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Nutrient and chemical changes in turfgrass sand-based root zones are not well understood. This study was conducted to characterize nutrient and chemical properties in putting greens influenced by root zone mixture and establishment treatment, putting green age, and soil depth. Putting greens were constructed and established with Agrostis stolonifera L. in sequential years from 1997 to 2000. Treatments included root zone mixtures of 80:20 (v:v) sand and sphagnum peat and 80:15:5 (v:v:v) sand, sphagnum peat, and soil, and accelerated versus controlled establishment. In the establishment year, the accelerated treatment received 2.6-, 3.0-, and 2.6-fold more nitrogen, phosphorus, and potassium, respectively, than the controlled treatment. Soil samples were taken in Fall 2001, Spring 2004, and Summer 2004 and were analyzed for nutrient and chemical properties such as pH, cation exchange capacity (CEC), organic matter (OM), total soluble salts (TSS), and 12 nutrients. The root zone mixture and establishment treatments had minimal effects on most nutrient and chemical properties with the exception of phosphorus and pH. Cation exchange capacity, OM, TSS, and all nutrients decreased with soil depth, whereas soil pH increased. The putting green age × soil depth interaction was significant for many of the nutrient and chemical properties, but separating soil samples into mat and original root zone instead of predetermined soil sampling depths eliminated most of these interactions. The mat layer had higher CEC and OM values and nutrient concentrations and lower pH values than the original root zone mixture.
`Beauregard' and `Centennial' were planted in plots of four different topsoil thicknesses (0, 3, 6, and 9 inches) to evaluate the effect of topsoil thickness on sweetpotato production. In 1994, the 0-inch topsoil treatment produced a greater total marketable yield for `Beauregard' than did the 6- and 9-inch topsoil for `Centennial'. The 0- and 9-inch topsoil produced a greater total marketable yield than did the 3- and 6-inch treatment. When averaged over 2 years, 1993 and 1994, there were no differences in total marketable yield in either `Beauregard' or `Centennial' due to topsoil thickness. Averaged over both years, topsoil thickness had no effect on weight, diameter, or length of `Beauregard' roots.
Cover crops relay-cropped with vegetables with conservation tillage were compared with fallow conventional production for 10 years. Conservation till-relay received no pesticide and only one-quarter the recommended fertilizers. Winter cover provided significantly better weed control than conventional. Weed problems in relay occurred only in the rows where vegetables were planted. Legume winter covers increased soilborne organisms but did not influence root disease severity or postemergence damping-off. Thrips, aphids, and whiteflies were most frequent. These pests remained below the economic threshold with winter cover crop-relay. However, infestation of these pests and Colorado potato beetles was severe in conventional plots. Winter cover crops provided habitat for more than 14 beneficial insects.
Abstract
Seedlings of Dizygotheca elegantissima (Hort. Veitch) R. Vig & Guillaum (false aralia) were grown for 90 days under maximum, photosynthetically active radiation (PAR) of 797 or 278 μmol s−1m−2 and then treated with 2 pesticides (diazinon or dicofol) in 2 formulations [emulsifiable concentrate (EC) or wettable powder (WP)]. Plants were sleeved, held under simulated shipping conditions for 5 days at 22° ± 1°C, followed by simulated foliage plant warehouse conditions for 10 days at 20° ± 1°. Root and shoot quality ratings were 2-fold better at 278 than 797 μmol s−1m−2 PAR. Light compensation points (LCP) and percentage of total nonstructural carbohydrate (TNC) levels were lower while root TNC levels were higher in plants grown under 278 than 797 μmol s−1m−2 PAR. The percentage of leaf abscission ratio of 278 and 797 μmol s−1m−2 PAR plants was similar to their LCP ratio. Plants had higher tissue levels of N, P, and K and lower levels of Mg and Ca grown at 278 than 797 μmol s−1m−2 PAR. Canopy width of dicofol WP-treated plants grown under 797 μmol s−1m−2 PAR decreased during simulated shipping and warehousing. Pesticide effects on other measurements were not detected.
