Statewide
Extra income is nice. Unexpected income is wonderful. Either might have a downside; our economists might call this an indirect cost or an “opportunity cost.”
Grain sorghum stalks in general have a crude protein content of about five to nine percent. Where a field’s stalks will fall in this range, will depend on the age of the stalks (assume less protein the longer stalks remain in the field) and how much leaf matter remains if the field is baled (higher leaf content will have higher protein). Absent actual hay forage test results, assume sorghum stalk %CP is 6.25%, which translates to 1.0% N content in the stalks. Thus for each ton of sorghum stalks removed per acre from the field, you have removed 20 lbs. of N per acre. What would it cost to replace that N? If your fertilizer cost is $0.65/lb. for actual nitrogen (unit of N), then it would cost you $13/A for each ton of sorghum stalks removed.
Other nutrients are also removed including phosphorus, potassium, and micronutrients. These typically calculate to be 1/4 to 1/3 of the value of the removed nitrogen, so add another $3-4/A to nutrient replacement costs. Now a ton of sorghum stalks removes about $16-17/A in nutrients based on their full nutrient replacement value; are you getting paid enough for the hay to justify this loss of nutrients? Whether you wish to sell the sorghum stalks or not is your decision, but if you get paid for half of the hay (the hayman does all the work and effectively pays you for half of the hay crop), then the value of nutrients leaving your field is double per ton of the sorghum stalks you get paid for! For example, if you receive $60/ton for the half of the hay, then over half of that income ($32-34) would be needed to replace the value of the nutrients leaving the field.
Is that a good deal? It isn’t ‘free’ money! This “income” has a very real cost.
Grazing sorghum stalks—This is a different situation. Only a fraction of the NPK and other nutrients leave the field in the animal in a grazing situation. Most of the nutrients are returned to the field in urine and feces so nutrient removal is nominal, even negligible.
Next Sorghum Tip: Baling Sorghum Stalks (II) — Loss of Soil Cover Protection
