growers contain little nutrient value. With the investment in plants, substrate, containers, water, and labor, growers need to be sure that they are using the correct fertilizer regimen for their production system. CRFs are part of common fertilization
Commercially propagated `Halward's Silver' spirea (Spiraea nipponica Maxim.) bareroot cuttings and cuttings with substrate around the roots (plugs) were transplanted into 3.8-L containers and fertilized with various P fertilizers to determine the effect of fertilizer source on P leaching and plant growth. The following fertilizer treatments were applied: 1) 100% of the recommended rate of P from controlled-release fertilizer (CRF), consisting of 22N-2.6P-10K; 2) 100% of P from triple superphosphate (TSP, 0N-20P-0K) with N and K provided by 22N-0P-10K CRF; and 3) 50% of P from CRF, consisting of 22N-1.3P-10K, plus 50% of P from TSP (CRF/TSP). The most P leached from cuttings transplanted as plugs or bareroot and fertilized with TSP, while the least P leached from cuttings transplanted as plugs and fertilized with CRF or CRF/TSP. Plants fertilized with CRF/TSP generally had larger root dry weights than did plants fertilized with CRF or TSP. Plants fertilized with CRF had the smallest stem dry weights. Shoot-to-root (S/R) ratio was largest in plants transplanted as plugs in substrate amended with TSP, but cuttings transplanted bareroot into CRF-amended substrate had the highest S/R ratio and the lowest stem P concentration. Incorporation of CRF/TSP into the container substrate can reduce P leaching compared with incorporation of TSP, and can increase root and stem dry weights of plants transplanted as plugs compared with incorporation of CRF.
25 to 400 acres. All growers used BMPs. Gross sales of participating operations were $5 million to $10 million. The most widely used BMPs were IPM, CRFs, and water recapture, including practices such as using ponds to recapture water ( Table 2 ). One
Poinsettia (Euphorbia pulcherrima `Gutbier V-14 Glory') were grown using commercially available poinsettia fertilizer of various combinations of controlled-release (CRF) and constant liquid fertilizer (LF). At the end of the production period, plants treated with 83, 165 or 250 mg/l LF only were 10% taller than plants treated with the same concentrations of CRF. The total number of cyathia and the number of open cyathia at harvest was 18% and 50% higher for plants treated with LF only compared to plants treated with CRF only. Plants treated with 165 CRF/ 83 LF or 83 CRF/250 LF were not different compared to 250 CRF/0 LF or 0 CRF/ 250 LF in height, number of cyathia at anthesis, and total number of cyathia at the end of the production period. When LF was changed to clear water 5 weeks before the end of production, nitrate runoff from 83 CRF/250 LF treatment was reduced 30% for the last two weeks, and from the 165 CRF/83 LF treatment nitrate leachate was reduced gradually from 33 to 66% over the 5-week period.
Poinsettias (Euphorbia pulcherrima 'Gutbier V-14 Glory'), chrysanthemums (Dendranthema grandiflora 'Tara') and geraniums (Pelargonium xhortorum 'Orbit') were grown using various ratios of controlled release:constant liquid fertilization as a percentage of recommended rates (%CRF:%CLF). While plants grown under the 100:0 CRF:CLF regime produced significantly less nitrates, phosphates and total soluble salts in the leachate than 0:100 or 50:50 CRF:CLF, quality rating, plant diameter, and leaf, bract and flower dry weight of poinsettias and chrysanthemums were reduced. Geraniums grown under 100:0, 50:50 or 0:100 CRF:CLF regimes were similar in quality rating, height, diameter, dry weights and days to anthesis. Poinsettias and chrysanthemums grown under 50:50 CRF:CLF were similar in height, days to anthesis, plant diameter, flower and stem dry weights and quality rating but produced less nitrates, phosphates and total soluble salts in the leachate than plants grown under 0:100 CRF:CLF. However, chrysanthemums grown under 50:50 CRF:CLF had lower leaf and root dry weights and poinsettias had lower leaf and bract dry weights than under 0:100 CRF:CLF regime.
Controlled-Released Fertilizer (CRF) has a great potential for applications in the nursery container industry. However, the specific mechanisms of the control are proprietary. The longevity claimed by manufacturers are unclear. The longevity of one CRF is claimed to be 2 to 3 months at 80 °F, resulting in a deviation of 30%. Thus, the actual release rate will have a 30% deviation from the claimed longevity. A preliminary study was conducted to test the longevity of two types of RCFs. 1.00 g (7.7% NO- 3-N, fast release) and 1.30 g (5.9% NO- 3-N slow release) of CRF was added to 500 ml distilled water in separate flasks and stirred continuously at a low speed during measurement period. A nitrate electrode and a reference electrode were set in the solution. The nitrate electrode responded to the increase in nitrate concentration caused by nitrate release from he CRFs. The response analog signal from the nitrate sensor was input to a 16-bit analog/digital converter with 1-minute interval for each measurement. The results indicated that 9% of the nitrate from the fast CRF (2- to 3-month longevity) was released in 10 hours. About 11.5% of the nitrate from the slow CRF (8- to 9-month longevity) was released in 260 hours. Based on the observed release rates, a 2- to 3-month longevity CRF will last about 111 hours in the stirred distilled water at room temperature. A CRF with 8 to 9 month longevity will last about 94.2 days. Even though field conditions are different from the experimental conditions, the real longevity of CRF in the fields may have to be further investigated. In the tropical southern Florida climate, the release rates of nutrients from CRFs are likely to be enhanced.
