Four-Year Foliar and Growth Response to Multinutrient Fertilization in Northeast Oregon

Results from this study show foliar nutrient deficiencies and multi-nutrient fertilization response for ponderosa pine, grand fir and Douglas-fir over a period of four consecutive growing seasons. Generally, through critical level or vector foliar diagnosis, N, S, B, Cu and possibly Mo were identified as being deficient for all species in this study. Additionally, Douglas-fir on the Noregaard site showed foliar K deficiency response. Distinct foliar nutrient response patterns were observed for those �strong responding� nutrients, particularly N and B where foliar response increased, peaked then declined in magnitude relative to the control as the year since fertilization increased. Delayed nutrient response may have been to spring fertilizer application not having manifested itself in time to show strong nutrient response one growing season after fertilization. Similar to foliar nutrient response, foliar needle weight growth increased, peaked then declined in magnitude relative to the control as the year since fertilization increased. Additionally, needle weight response was delayed due to spring fertilization. Needle weight response was significant for ponderosa pine and Douglas-fir but not for grand fir. Overall, four-year cubic foot volume response was significantly higher on the multi-nutrient treatment than the controls, with relative gross cubic foot volume response for both sites combined showing a 26.9% increase. Individual site response revealed that much of the combined relative cubic foot volume response was expressed on the Clear Creek site, which showed a 34% increase over the controls while the Noregaard site only showed a 3.9% increase. Periodic relative gross basal area response for both sites combined was greater in the first two-year period (26.9%) than the second two-year period (11.1%). Periodic relative basal area response for the Clear Creek unit was 32% the first two-year period and 23% the second two-year period while the Noregaard site response was 18.6% the first period and �6.5% the second