Police said the man, who lives at Gilbert Camp in the hills above the capital Honiara, had dug down several metres on Saturday, when he struck something metal.
When he discovered it was a WWII shell, he called police and an explosive ordnance disposal team then removed 101 highly explosive shells from the site.
They were 105mm shells of the kind widely used with light field howitzer artillery by US troops in the Pacific theatre.
Last week, a 105mm WWII shell detonated under a cooking fire in Honiara, fatally wounding two men and injuring another two other people.
