raymond@utpsych.toronto.edu (Raymond Shaw) (05/24/89)
This is probably a really stupid question, and this is probably the wrong place to ask, but I have this question that gets to me each time I mow my lawn: Would the lawn produce more oxygen (which I presume is good for the environment) if I didn't mow it, and just let it grow? Sorry if this is offensively naive, please e-mail answers, flames, etc. if you think that no one who reads this would be interested. Thanks. -Just a psychologist, not a biologist. -Ray Shaw raymond@psych.toronto.edu
steve@revolver.gatech.edu (Poppa Smurf) (05/24/89)
In article <1989May23.190505.18229@utpsych.toronto.edu+ raymond@psych.toronto.edu (Raymond Shaw) writes:
+This is probably a really stupid question, and this is probably the wrong
+place to ask, but I have this question that gets to me each time I mow my
+lawn:
+
+Would the lawn produce more oxygen (which I presume is good for the environment)
+if I didn't mow it, and just let it grow?
+
+Sorry if this is offensively naive, please e-mail answers, flames, etc. if
+you think that no one who reads this would be interested. Thanks.
+
+-Just a psychologist, not a biologist.
+
+-Ray Shaw
===========================
Ray,
You can stop worrying. Grass is biomass and perennial. It draws its
energy and nutrients from the sun and the soil. When it dies, the elements
return from whence they came. No net gain or loss in oxygen.Ram-Ashwin@cs.yale.edu (Ashwin Ram) (05/24/89)
In article <1989May23.190505.18229@utpsych.toronto.edu>, raymond@utpsych.toronto.edu (Raymond Shaw) writes: > Would the lawn produce more oxygen (which I presume is good for the environment) > if I didn't mow it, and just let it grow? Grass doesn't "produce" oxygen, it only gives off what it absorbed from the environment (in another form) to begin with. I imagine that if cut grass releases less oxygen into the atmosphere, it also absorbs less oxygen molecules to begin with. So you aren't "robbing" your environment of oxygen by mowing your lawn, though you may temporarily reduce the amount of free oxygen in the immediate vicinity of the grass by a negligible amount. Of course, if everyone cut down their grass and plants and all the trees all at the same time, it would be a disaster... -- Ashwin. Disclaimer: I'm not a biologist.
potency@violet.berkeley.edu (Tom Slone) (05/24/89)
In article <8323@pyr.gatech.EDU> steve%revolver@gatech.edu writes: >In article <1989May23.190505.18229@utpsych.toronto.edu+ raymond@psych.toronto.edu (Raymond Shaw) writes: >+Would the lawn produce more oxygen (which I presume is good for the environment) >+if I didn't mow it, and just let it grow? > You can stop worrying. Grass is biomass and perennial. It draws its >energy and nutrients from the sun and the soil. When it dies, the elements >return from whence they came. No net gain or loss in oxygen. The net loss to the environment has already happened when the lawn was installed in the first place: - Loss of native species (including native grasses) and habitat - Loss of species diversity (when the ecosystem was changed to a monocrop) - Reduction of biomass (from multi-foot high trees and shrubs to inch high grass) - Consequent loss of carbon bank, released as CO2 to the atmosphere - Potential releases of poisons to the environment from lawn maintenance chemicals and their production potency@violet.berkeley.edu {decvax|hplabs|ihnp4|decwrl|nbires| \ sdcsvax|tektronix|ulysses}!ucbvax!violet!potency
ray@Polya.Stanford.EDU (Ray Baxter) (05/25/89)
In article <1989May23.190505.18229@utpsych.toronto.edu> raymond@psych.toronto.edu (Raymond Shaw) writes: > Would the lawn produce more oxygen (which I presume is good for the > environment) if I didn't mow it, and just let it grow? In article <8323@pyr.gatech.EDU>, steve@revolver (Poppa Smurf) replies: > You can stop worrying. Grass is biomass and perennial. It draws its >energy and nutrients from the sun and the soil. When it dies, the elements >return from whence they came. No net gain or loss in oxygen. This response and another reponse by Ashwin Ram assume that the original question has to do with atomic oxygen, ie. atoms of O. I assume that it is more probable that the question is about oxygen gas, O2, this being one of the products of green plant photoysnthesis. In fact, grass (and all other green plants) do produce O2 and consume CO2 and H20 and solar energy. The reaction is: CO2 + H20 ----> CH20 + 02 where CH2O is generalized carbohydrate. This does not answer the original question which I interpret as asking how the height of grass influences the rate of O2 production. The answer to