Variation in nutrient absorption tendency of Thompson Seedless grape on own root and Dog Ridge rootstock

Abstract

A Study of the variation in the absorption of major nutrients on Thompson Seedless on its own roots and Dog Ridge rootstock, showed no correlation between soil and petiole nutrients, indicating strong interference of other nutrients. Path coefficient analysis was employed to assess the direct and indirect effects of nutrients on other nutrients in Thompson Seedless on its own roots and Dog Ridge rootstock. Correlation observed between any two nutrients is the outcome of direct effect modified by the indirect effects via other nutrients. The direct and indirect effects of nutrients on the absorption of a particular nutrient were different in Thompson Seedless vines on Dog Ridge rootstock compared to vines on their own root. Variation in the indirect effect of a pair of nutrients on the absorption of different nutrients was attributable to the complexity of the interrelationship among nutrients, relative abundance of nutrients, preferential absorption of roots, mobility of nutrients and ionic balance in foliar tissues. The direct and indirect effects indicated that restricting the application of P and K can limit the absorption of N in vines on their own root; whereas restricting the input of P and application of sulphur on Dog Ridge rootstock. Phosphorus absorption could possibly be increased by limiting the application of potash to vines on their own roots and foliar application of Mg to those on Dog Ridge in soils with high levels of available K and Na. Absorption of soil K by Thompson Seedless on own roots can be increased by higher rates of application of N, S and Mg, and reducing the application of P; and growing in soils with low levels of Na. Higher petiole N and P levels and soil S levels were found to restrict Na absorption.