Effects of Time and Height of Cut on Rooting Activity of Merion Kentucky Bluegrass as Measured by Radioactive Phosphorus Uptake
1970
O'Donnell, J. L. | Love, J. R.
Radioactive phosphorus provides a means by which the depth and lateral extent of ‘Merion’ Kentucky bluegrass (Poa pratensis L.) rooting can be measured over the growing season under field conditions. Each 15.2-cm (6-inch) depth increment, irrespective of the height of cut, was found to have 1.5 to 3 times as much root activity as the increment immediately below it. The depth of rooting activity was least in the spring (May) and increased to a maximum in the fall (October). The relative lateral distribution of root activity for both heights of cut was approximately 62, 27, 8, and 2% of the total activity for each 5.1-cm (2-inch) lateral strip from the line of injection. The lateral extent was least in the spring and greatest in the fall. Throughout the growing season there was more total root activity with the 4.4-cm (1 ¾-inch) cutting height than with the 2.2-cm (7/8-inch) cutting height. In comparison to the radioactive phosphorus method, the physical measurement of roots tends to overestimate the importance of the roots above 20.3 to 25.4 cm (8 to 10 inches) and underestimate the importance of the roots below this depth.
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