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Nitrogen Fertilization of Black Walnut (Juglans nigra L.) During Plantation Establishment. Morphology and Production Efficiency

Goodman, Rosa C.; Oliet, Juan A.; Pardillo, Guillermo; Jacobs, Douglass F.


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).


biomass allocation; fertigation; foliar nitrogen; nitrogen use efficiency; toxicity

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Forest Science
2013, Volym: 59, nummer: 4, sidor: 453-463 Utgivare: SOC AMER FORESTERS

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