Does organic fertilizer increase the risk of lawn fungus?

Discussion in 'Pesticide & Herbicide Application' started by scott martoccia, Feb 16, 2013.

  1. scott martoccia

    scott martoccia LawnSite Member
    Messages: 46

    I have had a problem with several lawns treated with granular organic fertilizer (summer app) developing brown patch and pythium. Sometimes severe within days of application. One property we treated rear yard organic and front synthetic. Clear cut difference. Can anyone shed some light on what may be going on?
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  2. Dave Stuart

    Dave Stuart LawnSite Member
    Messages: 98

    The summer months are not the most conducive periods for fertility, the plant ( monocot ) is using carbohydrate reserves to stave off heat and stay alive while dormant / under stress meaning high" respiration "or the use of reserves at a cellular level.
    At this time for C-3 plants ( cool season ) photosynthesis is very low or the production of food by the photo sites in the leaf.
    When nitrogen is applied ( especially soluble ) the plant will increase water uptake to move the nutrient through the transpiration stream or water conducting tissue called xylem this consumption causes increased cell turgor ( elasticity ) of the cell weakening the plant at a very susceptible time. Nitrogen is best utilized in the fall when plants are storing carbohydrates, also in early to mid spring during early stages of shoot growth when photosynthesis is high and the plant is producing abundant photosynthates with plenty of available water. The carbohydrates built off spring production are then utilized for periods of high respiration in summer.

    Organic matter such as the type utilized for fertility are converted to nitrate by a process called mineralization which includes dozens of bacteria which simplify and hydrolize to elemental ammonium then finally to a soluble form of nitrate. In the heat this process is accelerated, especially with materials that are susceptible to easy breakdown such as feces, blood meal, ect............

    Microbe activity is stimulated in the soil and thatch by organic materials, they strengthen the growth medium and the plant life, microflora such as fungi will fall into a natural spectrum of activity in a heathy organic soil plant spectrum and will rarely take out healthy organic managed turfgrass growing in healthy organic soil profile with all the natural predation thriving in that soil.

    Eventually a soil that is only sustained by synthetic materials will lose precious natural bacteria, and organic macro & micro fauna from excessive amounts of ammonium, urea, sulfur and the like. These plants are continuously on a jag. There needs to be a balance in the growth medium.

    If the scenario is what it seems to be then adding organic fertilizer in the dead heat of summer on a mostly synthetic managed medium microbes start feeding quickly on probably the only organic compounds there " the fertilizer " which would In that spectrum stimulate even the microflora ( fungi ) to a point.

    Soluble fertility usually curbs rhizoctonia " brown patch " activity ( in fact any fertility ) Pythium however is stimulated by nitrogen and will take off like wild fire. I believe your answer resides in something other than the fertilizers applied. What exactly did the material consist of ? We're all enviro/ cultural conditions similar such as shade & thatch? There is more to be questioned.......

  3. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,810

    Was it hot last year? LOL! Hot humid weather stimulates the spread of fungal diseases. Some ryegrass types are particularly sensitive. Red thread, gray leaf spot, and brown patch can be serious. Avoid nighttime irrigation. Irrigate between noon and 4 so that the grass leaf blade dries out immediately. Switch to irrigation no more than three days per week--so that the average humidity and leaf wetness are at a minimum.

    Low nitrogen makes red thread possibly the organic contained less nitrogen or released it more slowly.
    If disease becomes chronic every year...try to replace the area with bluegrass sod. Or perhaps tall fescue. Or perhaps overseed with a highly disease-resistant perennial rye. Make sure it is one of the top 10 in Rutgers NTEP tests. Their new variety called "Wicked" is excellent. Perhaps combine it with "Cutter II" which has very good red thread resistance.
  4. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Timing is everything... The soil needs to be fertilie B4 Summer sets in so theplants can utilize anything it needs, when it needs it...
    Organic Fertilizers "ROT" first,,, then sometime during that rotting process it produces N and Cycles the other nutrients as well...

    Whenyou have raw material that is ROTTING on your lawn, it is a crapshoot as to what microbes will take advantage first and thrive the best... The consumption phase of Organic Fertilizers should be done when the grasses are actively growing... it is a common mistake to putthings on the lawn that will feed the fungi, because the plants are NOT using it...

    This is a SIMPLE and GENERALIZED concept about the CYCLING of raw materials back into their constituent parts, so details and exceptions should only be addressed once the concept of UTILIZATION are clarified...
    IMO the N that cycles back into the soil during the Summer Heat from Grass Clippings is sufficient for that period of the lawns' life... :)
  5. scott martoccia

    scott martoccia LawnSite Member
    Messages: 46

    You may have a point about it being a crap shot....On one hand I rationalize using organic fertilizers during the summer as providing a more stable nitrogen source that theoretically should not encourage lucious surge growth and hence favorable disease conditions. On the other hand I suspect (like you said) that the organic fertilizer is directly feeding the disease source.
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  6. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    I believe it is definately worth consideration,,, similar to applying N to the lawn just B4 it freezes and the snow comes, plays a role in producing snow mold...

    I always consider the fact that organic materials need to 'rot' in order to cycle nutrients... that makes it simple, becuz we all have experiences with rot, decay, mold and even infections on our own skin...
    The grass is always greener around a cowpie,,, but barnyards STINK!!! :)
  7. phasthound

    phasthound LawnSite Fanatic
    Messages: 5,162

    An excellent detailed science based explanation.

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