As to the toxic effect of some of our nut trees upon growth of other plants growing near by, I rather expect we shall find as time goes on that instead of the trees having a toxic effect they have a robbing effect upon soil moisture and food. One thing that leads me to this belief is that years ago we taught that one reason for seeding a cover crop in the orchard was to have the cover take the moisture from the soil in the fall of the year and in that way check tree growth. We now know that a mature apple or peach tree will reverse this during the growing season and will take its full share of moisture and food from the soil and really take these away from the cover crop. We saw this occur during the dry years of 1929 and 1930 with covers that had been seeded in June. During both these years, in our orchard blocks where the water holding capacity of the soil was low, the cover died over the tree root feeding spaces. Some may have said that the trees were having a toxic effect upon the soil. This was not the case for, in 1932 and 1933, both years of plenty of moisture supply, the covers have grown well around the trees in these blocks. I shall now ask you to refer to the conclusions on page 3 of our Bulletin No. 294, issued by The Pennsylvania State College, which has just been distributed to you. These conclusions are, of course, based upon our work in an apple orchard but I believe they will apply closely to the management of nut orchards. Lessons from Fertility Studies in the Experiment Orchard Most of the experiments in this orchard have now completed 25 years; there have been few changes and these minor ones. Certain lessons may be drawn from this quarter century of research: 1. The fertility of an orchard soil is more than its plant food content. It involves the nature of the soil, its depth and topography, its previous treatment, the use of fertilizers and manures, the amount and nature of the cultivation and the covers or sods grown. Fertilizers are only part of the problem of soil fertility. 2. In this orchard any treatment that has influenced the trees at all has done so in the following order: first, the cover crops; perhaps several years later, leaf color; shortly after, branch growth and circumference increase; and last of all, yield. 3. The reason for this sequence of results is that the treatments, whether chemical fertilizers, manure, or cover crops, have influenced yields chiefly by changing the organic matter content of the soil; that is, those treatments which have resulted in the production of larger cover crops have ultimately resulted in the production of more fruit. 4. The organic content of the soil has been a considerable factor in determining the amount of water in this soil. Those treatments which have built up the organic content have kept the soil in condition to soak up rainfall rather than to lose it by surface run-off. A larger water supply, in turn, has produced more cover crops.