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Summary of results from the Regional Forest Nutrition Research Project and Stand Management Cooperative Rob Harrison, Dave Briggs, Eric Turnblom, Bob Gonyea, Bert Hasselberg. University of Washington. NUTSUPDM. Nutrient Supply and Use. POTENTIAL USE. SOIL SUPPLY. ACTUAL USE. REMOBILIZED.

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slide1

Summary of results from the Regional Forest Nutrition Research Project and Stand Management Cooperative

Rob Harrison, Dave Briggs, Eric Turnblom, Bob Gonyea, Bert Hasselberg.

University of Washington.

nutrient supply and use

NUTSUPDM

Nutrient Supply and Use

POTENTIAL USE

SOILSUPPLY

ACTUAL USE

REMOBILIZED

UPTAKE FROM SOIL

slide7

Results:

Pre-RFNRP

1950’s through 1960’s

slide8

N200

N300

Percent volume response

N200-P88-S154

N200-P88-S168+

N100

N52-P12-K220

N rate (lb N/acre)

slide9

N+P

N200-P88-S168+

N200-P88-S154

N100

N100

N300

N200

Percent volume response

N52-P12-K220

N52-P12-K220

N rate (lb N/acre)

slide10

N200-P88-S168+

N200-P88-S154

N100

N100

N300

N200

Percent volume response

N52-P12-K220

N52-P12-K220

N rate (lb N/acre)

slide12

Results of other studies

Hodge-podge of nutrients other than nitrogen makes conclusions difficult. Several studies indicate results similar to the 2nd above, and many indicate the central role of N.

Clearly, both response to N and other nutrients is site controlled. Indicates need for larger scale studies on a wide variety of sites to pin response to site variables.

slide13

Conclusions of early studies

“Nitrogen application evoked a growth response throughout a range of growing conditions. Magnitude of response is related to amount of nitrogen applied and response is still evident in 1975 from a 1962 application”.

“Apparent response to the application of other elements is quite variable and no consistent picture emerges. There is no evidence of an economic response to the other elements”.

slide14

RFNRP

1969-pres.

slide16

Installations of the PNW Stand

Management Cooperative

slide23

(1)

Overall results of SMC studies Response vs. N rate. Sidell thesis.

slide24

Table 2. Pilchuck Tree Farm study established 1994, measured through 2002 (8 y growth). Each treatment is replicated 6 times (two each installation).

slide25

Table 1. Oregon Dept. Forestry study established 1995, measured through 1999 (4 y growth). Each treatment is replicated 6 times (two each installation).

slide30

Results of RFNRP studies

N response averaging 20% (unthinned) -30% (thinned) with 400 kg N, highly site dependent.

Clearly, both response to N and other nutrients is site controlled. Indicates need for larger scale studies on a wide variety of sites to pin response to site variables.

Effects of N fertilization appear to be very long-lived.

slide31

SMC (1991+)

No multi-element additions. SMC

Type II, III and IV no fertilizer work at all

slide32

SMC Type I Installations

  • plantations with initial stocking 300-680 spa
  • Respace (PCT) before onset of competition
  • 7 core treatments (basic 7)
  • ISPHa, ISPHa/2, ISPHa/4,
  • ISPHa and ISPHa/2 min thin
  • ISPHa repeated thin
  • ISPHa heavy thin
  • 2-8 plots for other work, including fertilization
  • Eric Sucre did his M.S. on 7 fertilized sites
soil site properties examined
Soil & Site Properties Examined
  • Climatic data
  • Elevation
  • % Slope
  • Relative Density (RD)
  • Quadratic Mean Diameter (QMD)
  • Site Index (SI)
  • bulk density (Db)
  • pH
  • C:N ratio
  • cation exchange capacity (CEC)*
  • Inorganic nitrogen (NO3- and NH4+)*

*Mineral Soil only

slide36

Total volume and 4-year PAI relative response for each treatment regime at the respected treatment intervals (224 kg ha-1 of N as urea every 4 years). Standard errors are shown.

slide37

Multiple regression equations for the relationships between the unstandardized residuals of total volume (m3 ha-1) and 4-year PAI (m3 ha-1 yr-1) response to 224 kg N ha-1 as urea (dependent variables) and various soil, site and stand variables (independent variables).

slide38

Results of SMC studies

too few sites (7) for broad generalizations

Response to N is site and stand controlled. Indicates need to couple fertilization with other silvicultural treatments, particularly stocking, and use RD or other stand properties to drive time of fertilization.

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