The ornamental design for an agriculturaltank, as shown and described.
FIG. 1 is a side perspective view of an agricultural tank showing our new design.
FIG. 2 is a side view of FIG. 1; and,
FIG. 3 is a top perspective view of FIG. 1.
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.