The Importance of Fall Fertilization

The Importance of Late Fall Fertilization

by Doug Cherry, Synatek Solutions

Fall is the time of year when cool season Turfgrass recovers from summer stress-related conditions, such as: Drought, heat, humidity and disease. This year, turf-managers will be making late fall fertilizer applications with the hopes of improving turf vigor and recovery from injury next spring.

This article examines how late fall fertilizer applications influence turf performance, when to make your applications, as well as the recommended fertilizer and application rates to receive the best response to your turfgrass.

Why fertilize in late fall?

• Late fall fertilization has been promoted as a means of prolonging turf color of cool season grasses into early winter, without increasing the chance of winter injury and disease. • Late fall fertilization will also enhance spring green-up without the excessive growth that often accompanies early spring fertilization.

A small but potentially important increase in the plant’s carbohydrate reserves occurs when fertilizer higher in Nitrogen is applied in late fall instead of early spring. Turf accumulates carbohydrates in stems and rhizomes during fall. These carbohydrates help turf resist winter injury and aid in disease and environmental stress resistance the following spring and summer.

Because carbohydrates are tapped for energy by roots and shoots during periods of rapid growth, forcing excess growth with early spring fertilizer applications can deplete carbohydrates quickly, leaving turf vulnerable to spring and summer stresses. Late fall fertilizer applications do not force as much leaf growth in spring as equal amounts of early spring fertilizer do; thus, carbohydrates are not exhausted as quickly.

The result is a slight advantage to the turf in the form of better stress tolerance and disease resistance.

Another reported benefit of late fall fertilization is an increase in rooting. Maximum root growth of cool-season turf occurs in spring and fall. Some root growth will occur in winter if temperatures are above freezing, whereas little if any growth occurs in summer.

One reported advantage of late fall fertilization is that roots are still growing at a time when shoot growth has ceased, thus allowing the roots to make full use of the fertilizer.

Late fall fertilization is occasionally blamed for increased winter injury, snow mold, and annual bluegrass encroachment. A few studies have been designed to examine the influence of late fall fertilization on winter injury. But to my knowledge, none have conclusively demonstrated detrimental effects.

When to apply:

Most experts agree that late fall fertilization should take place when foliar growth stops (or slows to the point that turf no longer needs to be mowed), grass is still green, and before the soil freezes and as the soil temperatures start to go below 50 degrees. In Northern NJ, this period usually occurs around Thanksgiving. Application timing may vary from year to year, depending on weather conditions.

Turf Talk

2020!! No one has been spared the harshness of 2020, not even the lawns. I started out with pre-emergent as early as legally possible and I’m sure I am not alone in saying I had breakthrough weeds everywhere. The heat and extended dry periods in June led to cinch bug sod web worm. Will someone re-introduce Dursban already? And 2020 brought us such relentless fungus, it looked like powdered sugar on a funnel cake. To top that off, we only had 5 days in July and 4 days in August that were temperature friendly for applying weed killer. Oh, and how could I forget the nut grass. I’m beginning to think someone aerial seeded my lawns with nut grass seeds. September finally looked up as far as good weather for killing weeds and to begin to renovate lawns.

When we renovate lawns, it looks like the circus is in town. We show up with mowers to cut, aerators, rototillers to loosen up the really bad spots, slit seeders and topsoil. Some customers insist on topsoil, however; slit seeding is just as good with less cost to the customer. Everybody has to throw their own 2 cents in to the mix. When you seed, don’t forget the lime. I know, you are sick of hearing me saying it…LIME, LIME, LIME. But it really does make the difference in your percent of germination and viability of the newly germinated grass.

Good Luck and Keep Growing!

Greg Carpenter, CLT is co-owner of American Beauty Landscape since 1982. He attended the SUNY Farmingdale Turfgrass Program and is a Director of the NJLCA. Greg also serves on the Rutgers Turfgrass Advisory Board and the Bergen Community College Horticultural Advisory Board.

Fertilizer sources and rates:

• Most late fall fertilization programs include moderate amounts of nitrogen, minimal or zero phosphorus, and an adequate level of potassium. • Controlled-release nitrogen sources may be a better choice than soluble sources on sandy soils because of reduced potential for leaching. • Nitrogen fertilizer should never be applied to frozen soil due to the increased chance of nutrient runoff.

Although application timing is not as critical with phosphorus and potassium as it is with nitrogen, these elements can benefit turf when applied in the late fall. If your soil test report indicates a need for phosphorus, then it is a good time to fertilize for the phosphorous deficiency.

However, there is no need to apply additional phosphorus if it is present at sufficient levels.

Turf requires potassium in relatively large amounts, so annual applications are usually required. This element may enhance cold hardiness, disease-resistance, and wear tolerance. For these reasons, late summer and late fall are ideal times to fertilize with potassium.

Summary

Late fall fertilization should take place when shoot growth ceases, the grass is still green, and before the soil freezes.

Benefits of fertilizing in late fall include: 1. Better winter color. 2. Enhanced spring green-up. 3. Increased rooting.

Typically, moderate amounts of nitrogen provide good turf color without excessive shoot growth in early spring.

To avoid potential leaching and runoff problems, be sure to use slow-release nitrogen sources on sandy soils. Do not apply fertilizer to frozen soils.

Doug Cherry is a graduate of SUNY Cobleskill with a Bachelor of Technology in Plant Sciences. Doug has been serving his customers providing education and solutions for 26 years now in the Green Industry. He is a Technical Sales Representative for SynaTek Solutions working in the Lawn and Landscape division. Doug has a true passion for Horticulture along with a serious dedication to helping and solving customer’s problems which adds unique value to the growth and overall success of their business.