Limited effects of biochar application and periodic irrigation on jack pine (Pinus banksiana) seedling growth in northern Minnesota, USA

We tested the effect of biochar application on growth of planted jack pine on a sandy soil in northern Minnesota. Biochar was applied in combination with compost and with or without manual irrigation in a factorial design to isolate possible effects associated with nutrient or water availability. There were no differences among treatments in seedling annual diameter or height growth after 4 years. Watering increased mean needle mass, indicating the treatment was somewhat effective at increasing water availability and seedling performance. Watering increased foliage Mg and K concentrations and content, possibly indicating that these elements are limiting to jack pine growth on sandy soils. Biochar-only application decreased foliage Ca concentration relative to controls, likely due to increased nutrient immobilization when biochar is applied without a nutrient source. These findings and others from the region highlight that biochar does not increase planted jack pine seedling survival or growth on sandy soils.