Question about question 4 in lab 05

Dear Maja,

Since we define the density of soil extract as 1kg/L in question 3, which density should we use in question 4? Bulk density or 1kg/L? Question 4 is the furrow slice of the soil. It is different between soil extract in question 3 and soil in question 4.

Bill

YifeiShao (talk)‎

Bill, from question 3 you know the concentration in the soil mg/kg i.e. mg of element x / kg of soil. Question 4 asks you to extrapolate that concentration (mg/kg) over 1 ha area (20 cm deep) assuming a soil bulk density of 1200 kg/m3. Since your answer to question 3 is in mg/kg of soil you need to use the bulk density of the soil in question 4.

SandraBrown (talk)‎

But Dylan told me not to use bulk density... I am confusing...

YifeiShao (talk)‎

ok Bill, let's wait for Maja's response

SandraBrown (talk)‎

In question #3 you need to use density of water for your calculation, but in question #4 you need to consider soil bulk density, since question #4 is asking for re-calculation of element X in the soil.
Question #4 is illustration of the final step in determining how much of an element there is in the soil based on lab analysis. This type of re-calculation is needed to determine application rates of fertilizers or organic amendments.
So, Sandra's explanation above is correct and should be used in dealing with questions #3 and #4.

MajaKrzic (talk)‎