Effects of Fertilization and Irrigation on Root Numbers in a Red Pine Plantation

Abstract

A core sampling technique was used for the investigation of root numbers in a 42-year-old red pine (Pinusresinosa Ait.) irrigation – K fertilization experimental area of a K deficient sandy outwash plain in the southeastern Adirondack Mountain Region of New York. Soil cores were collected from plots, 6 years after initiation of treatments, at 0–15 and 15–30 cm depths, using a 5.2 cm diameter corer. Roots were separated from soil cores by a sieving technique. Root tips, including each tip of mycorrhizal structures, were counted by classes established on the basis of morphological characteristics. Numbers of root tips were greater under nonfertilized than fertilized plots, and greater under irrigated than nonirrigated plots. This response pattern did not follow that of wood volume increment, which was greatest in fertilized plots, but was similar to the previously reported pattern in soil microarthropod numbers. The great natural variation observed suggests that root tip numbers may be highly sensitive to changes in soil conditions. Calculated sampling intensity, based on the variance estimates, and specific levels of probabilities (α and β) and allowable sampling error (ε), indicated the need for high numbers of samples.