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Growth and mineral nutrient content of creeping bentgrass [Agrostis stolonifera (L.) var. palustris (Huds.) Farw.] in response to salinity and humic acid (HA) application were investigated, and the effects of HA application on salinity tolerance was evaluated. Bentgrass plugs were grown hydroponically in one-quarter-strength Hoagland's nutrient solution containing HA at 0 or 400 mg·L-1 with salinity levels of 0, 8.0, or 16.0 dS·m-1. Clipping dry weight (DW), tissue water content, and net photosynthesis (PN) were measured weekly for 1 month. Maximum root length, and root DW from 0 to 10 cm and >10 cm root zones were determined 31 days after treatment (DAT). The turfgrass plugs were mowed three times weekly, with clippings collected and dried for mineral nutrient analysis. Salinity was inversely related to clipping DW, tissue water content, PN, and maximum root length. Salinity had less effect on root growth than top growth. HA treatment did not affect tissue water content, PN, or root growth of salt-stressed turf. Salinity decreased uptake of N, P, K, Ca, and S; increased uptake of Mg, Mn, Mo, B, Cl, and Na; and had no influence on uptake of Fe, Cu, and Zn. Application of HA at 400 mg·L-1 during salinity stress neither increased uptake of the mineral nutrients inhibited by salinity, nor decreased uptake of nutrients which were excessive and toxic in the salinity solution. In general, application of HA did not improve salinity tolerance of creeping bentgrass.
Supplemental Fe fertilization to improve turfgrass quality has become an increasingly common practice on many turfgrass areas. Field studies were conducted to evaluate the nutrient uptake, growth, and quality of Kentucky bluegrass (Pea pratensis L.) treated with chelated Fe sources. Iron sources were evaluated over 2 years at 1.5,3.0, and 6.0 kg Fe/ha applied in May, July, and September of each year. Turf treated with an iron orthophosphate citrate source (Fe-PC) exhibited more foliar growth than nontreated turf on seven of 11 sampling dates during the study. Iron citrate sources [Fe-C(EI) and Fe-C(T)] and Fe-DTPA applications resulted in similar growth rates, never stimulating growth more than the Fe-PC source and rarely increasing growth compared with nontreated turf. Increasing the Fe rate within source did not typically increase growth. Iron-treated turf exhibited quality superior to nontreated turf throughout the study with all sources performing comparably. Increasing Fe rate did not result in a corresponding increase in quality, due to greater phytotoxicity at higher rates. Although several sources produced notable phytotoxicity at 6.0 kg Fe/ha, repeated application did not decrease turfgrass density. Iron tissue content increased linearly with rate on four of five sampling dates during the study however, no source resulted in tissue Fe content significantly higher than other sources. Application of sources containing supplemental P and/or K did not increase tissue P or K content. Chemical names used: iron citrate (Fe-C); iron diethvlenetriamine pentaacetate (Fe-DTPA); iron orthophosphate citrate (Fe-PC).
Environmental concerns associated with traditional methods of sludge disposal have spurred research exploring alternate avenues of disposal. A potentially significant alternative is the beneficial use of sludge as a turfgrass fertilizer. Studies were initiated during 1991 to compare a commercially available pelletized sludge to urea; 12-4-6; Ringer Lawn Restore; and Milorganite. Fertilizers were evaluated for their effect on turfgrass quality, color, and growth rate. Treatments were applied to a stand composed of 65% Kentucky bluegrass (Poa pratensis L. `Baron') and 35% Perennial ryegrass (Lolium perenne L. `Manhattan II') in South Deerfield, MA. Urea and 12-4-6 were applied at 49 kg N ha-1. Ringer Lawn Restore and Milorganite were applied at 98 kg N ha-1. Pelletized sludge was applied at 98, 196, 294, and 392 kg N ha-1 with all rates providing acceptable to good turfgrass color throughout the season. Rates of 294 or 392 kg seldom provided quality better than the 196 kg rate. While urea initially produced quality superior to pelletized sludge, all rates of sludge resulted in quality equal to or better than urea beginning one month after application and lasting approximately 11 weeks. Turf receiving similar rates of either pelletized sludge or Milorganite performed similarly. No sludge application rate produced burning or foliar discoloration. Clipping production was directly related to sludge application rate. Pelletized sludge applied at 98 kg N ha-1 resulted in growth comparable to similar applications of Ringer Lawn Restore and Milorganite. In summary, using pelletized sewage sludge as a turfgrass fertilizer promotes healthy turfgrass while creating an alternate avenue of sludge disposal.
