From March through June 1996, 15N-labeled fertilizer was applied to mature pecan trees [Carya illinoinensis (Wangehn.) K. Koch] in a commercial orchard to determine the fate of fertilizer-N in the tree and in the soil directly surrounding the tree. The concentrations of 15N and total N were determined within various tissue components and within the soil profile to a depth of 270 cm. By Nov. 1996, elevated levels of 15N were greatest at depths just above the water table (280 cm), suggesting a substantial loss of fertilizer-N to leaching. Recoveries of 15N from tissue and soil at the end of 1996 were 19.5% and 35.4%, respectively. Harvest removed 4.0% of the fertilizer-N applied, while 6.5% was recycled with leaf and shuck drop. In 1997, with no additional application of labeled fertilizer, the tissue components continued to exhibit 15N enrichment. By the end of the 1997 growing season, 15N levels decreased throughout the soil profile, with the most pronounced reduction at depths immediately above the water table. Estimated recoveries of 15N from pecan tissue (excluding root) and soil at the end of 1997 were 8.4% and 12.5%, respectively. In 1996 and 1997, 15N determinations indicated an accumulation of fertilizer-N in the tissues and a loss of fertilizer-N to the groundwater. Early spring growth, flowering, and embryo development used fertilizer-N applied the previous year, as well as that applied during the current year.
Rebecca A. Kraimer, William C. Lindemann, and Esteban A. Herrera
Rebecca A. Kraimer, William C. Lindemann, and Esteban A. Herrera
The recovery of late-season (September) 15N-labeled fertilizer (N at 55 kg·ha-1) was followed in mature pecan trees [Carya illinoinensis (Wangehn.) K. Koch] and soil (0-270 cm) from 1996 (application year) through 2001 (end of study). Recovery of late-season applied 15N was compared to the recovery of six 15N applications (March through June, N at 221 kg·ha-1) of a previously reported study. By Nov. 1996, both fertilizer schedules exhibited considerable 15N accumulation below the rooting zone and just above the water table (280 cm), with 43.4% and 35.3% 15N recovered from the soil sampling profile of the September and March-June schedules, respectively. 15Nitrogen recoveries from perennial storage tissues (root and wood) were 20.6% and 10.1% under the September and March-June schedules, respectively. The 15N recoveries from annual abscission tissues (leaf, shuck, and nut) were 1.4% and 10.6% under the September and March-June schedules, respectively. By the end of the 2001 growing season, 4% and 9% of the 15N remained in the soil following the September and March-June applications, respectively. Under both fertilizer schedules, >80% of the fertilizer-N was lost to the environment through natural processes and very little was removed during harvest. Nearly 6 years following application, perennial storage of 15N remained greater in the September application (4.3% of the 15N applied) than in the March-June application (2.7% of the 15N applied). Late-season application of fertilizer-N during the kernel filling stage was stored in perennial tissues for use the following year; very little was used for current year growth of annual tissues. Increased accumulation of perennial storage N by late-season application may reduce the depletion of N caused during a heavy-cropping on-year and may moderate the alternate-bearing trend in pecan by providing a greater reservoir of N the following year.
Hadi Susilo, Ying-Chun Peng, Shui-Cheng Lee, Yu-Chun Chen, and Yao-Chien Alex Chang
when studying use of N fertilizer using traditional methods. Nitrogen-14 and nitrogen-15 ( 15 N) are the two stable isotopes of N with atmospheric natural abundances of 99.6337% and 0.3663%, respectively. The latter is an important tracer element in
Marlene Ayala, Lorena Mora, and Joaquín Torreblanca
leaves of spurs and ES ( Lang, 2001 , 2005 ; Rivera et al., 2016 ). Ayala et al. (2014) reported that foliar application of 15 N-urea after harvest influenced N storage reserves in floral buds for the subsequent spring. Similarly, Ouzounis and Lang
Alejandro Rey, William C. Lindemann, and Marta D. Remmenga
Previous research on late-season N fertilization of pecans [Carya illinoinensis (Wangehn) K. Koch] has shown significant uptake and storage of N in perennial tissues (roots, trunk, and shoots) that was used in subsequent years. The objectives of this study were to follow the fate of 15N applied at three different stages during pecan kernel fill in both the soil and tree components. In August and September 2002, 15N-labeled ammonium sulfate (9.94% 15N atom excess) was applied (56 kg N/ha) to nine pecan research trees during the early [3 days into kernel fill (DIK)], middle (25 DIK), and late (38 DIK) stages of pecan kernel fill near Las Cruces, N.M. In November 2002, about 67% of applied 15N was recovered from the soil and 13% from tree components. More 15N was recovered in nuts from the early treatment than middle or late treatments. Recoveries for May 2003 were 27% and 60% for tissues and soils, respectively. Leaf recovery increased an average of 14% in May 2003 over November 2002 leaves. More 15N was recovered from the late treatment in all tree components for May 2003 than early or middle treatments. The primary source of N for spring growth was 15N stored in perennial tissues. Fifteen months after 15N fertilizer was applied during kernel fill in 2002 about 24% remained in the soil, 28% had been used by the tree, and 48% was lost to the environment.
