Q.Why Has My Once Lush Green Dwarf Mondo Grass Gone Yellow ?
The moss field above the grass was giving Cow manure & possible some drifted over to grass ???? I have sprinkled 10-10-10 on my grass in hope of bringing back the green ???? Thank you for any help you have for me !

Certified GKH Gardening Expert
Was the cow manure composted? If not, it can burn plants. The yellowing could be from too much fertilizer, too much water, or crown rot. These articles should help:
https://www.gardeningknowhow.com/ornamental/foliage/mondo-grass/mondo-grass-care.htm
https://www.gardeningknowhow.com/ornamental/groundcover/monkey-grass/monkey-grass-disease-crown-rot-causes-yellow-leaves.htm