Estimating Soil Nitrogen Supply and Fertilizer Needs for Short-Rotation Woody Crops

Short-rotation woody crops are becoming important supplies of hardwood fiber, but little is known about the early nutritional needs of these systems, especially on different site types. The study objectives were, on two young (ages 3-6) sweetgum plantations with contrasting soil types, to 1) determine the plant growth and foliar nutrition response to repeated nitrogen (N) fertilizer applications, 2) determine soil N supply, plant N demand, foliar N resorption, and soil and fertilizer uptake efficiencies, and 3) test a simple N supply model. In order to expand the findings to the range of sweetgum site types, the study objectives were also to 4) evaluate rapid methods for determining N mineralization potential, 5) characterize the soils of 14 sweetgum site types in the Atlantic coastal plain, and 6) review current N fertilizer prescriptions in forestry and recommend strategies for improvement. Two young sweetgum (Liquidambar styraciflua L.) plantations on a converted agricultural field and a pine cutover site in South Carolina were fertilized biannually with three rates of N fertilizer (0, 56, 112 kg N per ha). Fertilization doubled foliar biomass and leaf area on the cutover pine site in the years fertilizer was applied, and stem biomass increased 60%. Critical values, the N concentration required for 90% of optimum growth, is approximately 1.75%. Foliar N uptake increased at both sites when fertilizer was applied. Modeled annual soil N supply was within 20% of that measured on the two plantations even though monthly N supply was not accurately estimated. Potential N mineralization was accurately estimated with a 3-day incubation of rewetted soils that were previously dried, but not by hot salt extraction or anaerobic incubation. Across a spectrum of 14 sweetgum sites, the agricultural fields had lower mineralizable nitrogen (126 kg per ha) than the cutover sites (363 kg per ha). Current N fertilizer prescriptions are not sufficient for repeated fertilizer applications to fast-growing hardwood plantations, but simple models of soil N supply and an N-balance approach may improve prescriptions.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Forestry

Department dc:contributor.department

Forestry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2002

Author dc:creator

• Scott, David Andrew

Chair dc:contributor.committeechair

• Burger, James A.

Committee members dc:contributor.committeemember

• Alley, Marcus M.
• Wolfe, Mary Leigh
• Kaczmarek, Donald J.
• Aust, W. Michael
• Pu, Mou

• sweetgum
• nitrogen fertilization
• hardwood plantations
• nitrogen balance

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-10302002-115845

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/29402