Information on fertility optimization for container-grown ornamental grasses is limited. For ornamental grasses, growers are concerned with the degree of flowering, number of tillers, and height and width of the plants as well as other growth or ornamental components. Pennisetum alopecuroides divisions potted into 8.5-L containers were grown outdoors in a container nursery from May through September. The potting medium used was a 3 aged pine bark: 2 peatmoss: 1 sand nursery mix (by volume), amended with dolomitic lime 3 kg/yard3. Sierra 17-6-10 plus minors, 8 to 9 month controlled-release fertilizer (CRF) was top dressed at 20, 30, 40, 50, or 60 g/container. Foliage height increased linearly with increasing CRF rate. Flower height increased to a maximum at 40 g of CRF per container and then decreased with higher levels of CRF. Basal plant width exhibited a quadratic response to CRF rate, reaching a maximum at 40 g of CRF per container. The greatest number of flowers and tillers were obtained using 50 g of CRF per container. Maximizing the number of flowers is important for marketing of Pennisetum, since this plant is grown primarily for its flowering.
Best management practices (BMPs) for vegetable crops are under development nationwide and in Florida. One goal of the Florida BMP program is to minimize the possible movement of nitrate-nitrogen from potato (Solanum tuberosum) production to surface water in the St. Johns River watershed without negatively impacting potato yields or quality. Current fertilizer BMPs developed for the area focus on fertilizer rate. Controlled-release fertilizers (CRF) have long been a part of nutrient management in greenhouse and nursery crops. However, CRFs have been seldom used in field-vegetable production because of their cost and release characteristics. Nutrient release curves for CRFs are not available for the soil moisture and temperature conditions prevailing in the seepage-irrigated soils of northern Florida. Controlled-leaching studies (pot-in-pot) in 2000 and 2001 have shown that plant-available nitrogen (N) was significantly higher early in the season from ammonium nitrate, calcium nitrate and urea compared to selected CRFs. However, N release from off-the-shelf and experimental CRFs was too slow, resulting in N recoveries ranging from 13% to 51%. Cost increase due to the use of CRFs for potato production ranged from $71.66 to $158.14/ha ($29 to $64 per acre) based on cost of material and N application rate. This higher cost may be offset by reduced application cost and cost-share pro-grams. Adoption of CRF programs by the potato (and vegetable) industry in Florida will depend on the accuracy and predictability of N release, state agencies' commitment to cost-share programs, and CRFs manufacturers' marketing strategies. All interested parties would benefit in the development of BMPs for CRFs.
Controlled-release fertilizers (CRF), Nutricote 14N–6.2P-11.6K or Osmocote 14N-6.2P-11.6K, at the recommended rate (1×) and at half that rate (0.5×) plus 200 mg/l N of Peter's 20N-4.4P-16.6K water soluble fertilizer at every irrigation were applied to potted chrysanthemums cv. `Bright Golden Anne' and `Torch'. Production and postproduction quality was evaluated. CRF applications (1×) resulted in reductions of plant height (-10%), plant diameter (-17%), leaf area (-35%), and leaf dry weight (-47%), but did not affect number of flowers compared to plants receiving only water soluble fertilizer. Application of water soluble fertilizer with CRF (0.5×) increased foliar nutrient levels above water soluble fertilizer application alone, or above either CRF (1×). CRF applications (1×) resulted in improved floral longevity (up to +8 days) and flower color rating (up to +54%), and less foliar senescence (up to -45%) than the water soluble fertilizer application alone, or either of the CRFS (0.5×) used with water soluble fertilizer.
Recycled subirrigation systems are a possible solution to grower concerns over water use, ground water pollution, and regulations concerning these. The objectives of this experiment were to examine the differences between top- and subirrigated plants, with different fertilizer regimes and with mulches.
Six treatments of `Crimson Fire' and `Victoria' CVI geraniums were grown in 11 cm. pots. Treatments were: top irrigation, 100% N supplied with 20-10-20 soluble fertilizer; subirrigation, 100% N supplied with 20-10-20 soluble fertilizer; subirrigation, N supplied in equal portions of 20-10-20 soluble fertilizer and CRF, gel mulch; subirrigation, N supplied with CRF, gel mulch; subirrigation, N supplied in equal portions of 20-10-20 soluble fertilizer and CRF, wool mulch; subirrigation, all N supplied with CRF, wool mulch.
`Crimson Fire': fresh weight was not significantly different between top- and subirrigation; fresh weight at the same fertilizer level was not significantly different with either a gel or a rockwool mulch; all CRF resulted in the lowest fresh weights. `Victoria': top irrigated fresh weight was significantly higher compared to subirrigated. Gel mulched plants resulted in significantly lower fresh weights than wool mulched plants. All CRF resulted in the lowest fresh weights.