To guarantee that nitrogen levels in the crop do not exceed a certain limit.

So far, nitrogen levels have dropped 19.2 percent from 1990.

He described the mechanism by which this happened: The higher nitrogen level spurred greater plant growth.

I'm afraid the nitrogen levels may be too high.

But no matter how deep the seals dive, nitrogen levels in their blood rise little.

Agricultural land with light soil and low nitrogen levels tend to favor its development.

The goal is to reduce nitrogen levels in the pond, which flows into the Sound.

The colors that appear on the turf directly reflect the nitrogen levels in the plant.

The report offers two reasons why nitrogen levels have continued to rise in the waterways.

A final test is done on sample bottles to check the salt content, the nitrogen level and the color.