1. The soil and water supervisors of any soil and water district shall not

(1) Have or exercise the right of eminent domain;

(2) Incur indebtedness beyond available funds;

(3) Issue bonds;

(4) Levy taxes;

(5) Make or levy benefit assessments or any other kind of assessments;

(6) Take contributions from that soil and water district by exactions or persuasions;

(7) Engage in the marketing of farm products or in the buying and selling of farm supplies other than those products or supplies used or needed directly or indirectly in soil and water conservation work, subject to section 278.135;

(8) Engage in agricultural research or agricultural extension teaching except under the instruction of the Missouri college of agriculture.

2. They may accept voluntary contributions from any source, if the donations are offered for the sole and exclusive purpose of promoting the saving of soil and water within the soil and water district, and if the soil and water supervisors satisfactorily guarantee to the donors the faithful use of their donations for that purpose.