# Common Unit Conversions

For many transformations, particularly when automated, please use the udunits2 software where possible. For example, in R, you can use
library(udunits2)
## transform meters to mm
ud.convert(10, "m", "mm")
## equivalently, via the udunits synonym database
ud.convert(10, "meters", "millimeters")
## it can also handle more complex units
ud.convert(10, "m/s", "mm/d")
NB: Many of these conversions have been automated within PEcAn.
Useful conversions for entering site, management, yield, and trait data \label{tab:conversions}
 From ((X)) to ((Y)) Conversion Notes (X_2=)root production (X_1=)root biomass & root turnover rate (Y = X_2/X_1) Gill [2000] DD(^{\circ}) MM'SS XX.ZZZZ (\textrm{XX.ZZZZ} = \textrm{XX} + \textrm{MM}/60+\textrm{SS}/60) to convert latitude or longitude from degrees, minutes, seconds to decimal degrees lb kg (Y=X\times 2.2) ​ mm/s (\mu) mol CO(_2) m(^{2}) s(^{-1}) (Y=X\times 0.04) ​ m(^2) ha (Y = X/10^6) ​ g/m(^2) kg/ha (Y=X\times 10) ​ US ton/acre Mg/ha (Y = X\times 2.24) ​ m(^3)/ha cm (Y=X/100) units used for irrigation and rainfall % roots root:shoot (q) (Y=\frac{X}{1-X}) (\% \text{roots} = \frac{\text{root biomass}}{\text{total biomass}}) (\mu) mol cm(^{-2}) s(^{-1}) mmol m(^{-2}) s(^{-1}) (Y = X/10) ​ mol m(^{-2}) s(^{-1}) mmol m(^{-2}) s(^{-1}) (Y = X/10^6) ​ mol m(^{-2}) s(^{-1}) (\mu) mol cm(^{-2}) s(^{-1}) (Y = X/ 10^5) ​ mm s(^{-2}) mmol m(^{-3}) s(^{-1}) (Y=X/41) Korner et al. [1988] mg CO(_2) g(^{-1}) h(^{-1}) (\mu) mol kg(^{-1}) s(^{-1}) (Y = X\times 6.31) used for root_respiration_rate (\mu) mol mol (Y= X\times 10^6) ​ julian day (1--365) date ​ see ref: http://disc.gsfc.nasa.gov/julian_calendar.shtml (NASA Julian Calendar) spacing (m) density (plants m(^{2})) (Y=\frac{1}{\textrm{row spacing}\times\textrm{plant spacing}}) ​ kg ha(^{-1}) y(^{-1}) Mg ha(^{-1}) y(^{-1}) (Y= X/1000) ​ g m(^{-2}) y(^{-1}) Mg ha(^{-1}) y(^{-1}) (Y= X/100) ​ kg mg (Y=X\times 10^6) ​ cm(^2) m(^2) (Y=X\times 10^4) ​