Timothy K. Broschat

Release Rates of Ammonium‐Nitrogen, Nitrate‐Nitrogen, Phosphorus, Potassium, Magnesium, Iron, and Manganese from Seven Controlled‐Release Fertilizers

Abstract Samples of seven controlled‐release fertilizers, Nutricote Total 13–13–13, Nutricote Total 18–6–8, Osmocote Plus 15–9–12, Osmocote 13–13–13, Polyon 18–6–12, Polyon 14–14–14, and Plantacote 14–8–15, were placed in leaching columns containing acid‐washed sand. Samples of all leachates were analyzed weekly to determine release rates of ammonium‐nitrogen (N), nitrate‐N, phosphorus (P), potassium (K), magnesium (Mg), manganese (Mn), and iron (Fe). Release rates for P from all products were slower than those for NH4‐N, NO3‐N, and K. Release of Mg, Mn, and Fe was very poor, with less than 50% of the total amount of each of these elements ever being released from the prills for some products. Nutricote products released Fe and Mn more effectively than did Osmocote or Plantacote.

Fusarium oxysporum f. sp. palmarum, a Novel Forma Specialis Causing a Lethal Disease of Syagrus romanzoffiana and Washingtonia robusta in Florida

A new disease of Syagrus romanzoffiana (queen palm) and Washingtonia robusta (Mexican fan palm) has spread across the southern half of Florida during the past 5 years. The initial foliar symptom is a one-sided chlorosis or necrosis of older leaf blades, with a distinct reddish-brown stripe along the petiole and rachis and an associated discoloration of internal tissue. Within 2 to 3 months after onset of symptoms, the entire canopy becomes desiccated and necrotic but the leaves do not droop or hang down around the trunk. Based on pathogenicity and morphological and molecular characterization, the etiological agent has been identified as a new forma specialis of Fusarium oxysporum, designated f. sp. palmarum. Sequence analysis of a portion of the translation elongation factor 1-α gene (EF-1α) separated 27 representative isolates into two EF-1α groups, which differed by two transition mutations. Members of both EF-1α groups are pathogenic on both species of palm. A phylogenetic analysis inferred from partial EF-1α sequences from a genetically diverse set of F. oxysporum isolates, including three other formae speciales pathogenic on palm (i.e., f. sp. albedinis, f. sp. canariensis, and f. sp. elaeidis), suggested that f. sp. palmarum and f. sp. albedinis may be more closely related to one another than either is to the two other palm pathogens.

Oxalate content of palm fruit mesocarp

Abstract Fruit mesocarp of 60 species of palms were analyzed for total oxalate content. All species contained some oxalate, but concentrations varied widely among the seven palm tribes studied. Fruit oxalate concentrations were consistently low in the Phoeniceae, Borasseae, Lepidocaryeae and Cocoeae, high in the Hyophorbeae, Caryoteae and Cyclospatheae, and variable in the Areceae.

Nutrient Distribution and Sampling for Leaf Analysis in St. Augustinegrass

Abstract Leaf nutrient analysis for turfgrass is typically performed on clipping samples. However, since clippings of St. Augustingrass used in lawns consist primarily of the youngest leaves, they may not be the best material to sample, especially for mobile elements. This study examined the concentration gradients of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn) among leaves of various ages to determine their relative mobility within St. Augustingrass [Stenotaphrum secondatum (Walt.) O. Kuntze] plants, and to determine which age of leaves were the best indicators of plant nutritional status for each element. To provide varying levels of fertility on a Hallandale fine sand soil in southern Florida, a landscape area of “Floratam” St. Augustingrass was either not fertilized or fertilized with 4.9 g N m−2 every 3 months from either a mostly water soluble 16–4–8 (N–P2O5–K2O) fertilizer blend or an 8–4–12–4 Mg (N–P2O5–K2O–Mg) controlled-release fertilizer blend containing micronutrients. Leaf samples were obtained twice for analysis, once during the cooler winter months and once during the warmer summer months. About 50 shoots were sampled from each plot, and the leaves were separated according to their position on the shoot axis. Leaf samples were analyzed for N, P, K, Ca, Mg, Fe, Mn, and Zn content. Concentrations of each element in each leaf and fertilizer plot were used to determine which leaf position provided the best indicator of plant nutrient status for each element. Nitrogen, P, K, and Mn showed decreasing leaf elemental concentrations with increasing leaf age, as is typical for mobile elements, while Ca, Mg, and Zn had higher concentrations in the older leaves and were considered immobile in this species. Leaf Fe concentrations were not correlated with either fertilizer treatment or leaf position. Leaf 3, which is the oldest leaf, followed by Leaf 2, was found to be the best indicator of plant nutrient status for all elements, regardless of their mobility. Leaf 1, which is the primary component of turfgrass clippings, was generally the poorest indicator of plant nutritional status and is not recommended for leaf nutrient analysis.

