It is too early to know what winter has in store for us, but a fall application of fertilizer will encourage strong roots which will help the grass recover in the spring. I applied an organic based slow release fertilizer a couple weeks ago. Since then it has rained a couple times, but not heavily, which is ideal to ensure that the fertilizer is soaked into the ground to be used by the grass, and not running off into a ditch where is might make its way eventually to a wetland or stream. Although the fall is a great time of year to fertilize, if you live in the Northeast, or in an area with a similar climate, than fertilizer needs to be applied no later than October 15th while the grass is still growing and well before the ground freezes.
When you're applying fertilizer, be sure to use a rotary spreader and overlap the rows. This will ensure complete coverage. To ensure that you are getting the most out of the fertilizer, you should also test the pH of your soil and to apply lime if it is less than 6.0. If the soil is too acidic, this will impact the ability of turf grass to uptake nutrients necessary for growth. Lime should be applied with a drop spreader around planting areas since there are many plants and shrubs, such as rhododendrons, that prefer acidic conditions and will be adversely impacted by the addition of lime to the soil.
As beneficial as fertilizer can be, it can also be a source of surface water degradation if not applied correctly. More is not necessarily better. Over application of fertilizer can result in excess nutrients not being used by the grass, but instead running off into lakes and streams, or estuaries, if you leave near the ocean. Evidence of this can be seen with increased plant growth and algal blooms. An overabundance of aquatic plants or algae depletes oxygen that is necessary for survival of fish and other aquatic life. Further, certain algal blooms, such as cyanobacteria, can cause serious illness to people and pets if ingested. These types of blooms are becoming more frequent during the summer months, resulting in the beach closures. Over the past several decades the geographic landscape has changed from urban and rural, to a more developed suburban landscape. Trees and natural vegetation have been cut down and farmland has been subdivided to make room for more houses and their accompanying lawns. It is now recognized that the maintenance of this ornamental "crop" has become a significant contributor of pollution to nearby water bodies. To address the run-off of nitrogen and phosphorus from the over-application turf fertilizers, several states have passed legislation regulating the nitrogen and phosphorus content of turf fertilizer sold at retail. Minnesota was the first to initiate a statewide ban on phosphorus in lawn fertilizer in 2005. By 2012, eleven states had instituted similar bans. In 2013 New Hampshire enacted HB393 which places limits on nitrogen and phosphorus content in turf fertilizer and imposes certain labeling requirements. Since most soils in New Hampshire already have adequate amounts of phosphorus, the 2013 law prohibits turf fertilizer from exceed a 0.67% available phosphate unless it is labeled for establishing new lawns, seeding, or being used when there is a tested phosphorus deficiency. So next time you are shopping for a bag of fertilizer and you see that the middle of the 3 numbers on the bag is zero do not feel like you are getting a deficient product, but instead know, that the product still contains nitrogen and potassium to help your grass grow and stay healthy. And, never exceed application rates as directed on the package since whatever is not able to be used by your lawn will not only be wasted, but may also result in contamination to surface waters or even groundwater used for drinking.
Here is an excellent document produced by the University of Connecticut which provides recommendations for fertilizing lawns when protecting water quality is of concern: New England Regional Nitrogen and Phosphorus Fertilizer and Associated Management Practice Recommendations .
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