Nitrogen is gradually released from decomposing organic matter during the growing season, so less fertilizer N is required as soil organic matter levels increase. Removal of grass clippings also increases N needs. When using fertilizers containing quickly available forms of N, no more than 1 lb.
Higher rates can burn the grass.
They are also inefficient and pose a potential pollution problem, because not all of the N can be immediately utilized and it may leach through the soil and out of the plant root zone. Fertilizers containing slow-release forms of N can be applied at a rate of up to 2 lb. Late summer and fall are the best times of the year to fertilize lawns. This is contrary to the traditional springtime application of lawn fertilizer, but applying the majority of the fertilizer in the late summer or fall produces healthier lawns by improving the balance between root and shoot growth. Early spring applications of N can stimulate shoot growth that depletes stored energy reserves in plant roots.