256 Werner and Jull: Fertilizer Uptake, Partitioning, and Recovery in Container-Grown Trees fertilizer N that was stored in root tissues during periods of low aboveground demand (i.e., cessation of active growth cycles). At 14 days after treatment in Lisle, IL, total [N] in the root tissues of trees receiving 1.42 g N was 25% and 26% higher than values observed in trees receiving 4.27 g N and the con- trol trees, respectively. The lack of significant difference among treatment levels during the remaining harvest periods at Lisle, IL may be attributed to a persistent need for N resulting from the second flush of foliage. This conclusion is supported by substantially lower pre-treatment total [N] values, relative to those observed at Arlington, WI, and a continued decline in total [N] throughout the study period for all treatment levels. The rate of application significantly affected biomass weight- ed aboveground total [N] (Equation 3) 60 days after treatment at both Arlington, WI and Lisle, IL. At Arlington, WI, the bio- mass weighted aboveground total [N] at 60 days after treatment for trees receiving 4.27 g N was 22% greater than both the con- trol trees and trees receiving the 1.42 g N treatment (data not shown). At 60 days in Lisle, IL, the biomass weighted above- ground total [N] in trees receiving 1.42 g N was 11% lower than values observed in control trees and 20% lower than trees receiving the 4.27 g N treatment. Previous studies have demon- strated dormant season whole plant total N status in seedlings is positively correlated with future growth (Struve 1995; Cornelis- sen et al. 1997; Rose and Biernacka 1999). However, data from this study suggests fertilization had no significant effect on the whole plant [N] status upon entering dormancy (e.g., 90 days after treatment). The lack of treatment difference at 90 days or the inability to detect differences may, however, be the result of utilizing larger plants to study the effects of fertilization on whole plant [N] status. Larger plants typically possess greater percentages of metabolically inactive tissue relative to their to- tal aboveground biomass (Meerts 2002). Nitrogen tends to ac- cumulate in metabolically active sites within the tree, therefore, increases in the amount of inactive tissue relative to the whole plant biomass may have diluted the whole plant total [N] status. N Partitioning Foliage and stem wood were the largest N sinks (% of aboveg- round N) at both locations (Table 1; Table 2). At Arlington, WI, approximately 49%, 4%, and 46% of the N in aboveground tis- sues was contained in the foliage, current season stem wood, and stem wood, respectively. At Lisle, IL, the foliage, current season wood, and stem wood accounted for 40%, 4%, and 56% of the aboveground N, respectively. With the exceptions of foli- age at 30 days after fertilization at Arlington, WI, and current season stem wood at 90 days at Lisle, IL, the rate of applica- tion did not affect the partitioning of N among the tissues. At 30 days, the percentage of N in foliar tissues receiving 4.27 g N was 21% and 11% greater than trees receiving 0 or 1.42 g N, respectively (data not shown). In Lisle, IL, 90 days after treat- ment, total N in the current season stem wood of trees receiv- ing 4.27 g was 25% higher than values observed in control trees and 67% higher than trees receiving 1.42 g N. At both locations, stem wood accounted for an increasingly larger percentage of the aboveground N 60 and 90 days after treatment. These tem- poral shifts in partitioning patterns are associated with the re- trieval and storage of N removed from leaves prior to abscission. Nitrogen Derived from Fertilizer Results involving nitrogen derived from fertilizer (NDFF), fertilizer N partitioning, and fertilizer recovery were based on increases in 15 relative to baseline 15N values. The observed increases in 15 N N were the result of applying a fertilizer enriched with 15N. Consequently, control trees are excluded from the computations and subsequent discussions. At both locations, the percent NDFF (Equation 2) in above- ground tissues and roots increased significantly with increasing rates of application (Table 3). At both locations, the percent NDFF in tissues of trees receiving 4.27 g N was three times greater than values observed in trees receiving 1.42 g N (Table 4). Independent of application rate and location, the largest percent NDFF was found in aboveground tissues developed during the current grow- ing season, specifically, the foliage and current season stem wood. Trends in foliar NDFF differed between the two locations. At Figure 3. Total [N] in root tissues of common hackberry at (A) Arlington, WI, and (B) Lisle, IL in 2002. Symbols represent the mean (n = 5) ± adjusted standard error. Asterisk indicates signifi- cant difference at P ≤ 0.05. ©2009 International Society of Arboriculture Arlington, WI, fertilizer N tended to accumulate in the foliage through 30 days after treatment, then declined. At Lisle, IL, the percent NDFF in the foliage generally declined, although there was slight increases in the percent NDFF between the 60 and 90 days harvest periods. The observed declines at Lisle, IL may be the result of 15 N dilution associated with a continued demand for N to support the second flush of foliage and/or leaf expansion and maturation.
September 2009
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
