Impact of Forest Fertilization on Health of the Hood Canal Watershed Cindy Flint Advisor: Rob Harrison, UW April, 2007 Funded by: Green Diamond Resource Company Puget Sound Regional Synthesis Model (PRISM) (with support from the Stand Management Cooperative)

Objectives Does forest fertilization with urea result in N leaching out of rooting zone? Could this negatively impact Hood Canal.

Background “Sill” restricts flow in and out of the canal Historically had periods of low DO Anthropogenic N loading to canal is worsening this problem

Eutrophication in Hood Canal Additions of limiting nutrients Algal blooms Blooms die off Decomposition consumes 0 2 Low DO in water Fish kills

Potential Causes of N Loading Erosion? Fertilization? Forests Agriculture Lawns Septic systems?

Past Research NO 3 - -N peaks in streams 0.25 mg L -1 to 9.3 mg L -1 Peaks due to runoff and direct application Steep slopes – 15 % N in streams Buffers – 0.45 % N in streams NO 3 - -N additions lasted longer (up to 1 year) (Meehan et al., 1975; Malueg et al., 1972; Perrin et al., 1984; Hetherington, 1984; Cline, 1973; Bisson et al., 1992; McCall, 1970)

Purpose Does forest fertilization with urea result in N leaching out of rooting zone?

Methods 6 Sites Age: yrs Site Index: 70-90

Soil map Shelton Soil series Glacial till

Site Layout.2 acre Lysimeter nest Control Treatment Fertilized with 224 kg N ha -1 as urea, March 20th, 2006

Tension Lysimeters –20cm –100cm

Methods (cont.) Tipping buckets - rainfall Thornthwaite Method - evapotranspiration Nitrogen leaching (kg ha -1 )

Quantified: Overstory N pools (biomass equations and % N) Understory N pools (calculated biomass and % N) Soil N pools Methods (cont.)

Precipitation

Total N Concentration

NO 3 -N Concentration

NH 4 -N Concentration

DON Concentration

Leaching

Total N Leaching

NO 3 -N Leaching

NH 4 -N Leaching

DON Leaching

Total N Leaching – year following fertilization 2 % of applied N

Overstory Soil N Pools 26 % of applied N

Understory Soil N Pools 0 % of applied N

O Horizon Soil N Pools 27 % of applied N 18 % of applied N

B Horizon Soil N Pools 0 % of applied N 300 % of applied N

Implications for Hood Canal 215 ha yr -1 fertilized * 4.2 kg N ha -1 yr -1 = 903 kg N yr -1 total N load (Green Diamond) Total surface water TN load (Avg. ‘05 &’06) (Steinberg) = Total groundwater DIN load (Paulsen, 06) = 536,000 kg yr-1 138,000 kg yr ,000 kg yr -1 Fertilizer leaching = 0.13% total terrestrial N load to Hood Canal (Leaching)

Take home message If urea is allowed to infiltrate the soil, minimal leaching should occur. (in N limited forests) How to promote infiltration: Buffers!!! (unfertilized, vegetated) No application on steep slopes No application to streams

Thank You! Randall Greggs, Green Diamond Resource Company Puget Sound Regional Synthesis Model (PRISM) Stand Management Cooperative Rob Harrison, Advisor, College of Forest Resources, UW Brian Strahm, College of Forest Resources, UW

Soil pH

N limitation evidence Overstory % N Soil C/N Ratios