this is that it depends. Cutting the grass almost surely causes a transient decrease in the rate of oxygen (O2) prodution. Beyond that, it pretty much depends on how short the grass is cut. Empirically, as the surface area of plants (leaves only) increases from 0 to three times the surface area of the ground that it is covering, the rate of production over the whole stand increases. Once you get beyond a ratio of three, essentially all of the availible solar energy is captured and so there is no increase in photosynthesis and hence no change in the rate of O2 production. On the flip side, the whole plant is constantly consuming O2 as it respires. This reaction, which is merely the reversal of the equation above, yields energy to the plant rather than consuming solar energy. The rate of this reaction is more or less proportional to the mass of the plant. As the ratio of leaf area to ground increase above three, the mass of the plant and so the rate of O2 consumption continues to grow. (Much of this additional mass is allocated to supporting structures.) Putting the last several paragraphs together, you can see that the rate of O2 production will be a reasonably complicated function of the height of the grass. Cutting the grass can increase, decrease, or not change the rate of O2 production. (The time derivative of this rate is left as an exercise for the reader.) Ray Baxter ray@polya.stanford.edu
dd@beta.lanl.gov (Dan Davison) (05/25/89)
In article <1989May23.190505.18229@utpsych.toronto.edu>, raymond@utpsych.toronto.edu (Raymond Shaw) writes: > Would the lawn produce more oxygen (which I presume is good for the environment) > if I didn't mow it, and just let it grow? Yes. But the the amount is very, very small. Somewhat more than 50% of the world's oxygen comes from the top meter or so of the oceans. At least 30%, by the last estimate I remember, comes from forests, rain forests, and similar large-scale O2 producers. Your lawn does indeed contribute to the total O2, but I wouldn't worry about it. On the other hand, if I owned a house & thought could get away with letting the grass grow long, I would. The reasons not to do this include ticks, fleas, and assorted insects. dan davison/theoretical biology/t-10 ms k710/los alamos national laboratory los alamos, nm 875545/dd@lanl.gov (arpa)/dd@lanl.uucp(new)/..cmcl2!lanl!dd -- dan davison/theoretical biology/t-10 ms k710/los alamos national laboratory los alamos, nm 875545/dd@lanl.gov (arpa)/dd@lanl.uucp(new)/..cmcl2!lanl!dd
dd@beta.lanl.gov (Dan Davison) (05/25/89)
In article <61605@yale-celray.yale.UUCP>, Ram-Ashwin@cs.yale.edu (Ashwin Ram) writes: > In article <1989May23.190505.18229@utpsych.toronto.edu>, raymond@utpsych.toronto.edu (Raymond Shaw) writes: > > Would the lawn produce more oxygen (which I presume is good for the environment) > > if I didn't mow it, and just let it grow? > Grass doesn't "produce" oxygen, it only gives off what it absorbed from the > environment (in another form) to begin with. Right. CO2 -> O2+ carbohydrate > I imagine that if cut grass releases less oxygen into the atmosphere, > it also absorbs less oxygen molecules to begin with. technically correct, actually wrong. There is minimal loss of O2 out of the atmosphere, so in that sense the total content of O is constant. BUT, if the plants don't pull CO2 out of the atmosphere, it goes into the geochemical carbon cycle as carbonate. Less O2 is available in the atmosphere in this case, so yes, cutting your lawn *does* make a difference, a little teeny tiny difference. See the articles on the geochemical carbon cycle and the differences between the earth and mars atmospheres in Scientific American. (Last two years or so) dan davison/theoretical biology/t-10 ms k710/los alamos national laboratory los alamos, nm 875545/dd@lanl.gov (arpa)/dd@lanl.uucp(new)/..cmcl2!lanl!dd -- dan davison/theoretical biology/t-10 ms k710/los alamos national laboratory los alamos, nm 875545/dd@lanl.gov (arpa)/dd@lanl.uucp(new)/..cmcl2!lanl!dd
ajw@stout.cis.ufl.edu (Andy Wilcox) (05/31/89)
In article <24792@agate.BERKELEY.EDU> potency@violet.berkeley.edu (Tom Slone) writes: > >The net loss to the environment has already happened when the lawn was >installed in the first place: There are some important steps you can follow to make things better for the environment. * If you mow your lawn, don't use a gasoline powered mower. * If possible, blow your grass over your yard, and let it decompose there. Raw grass contains a sizeable portion of nitrogen that is returned to soil by this method. Leaving grass on the lawn does not cause thatch, which is most commonly caused by over fertilization. * If you bag your grass, be sure to compost it, and spread it back over your yard in the next season. Again, your lawn will love the nitrogen boost. --Andy
