2004 - Managing Nitrogen and Potassium in Brown Midrib Sorghum-Sudangrass
2003 - Managing Nitrogen and Potassium in Brown Midrib Sorghum-Sudangrass
2002 - Managing Nitrogen and Potassium in Brown Midrib Sorghum-Sudangrass
Managing Nitrogen and Potassium in Brown Midrib Sorghum-Sudangrass, 2004
Brown midrib sorghum-sudangrass (BMRSS) forage compares favorably with corn silage as feed for dairy cows in terms of milk production per acre, particularly in late-planted or droughty situations. While it has been shown to respond well to nitrogen (N), little is known about its potassium (K) requirements. This project aims to find the optimum rates of N and K for maximum yield and quality of BMRSS.
In 2002 and 2003, N applied at 100 lb/A for each cut increased yield 3-fold to 12 tons/A (at 35% dry matter) despite drought conditions. Applied K did not impact yield or quality. Milk production per acre was calculated to be optimized at the N rate for optimum forage yield...135 lb/A. The optimal N rate for BMRSS appears to be considerably higher than that of corn.
Additions of 200 lb K2O/A per cut supplied considerably more K than was removed. It raised forage K concentration above 3%, but maintained soil test K at the high level. The 100 lb/A rate of K2O supplied enough K to balance removal, but the soil test declined to the medium level. With no K applied, forage with low K levels suitable for dry cows was obtained, but soil tests declined rapidly to a rating of low.
In 2004, the project objectives shifted to more detailed examination of nutrient removal. Initial findings indicate that an average crop of 5.6 tons of dry matter would remove 70 lb P2O5/A. NY-05F