Now the following four methods are used to purchase grain : the state purchases grain through xed quotas ; the state purchases grain through negotiations with producers ; grain - processing enterprises purchase grain from the wholesale markets ; and farmers sell their grain at fairs 目前粮食收购主要有四种形式:国家定购、国家议购、粮食加工企业在批发市场上购买和农民在集市上销售。