Discussion after Mr. Wilkinson's paper.
Dr. Crane: "Minor elements are important in plant nutrition The problem of deficiencies is going to become very important. We do not keep the livestock we did and we are not returning to the land the manure and other fertilizers that contain the elements the trees need. Nitrogen, phosphorus, and potash, also magnesium are needed. We are taking more from the soil than we are putting back."
Corsan: "In Cuba there are hundreds of sharks. These make fine manure, wonderful for nut trees."
Prof. Slate: "How many sharks would you need for an acre of land?"