Abstract
Shading of nectarine [Prunus persica (L.) Batsch] scaffold limbs 45-58 days after full bloom caused seed discoloration and fruit abscission. Shading of peach [Prunus persica (L.) Batsch] scaffold limbs from 31-41 days after full bloom caused greater fruit adscisson than shading from 11-21 or 21-31 days after bloom. The photosynthetic inhibitor, 3-tert-butyl-5-chloro-6-methyluracil (terbacil), applied to whole trees 35 days after full bloom induced fruit abscission. Terbacil at 500 ppm or higher caused excessive thinning. Fruit size was larger than hand thinned fruit, since overthinning occurred. Fruit color, soluble solids, and firmness of fruit from the 500 ppm treated trees were similar to fruit from hand thinned trees. No leaves abscissed, but marginal chlorosis occurred on less than 30% of the leaves at harvest. Flower bud numbers per cm of terminal length were similar to the hand thinned trees, but much greater than unthinned trees. Residue analysis of fruit at harvest from the 500 ppm terbacil treatment revealed 0.07 ppm in the fruit.
The objective of this study was to relate the lethal freezing temperatures of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] genotypes, as measured by differential thermal analysis (DTA), to winter survival observed in the field. DTA-predicted lethal temperatures of 14 St. Augustinegrass genotypes ranged from –7.7 to –4.7C. Regression of field winter survival vs. DTA-predicted lethal temperatures resulted in an r 2 = 0.57 for one field trial that evaluated cultivars with a relatively narrow range of expected freezing tolerance. In a second study evaluating cultivars with a greater range of freezing tolerance, r 2 was 0.92 when winter survival was regressed on DTA-predicted lethal temperatures. DTA was successful in measuring freezing avoidance of St. Augustinegrass cultivars.
Thirty-three tomato (Lycopersicon esculentum Mill.) or L. pimpinellifolium (L.) Mill. accessions were inoculated with race T2 of Xanthomonas campestris pv. vesicatoria (Xcv) in a field experiment at Wooster, Ohio, in Summer 1995. These included accessions selected for race T2 resistance in greenhouse tests in Florida, and accessions from Hawaii, Brazil, and Bulgaria. One L. esculentum (PI 114490-1-1) and three L. pimpinellifolium (PI 340905-S1, PI 128216-T2, and LA 442-1-BK) accessions had no Xcv symptoms. This is the first report of resistance to Xcv race T2. Partial resistance was found in PI 271385, PI 79532-S1, PI 155372-S1, PI 195002, and PI 126428. Most of the 33 genotypes were tested for race T1 resistance in Presidente Prudente, Sao Paulo, Brazil in summer 1993. Hawaii 7983, PI 155372-S1, PI 114490, PI 114490-S1, and PI 262173 had greater resistance to T1 than the susceptible control `Solar Set'. Comparisons with earlier experiments in which accessions were inoculated with race T1 or T3 indicated that the most consistent source of resistance to all three races was PI 114490 or selections from it.
Abstract
Fourteen cultivars of turnip [Brassica rapa, rapifera group, also B. campestris L. ssp. rapifera (Metzg.) Sinsk.] recommended for human consumption of either tops or tops and roots and five cultivars recommended for consumption of roots were selected to compare glucosinolate (GS) levels in tops and roots. Also, two cultivars used for animal feed were included. The study revealed significantly lower levels of 1-methylpropyl-GS and 2-hydroxy-3-butenyl-GS in tops and roots of cultivars grown for greens, compared to those used for animal feed. Contents of 1-methylpropyl-, 3-butenyl-, and 4-pentenyl-GSs were higher in turnip tops than in roots, while 2-hydroxy-3-butenyl-, 4-(methylthio)butyl-, 4-(methylsulfinyl)butyl-, 2-hydroxy-4-pentenyl-, 5-(methylthio)pentyl-, 2-phenylethyl-, 3-indolylmethyl-GSs and total GS were all higher in the roots. GS patterns for seeds tended to correlate with those of the tops.
Abstract
A computer model was developed to predict autumn vegetative maturity, end of summer dormancy of red-osier dogwood (Cornus sericea L. syn. Cornus stolonifera Michx.). Empirical equations were developed from growth chamber data and applied to results obtained from lath house grown plants. The model required input parameters of 2-hourly temperatures and daylengths. From the data daily phototemperature values were determined. The empirical model over-estimated the time to maturity of the lath house grown plants by only 4 days, perhaps indicating the need for a more precise measure of the critical photoperiod.
Abstract
Shoot apices, excised from Citrus cultivars of known virus content, were successfully grafted in vitro onto disease-free rootstock seedlings and some virus-free plants were obtained. The prolonged juvenile phase which characterizes disease-free nucellar lines was bypassed by this procedure.