Fall fertilization can be beneficial in the landscape if you follow some simple guidelines. The following is more information.
In turf, a second or third fall fertilizer application is often recommended with moderate amounts of Nitrogen (N), low phosphorus (P), and moderate to high rates of potassium (K), of course depending on soil test results for P and K. Timing of this application can affect turf performance. October applications can promote continued top growth and excess N at this time can reduce winter hardiness. If applying fertilizer in October, use modest N rates. A later fertilizer application at the end of November, can help root systems continue to grow and keep turf greener, longer into December. However, excess N at this time may be subject to leaching losses so limit soluble N fertilizers to modest rates that roots can utilize. Fertilizers with higher percentage of temperature dependent slow release N are very appropriate for fall applications. Potassium is important for improved wintering over and P is important for root growth so added P and K can be beneficial in the fall if soil levels are not high (based on a soil test).
Most other landscape plants require little or no fall fertilization if they are in the middle of fertilized lawns or in well maintained long-term established mulched beds with high organic matter. However, new landscapes, plantings in poor (low organic matter) soils, or landscapes that have been under stress may need additional fertilization. Woody landscape plants and some perennials continue root growth until soils are at freezing temperatures so fertilization using materials with low to moderate N, some P, and higher K levels can be beneficial to winter performance. Root growth will be improved and bud health can also be enhanced. However, excess N in the fall can promote bud break and new growth, or continued shoot growth in some plants, leading to increased winter damage.
Gordon Johnson, Extension Agriculture Agent, UD, Kent County
Showing posts with label fall fertilization. Show all posts
Showing posts with label fall fertilization. Show all posts
Friday, October 16, 2009
Saturday, October 10, 2009
Landscape and Nursery - Fall Fertilization Pros and Cons
The following is a good article on the pros and cons of fall fertilization from Andrew Ristvey from the University of Maryland.
Fall fertilization of landscape plants is truly a beneficial practice as long as certain guidelines are followed. This has been a contentious issue with experience on both sides challenging fall fertility. Physiologically speaking, even though the tops of plants have gone dormant or have slowed down, fall is an active period for roots. They are still growing and absorbing nutrients for next year’s spring flush until soil temperatures inhibit biological activity. All of next year’s spring buds will grow from stored nutrients attained this year. So the most effective application of fertilizers for next year’s growth is during late summer and fall of this year. However, because of dry and hot weather often experienced in Maryland towards the end of summer, optimal fertility times are towards the fall period.
Certainly, the most important growth factor for plants is water, and that was made evident this past mid-summer, when plant water stress was high. In the landscape, especially where plants do not have the luxury of irrigation, hot summer weather will inhibit plant growth. Fertilization should be minimized or stopped until better climactic conditions promote growth.
It is true that an over-application of nitrogen in fall can potentially awaken near dormant buds and expose plants to damage from frost which is just around the corner in our region. One relatively new study in the Journal of Arboriculture reviewed past research and looked at the effect of fall nitrogen fertility on cold hardiness of 5 landscape trees including Leyland cypress, crape myrtle and red maple in North Carolina. In most cases the researchers found no significant differences in hardiness of spring bud tissue with different nitrogen treatments for all the species. So there exists some evidence that fall fertilization does not reduce winter hardiness. But I have seen a heavy application of nitrogen in container grown plants increase vegetative growth in fall resulting in frost damage. However, those plants had not become completely dormant.
Most fall-based fertilizers are low in nitrogen and have higher ratios of phosphorus and potassium. Obviously, a serious fertilization program should rely upon a soil fertility test so that adequate amounts of nutrients are applied without risking toxicities or antagonisms (one nutrient overapplied can affect the availability of other nutrients). However, in general, a half rate of a low nitrogen or a 50% WIN combination in October should be considered as long as there is no longer any shoot activity. In container culture, a very low soluble nitrogen application (with excellent irrigation management to prevent nutrient runoff) may be acceptable periodically until temperatures fall below 55 °F, especially if your controlled release fertilizer prills no longer contain nutrients. Remember that fruit tree nutrition is based on leaf samples which should have been taken before the harvest. Fertilize according to those samples.
Information and photo from the October 9, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Oct09L.pdf
Fall fertilization of landscape plants is truly a beneficial practice as long as certain guidelines are followed. This has been a contentious issue with experience on both sides challenging fall fertility. Physiologically speaking, even though the tops of plants have gone dormant or have slowed down, fall is an active period for roots. They are still growing and absorbing nutrients for next year’s spring flush until soil temperatures inhibit biological activity. All of next year’s spring buds will grow from stored nutrients attained this year. So the most effective application of fertilizers for next year’s growth is during late summer and fall of this year. However, because of dry and hot weather often experienced in Maryland towards the end of summer, optimal fertility times are towards the fall period.
Certainly, the most important growth factor for plants is water, and that was made evident this past mid-summer, when plant water stress was high. In the landscape, especially where plants do not have the luxury of irrigation, hot summer weather will inhibit plant growth. Fertilization should be minimized or stopped until better climactic conditions promote growth.
It is true that an over-application of nitrogen in fall can potentially awaken near dormant buds and expose plants to damage from frost which is just around the corner in our region. One relatively new study in the Journal of Arboriculture reviewed past research and looked at the effect of fall nitrogen fertility on cold hardiness of 5 landscape trees including Leyland cypress, crape myrtle and red maple in North Carolina. In most cases the researchers found no significant differences in hardiness of spring bud tissue with different nitrogen treatments for all the species. So there exists some evidence that fall fertilization does not reduce winter hardiness. But I have seen a heavy application of nitrogen in container grown plants increase vegetative growth in fall resulting in frost damage. However, those plants had not become completely dormant.
Most fall-based fertilizers are low in nitrogen and have higher ratios of phosphorus and potassium. Obviously, a serious fertilization program should rely upon a soil fertility test so that adequate amounts of nutrients are applied without risking toxicities or antagonisms (one nutrient overapplied can affect the availability of other nutrients). However, in general, a half rate of a low nitrogen or a 50% WIN combination in October should be considered as long as there is no longer any shoot activity. In container culture, a very low soluble nitrogen application (with excellent irrigation management to prevent nutrient runoff) may be acceptable periodically until temperatures fall below 55 °F, especially if your controlled release fertilizer prills no longer contain nutrients. Remember that fruit tree nutrition is based on leaf samples which should have been taken before the harvest. Fertilize according to those samples.
Information and photo from the October 9, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Oct09L.pdf
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