Salt of the earth What effects do de-icing salts have on plants? How can the problem be mitigated? - via the Internet

Chris Starbuck, woody ornamentals specialist for the state of Missouri, says de-icing salts adversely affect plant growth by interrupting water relationships between the plant and soil, thus making it more difficult for plants to take up water. De-icing materials such as calcium chloride, sodium chloride and potassium chloride will harm plants in this manner.

As far as corrective measures are concerned, Starbuck states that little can be done after the fact. Thus, the best method for mitigating these negative results is to keep the materials from reaching the soil in the first place. Creating a channel to divert runoff away from plants may do this. Starbuck also mentions that some people believe that adding gypsum to the soil may help. However, gypsum only works in sodic soils that have a high pH and a lot of sodium. The immediate problem is osmotic, and gypsum does little to relieve this.

Using non-salt materials may be the best choice for these areas. Sand, cinders and urea are non-salt alternatives that can be effective for increasing traction, though their melting ability is not as effective as traditional salts. However, dark-colored materials (such as sand and cinders) may act by absorbing heat from the sun and then providing some melting action. Also, calcium magnesium acetate (CMA) is being researched as an alternative for use around sensitive vegetation and seems to have little impact on plants.

Grass in ornamental beds How do I selectively remove grass that is growing throughout phlox? - Ohio (via the Internet)

For annual grasses, the best strategy is to use a pre-emergent. However, the problem with many ornamentals is not from annual grassy weeds, but from perennial grasses, including turfgrasses, that creep into and grow throughout plantings. Selective grass herbicides are ideal for such situations. Be sure to identify the grass species and make sure the herbicide is effective on the particular one you wish to eliminate. A test application on a small area also is a good idea to ensure plant tolerance before you perform a widespread application. There are several varieties each of the commonly used Phlox paniculata and Phlox subulata, so there may be tolerance differences.

Sethoxydim (BASF's Vantage) and clethodim (Valent's Envoy) both control several types of grassy weeds and are registered for application as an over-the-top spray in ornamentals. They specifically list phlox (Envoy lists it generically, Vantage lists Phlox paniculata) as a tolerant crop. Fluazifop-p-butyl (Syngenta's Fusilade II, PBI/Gordon's Ornamec) is another selective grass herbicide for such use. Though they don't list phlox, they are registered for use in many other ornamentals.

Iron supplement At what rate would a 13 percent iron supplement (in powder form) be applied as a foliar spray combined with 18-3-6 liquid fertilizer, an insecticide and a fungicide? - via the internet

I can't give you any universal "rule of thumb" for iron applications, except to follow the instructions provided for the product. The rate of iron - barring any tank-mix incompatibilities - has nothing to do with the other ingredients in the mix. It should be the same as you would apply it all by itself.

The ideal amount of iron to apply, from a plant-nutrition perspective, depends on what you're applying it to - different plants have different needs. Most labels for general-purpose iron products list rates safe for nearly all plants, because it would be impractical to mix a different rate for each species of turf and ornamental present. The iron product should include a label that tells you how much powder to mix with "x" amount of water/solution to be applied to "x" number of square feet of turf. For ornamentals, most labels will tell you to apply a directed spray of a specified concentration to wet the leaves of the plants, usually "to the point of runoff". If your label does not list clear recommendations, you should switch to a product that does. The only exception is if you have conducted a lab analysis, in which case you should follow recommendations provided by the lab.

Most pesticide labels will tell you about known tank-mix incompatibilities. However, considering all the ingredients you're seeking to add to your mix, you need to perform a test for compatibility.

Buffalograss (Buchloe dactyloides) has received a fair amount of attention as a low-maintenance turfgrass owing to its heat and drought tolerance. However, its ability to tolerate low mowing - and, therefore, its suitability as a fairway turfgrass - has only recently been investigated.

Buffalograss has a prostrate (low-growing) habit and is stoloniferous, making it similar in these respects to bentgrass and bermudagrass. Would it also show similar tolerance to low mowing? That was the subject of a study by University of Nebraska researchers P.G. Johnson, T.P. Riordan and J. Johnson-Cicalese.

The researchers established buffalograss in two study plots: one in 1990 and the other in 1993. The first plot was established with 97 vegetative varieties and 1 seeded variety; the second plot held 53 vegetative varieties and 21 seeded varieties. The plants came from various locations throughout the Great Plains, with the majority originating in Colorado, Kansas and Nebraska.

All of the plots were mowed at 7.6 cm during establishment; then mowing height was gradually reduced to 1.6 cm (about 5/8 inch). The plots were only irrigated during establishment. The most tolerant selections were cross-bred and the resulting progeny were established in a new plot in 1996.

The researchers found several cultivars that could tolerate fairway mowing heights. Interestingly, the researchers discovered that the top performers in each plot were predominantly female plants. In addition, the offspring established (in 1996) from the seed of the best low-mowing performers exhibited superior tolerance to low mowing. This confirmed that tolerance to low mowing is heritable in buffalograss and the potential for developing cultivars for fairway turf.

The investigators discovered another interesting result. Several varieties could not withstand cold temperatures when mowed low, but remained vigorous when mowing heights increased. The researchers noted that these varieties should still be investigated for use in climates south of Nebraska and may prove suitable where winter temperatures are slightly warmer.

Plants that exhibited good summer color did not exhibit good fall color. Conversely, southern varieties exhibited excellent fall color but had low overall quality ratings due to poor winter hardiness in Nebraska.

The researchers acknowledge that buffalograss does not yet rival the qualities of irrigated bluegrass, ryegrass or bentgrass. However, in the real world, most golf courses operate with budget restraints. Therefore, considering the low inputs needed for buffalograss, quality might be considered acceptable at some sites, especially in semiarid and arid regions where water is expensive and courses may operate under water-use restrictions. The researchers also note that other studies indicate buffalograss displays good recuperation following traffic and divoting, another necessary quality for fairway use.

Researchers at the University of Missouri have created a machine to test different root-zone mixes and depths for use in athletic turf. Shallower root zones are far less expensive to establish than the 12-inch root-zone mixes that are standard for many colleges and professional sports fields. The researchers hope to find a mix that provides an acceptable surface with a 6-inch root-zone depth.

The machine is designed to simulate athletic-field wear and tear. Using a torque wrench with the machine, the researchers can measure how much force is needed to tear the sod. The plots use various root-zone mixes ranging from 100 percent sand to 100 percent native soil. They are are sodded to imitate the standard process for athletic turf establishment. The researchers core the established plots to determine the root mass within the various mixes. Data is collected 4, 6, 8 and 10 weeks after sodding and the torque measurements are correlated with root mass in hopes of determining which mixes promote the densest, most stable, root system in the shortest period of time.

Typically, college and professional playing surfaces are developed using USGA standards for golf course greens, says Chad Follis, a turfgrass researcher at the University of Missouri. These surfaces drain well, but they aren't the most stable surface for high-impact sports. Therefore, player safety concerns are an issue. "Also, athletic field construction is sometimes completed in the summer and use is expected in the fall before complete root establishment occurs," states Follis. "Therefore, it is essential for mixes to be inherently stable and allow rapid root penetration to occur following sodding."

An ideal root-zone mix would be inexpensive to install, decrease water and fertilizer inputs and thus lower overall maintenance costs. Follis states, "this is an important consideration for high school and recreational playing surfaces that are maintained on limited budgets." Follis also says, "establishing natural turf with a 12-inch root zone and subsurface drainage in professional stadiums can cost well over $800,000. But, with a shallower root zone that does not require subsurface drainage and that uses fewer materials, a quality athletic turf can be established for much less."

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