Nitrogen Fertilization of Black Walnut (Juglans nigra L.) During Plantation Establishment. Morphology and Production Efficiency
Grafted, Tippecanoe 1 cultivar black walnut (Juglans nigra L.) trees were planted and grown in an intensively managed plantation in west-central Spain and subjected to six fertilizer treatments (defined as 0, 25, 50, 75, 150, and 300 g tree−1 nitrogen [N]) delivered
via daily fertigation during the 1st year after outplanting. Stem diameter, volume, and mass increased from the unfertilized control to the second fertilizer treatment (50 g N) but showed no gains thereafter. N utilization efficiency (stem volume growth per unit fertilizer) was greatest for
the 25 and 50 g tree−1 N treatments, and fertilizer N use efficiency (gain in stem volume growth over the unfertilized control per unit fertilizer) was greatest at 50 g tree−1 N. Foliar N concentrations in mid-July provided the best predictors of seasonal
stem volume growth. Optimal foliar N was 3.2%, which is higher than values recommended for other black walnut production systems: less than 2.8% was deficient, 3.0% was sufficient, and more than 3.4% suggested toxicity. Branch biomass and branch mass/trunk mass ratio were greater in all fertilizer
treatments than in the unfertilized control, indicating that high fertilization rates may shift biomass allocation away from the desired product (stem wood).
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
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