Potato production in the Tri-County Agricultural Area of northeast Florida accounts for nearly half of the state's $120 M, 18-K hectare annual crop. Concern over nitrate movement into watersheds from potato production have stimulated research into alternative fertilizer sources and practices. This study evaluated the potential of several controlled-release fertilizer (CRF) products to release nutrients over a 100-day growing season under field temperature and precipitation conditions. In 2003 and 2004, 6 and 3 CRF products were evaluated, respectively. Meshbags containing 3 g of product mixed with 200 g of soil were buried 15 cm below the top of the potato row. Meshbags were removed at 2-week intervals. Samples were dried and sieved to remove soil. Fertilizer prills were ground and mixed with DI water to dissolve residual fertilizer. Samples were analyzed for total N by the Dumas (combustion) method (2003) or for TKN (2004). In 2003, initial release (after 20 days) ranged from 23% to 85% for the six products. In 2004, initial release (after 9 days) ranged from 34% to 65% for the three products. In 2003, total N release from CRF prills after 104 days ranged from 72% to 99%. In 2004, total N release from samples ranged from 79% to 92% release after 91 days. The shape of the release curve described some release patterns comparable to water-soluble fertilizers while others exhibited sustained-release properties. If release characteristics are designed to match potato plant uptake requirements in time and quantity, CRF products may be used to reduce off-site N movement while maintaining potato production.
Abstract
A 2 × 4 × 4 factorial experiment was conducted to test the effect of combinations of soluble fertilizer (20N–8.8P–16.6K) and controlled-release fertilizer (14N–6.2P–11.6K, Osmocote) on flowering, growth, and quality of Hibiscus rosa-sinensis L. grown under two light levels, 840 μmol·s-1·m-2 (full sun) and 420 μmol·s-1·m-2 (50% shade). Plants grown in full sun flowered earlier and had a larger number of buds and flowers than those in partial shade; how ever, flower diameter was greater with 50% shade. Plants grown in 50% shade were larger and had a darker green color and higher plant quality than those grown in full sun. Light level determined the effect of soluble fertilizer on number of buds, flowers, plant size, leaf area, fresh weight, foliar color, and plant quality. The effect of controlled-release fertilizer (CRF) on flower diameter, leaf area, and foliar color was influenced by light level. Soluble fertilizer and CRF interacted on total buds, flowers, plant size, foliar color, and plant quality. The optimum conditions for growth of high-quality hibiscus plants was found to be 50% shade and a fertilizer combination of 200 ppm N/12 g CRF per 18-cm pot.
Seven nursery grade (8- to 9-month duration), polymer-coated, controlled-release fertilizers (CRF) were topdressed or incorporated to a peat: sand: vermiculite medium to yield the same amount of N per container. The pots were uniformly irrigated with DI water every week. Leachates were collected and analyzed for N (ammonium plus nitrate) concentration. Two distinct N release (NR) patterns were observed over the 180-day experiment. Osmocote 18–6–12FS, Prokote-P 20–3–10, Osmocote 24–4–8HN, and Polyon 25–4–12 exhibited a NR pattern that closely followed changes in average daily ambient temperatures (AT) over the season. This relationship was curvilinear in nature, with NR being highly responsive to AT up to 25°C. Conversely, Osmocote 18–6–12, Nutricote 18–6–8 (270), and Woodace 20–4–12 showed a stable NR pattern over a wider range of AT, with NR rates 30% to 60% lower than those in the temperature-responsive CRF. Incorporation produced significantly higher cumulative N releases than topdressing but without effect on the actual pattern of NR over the season. Regardless of the N formulation in the CRF, >80% of the N recovered in the leachates was in the nitrate form.
Four experiments were conducted over 2 years focusing on water and fertilizer delivery methods with emphasis on minimal resource use. Poinsettia `Freedom', `Celebrate 2'. `Peppermint Pink', `Angelika White', `Lilo' and `Angelika Marble' and geranium `Kim', `Aurora', Ritz', and `Melody' cuttings were grown in 6 inch pots with peat-lite mix and were harvested at marketable size. Nitrogen efficiency was compared by replicating each irrigation treatment with soluble fertilizer (SF) and controlled release fertilizer (CRF). Crops grown with SF were started at 225ppm N for several weeks, then finished at 125ppm N after monitored EC had dropped below 1000μS. CRF treatments were potted up with 1.6 total grams of N available to the plant and irrigated throughout production with tap water. Irrigation treatments included: drip tube leaching, drip tube, ebb & flow, trough. trough lined with capillary mat, trough lined with plastic-covered capillary mat, flats of capillary mat, flats with plastic-covered capillary mat. Daily irrigation volumes were recorded. Weekly data collection included EC, pH, nitrate nitrogen. and ammonium nitrogen. Harvest data included plant dry weight, and total nutrient analyses of plants and substrate. Water efficiency was significantly improved in recirculating systems and with capillary mat systems. No significance was noticed in dry weight or final nutrient analyses across treatments. Significance existed in water quality throughout crop production.
