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Raul I. Cabrera, Richard Y. Evans, and J. L. Paul

Nitrogen leaching losses of 21, 40 and 49% were measured from container-grown `Royalty' roses irrigated for one year with nutrient solutions containing 77, 154 and 231 mg N/l. There were no significant differences in number of flowers per plant or dry matter per plant. The N present in the harvested flowers accounted for 43, 27 and 17% of the N applied for the 77, 154 and 231 mg N/l treatments, respectively.

Plants receiving 154 mg N/l at leaching fractions of 0.1, 0.25 and 0.5 had corresponding N leaching losses of 22, 38 and 56%. In this experiment, however, the 0.5 leaching fraction produced yields significantly higher than those of the 0.1 and 0.25 treatments. The N recovered in the harvested flowers accounted for 28, 25 and 19% of that applied to the 0.1, 0.25 and 0.5 treatments, respectively.

The results of these studies suggest that modifications in current irrigation and fertilization practices of greenhouse roses would result in a considerable reduction of N leaching losses and enhance N fertilizer use efficiency, without loss of cut flower yield and quality.

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Sueyde Fernandes de Oliveira Braghin, Simone C. Mello, Jéssika Angelotti-Mendonça, Keigo Minami, and Yuncong C. Li

Fertilizer management is an essential step in the production process, as it allows the plant to use its productive capacity to the fullest extent possible. Researchers have tested maximum nutrient use with reduced losses to the environment aiming to increase productivity with fewer environmental impacts. This study compared the effects of controlled-release fertilizers (CRFs) with water-soluble fertilizer (WSF) and clear water (control) on the growth and nutrient uptake of croton (Codiaeum variegatum L.) and nitrogen leaching. The experiment was conducted with three replications and six treatments: two rates (1.5 g and 3.0 g per liter of substrate) of two CRFs [Osmocote Plus (15% N, 3.93% P, and 9.96% K) and Basacote (15% N, 3.49% P, and 9.96% K)], WSF, and clean water as control. All CRFs were applied before planting and WSF was supplied as nutrient solution through automated moisture sensor activated irrigation system. Plant growth (number of leaves, leaf area, stem height, root volume, and shoot and root dry weights) and total nutrient contents in the leaf tissue were evaluated every 30 days. Electrical conductivity (EC), pH, nitrate, ammonium, and total nitrogen contents were measured in the leached solution. Indeed, results showed that CRFs at a low rate provided similar development and quality of croton plants compared with WSF. Plant growth indicators were similar until 90 days after transplanting (DAT). After that, at 150 DAT, the highest values to number of leaves and leaf area occurred with WSF and with the lowest CRF rate as compared with the other treatments and control. The highest root volume was found with the WSF, which resulted in larger roots compared with the other treatments. These results showed WSF can be replaced by CRFs at low rates on croton growth. Moreover, according to the visual scale, the best treatments were WSF and Basacote at the low rate, where plants were bright, with multicolored leaves with prominent orange shades. However, CRFs maintained pH and EC within the recommended range for the growth of croton and reduced the nitrogen leaching from the pots.

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Emmanuel Genio, Tom Garrett, Greg Hoyt, Gary Wells, Larry Bauer, Dean Batal, Doug Sanders, and Contact G. Wells

The cost-effectiveness of using winter cover crops to reduce nitrogen leaching was estimated. Costs were based on cucumber and sweetpotato grown in rotation, three fertilizer application levels (0, 60, and 120 kg N/ha), and three winter covers (weeds/bare, wheat, and clover). Soil N was measured in 15-cm intervals to a depth of 90 cm at the 1993 harvest and 1994 planting. The cover crop biomass was also analyzed. Nitrogen trapping by wheat and clover was compared to bare ground with adjustment for N fixing by clover. Four scenarios—sweetpotato/both covers/high N and cucumber/wheat cover/low and medium N—yielded increased leaching compared to their bare ground counterparts. Leaching prevented from the other scenarios ranged from 1.07 to 20.11 kg·ha–1. Costs, yields, and vegetable prices were used to calculate profit changes from the bare ground method on a dollar/kg basis. Profit changes ranged from negative $2372.74/kg for cucumber/wheat cover/high fertilizer to the only positive change of $16.53 for sweetpotato/clover/medium fertilizer. Negative costs resulted from yield increases when nonwinter weed covers were used.

