Environmental Studies 100
Nutrient Budget
Michael Pollan. 2002. “Sustaining Vision”. Gourmet Magazine.
Your goal is to determine if Joel Salatin’s farm is sustainable with regards to nitrogen use. In this context, sustainability means that the inputs of nitrogen balance the losses, and that there is not a net loss of N over the years. To figure this out, you will need to put together a nitrogen budget for the farm. First you will calculate how much nitrogen is coming into the farm in the form of hay and chicken feed. Then you will calculate how much is leaving the farm in the form of animals that are exported.
Part 1. Inputs:Unit conversions: 1 acre = 0.405 ha
1 kg = 2.2 lbs
Assume: Hay 1% N by weight
Chicken feed is 3.5 % N by weight
1. What is the total area of the farm? What is it in hectares?
2. How much hay do (all of) the cattle consume each year? Assume they eat hay for 100 days each year.
3. How much nitrogen is in this total amount of hay?
4. How much N is brought into the farm in hay each year? Your answer should be in this form: kg N yr-1.
5. From Joel Salatin’s website, I found out that he imports 7605 lbs of chicken feed to the farm each year. How much N is brought into the farm in chicken feed each year? Your answer should be in this form: kg N yr-1.
6. Adding together imports in hay and chicken feed, how much nitrogen is brought into each hectare of the farm each year? Your answer should be in this form: kg N ha-1yr-1.
Part 2. Outputs:
1. Which animals are slaughtered and dressed on the farm? Which are slaughtered offsite? How does this make a difference for the export of nitrogen?
Assuming the following, fill in the table below:
a.) 1 kg = 2.2 lbs
b.) For cows and pigs, the weight of the meat is 60% of the weight of the total animal.
Kg of meat = (0.60) * weight of total animal
For example: 13,636 kg of beef = 22,726 kg of cow
c.) The edible portions of one chicken weigh 1.2 kg
d.) The edible portions of one rabbit weigh 1.4 kg
e.) The edible portions of one turkey weigh 5 kg
f.) A cow’s whole body is 18% protein
g.) A pig’s whole body is 12% protein
h.) Chicken, rabbit, and turkey meat is 20% protein
i.) All animal protein is 16% nitrogen
j.) 1 egg contains 1 gram of nitrogen
Animal product exported from the farm / Amount of product exported from the farm / Weight (kg)of exported products / Protein content of exported products / Nitrogen content of product exported
(kgN yr-1)
Beef
Pork
Chickens
Rabbits
Turkeys
Eggs / ------/ ------
Total N exported from the farm
Total N exported (kg N ha-1 yr-1)
Part 3. Synthesis: Calculate N Budget
Is there a net surplus or deficit on the farm?
Where could the missing N be coming from?