leaf cuticular alkanes of cultivated Polyscias

Abstract Leaf cuticular alkane analysis of 34 cultivars of Polyscias generally supported morphological classifications of this genus, but variability within groups such as P. crispatum suggested that alkane data by itself is insufficient for classification of the various cultivars into species. Alkanes with 27–33 carbon atoms were present in most species, with C 31 predominating.

Effects of Fertilizer Type and Rate on the Quality and Nutrient Concentrations of Three Species of Field-grown Shrubs in South Florida

Three species of tropical shrubs, bush allamanda (Allamanda schottii), ixora (Ixora ‘Nora Grant’), and surinam cherry (Eugenia uniflora), were planted into a native sand soil and a calcareous fill soil in south Florida and were fertilized with a 24N–0P–9.2K (24–0–11) turf fertilizer or an 8N–0P–10K–6Mg plus micronutrients (8–0–12) palm fertilizer at rates of 10 or 20 g of nitrogen (N) per shrub four times per year. Two additional treatments using a 0–0–13.3K–6Mg plus micronutrients (0–0–16) palm fertilizer were applied at equivalent rates of potassium (K) (12.5 or 25 g/shrub of K) to that applied in the two 8–0–12 palm fertilizer treatments. Shrub size measurements, nutrient deficiency severity ratings, number of flowers, and shrub density ratings were determined at 6 months after planting (establishment period) and at 3 years after planting (maintenance phase). Data from these measured variables were subjected to principal component analysis to obtain a single measure of overall quality, namely, the scores for each plant on the first principal component. During the establishment period, ixora fertilized with the high rate of 8–0–12 had the highest quality on the sand soil, but there were no differences among treatments on the fill soil for this species or on either soil type for allamanda and surinam cherry. After 3 years of growth, ixora showed no differences in quality on either soil in response to the fertilizer treatments. On the sand soil, allamanda receiving the high rate of 24–0–11 or the low rate of 8–0–12 had significantly higher quality than unfertilized control plants, and the low rate of 8–0–12 produced the highest quality plants on the fill soil. Surinam cherry grown on sand soil had the highest qualities when fertilized with the high rates of either 24–0–11 or 8–0–12. In general, leaf nutrient concentrations were inversely correlated withoverall shrubquality,with largest, highest quality plants having the lowest nutrient concentrations because of dilution effects. However, leaf manganese (Mn) concentrations were consistently within deficiency ranges for all species under most treatments, suggesting that Mn deficiency was stunting shrub growth on both soil types.

Effects of Fertilizer Type and Rate on the Quality and Nutrient Content of Four Species of Trees Growing in Sandy South Florida Soils

Broadleaf ornamental trees are known to vary widely in their responses to fertilization, depending on the species and soil and other environmental factors. Thus, it is important to study the responses of a wide range of tree species to fertilization, especially on nutrient-poor soils. Four species of temperate to tropical trees, live oak (Quercus virginiana), west indian mahogany (Swietenia mahagoni), black olive (Bucida buceras ‘Shady Lady’), and beautyleaf (Calophyllum brasiliense), planted into a sandy native soil in south Floridawere fertilizedwith a 24N–0P–9.3K turf fertilizer or an 8N–0P–10K–4Mg plus micronutrients palm fertilizer at rates of 10 or 20 g of nitrogen per tree four times per year. Tree height, width, caliper, and nutrient deficiency rating scores for nitrogen, potassium, and magnesium were determined at 1 year after planting (establishment period) and at 3 years after planting (maintenance phase). Data from these measured variables were subjected to principal component analysis to obtain a single measure of overall quality, namely, the scores for each tree on the first principal component. West Indian mahogany showed no response to fertilization during or following establishment. Either fertilizer type or rate improved live oak, black olive, and beautyleaf quality over that of unfertilized controls during both establishment and maintenance phases, but the high rate of the palm fertilizer was superior to either rate of the turf fertilizer for beautyleaf both during establishment and afterward. Leaf nutrient concentrations generally were poorly correlated with overall tree quality, but manganese concentrations differed significantly among treatments for all four species. Based on these results, fertilization of West Indian mahogany is not recommended, but live oak, black olive, and beautyleaf will benefit from fertilizer applied at the time of planting and after establishment.