Responsible Phosphorus Use in Iowa

Phosphorus (P) is an essential macronutrient that all plants need in relatively large quantities. The amount of P fertilizer needed by turfgrass is usually significantly less than nitrogen or potassium. However, P is particularly important during early grass seedling growth and development stages.  Phosphorus plays a role in establishment, rooting, maturation, growth, and reproduction of plants. Plants can extract the relatively immobile soil P as dihydrogen phosphate (H₂PO₄^-) or hydrogen phosphate (HPO4^-2). The terms available phosphate, available phosphorus, available phosphoric acid, and P₂O₅ may be used to refer to phosphorus fertilization.

While P is an important nutrient for grasses and other plants, it is also a vital nutrient for algae and weeds in our lake systems. Phosphorus is usually the least abundant nutrient in freshwater lakes, and is often a limiting factor for the growth of algae and weeds. Lake enrichment of P can cause undesirable algal blooms and increased aquatic weed pressure, a process termed eutrophication. A result of eutrophication is an environment unsuitable for many fish and wildlife inhabitants. 

Turfgrass P deficiencies are usually first recognized by stunted growth and reduced seedling vigor. It is unusual to see a P deficiency in a mature plant. In addition to the reduced growth, leaf blades can turn a purple to reddish color. The turf stand will begin to decline in quality, if the deficiency is not addressed.

Most soils in Iowa contain adequate amounts of phosphorus and no additional phosphorus should be used in a fertilizer program unless indicated by a low soil test. A 1.0 lb. of P₂0₅ per 1000sq. ft. is permitted for establishment purposes; however, it is still strongly recommended that this application follow a low soil phosphorus determination.

Recent regulations in Minnesota and Wisconsin restrict residential landscapes phosphorus applications in an effort to minimize environmental threats. While there are no phosphorus restrictions in Iowa, phosphorus should only be applied when a soil test has indicated a need for additional amounts. The Iowa Professional Lawn Care Association (IPLCA) has placed a self-enforced restriction on the use of P fertilizers on lawns surrounding lakes and other waterways. They will use P containing fertilizers in these areas only at the time of establishment. They are also careful to remove all fertilizer from hard surfaces to prevent movement into sanitary sewer systems.

The entire extension publication is attached in pdf form.  To download the publication, click on the following link Phosphorus Publication.   

or use the following address:   

https://drive.google.com/file/d/0BzSKKI3Akgy_NEpZUGFDZmRrb0U/edit?usp=sharing

 

WILL TENACITY (MESOTRIONE) KILL QUACKGRASS?

Nick Christians
May 27, 2014
nchris@iastate.edu

Quackgrass (Elymus repens) is the hardest turf weed to control that I know of.  You can identify it by the long clasping auricles on its collar (Fig. 1) and by its extensive rhizome system (Fig. 2).  I get the question occasionally whether the new herbicide Tenacity (mesotrione) will selectively control this species.  The answer is “no”. 

Figure 1. Auricles

 Figure 2.  Rhizomes

We just treated the Kentucky bluegrass (Poa pratensis) turf at the research station shown in Figure 3.  The result is that the quackgrass turns white, as can be seen in the picture.  That always gets peoples hopes up, including mine when I first started working with this product.  Unfortunately, the quackgrass always recovers and comes back as bad as ever.  Repeat applications do not work either.  I tried for 4 seasons to kill patches in my own lawn, hoping that my tenacious applications of Tenacity would kill it.  I lost, and the quackgrass was not even reduced in severity by my repeated applications.

 

Figure 3. Quackgrass turned white by Tenacity.

The only way to control it remains non-selective applications of Roundup (glyphosate).  The rhizomes are very hard to kill and repeated applications of Roundup will be necessary.  If you have this problem and want to get rid of the quackgrass, start now in May by killing the infested areas.  Then repeat apply every time the quackgrass comes back from rhizomes.  You should set a goal of reseeding in mid-August.  

Even a better solution would be to sod over the dead areas.  The rhizomes have a harder time emerging through sod than they do into a newly seeded area.

 

Why Was Winter 2013-14 So Hard On Our Landscape Plants?

I think we’d all agree, the past winter season was a long and difficult one.  Even now, in the third week of May, temperatures are struggling to reach 70^°.  And the three overriding questions remain…will summer ever arrive?  How do I explain to my boss, club members, clients, etc. why so many plants look dead after the winter of 2013-14?  And perhaps most importantly, why was this past winter so tough on landscape plants? 

Consider these events important events:

• As we entered late fall and early winter, soil conditions were very dry.
• As a result, many landscape plants entered winter under stress or in a weakened condition.
• Severe low temperatures (before measureable snowfall) caused the soil to freeze to impressive depths.  This could have resulted in root death to sensitive or stressed plants.
• When snowfall eventually arrived, it blanketed the ground without interruption, persisting until early spring in some locations and ensuring frozen soil until late March/early April.
• Strong winds seemed to be an everyday occurrence.  When coupled with high light intensity and frozen soil conditions, the damage to evergreens became a foregone conclusion.
• Finally, low temperatures, the likes we haven’t seen for many years, helped create the perfect storm.

