for alfalfa at both sites and for bromegrass at Ridgedale. In 1995 and 1996, tillage had no effect on forage yield in most cases. The 3‐year forage production was greater under ZT than CT for alfalfa by 647 and 770 kg ha^?1 at Gronlid and Ridgedale, respectively, and for bromegrass at Ridgedale (by 697 kg ha^?1), with the opposite result at Gronlid (by 237 kg ha^?1). The effect of seeding time on forage production was not consistent. The seed yield in 1995 and 1996 was somewhat greater with ZT than CT, with autumn than spring seeding, and with May than June seeding for alfalfa, whereas the opposite was true for bromegrass, except at Ridgedale when autumn seeding produced greater seed yield than spring seeding. In summary, the lower plant population under ZT than CT in the establishment year did not necessarily result in lower forage and seed yield of alfalfa and bromegrass, suggesting that ZT can replace CT for forage production, and seeding time effect was mainly observed in the first year.     

Effect of plant growth-promoting Bacillus sp. on color and clipping yield of three turfgrass species

A two-year irrigated field study was conducted to determine the effects of plant growth-promoting rhizobacteria (PGPR; Bacillus subtilis OSU-142 and Bacillus megaterium M3) as biofertilizer, and in combination with a chemical nitrogen (N) fertilizer, on turf color and clipping yield, and interaction of biofertilizer and chemical N fertilizers in perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea L. Schreb.), and Kentucky bluegrass (Poa pratensis L.). The three turf species were tested separately in split-plot design experiments with three replications. Three fertilizer sources (ammonium nitrate only, ammonium nitrate + B. megaterium M3, and ammonium nitrate + B. subtilis OSU-142) were the main plots. N applications with monthly applications of 0.0, 2.5, 5.0, and 7.5 g N/m² were the subplots. Color ratings and clipping yields increased with increasing chemical N fertilizers in all species. Both Bacillus sp. significantly increased color ratings and clipping yields in perennial ryegrass and tall fescue. However, there were no significant differences among the three fertilizer sources in color and clipping yield of Kentucky bluegrass. The experiments showed that there is a small but significant benefit from applying biofertilizers for turf color, and that N fertilization may be reduced in some turf species when biofertilization are made for this purpose.     

Nodulation competitiveness of Rhizobium leguminosarum bv. phaseoli and Rhizobium tropici strains measured by glucuronidase (gus) gene fusion

Summary The nodulation competitiveness of 17 Rhizobium leguminosarum bv. phaseoli and 3 R. tropici strains was analysed in growth pouches, at pH 5.2 and 6.4. All 20 strains were coinoculated with a gus ⁺ strain of R. leguminosarum bv. phaseoli strain KIM5s. The gus⁺ phenotype, carrying the glucuronidase gene, was used to type nodules directly in the growth pouches. Nodule occupancy ranged from 4% for the least competitive to 96% for the most competitive R. leguminosarum bv. phaseoli strain. The R. tropici strains showed low rates of nodule occupancy at pH 6.4 but their competitiveness improved significantly under acid conditions. CIAT 895 was the only R. leguminosarum bv. phaseoli strain that was less competitive (P<0.05) at the lower pH. The competitiveness of all the other R. leguminosarum bv. phaseoli strains was unaffected by pH. Various physiological and genetic properties of the strains were analysed in search of correlations with nodulation competitiveness. Hybridisation patterns with three different DNA probes (nif KDH, common nod genes, and hup genes) and the metabolism of 53 different C sources were compared. No general correlations were found between hybridisation or growth pattern and competitiveness. The less competitive R. tropici strains had a unique DNA hybridisation pattern and were not able to use shikimate, ferulate, coumarate, or asparagine as C sources. Most of the less competitive R. leguminosarum bv. phaseoli strains could not metabolize either ferulate or coumarate. This might indicate a relationship between nodulation competitiveness and the ability to degrade aromatic compounds.