Wood Ash Fertilization of Irrigated Pasture In Northeastern California.

Wood ash is commonly applied to pastures in Northeastern California, but evidence of comparative effects to commercial fertilizer is scant. The effects of P fertilizer and wood ash upon total forage yield, P, Zn, and Cu uptake, and forage quality were tested on a native irrigated pasture (grass/clover) site in Eastern Shasta County CA on a Lava Flow-Lithic Xerochrepts complex soil with a low P soil (8 ppm Olson, pH 6.3).  Treatments of a common P fertilizer rate (105 lb/A P₂O₅), a comparable P₂O₅ equivalent with wood ash (3.6 tons/A @ 20% moisture wood ash) and the standard rate recommended by UC Publication 21573 “Agricultural Use of Wood Ash in California” (20 tons/A @ 20% moisture on p 4) were applied to individual plots (6.1 m²) in three replicated blocks on February 23, 2010.  Supplemental urea was used to equilibrate all treatments to the N rate of the commercial P fertilizer treatment (11-52-0).   Plant height was recorded monthly (April-November).   Monthly forage yield was measured by clipping 1 m² samples.  At the end of the season soil samples were collected and analyzed for Olsen P.  Season long yield samples were pooled by replicate and analyzed for ADF, crude protein, phosphate phosphorous (PO₄-P), zinc and copper.