Aloe barbadensis (Aloe vera) plants remain in production fields for several years, with their lower leaves harvested periodically. A long-term experiment was initiated in November 1993 to determine the effects of fertilization and severeness of harvest on leaf yield. Plants were grown in large pots with or without monthly applications of a 20N–8.6P–16.6K soluble fertilizer from March to October. Beginning in June 1994, the lower leaves were harvested quarterly to have 18, 15, or 12 leaves remaining. Fertilization doubled the number of leaves harvested and tripled the total yield over a 2-year period. The lower leaves on the nonfertilized plants, particularly on plants with 18 leaves remaining, sometimes became dry or partially dry at harvest. The initial quarterly yield and cumulated yield were higher in plants with 12 leaves remaining; however, this trend disappeared over time. The fertilized plants produced an average of 10 kg per plant, while the nonfertilized plants produced only 3.2 kg per plant annually. At several harvests, plants with 18 leaves remaining had higher % dry mass in the inner semi-translucent tissue than those having 12 leaves. Leaves of nonfertilized plants had high % dry mass in the inner leaf tissue when harvested in June and September 1995. Plants with 12 leaves remaining can become unstable and the tops break off in gusty wind.
`Classic' eggplant (Solanum melongena L.) responses to K fertilization were evaluated in Spring and Fall 1991 at Live Oak, Fla., on soils testing low in Mehlich-1 extractable K. Total season yield leveled off at 51.1 t·ha-1 with 94 kg K/ha fertilization in spring and at 53.3 t·ha-1 with 60 kg K/ha in fall. Critical K concentrations (in grams per kilogram) in whole leaves were ≈45 at first flowering, 35 at early fruiting, 30 during harvest, and 28 at the end of seven harvests. Fresh petiole-sap K critical concentrations (in milligrams per liter) were ≈4500 to 5000 before harvest and 4000 to 4500 during harvest. Less than 3500 mg K/liter in fresh sap indicated K deficiency in fruiting plants. The Mehlich-1 soil extractant procedure predicted similar responses at the two sites; however, yield responses showed that the two sites differed in fertilization requirements. Fertilizer recommendations for K at both sites exceeded eggplant K requirements.
A capillary watering system can easily control water supply to cyclamen and can save nutrient losses by leaching. Introduction of single basal placement using MEISTER will be useful to innovate the traditional cyclamen culture. The conventional cyclamen culture using Nutricote needs double transplanting and double fertilization. In the new cyclamen culture, cyclamen seedlings (sowed on the plug tray in early January) were transplanted to 15-cm pots fertilized with MEISTER in early June. The selected MEISTER was one belonging to the sigmoid dissolution group, which showed delayed release during summer and the maximum release in early September. The new fertilization supplied N to the plants until the end of growing season. The growth of cyclamen plants on two experimental plots were compared at the flowering stage. Numbers and weight of flowers per pot and bulb weight were greater in the new culture than in the conventional culture though the total volume of leaves was less in the former. Regarding the nutrient absorption, the plants of the new culture showed lower concentrations of N and P in the leaves but higher concentrations of Ca and Mg compared to those in the conventional culture. Such nutrient uptake could contribute to preventing the occurrence of tipburn in the new culture.
Multiple branched liners of `Mrs. G. G. Gerbing' azaleas (Rhododendron L.) were greenhouse-grown for 16 weeks in 3-liter containers with a common nursery medium. The growth medium of each plant was amended with either 0.5, 1.5, or 2.5 g N from Osmocote 14N-6P-11.6K and irrigated with either 920 ml water twice a week or evapo-transpiration (ET) plus 10%, 30%, or 50%. Shoot dry weights (35 and 35 g, respectively) for plants irrigated with ET plus 30% or 50% and fertilized with 1.5 g of N were larger than plants fertilized with 0.5 or 2.5 g N and irrigated with ET plus 10%, 30%, or 50%. Shoot dry weights of plants irrigated with ET plus 30% or 50% were similar to plants irrigated with 920 ml twice a week when plants received 1.5 g N. Plants that received 920 ml twice a week and 2.5 g N had larger shoot dry weights than plants irrigated with ET plus 10%, 30%, or 50% and fertilized with 2.5 g N. Shoot dry weights increased from 17 to 46 g for the 0.5 and 2.5 g N treatments, respectively, when plants were irrigated with 920 ml.
