Efficiency is the name of the game in landscape management. How can we achieve the same or better results with fewer applications, fewer miles on the truck or fewer employees? Many operators are looking at how to streamline their turfgrass management plans. This often leads them to choose a fertilizer “+ etc.” combination product.
It now seems that there isn’t anything we can’t add to a general N-P-K fertilizer — herbicides, insecticides, fungicides, soil amendments, microbes, surfactants, carbon sources, biosolids and micronutrients. Adding the considerations of slow-release versus quick-release nutrients and the various available nutrient sources can confuse even the most experienced turfgrass practitioner.
Feeding turfgrass
Let’s start with nutrition. After all, this should be the cornerstone of choosing which products to apply. Correctly fed turfgrass should require fewer of the above-listed add-ins to achieve sustained quality. The time of year and how long you’d like to go between site visits will determine what percentage of slow-release nitrogen to use. For extended feeding, a base level of 50 percent slow-release is optimal.
We can achieve this by mixing two nitrogen sources — for example, a poly-coated urea and a noncoated ammonium sulfate — giving the added benefit of quick green-up and extended feeding. This also pairs well with many control products with two-plus month effective timespans.
Slow-release versions of phosphorus and potassium are also available, although they increase the complexity (and cost) of a fertilizer product. But if you are considering a 70-plus day application interval, you should consider slow-release forms of all nutrients. You don’t want other nutrients to fall short at day 45 while nitrogen supplies are still adequate weeks later.
The most common value-add to a general N-P-K fertilizer is a control product, usually a herbicide, insecticide or both. Picking the level of active ingredient for each control product can be an issue. Again, you need to pair this with the correct percentages of slow-release nutrients. Fertilizer manufacturers often have these choices dialed in since combination products are common and have proven manufacture/efficacy track records.
To add or not to add?
Incorporating a third or fourth value-added component to a fertilizer is where things get complicated. Adding a biosolid filler or fertility source can affect the ability to utilize control products or quick-release fertility. But biosolids can be excellent carriers for surfactants or microbes and are often great carbon sources. The downside is low nutrient content, which may not support our do-more-with-less mentality.
Soil amendments such as humic acid or gypsum can be excellent additions to a fertilizer, often replacing rock limestone as a filler, making every component in the bag beneficial to the turfgrass system. Soil amendments also mix or blend well with standard N-P-K components. Humic acid especially has been shown to reduce the overall nutrient amounts necessary to produce quality turfgrass. When blended with the correct ratio of slow- and quick-release nitrogen, soil amendments have the benefit of extended application intervals.
We can’t forget what hides in the shadow of N-P-K: micronutrients. Consider using fertilizers with added manganese, magnesium and sulfur. As turfgrass managers have employed reduced N-P-K rates over the past 20 years, micronutrient levels have dropped.
Thankfully, micronutrients come along with soil amendments or you can easily add them to fertilizer formulations on their own. You can add as much nitrogen as you like, but without correct micronutrient levels, the turf may not respond accordingly.
While it may be tempting to add five or six components to a fertilizer blend, that is not often feasible from a manufacturing or cost standpoint. The real all-in-one fertilizer may better exist as a theme across a few complementary, well-planned applications.
