The lateral distribution of potassium in an orchard soil
1939
Gourley, J.H. | Wander, I.W.
This investigation of potassium movement in the soil is of interest to horticulturists from several standpoints, particularly to those who have to deal with a deficiency of this element in orchards. The first objective was that of determining whether there would be a lateral movement of sufficient extent to make potassium available to a mass of tree roots without injury to the new ones which develop in such a zone. It is interesting to note that these areas represent from 1.4 to 2.2 cubic feet of soil per core in which the available K has become very high within a period of 3 years. Assuming all areas affected by the cores to be similar under the same tree, approximately 22.4 to 35.2 cubic feet of soil per tree would be affected by the 16 cores per tree. This means that, under an experimental test, from 1.6 to 2.5 per cent of the total soil 13 feet away from the tree trunk and 2 feet deep has been increased from a low or very low available K content to a very high available content. That roots would develop in this area and not be injured is worthy of note, although quantitative determinations of the root population was not attempted. From a practical standpoint, it would mean that potash fertilizers could be dropped behind a deep tillage tool, such as a Killifer disk or coulter, to a depth of 16 to 18 inches. This would be within the active absorbing zone of the tree roots in most eastern orchard soils and also below the zone in which potassium is fixed by alternate wetting and drying. Its lateral movement should then be ample for supplying the needs of the tree.
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