Mitigating Winter Injury

Winter injury may not be immediately apparent when plants resume growth in the spring. Some plants may actually leaf out and appear quite normal for a time, only to decline and die later during stressful summer conditions.  To minimize unsightliness and promote plant health, dead wood should be pruned out as it becomes apparent. 

Providing appropriate amounts of water to compromised plants may be the most important task for landscape managers.  Plants already suffering from winter injury may die quickly if forced to cope with drought stress.  Mulching the area around trees and shrubs with organic materials like wood chips or shredded bark will help conserve soil moisture and keep lawn maintenance equipment away from sensitive bark and stem tissue. 

Finally, it is important to remember that fertilizer is not a cure-all for winter-injured plants.  If a soil test determines that mineral elements are deficient, then applying an appropriate fertilizer makes perfect sense.  But high rates of fertilizer will not miraculously close sunscald wounds, restore life to killed roots or buds, or reverse any of the other negative effects resulting from the memorable winter of 2013-14.

  

Jeff Iles

Department of Horticulture

Iowa State University

Below you will fine a few pictures taken by Dr. Iles around Ames. 

Persistent Wind Causing Delayed Liquid Preemergence Application

Last week I traveled to Davenport, Maquoketa, Dubuque, and Waterloo/Cedar Falls. I saw very diverse conditions throughout my travels; however, there were some collective issues. Davenport offered similar circumstances to central Iowa, with large areas of rye and Poa annua winterkill. Overall greens are looking better, but are still a little behind with our consistent nights in the low 40’s.  As I moved north to Maquoketa, I observed less widespread winter damage, and golf courses coming out of the ruthless winter well.

Across the state, turf managers are struggling to find windows for their liquid preemergence applications. The weather has not cooperated, with consistent winds in the 15+ mph range and extensive rainfall. Friday morning, we were finally able to apply our preemergence herbicide at the research farm (latest application to date during Dr. Christians tenure at Iowa State). I would remain aggressive in an attempt to apply a preemergence herbicide and believe you will receive some control. Nearly all preemergence herbicides offer a little post control with the best being dimension (dithiopyr).  Yesterday, I talked to Dan Smith at Carroll Municipal golf course after our IGCSA event and over the years he usually applies his preemergent about May 10^th and receives great control.  Only time will tell the overall efficiency of our mid-May applications. I have attached a picture (Photo 1) below of some crabgrass emergence at the ISU turf research facility from yesterday. 

In Davenport (Palmer Hills) and Dubuque (Bunker Hill), I was presented with a new challenge on the amount of damage caused by cross-country skiers. Both public golf courses deal with dead turf in fairways each year from skier traffic. The below pictures are courtesy of Tim Johansen at Palmer Hills. Tim mentioned that the turf does not usually recover until late June. I have also noticed extensive damage to many of the evergreen trees/shrubs in Iowa and I will address options in future blogs. 

SPORTS TURF RESEARCH AT IOWA STATE-KEVIN HANSEN 2014

Nick Christians
May 8, 2014
nchris@iastate.edu

Kevin Hansen
kevinh@iastate.edu


The following is from Kevin Hansen, a graduate student at Iowa State, who is working on his masters degree in professional agriculture.  It concerns his work with fraise mowing and establishment of sports turf areas.

Kevin Hansen:

My name is Kevin Hansen.  I am a full time employee of the Iowa State University (ISU) Athletic department working with sports turf management.  I am also working on a masters of professional agriculture, with a specialization in sports turf management.

My project centers around establishment of turf areas following fraise mowing (see earlier blogs).  I have been involved in the renovation of the football practice field at ISU and am conducting additional work on the process for my creative component.

The objectives of the research are:


1.  To determine the best establishment method for fraise mowing.
2.  To determine if covers are needed for spring establishment.
3.  To evaluate different seeding rates for establishment.

We established the study in a randomized complete block design with three replications.  The treatments are as follows: 
  1 .      Control 
  2.      Fraze mowed and grow tarp 
  3.      Fraze mowed, grow tarp, and 5lb per 1000 sq ft 
  4.      Fraze mowed and 5lb per 1000 rate 
  5.      Fraze mowed, grow tarp, and 10lb per 1000 rate 
  6.      Fraze mowed and 10lb per 1000 rate

     

     The study was initiated on April 7, 2014.  We pulled the tarps off on May 6.  I will be collecting data throughout the spring.

                      Here is the area right after fraise mowing on April 7, 2014.

                      The area after seeding and after tarps are laid.

                     May 6, 2014

      

           Tarps made a big difference initially.