Irrigation system having improved construction system and adjustable crown height

An adjustable truss joint adapted to control a tension load of a truss rail having a plurality of truss rods coupled end-to-end, the adjustable truss joint comprising:

• a first truss rod having a first head;
• a second truss rod having a second head;
• a first mating member having a first contoured shape;
• and
• a second mating member having a second contoured shape,
• wherein the first contoured shape and the second contoured shape cooperate to define a first passageway having a first diameter through which a portion of the first truss rod extends, a second passageway having a second diameter through which a portion of the second truss rod extends, and a retaining pocket within which the first head and the second head are held,
• wherein the first head is larger than the first diameter and the second head is larger than the second diameter;
• wherein the truss rail is configured to selectively deflect between at least a first position and a second position, the truss rail being in the first position when no shims are present in the retaining pocket, the truss rail being in the second position when a first shim is positioned in the retaining pocket between the first head and the first passageway.