Nutrient and Water Retention Dynamics of Biochar Produced from Pinyon- Juniper Forest Thinning in Nevada.

Many western federal and state agencies are managing encroaching Pinyon-Juniper woodlands with little utility for the woody biomass produced. One potential benefit to be gained from this forest resource is producing biochar to be used as a soil amendment. Some agronomic applications of biochar have been hampered by economic limitations that necessarily reduce the application rates and thus minimize biochar benefits. Targeted applications of large biochar amounts in nurseries, compost facilities, urban/suburban gardens, and street trees may increase carbon sequestration, improve plant available water and plant growth. Pinyon, Juniper and a combination of the two species were used to produce biochar under controlled temperature conditions in a lab, and within a transportable metal kiln used by Nevada foresters to determine biochar property differences. The kiln allows little control of temperature, but it is transportable, can integrate whole logs (not wood chips), can be utilized by low-skilled staff and inmate labor, and is inexpensive and transportable enough that several kilns can be integrated in to the activities of western foresters. Biochar was analyzed for water content and potential, pH, total carbon, plant macronutrients (P, N, Ca, Mg, K), C-N ratio, cation exchange capacity, phosphorus retention capacity and the influence on plant growth was determined at application rates of 5, 15 and 30% m/m. Our results indicate that although there is some variation in biochar produced at different temperatures, the kiln-produced biochar compares favorably to the other biochar in terms of cation exchange capacity, exchangeable K, available P, while having a higher pH and lower Ca content. Phosphorus isotherms indicate that at environmentally-relevant concentrations the phosphorus release of soil-biochar mixtures does not depend on the temperature, feedstock type, or production methodology (kiln vs lab) of the biochar. Although there is some evidence that under high phosphorus loading, biochar improves the P-retention capacity of soils. Overall nutrient content, cation exchange capacity and P-retentive capacity of biochar were not substantial. Plant growth impacts were generally neutral to positive at all production temperatures even at application rates up to 30% m/m. Lastly, biochar of different particle sizes and application rates was mixed with a variety of mineral soil types and potting media and monitored after a simulated rainfall or irrigation event. These preliminary results indicate the potential of utilizing kiln-produced biochar within these more targeted applications (street trees, urban soils, nurseries, gardens) to increase plant available water in western states. Ongoing studies are being done to determine the influence of biochar particle size on soil moisture content and drainage, verifying the phosphorus retentive capacity under high loading conditions, and integrating biochar in to urban soils and street trees.