The ornamental design for an agriculturaltank, as shown and described.
FIG. 1 is a left side perspective view of an agricultural tank showing our new design;
FIG. 2 is a front perspective view thereof;
FIG. 3 is a left side view thereof; and,
FIG. 4 is a top view thereof.
The broken lines illustrate environmental structure which forms no part of the claimed design. Applicant hereby disclaims the bottom surface of the agricultural tank as forming no part of the claimed design.