Effects of Biochar Application on Soil Chemistry and Plant Uptake in Fescue-Dominated Pasture in Middle Tennessee.

Biochar is produced by thermal decomposition of organic matter. It has been used as soil amendment for thousands of years; however, its benefits vary depending on feedstock type, amount applied to the field and time since application. To determine the effects of biochar amendment on soil properties and plant growth in the cropping systems of Tennessee, we started a field experiment in Lebanon, TN. The soil at this site was Bradyville (fine, mixed, semiactive, thermic Typic Hapludalfs). We surface applied different rates of biochar on tall fescue (Festuca arundinacea) dominated pasture in April 2017. The six treatments were an untreated control treatment (0 T biochar/ha) and five biochar treatments (4.48, 8.96, 13.44, 17.92, and 22.4 ton/ha) with 4 replications per treatment. The biochar used in this study was prepared by mixing 97% hardwood woodchips (mainly Populus spp.) and 3% biosolids. To evaluate the effect of time since biochar application on soil properties, we plan to collect and analyze soil samples every 6 months. The first soil sampling was conducted in June 2017 from 0-15 cm depth along with the harvest of fescue plants. We determined plant yield and plant nutrient status as well as soil properties such as soil pH, gravimetric moisture content, soil organic carbon, microbial biomass, total soil nitrogen, inorganic nitrogen and extractable phosphorus and potassium. The results showed increased potassium in plants with 22.4 ton/ha as compared to the control. None of the soil properties were significantly different across the treatments except soil ammonium-N, which decreased significantly with increased biochar application rate. General lack of soil response to biochar application is justifiable as these results were based on samples collected after 2 months of biochar application. We will be conducting second sampling in Nov 2017 and the results will be discussed at the meeting.