C.A. Sanchez, H.Y. Ozaki, K. Schuler, and M. Lockhart
Experiments were conducted from 1985 to 1989 to evaluate the response of radishes (Raphanus sativus L.) to N fertilization on Histosols. Three of these experiments used 15N-labeled fertilizer to evaluate the recovery of N by radishes. There was no response to N fertilization in seven of the eight experiments, even though some of them were conducted under conditions of high rainfall. The one experiment in which radish yields increased with N was conducted in a poorly drained, waterlogged field that was atypical of normal radish production fields. Recoveries of fertilizer N in the marketable radish roots averaged 19%. The results of N and 15N analysis showed that although fertilizer N was available for uptake, so was an ample amount of soil mineralized N. These results indicate that under typical growing conditions, radishes produced on Florida Histosols do not respond to N fertilization.
Yang Fang, Jeffrey Williamson, Rebecca Darnell, Yuncong Li, and Guodong Liu
immobilize fertilizer N, it was pretreated 2 months before planting with a liquid fertilizer UAN-32 (32N–0P–0K) at the rate of 0.15 g/L N ( Krewer and Ruter, 2009 ). Treatments. Treatments consisted of applying 10% 15 N labeled fertilizer as ammonium sulfate
Wei-Ling Yuan, Shang-yong Yuan, Xiao-hui Deng, Cai-xia Gan, Lei Cui, and Qing-fang Wang
objectives of this study were to determine the effects of N fertilizer management on root yield in radish, and calculate N recovery efficiencies using 15 N-labeled fertilizer methods, as affected by splitting N application and two different N rates
Xiaojie Zhao, Guihong Bi, Richard L. Harkess, Jac J. Varco, Tongyin Li, and Eugene K. Blythe
design was a factorial of five 2012 N rates and two 2013 15 N rates. On 7 May 2013, five plants from each 2012 and 2013 fertigation combination were randomly selected and destructively harvested. During the growing season, data for flowering (number of
Douglas D. Archbold and Charles T. MacKown
As the primary nutrient applied to and used by strawberry, N allocation and cycling within the plant may play an important role in determining plant vigor and productivity. Our objectives were to determine 1) how N availability and fruit production affect N and fertilizer N (FN) partitioning among and within the vegetative tissues of `Tribute' strawberry (Fragaria ×ananassa Duch.) and 2) if the root N pool is temporary storage N. Plants were fed 15N-depleted NH4NO3 (0.001 atom percent 15N) for the initial 8 weeks, then were grown for 12 weeks with or without NH4NO3 with a natural 15N abundance (0.366 atom percent 15N), and were maintained vegetative or allowed to fruit. The vegetative tissues were sampled at 6 and 12 weeks. Neither N availability or fruiting had consistent effects on dry mass (DM) across all tissues at 6 or 12 weeks. At 6 weeks, the total N content of all tissues except the roots were higher with continuous N than with no N. Nitrogen availability was the dominant treatment effect on all plants at 12 weeks; continuous N increased leaflet, petiole, and total vegetative DM and total N of all tissues. Insoluble reduced N (IRN) was the major N pool within all tissues at 6 and 12 weeks regardless of treatment. Fruiting inhibited root growth and N accumulation at 6 weeks but had little effect at 12 weeks. The roots were a strong dry matter and N sink from 6 to 12 weeks. The FN pools, from the 15N-depleted FN supplied during the initial 8 weeks, exhibited changes similar to those of total N in plants not receiving N, in contrast to plants receiving continuous N where total leaflet and petiole N content increased while FN content declined. Total FN per plant declined nearly 26% over 12 weeks; the decline was greater in plants receiving N continuously than in those not receiving N, but the magnitude of the decline was not affected by fruiting. Increasing atom percent 15N values, primarily in plants receiving continuous N after the initial 8 weeks of receiving 15N-depleted FN, indicated that N cycling occurred through all tissues and N pools, proportionally more in the soluble reduced N pool but quantitatively more in the IRN pool. The root N pool was not a “temporary” N storage site available for re-allocation to other tissues, although N cycling through it was evident. Rather, leaflet N was primarily remobilized to other tissues.