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Amaya Atucha, Ian A. Merwin, Chandra K. Purohit, and Michael G. Brown

, recycling pools, and outputs from the crop-soil system are quantified, the retention or transfers of nutrients from one system component to another can be budgeted on a year-round basis ( Haynes, 1988 ; Palmer and Dryden, 2006 ). Nutrient budgeting is a

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John D. Lea-Cox, James P. Syvertsen, and Donald A. Graetz

15Nitrogen uptake, allocation, and leaching losses from soil were quantified during spring, for 4-year-old bearing `Redblush' grapefruit (Citrus × paradisi Macf.) trees on rootstocks that impart contrasting growth rates. Nine trees on either the fast-growing `Volkamer' lemon (VL) (C. volkameriana Ten & Pasq.) or nine on the slower-growing sour orange (SO) (C. aurantium L.) rootstocks were established in drainage lysimeters filled with Candler fine sand and fertilized with 30 split applications of N, totaling 76, 140, or 336 g·year-1 per tree. A single application of double-labeled ammonium nitrate (15NH 15 4NO3, 20% enriched) was applied at each rate to replicate trees, in late April. Leaves, fibrous roots, soil, and leachates were intensively sampled from each treatment over the next 29 days, to determine the fate of the 15NH 15 4NO3 application. Newly developing spring leaves and fruit formed dominant competitive sinks for 15N, accounting for between 40% and 70% of the total 15N taken up by the various treatments. Large fruit loads intercepted up to 20% of this 15N, at the expense of spring flush development, to the detriment of overall tree N status in low-N trees. Nitrogen supply at less than the currently recommended yearly rate of 380 g/tree exceeded the requirements of 4-year-old grapefruit trees on SO rootstock; however, larger trees on VL rootstock took up the majority of 15N from this rate over the 29-day period. Nitrogen-use efficiency declined with increasing N rate, irrespective of rootstock. The residual amounts of 15N remaining in the soil profile under SO trees after this time represented a significant N leaching potential from these sandy soils. Therefore, under these conditions, present N recommendations appear adequate for rootstocks that impart relatively fast growth rates to Citrus trees, but seem excessive for trees on slower-growing rootstock species.

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James S. Owen Jr, Stuart L. Warren, Ted E. Bilderback, and Joseph P. Albano

. A P nutrient budget was developed for each treatment ( Eq. [5] ). which included P absorbed by plant, loss in effluent, remaining in the substrate, or remaining in the fertilizer prill. The nutrient budget was used to calculate P uptake

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Hector Valenzuela, Roger Corrales, and Ted Goo

A major issue in the preparation of nutrient budgets for organic farmers is the residual nutrient effect from organic amendments available for follow-up crops in year-round rotation systems. A series of separate experiments were conducted to evaluate: 1) the residual nutrient effects on double-cropped sweet corn from initial applications of several organic amendments locally available in Oahu, Hawaii; 2) the residual effect of double cropped zucchini; and 3) mustard cabbage from the application of similar organic amendments. The sweet corn experiment consisted of six treatments, with organic amendments applied only prior to the first planting. The second follow-up sweet corn planting was grown without additional amendment applications. Treatments included: 1) a fruit fly based compost; 2) aged chicken manure; 3) bone meal; 4) synthetic fertilizer (farmer's practice); 5) a combination of compost and fertilizer; and 6) a combination of compost and chicken manure. The experiment was arranged with a randomized complete-block design. Each treatment plot consisted of two 20-m long rows of corn with five replications per plot for a total of 30 treatment plots. On a separate location similar trials were conducted on long-term organic farming plots, with double cropped zucchini and with double cropped mustard cabbage. The results from this research shows that crop yields were similar or greater under the organic amendment plots compared to the synthetic fertilizer plots. In crops with a high N uptake demand, yields from the organic amendment plots declined by about 10% in follow-up plantings. This data will allow organic farmers to prepare nutrient budgets to better match their organic fertilizer applications with crop nutrient demands.

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Brian A. Birrenkott, Joseph L. Craig, and George R. McVey

A leach collection unit (LCU) was assembled to capture all leachate draining from a nursery container. An injection molded 2.8-L nursery container was plastic welded into the lid of a 7.6-L black plastic collection bucket so that the bottom 2.5 cm of the nursery container protruded through the lid. The LCU was designed to track total N release from CRFs without confounding effects of plant uptake or N immobilization. Total N released between any two sampling periods is determined by multiplying the N concentration in a leachate subsample × total leachate volume. The LCU were placed in a container nursery area with overhead irrigation. LCU were thoroughly leached before sampling the leach solution. To study the effects of substrate on N leach rates, Osmocote 18.0N–2.6P–9.9K (8 to 9 months 21 °C) was incorporated at 1.8 kg N/m3 using a locally available, bark-based substrate or medium-grade quartz sand. The experiment was conducted at Scotts Research locations in Apopka, Fla., and Marysville, Ohio. Osmocote incorporated into either a bark-based substrate or sand resulted in similar N release profiles. Although substrate did not affect N leach rate, quartz sand was recommended as the substrate in the leach collection system for polymer-coated CRFs. Quartz sand is chemically and biologically inert, does not immobilize nutrients and has low ion exchange capacity compared to bark-based potting substrates. More than 90% of the total nitrogen applied from Osmocote was recovered from leachate and unreleased N in fertilizer granules. This research has demonstrated the leach collection system as a reliable means to quantify nitrogen release rate of a polymer-coated CRF under nursery conditions. The LCU, when used with a crop plant, allows nutrient budget and nutrient uptake efficiency to be determined for CRFs.

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Elsa S. Sánchez and Heather D. Karsten

immobilization of N were cited as possible reasons for deficiency ( Clark et al., 1999 ; Liebhardt et al., 1989 ; Pimentel et al., 2005 ). In addition, recent soil tests from organic farms and nutrient budget analysis indicated that organic nutrient amendments

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Michelle S. McGinnis, Stuart L. Warren, and Ted E. Bilderback

nutrient contents, nutrient budgets, and nutrient use efficiencies (nitrogen and phosphorus). A nutrient budget was developed for each treatment to quantify the water-soluble fate of N and P added as CRF and VC. Recovered nutrient (RN) for N (RN N ) and P

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Robert L. Mikkelsen

extracted the reserves of K and P that were built up during the previous years when the farms were operated with conventional management ( Gosling and Shepherd, 2005 ). Although some excellent nutrient budgets have been developed for European organic farms

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Carolyn DeMoranville

system ( Howes and Teal, 1995 ), the annual nutrient budget showed a calculated N discharge of 22 kg·ha −1 per year and a P discharge of 9.9 kg·ha −1 per year. Spurred by increasing environmental pressure regarding the protection of surface water

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Andrew G. Ristvey, John D. Lea-Cox, and David S. Ross

ornamental studies have provided total nutrient budgets for plant uptake and loss. Also, few studies have related N and P availability (from fertilization) to nutrient uptake and nutrient uptake efficiency by ornamental species. Little is also known about how