Phosphorus is considered a major pollutant of lakes in central Florida, and growers producing crops in the Lake Okeechobee watershed are being challenged to reduce use of P fertilizer. Caladium (Caladium×hortulanum Birdsey) tubers are produced on organic soils within this area. This study was done to determine if current commercial P fertilization rates could be reduced or eliminated, since these organic soils have high levels of water extractable P (Pw). Two farms were selected with low (Farm A 19 lb/acre; 21 kg·ha-1) or high (Farm B 59 lb/acre; 66 kg·ha-1) preplant Pw levels. Production of caladium tubers with the standard grower P fertilization practice (Farm A = P at 39.2 lb/acre; 43.9 kg·ha-1, or Farm B = P at 15.9 lb/acre; 17.8 kg·ha-1) was compared to production with either one-half the standard grower rate of P or no P. The percentage of harvested tubers in each of five grades and the estimated harvested tuber value index were similar irrespective of the amount of P fertilizer used on either farm. These results indicate that P could be eliminated from the fertilization program for caladium tuber production on organic soils.
Abstract
Pine bark-filled containers were subjected to 10°, 20°, 30°, or 40°C for 24 days and fertilized periodically with 210 ml of a solution containing 100 ppm NH4-N. Every 6 days, medium solutions were tested for NH4-N and NO3-N concentrations and a NO3-N accumulation rate (NAR) was determined. Medium solution NH4-N concentrations were lower at 20° and 30° than at 10° and 40°, while those at 40° were considerably greater than at other temperatures and increased over time. In general, medium solution NO3-N concentrations at 10°, 20°, and 30° were comparable and higher than at 40°. Over time, the general order of NAR was 20° = 30° > 10° > 40°.
We investigated pollination and fruit set parameters in `Manzanillo' olive (Olea europaea L.) following self-pollination and pollination with `Sevillano', `Ascolano', and `Mission' pollen. Results of analyses and experiments conducted over 2 years in central California indicated that `Manzanillo' behaves as a self-incompatible cultivar (index of self-incompatibility = 0.22 to 0.24). Pollination with `Sevillano' resulted in a more than 4-fold increase in fruit set over self-pollination. When `Mission' or `Ascolano' pollen was used, there was no increase over self-pollinated samples. Analyses of pollen tube growth, fertilization, initial fruit set, and final fruit set were consistent with `Manzanillo' being considered as a self-incompatible cultivar cross-incompatible with `Mission' and `Ascolano'. Our results indicate that `Manzanillo' is likely to be more productive when interplanted with `Sevillano' rather than when planted without a pollinizer or with `Mission' or `Ascolano'.
Nutrient uptake by `Apache', `Jersey City', `Peoria', and `Philadelphia' snapdragons (Antirrhinum majus L.) was compared at three developmental stages: Stage I, vegetative to bud initiation; Stage II, bud initiation to visible bud; and Stage III, visible bud to anthesis. Significant differences in uptake occurred between one or more developmental stages for all nutrients tested:
Flowers of two cultivars of Rosa hybrida were treated or not with putrescine before being pollinated from 2 to 8 days after anther emasculation. On both cultivars the 10-3 M putrescine treatment extended the effective pollination period, as shown by the best hip formation rates and mean number of seeds per hip. On one cultivar, the 10-5 M putrescine treatment increased fertilization efficiency (more hips obtained). The effect of putrescine was proportionally more important on the cultivar characterized by the highest stigmatic exudate pH. Putrescine also influenced in vitro pollen germination by increasing the length of emitted pollen tubes (10-3 and 10-5 M-putrescine) and the quantity of germinated pollen grains (10-5 M putrescine).
Decades of heavy phosphorus (P) fertilization of vegetable crops in the Salinas Valley of California has increased soil test P (STP) levels, with bicarbonate-extractable P (Pbc) values >50 mg·kg–1 now common. To evaluate the response of lettuce (Lactuca sativa L.) to P fertilization in fields with elevated STP levels, 12 trials were conducted in commercial fields during 2002–03. Initial Pbc at the trial sites varied from 53 to 171 mg·kg–1. In each trial, four replicate plots receiving the growers' P application were compared with paired plots in which no P was applied. Leaf P was monitored at midseason and at harvest. At harvest, mean whole and marketable plant mass and percent of marketable plants were recorded. A significant increase in lettuce yield with P fertilization was achieved at only one trial site, a spring planting with 54 mg·kg–1 Pbc; at all other sites, including three with Pbc <60 mg·kg–1, P application resulted in no significant yield increase. Phosphorus application resulted in only a marginal increase in plant P uptake; in the nonresponsive fields leaf P concentration of nonfertilized plots was in excess of established sufficiency levels. In a laboratory study, the correlation of Pbc to bioavailable P (Pba) was evaluated using 30 representative Salinas Valley soils; Pbc varied among these soils from 15 to 177 mg·kg–1. Pba was estimated by P adsorption on an anion resin membrane during a 16 hour incubation. The effect of temperature on P bioavailability in six of these soils was estimated by conducting the Pba incubation at 5, 15, and 25 °C. Pba was highly correlated with Pbc (r = 0.89), and increased about 40% across soils with each 10 °C increase in soil temperature. Therefore, Pbc was determined to be an accurate reflection of bioavailable P in these soils, although the addition of a temperature correction factor in setting threshold values is desirable.