Late Season Fertilizing for Perennial Landscapes and Gardens

Most growers become excited when the soil begins to thaw, landscapes begin to gain color and the days grow longer.  This is also when many people start to think about their lawn and gardens.  One step to having a successful growing season is ensuring the correct soil fertility is in place for the crops or lawn to grow.  While coming out of hibernation is a fun time to think about this, late summer and fall applications can be very beneficial. 

Some applications made well in advance have a better chance of undergoing certain microbial and chemical changes as they interact with soil/growing mediums.  The first step to late season fertility adjustments is pH.  Once the results from the soil test are received, a plan can be made for adjusting pH from a variety of sources.  For a fall pH adjustment, the liming material will dictate its neutralizing capacity and longevity.  Ag lime, and coarser materials, are perfect for fall applications.  These will have the longest neutralizing capacity and will benefit from incorporation the fall before.

Nitrogen is not recommended for late season applications.  This applies to all anions or negatively charged compounds.  An exception to this would be elemental sulfur which may take longer to convert to an acidifying form.  Nitrogen will promote vegetation when the plant needs to be transferring energy to the root system.  This will protect the plant’s growing point below freezing temperatures and store enough energy to grow the following season.

Manure applications can be made in the late fall as soil temperatures start to decline, and the plants are dormant.  Manure, along with other applications, should be incorporated into the soil.  This will decrease surface runoff and bind certain forms of nutrients.  For perennial plants, manure applications must be used with caution.  Some manure sources are high in nitrogen and will cause root burn through osmosis.  The concentrations of salts in the fertilizer takes water out of plant roots and leads to dehydration and damage.  It is best to use a composted form or low risk source. 

It is best to address soil nutrients that require long conversion times and stable forms for late season applications.  If larger quantities are recommended, in reference to a soil test, applying half late in the season and half in the spring would be another option.  While in-season applications focus on feeding the plant, another way to view late season applications is building the soil to then feed the plants the next season as soil temperatures increase and biological/chemical processes increase.