“Gypsum can work wonders.”  
Dr. Wallace – Wallace Laboratories

A soil amendment and fertilizer for over 200 years, Gypsum helps break up compacted soils and improves water use efficiency (providing up to 100 per cent more water to roots in treated soils). Calcium helps grass plants absorb nutrients, so you get more from fertilization.
Experts recommend Gypsum treatment every one to two years, 
(more often in high-traffic lawns).