Agricultural sampling system and related methods

A coulter assembly for collecting soil samples from an agricultural field, the assembly comprising:

• an annular collection blade configured for penetrating soil to capture a sample;
• an annular indexing ring configured for stationary mounting to a frame of an agricultural vehicle or implement, the annular indexing ring comprising a first major surface facing the annular collection blade and an opposite second major surface;
• the annular indexing ring comprising at least one indexing segment disposed on the first major surface, the at least one indexing segment comprising an undulating configuration comprising raised portions and recessed portions;
• a blade hub coupled to the annular collection blade for rotatably supporting the annular collection blade from the annular indexing ring, the annular collection blade rotatable about a blade axis of rotation relative to the annular indexing ring;
• an elongated sample collection shaft rotatably supported by the annular collection blade and defining a radial axis of rotation perpendicular to the blade axis of rotation;
• the sample collection shaft comprising a sprocket configured to engage the at least one indexing segment of the annular indexing ring as the annular collection blade rotates, the at least one indexing segment of the indexing ring operable to cause rotation of the sample collection shaft about its radial axis of rotation;
• the sample collection shaft comprising at least one laterally open sample collection port which alternatingly opens and closes for capturing and retaining a soil sample as the sample collection shaft rotates when the annular collection blade is rotated through the soil.