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Amy L. Shober, Andrew K. Koeser, Drew C. McLean, Gitta Hasing, and Kimberly K. Moore

. R package version 1.1-6 Erickson, J.E. Cisar, J.L. Snyder, G.H. Park, D.M. Williams, K.E. 2008 Does a mixed-species landscape reduce inorganic-nitrogen leaching compared to a conventional St. Augustinegrass lawn? Crop Sci. 48 1586 1594 Fisher, P

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Edward F. Gilman, Thomas H. Yeager, and Diane Weigle

Columns (4 × 15 cm) of incubated (25C, 7% volumetric moisture) milled cypress [Taxodium distichum (L.) L. Rich] wood chips received 180 mg of each ionic form of N applied to the surface from dry NH4NO3, KNO3, or (NH4)2SO4 and were leached daily with 16 ml deionized water (pH 5.5). After 10 days, >85% of applied N leached from the columns in all treatments. After 25 days, all N leached from the NH4NO3 and KNO3 treatments, and 93% leached from the (NH4)2SO4 treatment. In subsequent experiments, columns received 360 mg N from NH4NO3 and were leached daily with either 16, 32, 48, or 64 ml of deionized water for 50 days. The rate of N leaching increased with increasing water application rate, although total N leached per column was similar for all water rates after 25 days. Columns that received 45, 90, 180, or 360 mg N/column were leached daily with 16 ml of deionized water. Nitrogen concentrations in the leachate ranged from 3406 ppm \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\mathrm{-}\mathrm{N}\) \end{document} and 2965 ppm \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{4}^{+}\mathrm{-}\mathrm{N}\) \end{document} at day 5 for the 360-mg rate to 3 and 5 ppm, respectively, at day 35 for the 45-mg rate. In all experiments with NH4NO3, more \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\mathrm{-}\mathrm{N}\) \end{document} leached than \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{4}^{+}\mathrm{-}\mathrm{N}\) \end{document} and more \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\mathrm{-}\mathrm{N}\) \end{document} leached than applied, indicating vitrification occurred. \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{4}^{+}\mathrm{-}\mathrm{N}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\mathrm{-}\mathrm{N}\) \end{document} broadcast over cypress wood chips in the landscape would leach quickly into the soil.

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Thomas Yeager, Ed Gilman, Diane Weigle, and Claudia Larsen

Columns (4 × 15 cm) of a pine bark medium amended with the equivalent of 4.2 kg per cubic meter of dolomitic limestone and either 0, 2.4, 4.7, 7.1 or 9.5 mg of urea-formaldehyde (38% N) per cubic centimeter of medium were leached daily with 16 ml of deionized water (pH 5.5). Leachate total N, NO3 --N and NH4 +-N concentrations were determined on day 1, 3, 5, 7, 14, 28, 49, 91, 133, 203, 273 and 343. Leachate total N ranged from 600 ppm on day 1 for the 9.5 mg treatment to 4 ppm on day 273 for the 2.4 mg treatment. Leachate NH4 +-N concentrations ranged from 38 ppm c4 day 3 for the 9.5 mg treatment to less than 1 ppm on day 7 for the 2.4 mg treatment and were less than total N concentrations at each sampling time. Leachate NO3 --N was not detectable during the experimental period. Eleven, 16, 20 and 25% of the applied N leached from the columns amended with 2.4, 4.7, 7.1 or 9.5 mg of urea-formaldehyde per cubic centimeter of pine bark, respectively, during the 371 day experiment.

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Robert H. Stamps

Established leatherleaf fern was grown for one year in a glasshouse in intact soil columns (Astatula fine sand, 21 × 61 cm) contained in drainage lysimeters. Columns were fertilized at rates of 224, 448, or 672 kg N ha-1 yr-1 using controlled-release (CR) fertilizer, either 360-day (360CR) or 180-day (180CR) term, or weekly applications of liquid (L) fertilizer. Water use, yield (number of harvestable fronds) and average frond weight increased linearly with increasing fertilization rate and more fronds were produced using L than CR fertilizers. Frond color measurements paralleled yield results. During cool weather when vase life is greatest, fronds from L fertilizer lysimeters lasted longer than fronds from CR treated plots. During warmer weather, treatments had no effect on vase life. Nitrate nitrogen (NO3-N) leaching increased with fertilization rate and exceeded 10 ppm in leachate from the L and 180CR treatments at all application rates. NO3-N in leachate from 360CR lysimeters never exceeded 8 ppm at any application rate.

