Integration of potato production, dairy forage and manure management systems: Nitrogen dynamics and agronomic implications
The integration of potato and livestock agronomic operations has been proposed as a means by which to improve overall system productivity and long-term sustainability. Two-year potato (Solanum tuberosum L.) rotations with alfalfa (Medicago sativa L.) and sorghum-sudangrass (Sorghum bicolor L. x S. bicolor L.) and 3-year potato rotations with 2-year stands of alfalfa and festulolium ( Festuca pratensis Huds. x Lolium perenne L.) were compared to the regionally prevalent 2-year corn (Zea mays L.) - potato rotation. Liquid dairy manure was applied at 12,260 L ha -1 and evaluated against equivalent mineral fertilizer applications balanced on available nitrogen. Forage crop rotation and manure application increased soil N levels and potato petiole N throughout the growing season in 2003 and 2004. Crop rotation was a more determining factor of N levels in potato systems than manure application. Manure was more effective at increasing potato yield than crop rotations alone; the synergistic effect of manure amendment and crop rotation produced more significant increases in potato yields than either treatment alone. C4 grasses corn and sudex increased potato yield more than C3 grass festulolium or legume alfalfa. Manure application did not affect tuber scab disease in 2002 or 2003, but did increase scab in 2004. Festulolium yields increased with manure application in 2003, but not in 2004. Additions of high quality forage rotations and manure amendment can improve N synchrony with potato N demand resulting in increased potato yields.