# How many kg $ha^-$$^1 of exchangeable Mg^2$$^+$ is there in the top 15cm of this field?

Soil testing from a well-drained soil sample in 0-15cm depth of a farmers field provides the following information:

• Wet weight of a soil sample from a volume of 100 $$cm^3$$: 200 g

• Moisture content: 20%

• Soil chemical properties (in cmol/kg):

Exchangeable K: 2

Exchangeable Ca : 10

Exchangeable Mg: 4

Exchangeable H: 8

• Molar mass of $$H^+$$= 1; $$Mg^2^+$$ = 24; $$K^+$$ = 39; $$Ca^2$$+ = 40

1.What is the bulk density of this soil?

in here i did MS=(W-D)/W=0.2=(200-D)/200 SO Dry soil =160, Bulk density =160/100=1.6

2.How many kg $$ha^-^1$$ of exchangeable $$Mg^2^+$$ is there in the top 15cm of this field?