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Boron in their water Our irrigation water has excessive amounts of dissolved boron. What steps can we take to decrease boron problems? Our soil is a clay loam.--California

Boron is a tricky element with which to work. If, as you state, the boron is present in your water (as opposed to originating in your soil), you can do little to eliminate the problem aside from finding an alternate source of water to replace, or at least blend with, your current irrigation water.

Generalizing about boron levels is difficult because plant sensitivity varies a great deal according to species. Levels above 3.0 ppm in irrigation water can harm even relatively tolerant plants, while sensitive plant species may suffer harm at only one-third that level. Boron--in small amounts--is a vital plant nutrient, and deficiencies are not unheard of. However, a mere 0.02 to 0.08 ppm is adequate for most plants.

According to Steve Ninemire, a water-quality specialist with the 9Mire Group (Prosper, Texas), boron will leach more readily in acidic conditions. This is relative, however--boron is not likely to leach readily enough in any condition to solve the problem completely. Still, some grounds-care operations use acid-injection systems to acidify their irrigation water to promote leaching of boron. Soils with higher cation-exchange capacities hold more boron than, for instance, sandy soils. So the effectiveness of leaching also depends somewhat on soil type.

Ninemire also points out another consideration: site use. Turfgrass is not particularly vulnerable to boron toxicity because this element accumulates in leaf tips. Thus, removal of clippings also eliminates boron. Unfortunately, the same does not apply to ornamentals, which exhibit scorched leaves or leaf margins with excess boron.

You can find lists of boron-tolerant species in a few references, but most available information applies to food crops. Therefore, pay close attention to which plants exhibit boron symptoms and avoid using these species whenever possible. This is one way to cope with the problem, but it has its limits. As long as you keep applying boron-laden water to the landscape, it will probably build up to toxic levels eventually. Conversely, if you use low-boron water, the problem should eventually lessen. Thus, as stated previously, you should, if possible, find an alternate source of water.

Seed-mix ratio Is 70/30 a good ratio for a Kentucky bluegrass/perennial ryegrass mix? I think 80/20 or even 90/10 would give the bluegrass a better chance. Also, our distributorship occasionally has customers that request such seed mixes by seed-count ratio rather than by weight ratio. How do you convert these numbers?--Arkansas

Perennial ryegrass (PR) always germinates more quickly and at lower temperatures than Kentucky bluegrass (KBG). Therefore, to obtain a stand with an adequate amount of Kentucky bluegrass (KBG), many experts suggest no more than 10 to 20 percent PR in such a mix. That being said, be aware that no single proportion is ideal for all mixes because speed of germination varies among varieties of both species (this is one way that breeders are seeking to improve KBG). Therefore, the best proportion depends on the varieties in the mix as well as environmental factors, and some 70/30 mixes may work well in some situations. Nevertheless, 80/20 or 90/10 ratios generally are much more likely to provide a stand with an adequate population of KBG.

Work on this issue with the seed companies from which you obtain seed. They should be able to supply you with information to help you develop proper ratios for their varieties. Because KBG seed is more costly than that of PR, 70/30 mixes are less expensive than those with more KBG. Thus, people who shop for such a mix based on price alone are likely to end up with a relatively high proportion of PR seed. However, the savings is hardly worth it if you end up with a stand that's all PR. Therefore, it's best to shop for quality, even if the seed ends up costing more.

The math for converting weight ratios to seed-count ratios is fairly easy to perform. Simply multiply the percentage of each type of seed by the seeds-per-pound of that species. For example, let's work with 1 pound of a 70/30 mix of KBG and PR. KBG seed numbers about 1,500,000 per pound, while perennial ryegrass is around 225,000 per pound (these figures vary somewhat by variety, but are close enough for our purposes). Seventy percent of 1,500,000 is 1,050,000 (KBG seeds). The same operation for the PR (30 percent of 225,000) yields 67,500 seeds. 1,050,000 4 67,500 = about 15, so this is a ratio of 15:1 by seed count, even though the mix is 7:3 by weight. (The fact that even this lopsided ratio may not be enough of an advantage for KBG shows just how much more competitive PR is during establishment.)

If you need to work backward--for example if a customer requests a certain seed-count ratio and you need to convert it to a weight ratio to package it--the math is a little more involved. For example, assume you need a KBG/PR mix with a 20-to-1 seed-count ratio.

Start with 1 pound of KBG and 1 pound of PR. This gives you a ratio of 6.6 KBG seeds to 1 PR seed (1,500,000 KBG seeds per pound 4 225,000 PR seeds per pound = 6.6). Because you need 20 KBG seeds to each PR seed, you must multiply the 1 pound of KBG by the amount that gives you a total of 20 to 1. That amount, in this case, is about 3 (20 4 6.6 = 3)--the number of pounds of KBG seed that gives you 20 seeds to each seed in 1 pound of PR.

