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 .
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?
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.
d.1.67%
a) To calculate how long it will take to erode the entire Ah horizon of this soil, we need to convert the given values to a common unit.
1. Convert the initial thickness of the Ah horizon from inches to meters:
7 inches = 7 inches * 2.54 cm/inch * 1 m/100 cm ≈ 0.178 meters
2. Convert the bulk density of the soil from g/cm³ to tonnes/m³:
1.25 g/cm³ = 1.25 tonnes/m³
3. Calculate the initial mass of the Ah horizon:
Initial mass = initial thickness * bulk density
Initial mass = 0.178 meters * 1 hectare * 1 hectare / 10,000 m² * 1 hectare * 1 hectare * 1 hectare * 1,000 kg/tonne * 1.25 tonnes/m³
Initial mass = 0.178 * 1 * 1 * 10,000 * 1 * 1 * 1,000 * 1.25 kg
Initial mass = 2,237.5 kg
4. Calculate the rate of soil loss per year per hectare:
Soil loss rate = 14.0 metric tonnes/ha/yr
5. Calculate the time it will take to erode the entire Ah horizon:
Time = initial mass / soil loss rate
Time = 2,237.5 kg / 14.0 tonnes/ha/yr
Time = 2,237.5 kg / (14.0 * 1,000 kg/ha/yr)
Time = 2,237.5 kg / (14,000 kg/ha/yr)
Time = 0.1598 years
Therefore, it will take approximately 0.16 years (or about 2 months) to erode the entire Ah horizon of this soil.
b) To calculate the amount of manure needed to replace the lost organic matter, we need to calculate the amount of organic matter lost first.
1. Calculate the mass of organic matter lost per year per hectare:
Mass of organic matter lost = soil loss rate * organic matter content
Mass of organic matter lost = 14.0 metric tonnes/ha/yr * 3.8%
Mass of organic matter lost = 14.0 tonnes/ha/yr * 0.038
Mass of organic matter lost = 0.532 tonnes/ha/yr
2. Calculate the amount of manure needed to replace the lost organic matter:
Amount of manure needed = mass of organic matter lost / organic matter content in manure
Amount of manure needed = 0.532 tonnes/ha/yr / 100%
Amount of manure needed = 0.532 tonnes/ha/yr
Therefore, you would need to add approximately 0.532 tonnes of manure per year per hectare to replace the lost organic matter, assuming the manure is 100% organic matter.