Agri-Growth International

Discussion in 'Organic Lawn Care' started by Whitey4, Feb 1, 2008.

  1. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    Are you saying that you think large tracts of turf that aren't irrigated are high water use landscapes?
  2. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,335

    Without going into alot of detail, yes. It is not a function of where the water is coming from, but how much water is being used (ET). Water lost to ET is water potentially lost for potable purposes.

    Naturally supplied water (rain) is leaps and bounds better than irrigation, especially if you allow the turf to go dormant during droughts. It is also far more sustainable with respect to water than irrigated turf. However, in areas of the country where water rights are tightly managed, large expanses of turf (or in some cases any turf) could be construed as a violation of those rights. A perfect example of this is Colorado.

    Shocking, yup. Is this an indication of what is happening around the country? Perhaps not to that degree, but the severe droughts in the South-East this past year (and currently) have caused alot more people to think real hard about water issues and how landscapes contribute to those issues.
  3. Whitey4

    Whitey4 LawnSite Silver Member
    Messages: 2,448

    Well, as I had mentioned, I tend to think locally.... and I don't see much of a connection with drought and water use issues here as opposed to elsewhere. After all, here is where I work.... not "there". LI is quite humid in the summer, and evaporation as a result is greatly reduced. That doesn't mean I condone poor water supply management either, however. I just don't see turf as a "water waster" here, while offering the caveat that I am by no means an authority in any definition on the subject.

    Rainwater runoff here goes into the sewer system. That runoff gets fed into large basins that do a poor job of natural filtration as they are deep, very close to the water table and are mostly sand. Turf absorbs a significant amount of rainfall (and trust me, this stuff blowing in from the midwest coal plants needs as much filtration as possible) and the less runoff the better.

    Turf has it's advantages, including something of an air conditioning effect when temps get high. Is it right for very situation? Of course not. But it has it's place. You can't play croqeut in a patch of sweet woodruff.
  4. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Please be patient here, but this makes no sense to me. Tell me what I am missing.

    On the one hand we have grass that sucks water out of the top 2-6 inches of soil and is almost a 2 dimensional surface when the wind blows across it to evaporate its stomata. Once a significant rainfall gets beyond that root zone it is free and clear all the way to the water table through 40 feet of sand or whatever.

    On the other hand once a rain drop breaks through the sponge of the surface growth it is not going to go anywhere but to the shrub, perennial, or tree root that is running under the surface planting. Then when the wind blows to evaporate the stomata it is not only drawing from the horizontal plane , but from a vertical as well.

    It is a basic principle that applies to spreading your shirts on the ground to dry vs. hanging them on the clothesline. Which will dry first?
  5. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,335

    How good are your math skills?

    THE Penman-Monteith Method

    Chapter 2 - FAO Penman-Monteith equation

    Couple of things to point out.

    1) We can't assume 2 dimensions here.

    2) Wind is not the only factor that drives ET.

    3) It is not accurate to state that water which is outside the effective root zone will all drain to the water table, or that once it is outside the effective root zone it is unavailable to the plant.

    Couple of problems here.

    1) You have made an assumption with turf but have not carried it over to trees/shrubs/perennials, in that water outside the root zone will return to the water table.

    2) Your assuming here that all water in the root zone will go to the plants. If we just look at roots, how much water is available to the plant is a function of root density. Generally speaking, turf has a higher root density than trees/shrubs/perennials in a given volume of soil.

    3) Yes, you do have a larger vertical component, but you neglected the other factors that contribute to ET, such as mulching, shading, leaf physiology, net leaf area, etc... When adding it all up, generally it will lead to a lower ET value than turf, even with a larger vertical component.

    My suggestion if you want to observe the drying profile of a soil with turf vs. a mulched tree/shrub/perennial planting bed, pick an appropriate site and take cores of the two areas this spring (every couple of days or so) as the soil drys out naturally.

    If you have a moisture meter you can skip the cores and use that to map the drying profile (make sure your sampling at the same depths and location in both areas). If you really want to get fancy, record the values and time in a spreadsheet so you can plot it. :)
  6. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,335

    :laugh: touche
  7. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Thanks for replying and showing where you get the idea from. The experiment you suggested is not considering the total volume of water going through the plant from all sources. A water meter stuck in one level of the ground is pretty limiting.

    Let's do a more comprehensive experiment :) put a shrub in a 5 gallon planter with the dish under it to catch the water. Same for some turf in the same volume of dirt.

