Assessment Of Pinyon and Juniper Derived Biochar As a Soil Amendment To Improve The Survivability Of Urban Trees and Landscapes.

The Nevada Division of Forestry (NDF) thins Pinyon-Juniper woodlands to maintain fire-appropriate tree densities and improve the habitat of rare species such as the sage grouse, which produces a readily available supply of waste biomass. Beneficial re-use of this biomass can promote sustainable land management by reducing the waste stream and generating a constructive purpose for a waste product previously left to decompose on site. One potential application for this waste biomass is the production of biochar. Biochar is produced when biomass is heated with limited exposure to oxygen (pyrolysis). Interest in biochar as a soil amendment has heightened due its potential to sequester carbon, increase soil water content and reduce fertilizer or manure requirements. One promising avenue of biochar application is the promotion of healthy urban street trees and landscapes in arid regions like Nevada, which often endure water and nutrient stresses exceeding other forest types. Unlike other soil amendments that require periodic application, biochar is resistant to microbial degradation and can therefore provide benefits to urban forests for long durations and reduce maintenance costs. Before widespread application of biochar to urban plantings occurs, careful analysis is necessary to produce a biochar which is suitable for this approach, and that will increase plant growth and survival. In this pilot-study, biochar was produced from separate Pinyon and Juniper feedstocks at temperatures of 350, 500 and 700°C with a 1-hr holding time and in a mixed feedstock produced under less controlled conditions in a transportable metal kiln. As a first step towards providing guidelines for urban forest implementation, sagebrush (Artemisia tridentate) was grown in mixtures of the various biochar treatments and nursery potting media of 5, 15 and 30 (%mass/mass) in the NDF nursery. In addition to plant growth assessments, soil mixtures and pure biochar were analyzed for pH, cation exchange capacity, C-N ratio, available P, K, Mg, and Ca and water holding capacity. From the greenhouse study and the soil analyses, results will be presented on the influence of application rate and biochar production temperature on plant survival and influential soil properties. The findings of this work will be relevant to plant nurseries and urban foresters in arid regions throughout the U.S.