Nebraska Extension’s lawn grass specialist Bill Kreuser says that new lawns or lawns on poor soil benefit from three to six fertilizer applications per year. Old lawns or lawns on fertile soil may only require zero to two applications per year to look attractive.
The best time to apply
The freezing and thawing of the soil over the winter, combined with the microbial activity of the soil, leads to the decomposition of the soil’s organic matter, resulting in a naturally higher level of nitrogen available for grass growth in spring. It is common for grass growth to increase sharply in spring. But too much nitrogen in spring leads to increased susceptibility to disease, increased mowing, decreased root growth and the formation of straw. So why not save your fertilizer job for later in the year when more is needed?
Lawn growth in the early season slows down in June when the naturally available nitrogen is depleted. The lawn specialist has been warning against fertilizing lawns in midsummer for many years, but recent research points to the benefits of using it from mid to late June.
Eventually, turf grass growth slows down in late fall and plants absorb less nutrients. At the same time, the nitrogen leaching potential is highest in autumn. For these reasons, the recommendation for heavy use of slow release fertilizers in late autumn is discarded. If a late fall application is made, it should be a light application of a water soluble product made before the end of October.