No person, as agent or employee of any person, shall enter into an agreement, expressed or implied, by which it is stipulated that grain, seeds or hay shall not be shipped by the producer or local buyer unless accompanied with warehouse receipts or that the same shall in any manner be under the control of any warehouseman or agent as a condition precedent to the marketing of such grain. All such agreements shall be deemed and are hereby declared unlawful and in violation of this act.
K.S.A. 50-133