    Flood them both and keep them in the same environment and even mulch over the top of the 5 gal. pot if you want. The totality of your water 'is' in the 5 gallon container, so you can chart it how ever you want.

    If your shrub is alive it should suck the water out of the basal dish within one day and show signs of stress in a week. The grass pot will probably start to stink of stagnant water by then.

    I agree that the turf has root density greater than an oak tree but 'root volume' is the important factor here. One prevents the erosion of surface soil the other protects the larger mass of supporting soil.

    This is an example of what I meant earlier about 'education' vs. 'indocrination'. If I had bought into your premise (the experiment) I would have had to buy into your conclusion. Don't be offended, but I don't buy it and have demonstrated why.
  8. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,335

    No offense taken. Let me explain.

    A few acronyms first.

    ET = EvapoTranspiration
    SMS = Soil Moisture Sensor/Sensing
    WHC = Water Holding Capacity
    AD = Allowable Depletion

    What I have presented is not an idea nor is it scientific speculation. These methods (ET and SMS) have been used for a very long time, primarily in Ag, but have begun to slowly trickled down to landscapes.

    Irrigation/water management is one of the primary things I do. Not only have I run ET calculations more times than I can count, but I have personally observed and measured what I have described in my previous post for many years. In my region, lawn sprinklers need to be started anywhere from 6-8 weeks (on average) before the rest of the landscape, depending on the age and plant types.

    I did an experiment one year where I let an established landscape consisting primarily of trees & shrubs go without water to see how long it would take to show signs of water deficit. I was well into June before the plants started to decline due to lack of water. On this particular site, the turf sprinklers generally need to be started in early to mid March. Keep in mind, once the winter rains stop in my region, that is all the rain we get 99% of the time until next winter.

    I fail to see why not. You have a given volume of soil that you need to keep from going below a certain point (AD). What better way to determine the entire amount of water lost to ET than to measure the water content of the soil that is representative of the effective root zone of the plants over time? Once your soil has drained to field capacity, then it is a pretty safe bet the vast majority (if not all) of your losses from that point on can be attributed to ET.

    I disagree. Measuring of soil moisture content is the most accurate way to determine system water use (assuming homogenous soil characteristics with respect to WHC). ET calculations attempt to do the same thing as soil moisture sensors by using plant characteristics and environmental conditions.

    I cannot see how a controlled experiment that is not representative of field conditions is more comprehensive than a field experiment on the site under study. Here are a couple of problems I see with your experiment.

    1) You should not have a dish
    2) It is highly unlikely your leaf area is the same
    3) You have not indicated the age of the plants

    There are more problems, but you get the idea. What you setup here can be likened to drinking a beer with a straw vs. drinking it shotgun style. You have not normalized the other variables of your experiment and therefore cannot draw any reasonable conclusions from that experiment.
  9. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    I am certainly not trying to dis your ability in doing what you do for a living and I agree that most landscapes survive quite well without irrigation once established. I have noticed that very thing myself. We seem to disagree on the reason for that.

    I agree with the concept of draining to field capacity then the remainder of the water being lost to ET. The 'effective root zone' that you mentioned would be different from in a forest than it would a lawn. Trees have a root zone of many cubic yards under the surface whereas grass makes it living on the top few inches of soil. I see that as a significant difference.
    In fact I can see a grassy knoll protecting the field capacity of moisture underneath its cover whereas trees will continue to draw well beneath the surface for as long as they are able.

    Ok let's try a real life scenario that I as a landscape pro needed to present solutions for.
    There is a garden about a 1/4 of the way down the hill to the lake. This is an area that was terraced for the roadway years ago, but they went too deep. The downhill side of the road is higher ground than the road so it is more of a bowl than it is a terrace. Flooding the roadway and part of the garden even with moderate rains.
    At the low end of the garden I dig a drainage hole by removing the topsoil and leaving behind the sand that makes up this hill. Water would stand on the road for a couple of days, now it is gone in less than 12 hours most generally.
    However we would like something that dries up that hole quickly so the surrounding heavy topsoil doesn't stay so mucky for so long.
    Plant grass or sunflowers?
  10. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,335

    I wasn't going to post this originally because it is more or less region specific, but the principles still hold, and if you can match up your plant zone (smallaxe you won't be able to) then you can still use it. In any event, I suggest anyone who is involved with irrigation read it. This is the method I use to determine landscape water needs, plus site measurements and observations to fine tune.

    Water Use Classification of Landscape Species

    Is this a trick question? My answer is neither -> put in some appropriate drainage. :)

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