Applying too much Milorganite on your lawn can cause problems, which include poor root growth, thatch build-up, and burnt grass.  Bear in mind that Milorganite has a high nitrogen content and it releases nutrients slowly into the soil. So it takes about 8 to 10 weeks before the fertilizer releases all its nutrients into your turf.  If you keep on applying Milorganite every month, it will have a negative effect on your lawn.