GolfClubAtlas.com > Golf Course Architecture Discussion Group
The importance of agronomy to a golf designer
RJ_Daley:
Some architects have the knowledge and credentials to make informed decisions to deviate from conventional wisdom like the USGA formula and construction method of greens construction because they understand the sites agronomy aspect. To modify the formula and construction method is to take a risk. If the archie can save the budget by recognition that soil and weather conditions allows for certain modification, he can save a bit on the budget. But, he has to know whether a penny saved now in construction and turf selection will be a dollar of maintanence later.
It isn't just which species of turf on a given soil and micro climate and end user profile, but which cultivars and what if any diversity % to use. If the developer is a chintz and doesn't have a turf professional and soil agronimist on board from the planning stage, the archie darn well better know something! :-/ :-[
Forrest Richardson:
Avg. Pan. Evap. Rate (Phoenix) = .8
RJ_Daley:
Oh Forrest ;D ::), pan evapotranspiration figures are so passe for the turf manager. Below is more specific ET/o method for the modern GCA and his faithful sidekick turf professional... :P
Derivation of the FAO Penman-Monteith equation for the hypothetical grass reference crop:
With standardized height for wind speed, temperature and humidity measurements at 2 m (zm = zh = 2 m) and the crop height h = 0.12 m, the aerodynamic and surface resistances become (Boxes 4 & 5):
ra = 208/u2 s m-1, (with u2 wind speed at 2 m height)
rs = 70 s m-1
(1 + rs/ra) = (1 + 0.34 u2)
Rn and G is energy available per unit area and expressed in MJ m-2 day-1. To convert the energy units for radiation to equivalent water depths (mm) the latent heat of vaporization, l is used as a conversion factor (Chapter 1). The conversion from energy values to equivalent depths of water or vice versa is given by (Eq. 20):
By substituting cp with a rearrangement of Eq. 8:
and considering the ideal gas law for r a:
where TKv the virtual temperature, may be substituted by:
TKv = 1.01(T+273)
results in:
[MJ m-2 °C-1 day-1]
where
cp specific heat at constant pressure [MJ kg-1 °C-1],
r a mean air density at constant pressure [kg m-3],
ra aerodynamic resistance [s m-1],
g psychrometric constant [kPa °C-1],
e ratio molecular weight of water vapour/dry air = 0.622,
l latent heat of vaporization [MJ kg-1],
u2 wind speed at 2 m [m s-1],
R specific gas constant = 0.287 kJ kg-1 K-1,
T air temperature [°C],
P atmospheric pressure [kPa],
[MJ m-2 °C-1 day-1]
or, when divided by l (l = 2.45),
[mm °C-1 day-1]
All of which goes to show that we are certainly in over our heads... :-/ :P ;D
Steve Lang:
;D :o
RJ_D, I wondered where Forrest was..
Shucks, with spreadsheets these days ???, this stuff is easy, in older days or daze, more pain setting something like this problem up under Fortran or Basic programming options let alone by hand for more than several conditions..
why didn't you show the folks the P-M basis skematic?
Maybe 98% do need to set their sprinklers to supplement mother nature.. and just get the grass cut.. but in the 21st Century there are more tools available if folks want to avail themselves..
RJ_Daley:
;D ;D ;D
Criminy sakes Steve, I'm lucky I can cut and paste text from the FAO, not schematics. You don't think I'm a braniac that actually understands this stuff do you? Why, I'd have to be some kind of a golf course architect or something. :-[
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