Plants take up nitrogen and absorb it into their organic matter via their roots in a process .

The answer is Assimilation

Explanation: Got it from the original text.

Nitrogen fixation is NOT the answer, It's just the first stage in the Nitrogen cycle.

1. loamy sand is about 80% sand with 10% clay and defined mostly by sand particles with some clay to provide structure and fertility. the sand particles are easily visible and the soil holds structure but breaks apart easily.

2. scott sand can improve his soil quality by incorporating more silt and organic matter into the soil. peat moss and organic matter can also be incorporated.