Land growing continuous grain corn as a cash crop loses soil at a rate of
14.0 metric tonnes ha-1 yr-1. This is a fertile soil, which has an organic matter content of 3.8% and nitrogen content of 0.35% (both by mass).
a)Calculate how long it will take to erode the entire Ah horizon of this soil. Assume an initial Ah thickness of 7 inches and a bulk density of 1.25 g cm-3 prior to the onset of cultivation
b)If the entire Ah horizon is lost, calculate how many kg of manure you would need to add per hectare in order to replace the lost organic matter if manure is assumed to be 100% organic matter .
Math - Ramya's work so far, Thursday, November 12, 2009 at 11:32am
Ok, so when your trying to find volume you multiply 7 inches by the 14 ton/ha/y. I know u need to convert it but my question is do i need to take the tones part into account or can i do it like this :
7 inches *( 217000434.00 in^2)<--[ that is 14 ha into inches sqaured].... and get the volume?
Math - bobpursley, Thursday, November 12, 2009 at 12:18pm
lost soil=soil mass
14000kg/10000m^2 yr * time=7in*1m/39.37in*1.25E3kg/m^3
time=7/39.37 * 1.25E3 /(14) years
check that. It seems to me to be easier working it in metric.
HELLO, sorry to bug u again ,but u said 14 years. i was just wondering shouldnt it be 1.4 years instead?. and if you convernting 1.25g/m3 to kg. should it be .. 1.25e-3?......im not completely sure however i still wanted to make sure.. thank you!
Yes, 14000/10000 is 1.4, and that should end up in the denominator. I have a eye going blind, and my computer screen sometimes lies to me about zeroes. That is why I always depend on students to "check that".
thanks.
Put 1.25g/cm^3 into your google search window like this:
1.25g/cm^3 in kg/m^3
Viola.