Previous studies have shown that plants grown exclusively with controlled-release fertilizers (CRF) at recommended rates dramatically reduced N and P runoff but did not provide sufficient nutrients for optimum plant growth. `Gutbier V-14 Glory' poinsettias were grown in 15-cm pots ammended with CRF and drenched with 300 mg liter-3 NH4NO3 at: 1 week; 2 weeks; 1 and 3 weeks; 1, 3, and 7 weeks; 1, 3, 7, and 11 weeks after potting. Half the plants were grown with saucers underneath the pot to allow plants to reabsorb all leachate (no-leach). Control plants remained undrenched. For plants without saucers, all drenching treatments increased bract dry weights when compared to undrenched plants. Leaf dry weight increased with all drenching treatments except for 2nd week only treatment. Plants grown without saucers had greater leaf, stem and root dry weights, but similar bract and flower dry weights when compared to plants grown with saucers. Regardless of the use of saucers, nitrogen concentration in the leaf tissue tended to increase with greater number of NH4NO3 drenches and visual ratings were similar.
Dendranthema grandiflora Tzvelev., `Spirit' and `Torch' were produced under three water-soluble fertilizer (WSF) and one controlled-release fertilizer (CRF) regimes, with or without weekly CaCl2 sprays during the last three weeks of production to evaluate their influence on postproduction foliar longevity. Foliage of plants produced with 400 mg·liter–1 N (Peter's 20N-4.4P-16.6K) declined 1 to 2 weeks earlier than those produced with 400 mg·liter–1 N (Hydrosol + NH4 NO3), and 3.5 to 5 weeks before plants fertilized with 100 mg·liter–1 N (Hydro-sol + urea + NH4 N03) or 1 kg N·meter–3 growing medium (Osmocote 14N–6.2P–11.6K). Calcium chloride had no influence on foliar longevity. Plants receiving either 400 mg·liter–1 N treatment were generally larger (plant height and diameter), fuller (total and average leaf area), more vigorous (leaf dry weight per unit leaf area), and darker green in color (`Spirit' only, chlorophyll content per unit leaf area). Plant receiving WSF treatments had less than 0.5x the root system (dry weight) of CRF plants at harvest. Postproduction foliar longevity was most significantly and consistently correlated with foliar and growing medium nitrogen content. Relationship of postproduction foliar longevity with leaf soluble protein, carbohydrate, and starch content will be presented.
Government of Galicia (Spain). Jorge J. Magallanes thanks two grants from the University of Santiago de Compostela (Spain) and the University San Luis Gonzaga (Peru). We are grateful to James R. Myers and Pedro Revilla for reviewing the manuscript and to CRF
fellowships from the Galician Government and the University of Santiago de Compostela to Ana B. Monteagudo. We are also grateful to the CRF-INIA (Alcalá de Henares, Spain) for supplying seeds of some common bean accessions, the University of Idaho and Seminis
Wet Earth (WE) is a recycled paper product being tested as a potential plant growth substrate. It is composed of 80% recycled paper, 18% diatomaceous earth, 1% CaO, and 1% humic acid by volume. Use of WE by commercial growers would reduce demand for both landfill space and for slowly renewable resources such as peat and pine bark. Evidence also suggests that WE reduces nitrate runoff. Objectives included: determining effects of WE on plant growth, examining effects of WE on NO3 and NH4 runoff from container plant production, and determining the chemical and physical properties that characterize WE as a growth substrate. Ratios of pine bark to WE tested were 100% pine bark, 1:3, 1:1, 3:1, and 100% WE by volume. Fertilizer treatments included: 100% of the recommended rate of controlled release fertilizer (CRF), 50% CRF plus 50% liquid fertilizer (LF) and 100% LF. Plant heights, widths, and visual quality ratings were obtained monthly throughout the 16-week experiment. Leaf, shoot and root dry weights were determined at harvest. Nitrogen content of roots, shoots, and substrates were determined at planting and harvest, while NO3 and NH4 content of leachate was determined at each irrigation. All substrates were analyzed at planting and harvest for pH, soluble salts, exchangeable cations, and CEC. Changes in volume, bulk density, porosity, and air space were also measured. Plant size and quality varied significantly between substrate mixes. Mortality was significantly higher in mixes containing 75% and 100% WE. Changes in volume, bulk density, and percent air space were also significant and inversely related to WE concentration.
plants fertilized with wastewater-grown algal materials with those traits of plants fertilized with two commercially available fertilizers, a synthetic controlled-release fertilizer (CRF) and a bio-based wastewater treatment coproduct that supplied N in