Now you need to convert this 3:1 ratio to a percentage. Your customer probably is going to tell you he needs a certain amount--say, 100 pounds. If the desired mix contains 3 parts KBG and 1 part PR, it consists of 4 "parts" altogether. Because 100 pounds/4 = 25 pounds (each part), you'll need 25 pounds (1 part) of PR and 75 pounds (3 parts) of KBG. To double check the math, multiply these amounts by the seeds-per-pound of each species. 75 pounds of KBG seed x 1,500,000 seeds per pound = 112,500,000 seeds, and 25 pounds of PR seed at 225,000 per pound = 5,625,000. To finish, 112,500,000 4 5,625,000 = 20--the correct ratio.

After doing this a couple of times, you'll likely find it easier to just educate your customers to use an 80/20 or 90/10 mix and not worry too much about the exact seed-count ratio.

Ectomycorrhizae are fungi that colonize roots, forming beneficial symbiotic relationships that contribute to plant health. These fungi naturally occur on roots, but commercial preparations are useful for establishing trees in reclaimed ground and other difficult sites, as well as in forestry applications. However, their benefits also should be useful in urban landscapes where established trees struggle from poor soil conditions, confined spaces and other stressful conditions.

To confirm this, researchers from Bartlett Tree Research Laboratories and Plant Health Care Inc. injected mycorrhizal treatments into the root zones of established landscape trees. The treatments included: * Spores of the ectomycorrhizal fungus Pisolithus tinctorius (Pt) * A slow-release complete fertilizer * A combination of both Pt and fertilizer.

The researchers injected these treatments into the soil to a depth of 8 inches at a 3- by 3-foot spacing within the dripline of trees. The tree species included red oak, willow oak and pecan, all growing in urban landscape settings.

To determine treatment effects on root growth, the researchers placed root ingrowth cores (RICs) in the soil within 6 inches of the injection sites. RICs, essentially screened cages, allow roots to grow into the soil they contain. The researchers extracted the RICs several months after the treatments and evaluated root growth.

In the treatments that included the Pt (with and without fertilizer), the researchers found significant increases in fine-root dry weights and ectomycorrhyzae root colonization compared to the untreated controls. The treatments that included Pt + fertilizer showed increases over the Pt-only treatment in some cases, but not all. The fertilizer-only treatments also produced root increases, but generally less than those of the treatments that included the Pt.

The researchers caution that other investigators need to conduct similar experiments in other regions to confirm the benefits of ectomycorrhizae for urban trees. However, this study suggests significant potential for increasing tree-root growth. Thus, these fungi may be able to increase established trees' tolerance to poor soil conditions and other stresses by increasing root uptake of water and nutrients. In addition, they may benefit newly planted trees by encouraging rapid development of fine roots.

The array of slow-release turf fertilizers now available to turf managers can be confusing. However, you should avoid the temptation to group them together by assuming that all slow-release products provide similar performance, even those with similar nitrogen (N) carriers. A recent study conducted by a University of Georgia researcher, who looked at the performance of a variety of slow-release products, underscores this advice.

The researcher examined N-release patterns over several months on the basis of bermudagrass-turf quality. He included various commercially available formulations of polymer-coated urea (PCU), polymer-coated sulfur-coated urea (PCSCU), ureaformaldehyde (UF) and several natural-organic sources. He used urea as a control. The study compared the quality of turf to which these products were applied at 0 to 30, 31 to 60 and 61 to 95 days after application.

The study yielded several interesting results:

* Among the PCSCU and PCU products, smaller particle size did not necessarily translate to more rapid N response. Instead, coating weight (percent sulfur or polymer) had the greatest effect on N release. (This is consistent with previous research about SCU and PCU.) * Natural-organic "bridge" products--those that include a quick-release N source to supplement long-term N release--performed significantly better than those products whose N was 100-percent natural organic and better than many of the coated products. * Only one product produced significantly better average turf quality over time than urea--a UF product. * Within each N class, release patterns varied substantially. Thus, turf managers should avoid blanket judgments about the performance of slow-release products.

The results of this study underline the differences in N release between slowly available N sources and quickly available sources used in this study. As the name implies, slowly available N sources provide good long-term turf response, but initial turf response is slow. Conversely, urea offers quick but short-lived turf response. No product in this study provided rapid N release and good long-term performance. As the addage goes, "You can't have your cake and eat it too."

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