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Kathryn S. Hahne and Ursula K. Schuch

Velvet mesquite [Prosopis velutina Woot., Syn.: P. juliflora (Swartz) DC. var. velutina (Woot.) Sarg.] has become more popular in arid landscapes of the southwestern U.S., but little information on N requirements during the seedling stage is available. In addition to optimize growth of seedlings, minimizing N in runoff during production is an important consideration. Experiments were conducted to determine how biomass production and N leaching were affected first by different ratios of ammonium and nitrate N in sand culture and second by different N concentrations when seedlings were grown in two substrates. Mesquite seedlings produced the greatest biomass after 120 days when fertigated with a solution of 33 NO3 : 67 NH4 +. Loss of N through leachate was 40% greater when NH + 4 comprised two thirds or more compared to one third or none in the fertigation solution. Nitrogen in leachate was highest after 16 weeks of treatment, coinciding with the reduced growth rate of seedlings. The second experiment utilized either sand or commercial growing media and a fertigation solution of 33 NO3 : 67 NH4 +. Fertigation with 200 mg·L–1 N after 60 days in either substrate produced greatest biomass, while rates of 25, 50, or 100 mg·L–1 N produced about half of that biomass. With few exceptions, less N in either form was found in leachate when seedlings were grown in media and were fertigated with the two higher N rates compared to seedlings grown in sand at the two higher N rates. Plant morphology, biomass accumulation, photosynthate allocation, and the fate of N in the growing substrate and in leachate were strongly affected by the choice of growing substrate.

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J.E. Ells, A.E. McSay, P.N. Soltanpour, F.C. Schweissing, M.E. Bartolo, and E.G. Kruse

Water and nitrogen (N) are major inputs in the production of onions in the Arkansas Valley of Colorado. Because nitrates move with irrigation water, the effect of different rates of application of both N fertilizer and water on nitrate leaching were studied simultaneously. After a 2-year field study (1990-1991), it was concluded that >50 t·ha-1 of onions could be obtained without any N fertilizer when >42 ppm of nitrate nitrogen (NO3-N) were initially present in the top 33 cm of soil and up to 112 cm of irrigation water was applied. Total onion yield was not improved by applying more than the calculated irrigation requirement. The 2-m profile of soil under these experiments was found to contain >1400 kg·ha-1 of residual NO3-N prior to fertilizer treatments. When twice the estimated irrigation requirement was applied, >1000 kg·ha-1 of NO3-N was unaccounted for and presumed to have been mostly leached below the 2-m profile and partly denitrified. In both years, the onions were planted on land that had been fallowed the previous season, which does not help explain the presence of the high levels of nitrates found in the soil profile. It was concluded that sound water and N management practices in onion fields are crucial for preservation of water quality.

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Raul I. Cabrera

Seven nursery grade (8-9 month duration), polymer-coated, controlled-release fertilizers (CRF) were topdressed or incorporated into a 2 peat: 1 vermiculite: 1 sand (by volume) medium to yield the same amount of N per container. The pots (0.5 L) were uniformly irrigated with DI water every week to produce a target leaching fraction of 25%. Leachate N contents (ammonium plus nitrate), employed as indicators of N release, allowed for comparison of CRF performance as a function of temperature changes over a season. Two distinct N leaching (i.e., release) patterns were observed over the 180-day experimental period. The fertilizers Osmocote 18-6-12FS (Fast Start: OSM-FS), Prokote Plus 20-3-10 (PROK), Osmocote 24-4-8HN (High N: OSM-HN) and Polyon 25-4-12 (POLY) exhibited a N leaching pattern that closely followed changes in average daily ambient temperatures (Tavg) over the season. This relationship was curvilinear, with N leaching rates per pot (NLR) being highly responsive to Tavg changes between 20 and 25 °C. Temperatures above 25 °C produced an average maximum NLR of 1.27 mg·d-1 for these fertilizers. OSM-FS, PROK, and OSM-HN had the highest cumulative N losses over the experimental period. In contrast, the CRF group formed by Nutricote 18-6-8 (270: NUTR), Woodace 20-4-12 (WDC), and Osmocote 18-6-12 (OSM) showed a more stable N leaching pattern over a wider range of temperatures, with rates about 30% to 40% lower than those in the temperature-responsive CRF, and averaging a maximum NLR of 0.79 mg·d-1 for Tavg >25 °C. NUTR and WDC had the lowest cumulative N losses over the season. Soluble salt readings paralleled N leaching for each CRF, indicating similar leaching patterns for other nutrients. Incorporation produced significantly higher cumulative N losses than topdressing, but without effect on the actual N leaching pattern over the season. Regardless of the N formulation in the CRF, over 85% of the N recovered in the leachates was in the nitrate form.