rbc@cuuxb.ATT.COM (~XT6511100~Rick Clark~C24~H15~6011~) (06/01/89)
In article <20388@uflorida.cis.ufl.EDU> ajw@manatee.cis.ufl.edu (Andy Wilcox) writes: > * If possible, blow your grass over your yard, and let it decompose > there. Raw grass contains a sizeable portion of nitrogen that is > returned to soil by this method. Leaving grass on the lawn does > not cause thatch, which is most commonly caused by over > fertilization. I do not bag my clippings, and I have a dog that "selectively fertilizes" my lawn, so I have a some good first hand data on thatch vs. fertilization. FACT MODE ON: On my lawn (northern Illinois clay in almost full sun): No fertilizer == thatch. Good fertilizing == no thatch. Over fertilizing == no grass. FACT MODE OFF, PONTIFICATION MODE ON: Grass clippings return nitrogen to a dense stand of grass. Grass clippings speed the thatching rate of a sparse stand of grass without returning much nitrogen to the soil (it is released to the air instead of the soil by the sunlight exposure). Partial shade also beats thatch in my lawn. I suspect watering copiously and regularly would too. I think manicured lawns are silly for this part of the country too, but I also think it is important not to spread misinformation, regardless of the cause. -- =Richard B. Clark Lisle, IL ...!{att,lll-crg}!cuuxb!rbc OR cuuxb!rbc@arpa.att.com
ries@arcturus (Marc Ries) (06/01/89)
In article <20388@uflorida.cis.ufl.EDU> ajw@manatee.cis.ufl.edu (Andy Wilcox) writes: >In article <24792@agate.BERKELEY.EDU> potency@violet.berkeley.edu (Tom Slone) writes: >> >>The net loss to the environment has already happened when the lawn was >>installed in the first place: Last time I heard, concrete doesn't provide oxygen to the atmosphere. >There are some important steps you can follow to make things better >for the environment. There are. Only lets get them CORRECT! > * If you mow your lawn, don't use a gasoline powered mower. Let's be more specific. Use a push mower. An electric mower requires juice from the utility Co. which has to be produced somehow (burning coal, gas, nuclear, etc.). > * If possible, blow your grass over your yard, and let it decompose > there. Raw grass contains a sizeable portion of nitrogen that is > returned to soil by this method. Leaving grass on the lawn does > not cause thatch, which is most commonly caused by over > fertilization. Unfortunately, raw "grass" clippings actually USE UP available soil nitrogen in the process of decomposition. It's crops like CLOVER (that turn fixed nitrogen [nitrogen in the soil that other plants can't utilize] into free nitrogen [nitrogen that plants can utilize]) that release their accumulated nitrogen in the decomposition process. RTFM 8-) You should actually ADD free nitrogen so that the decomposing grass does not deplete the nitrogen in the soil. While letting grass clipping stay in the grass does not guarantee a thatch problem, it won't help. Thatch is a layer of dead organic matter, not yet decomposed, that hinders the infiltrations of air, water, and nutrients to the grass roots. Mechanical aeration or increased microbial activity (to decompose the thatch) will help control "thatch". > * If you bag your grass, be sure to compost it, and spread it back > over your yard in the next season. Again, your lawn will love the > nitrogen boost. It may help the soil by providing organic matter to aerate the soil and improve microbial activity, but composted "grass" does NOT give your lawn a nitrogen "boost"! Marc Ries <somewhere>!ries "PHOTOVOLTAICS: safe/clean Electricity from the SUN"
rbc@cuuxb.ATT.COM (~XT6511100~Rick Clark~C24~H15~6011~) (06/03/89)
In article <1785@spp2.UUCP> ries@spp2.UUCP (Marc Ries) writes: >In article <20388@uflorida.cis.ufl.EDU> ajw@manatee.cis.ufl.edu (Andy Wilcox) writes: >> * If possible, blow your grass over your yard, and let it decompose >> there. Raw grass contains a sizeable portion of nitrogen that is >> returned to soil by this method. Leaving grass on the lawn does >> not cause thatch, which is most commonly caused by over >> fertilization. > > Unfortunately, raw "grass" clippings actually USE UP > available soil nitrogen in the process of > decomposition. It's crops like CLOVER (that turn Are you sure about that Andy? I recall from my MSU crop and soil science courses that straw decomposition is a net consumer of nitrogen but that hay was a net contributor. (They didn't specify clover or timothy). I suspect the fresh clippings are analogous to hay and the thatch is analogous to straw (clippings with the nitrogen decay products already leached into soil and air by rain and sun). If you can compost the clippings or get them into dense shade at roots of good grass to rot quickly, I think they do return more nitrogen than they consume from the decay process. They do NOT return more nitrogen than they originally took from the soil (like clover can), but it is better than not returning anything. -- =Richard B. Clark Lisle, IL ...!{att,lll-crg}!cuuxb!rbc OR cuuxb!rbc@arpa.att.com
