The process whereby phosphorus is drained away into ground water is called agriculture
decomposition
leaching
sedimentation

When soluble soil nutrients from the soil are washed away due to to effects of rain,floods or irrigation from agricultural practices the process by which this occurs is called LEACHING. As water molecules pass through different soil layers,soluble soil minerals are dissolved and carried by the water  into the ground water.

Phosphorus is a soluble mineral which  is easily carried away by the passing water molecules,and therefore drained from plants' roots.

if these were leached  into rivers and drinking water,this may affect the water supply of the community as the percentage of Phosphorus increases in the water especially if  NPK fertilisers were used.

In addition, some important solid nutrients are also leached into the underground soil layer leading to deficiencies in the plants.

Explanation:

layer 3 is younger than layer 6.