Abstract
We collected lemon leaves from 25 trees growing in control and artificially salinized plots at Indio, California, 4 and 6 weeks after beginning of irrigation with water carrying 5,000 ppm total salt. Chloride content of the leaves was directly correlated with their ethylene production. Leaves with visible injury from high Cl produced more ethylene than those with no visible injury from salinized plots; foliage from the latter treatment produced more ethylene than those from nonsaline control plots. The correlation coefficient was significant at odds of 19:1 at 4 weeks and 99:1 at 6 weeks.
Humic acids (HA) reportedly enhance the growth of numerous crops; however, little information is available as to their effects on turfgrasses. Experiments were conducted to evaluate the effect of a commercial preparation of HA on the photosynthesis, chlorophyll concentration, rooting, and nutrient content of `Crenshaw' creeping bentgrass (Agrostis stolonifera L.). Bentgrass plugs were grown hydroponically in one-quarter-strength Hoagland's nutrient solution containing HA at 0, 100, 200, or 400 mg·L-1 with measurements made weekly for 1 month. The photosynthetic rates of plants growing in 100 or 200 mg·L-1 rarely differed from that of the control, but 400 mg·L-1 significantly enhanced net photosynthesis on all four observation dates. Chlorophyll content was unaffected by HA rate on all observation dates. Root dehydrogenase (DH) activity and root mass regrowth were significantly increased by HA at 400 mg·L-1 on all dates. The 100 and 200 mg·L-1 rates increased root DH activity on two of four observation dates, but root regrowth was unaffected. At one or more of the rates used, HA increased tissue concentrations of Mg, Mn, and S and decreased those of Ca, Cu, and N, but had no influence on the concentrations of P, K, Fe, Mo, and Zn.
Field experiments were conducted to determine the response of five widely used Kentucky bluegrass (Poa pratensis L.) cultivars (Adelphi, Baron, Bensun, Merion, and Touchdown) to preemergence applications of the herbicide pendimethalin. Pendimethalin applied during 2 years at 1.7 or 3.4 kg·ha-1 (a.i.) controlled smooth crabgrass [Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl.] effectively without injury to turf. Pendimethalin at 3.4 kg·ha-1 resulted in a short-term suppression of root growth immediately following application in the first year of the study. The reduction was transitory and subsequent rooting and rhizome growth were unaffected by pendimethalin. Cultivar × pendimethalin level interactions were not significant during the study. Thus, the herbicide appears to be a safe, effective preemergence material for crabgrass control in Kentucky bluegrass turf. Chemical name used: N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin).
Zonate leaf spot (ZLS) caused by Cristulariella moricola, apparently a rare disease of tomato, was identified in a commercial tomato field in southeastern Arkansas in June, 1991. Although lesions of ZLS were similar to early blight (Alternaria solani) lesions, which were also present, there were several distinctions between the lesions: the concentric rings in lesions of ZLS were more symmetrical than early blight lesions, no distinct chlorosis was associated with the lesions, and ZLS lesions were not localized near the bottom of the tomato canopy. Koch's postulates were completed on several greenhouse grown tomato cultivars. Inoculum was produced on autoclaved tomato leaves incubated at 20 C and consisted of large (300-400 um long) “Christmas tree” shaped propagules. When free moisture was maintained at 20 C, large (> 1 cm), rapidly expanding, water-soaked lesions were observed on leaves of inoculated plants 1-3 days after inoculation. Lower humidities caused lesions to rapidly dry out. Epidemiological factors, such as temperature, leaf wetness, and cultivar susceptibility also have been examined.
Abstract
Succinic acid-2,2-dimethylhydrazide (daminozide) applied to ‘Raven’ blackberries at 4000 ppm and to ‘Raven’ and ‘Brazos’ at 2000 ppm between full bloom and first color development and at 2000 ppm in a multiple application applied at full bloom, 2 weeks, and 3 weeks after full bloom resulted in reduced berry size and yield with no beneficial effects on fruit quality. (2-Chloroethyl) phosphonic acid (ethephon) applied to the same cultivare at 1000 ppm 4 days prior to the first harvest increased the amount of fruit mechanically harvested on the first harvest. Ethephon treatment improved color but resulted in mechanically harvested fruit having lower soluble solids and acidity.
Abstract
Multiple preharvest applications of CaCl2 at 1000, 2000, or 4000 ppm (actual Ca) had little effect on fruit firmness of blackberry (Rubus sp.) at harvest. After a 24 hour holding, fruit from the first harvest was firmer if treated with Ca. Preharvest Ca treatments reduced soluble solids accumulation in fruit and 4000 ppm caused foliar damage. Ca had little effect on acidity or color at harvest, but reduced the rate of ripening during postharvest holding.