One function of roots is to absorb soil water and move it upward to keep foliage green. Roots need air in the soil to remain active. Soil air is the same as the ambient air at the surface of the lawn. Factors such as traffic, rainfall, irrigation ... compact lawn soil, thus reduce air among soil particles. Consequently, roots die from lack of air and lawn foliage changes from dark green with sufficient air in the soil to yellow from lack of air in the soil. Yellow foliage is not necessarily caused by lack of air because there are many causes to this yellowing. The soil compaction tester is a specialized instrument used by Services Pro-Vert to detect the degree of soil compaction of your lawn and correlate it to lack of soil air. Benefits of soil aeration to your lawn: a.Water from rain or irrigation infiltrates the soil to be absorbed by roots instead of being lost on lawn surface. b.A deeper rooting for better foliage. c.Lime and fertilizers are better absorbed by roots rather than being lost by run off water. d.Improved soil biological life with more air.