logant@lafcol.UUCP (Tracy Logan) (06/05/89)
The worries about clippings and nitrogen puzzle me. We put the clippings from a lawn (we didn't feed it, it fed us, dandelions) onto a fairly large vegetable garden. Seems like they kept down weeds, disappeared pretty fast. I find it hard to believe those clippings REDUCED the fertility of the garden, but I only ate from it, never tested its soil. If they take nitrogen from the soil to decompose, it would seem the N would then be available. It doesn't go off as NOx, does it, nor as NH4 in those aerobic conditions? My logic was: I disrupted a steady-state situation by eating the chinese-cabbage, so I put the clippings there to replace it. Is that fundamentally false? Tracy Logan uucp : rutgers!lehi3b15!lafcol!logant Academic Computing Services Bitnet : LOGANT@LAFAYETT Lafayette College Internet: logant%lafayett.bitnet@CunyVM.CUNY.EDU
ray@Polya.Stanford.EDU (Ray Baxter) (06/07/89)
In article <1277@lafcol.UUCP>, logant@lafcol (Tracy Logan) writes: >The worries about clippings and nitrogen puzzle me. Don't be puzzled. These claims are simply wrong. There is no way that returning grass clippings to your lawn will reduce the availible soil nitrogen, as compared to say bagging the grass and carting it off. The original poster seemed to believe that because only legumes (such as clover) fixed nitrogen from atmospheric N2, the nitrogen present in non-legumes was not returned to the soil. While it is true that only legumes can cause a net increase in soil nitrogen, there will be more nitrogen in soils where the grass clipping are returned.
jma@abel.UUCP (Jeff Abrahamson) (06/08/89)
Several people have debated the pros and cons of fertilizer w.r.t. thatch. Could someone clue me in on why you don't want thatch? Unless you cut your grass quite short (which wastes water in all but the wettest areas), you shouldn't see much brown through the green. And thatch makes for a softer lawn. When I walk (--> barefoot) or lie on grass, I much prefer to see grass and thatch than topsoil (as I do on some well-raked lawns). -- ---------- Jeff Abrahamson jma@abel.uucp, abel!jma@manta.pha.pa.us UPenn Mathematics jma@grad1.cis.upenn.edu Bicycle Coalition of the Delaware Valley
rbc@cuuxb.ATT.COM (~XT6511100~Rick Clark~C24~H15~6011~) (06/09/89)
In article <415@abel.UUCP> jma@abel.UUCP (Jeff Abrahamson) writes: > > Several people have debated the pros and cons of fertilizer >w.r.t. thatch. Could someone clue me in on why you don't want thatch? > > Unless you cut your grass quite short (which wastes water in >all but the wettest areas), you shouldn't see much brown through the >green. And thatch makes for a softer lawn. When I walk (--> >barefoot) or lie on grass, I much prefer to see grass and thatch than >topsoil (as I do on some well-raked lawns). >-- >---------- >Jeff Abrahamson jma@abel.uucp, abel!jma@manta.pha.pa.us >UPenn Mathematics jma@grad1.cis.upenn.edu >Bicycle Coalition of the Delaware Valley Well, there is thatch, and then there is THATCH. This is more of a problem in parts of the country drier than your Delaware Valley. Thatch in good, barefoot turf you can only see by looking carefully deep in between the blades. THATCH, on the other hand makes the lawn look like thin, green streaks on a background of pale brown that glares in the sunlight. In bad cases, the grass retreats to little islands of struggling green, and there are many pock marks as big as your fist with no grass at all. THATCH is definitely not pleasant to walk or lay on. The grass gets into lumpy tufts. The grass blades develop stiff, protective sheathes that poke tender skin. the ground gets compacted under the thatch without grass roots to aerate it. The grass is not dense enough to maintain a cool, moist microclimate. It feels like it reflects nearly as much heat on a pedestrian as a concrete sidewalk. Ants and large weeds however, think THATCH makes a major improvement in a lawn. -- =Richard B. Clark Lisle, IL ...!{att,lll-crg}!cuuxb!rbc OR cuuxb!rbc@arpa.att.com