Just as nitrogen plays a role in allowing the plant to absorb sunlight, phosphorus is responsible for how energy is transferred throughout the plant. Think of phosphorus as the plant's subway system. Phosphorus is also responsible for cell division, allowing plants to adapt to different environmental conditions. Like nitrogen, not all forms of phosphorus can be utilized by roots. The most accessible form of phosphorus is Soil Soluble Inorganic Phosphorus. Usually we think of "organic" as a good thing, but here "inorganic" is better, meaning that plants can absorb it.
In the 2015 San Juan Study, when the farms grew dry beans, the team saw a significant rise in Soil Soluble P, or plant available phosphorus, from the biochar plots compared to the control plots (35% increase), but little change comparing the poultry litter to the charged charcoal plots.
In 2016, when the farmers grew winter squash, the team found opposite results, with almost no change in the biochar plots, but a 160% increase in the charged charcoal plots in comparison to the fertilized plots. This illustrates how charcoal interacts with different crops and seasonal climatic patterns in unique ways.