The short event kicked off at 7am, with a performance from the Waddington military wives.
A two minute silence was observed at 7.28am, to commemorate the very moment soldiers went over the top at the Somme 100 years ago.
Jon Hogan, public engagement manager for heritage and culture, said: “This is an incredibly important day as we remember the sacrifices of those who gave their lives at the battle.
“Today’s ceremony was made possible by people from all parts of the community, coming together in a fitting and poignant tribute. I’d like to say a huge thank you to all involved.
“Following on from this morning, we have a special weekend of free events at the Museum of Lincolnshire Life to remember the Somme and learn more about WW1.
“Come and meet the soldiers, the horse-mounted Lincolnshire Yeomanry Cavalry and see authentic Vickers and Lewis machine guns.”
This morning’s event marked the beginning of a week of commemorations.
At 5pm, every evening from July 1 to 6, a bugler will play the Last Post over Castle Hill from the battlements of Lincoln Castle’s West Gate.
This will be followed by a student from a local school reading out 26 names of the fallen from Lincolnshire in the Battle of the Somme.
Events conclude on Thursday July 7 at 5pm on the South Lawn at Lincoln Castle, when, in view of Poppies: Wave, The Band of the Royal Air Force College Cranwell will play a special antiphonal rendition of The Last Post, culminating with a flypast of a BBMF Spitfire, weather permitting.