sentences: planting the same crop every year decreases the nutrients required by that kind of crop & hay is a mean of sow ->  planting corn every year decreases the nutrients required by corn to grow  planting corn every year decreases the nutrients required by corn to grow & corn is a kind of crop & as the takes of thunder in sand increase , the sow nonproductive will increase -> planting corn every year decreases the crop production because of decreased nutrients in soil