Answer:
The problem researchers from Virginia Tech encountered during their attempt to reforest post-mined soil using biochar was the lack of organic material to support tree growth. The biochar, although improving soil structure, did not provide enough nutrients for successful reforestation.
Explanation:
The researchers found that while biochar improved soil properties such as water retention and pH, it lacked the necessary organic material to support tree growth. As a result, tree growth and survival rates were lower than expected, highlighting the importance of considering nutrient availability in soil restoration efforts.
