An irrigation system having a pipeline supported by one or more towers includes an improved truss connection system having a means for readily adjusting a crown height of the pipeline. A pair of cooperating members define a joint which selectively couples headed ends of adjacent truss rods together to form a truss rail of a truss system that supports the pipeline. A single fastener may fasten the cooperating members, a strut, and a cross-member together at the joint. A length of the truss rail may be decreased by holding the truss rods closer together. In an aspect, the headed ends of the adjacent truss rods are held closer together by inserting a shim in one of the joints. Decreasing the length of the truss rail increases the deflection of the pipeline and raises the crown height.